Left: J-band polarized intensity (P⊥) images. Right: P⊥ scaled by r2, where r is the distance in pixels from the central binary, corrected for projection effects. Both images are shown on a linear scale and oriented north up and east left. The coronagraph is represented by the black filled circles.
Astronomers using the Gemini South telescope in Chile have discovered striking new evidence for planet formation in a dusty disk surrounding a pair of stars in Sagittarius. The team took advantage of an offering for Early Science using the Gemini Planet Imager to study infrared light scattered off dust grains in the disk around the binary system V4046 Sgr. "The Gemini Planet Imager allows us to study nearby planet forming disks in sufficient detail that we can obtain direct-image evidence for young planets in orbits similar to those of the giant planets in our own solar system," says Valerie Rapson of the Rochester Institute of Technology, who led the research team. Indeed, the GPI imaging reveals an intriguing double ring structure around the V4046 Sgr binary that is most likely due to the formation of a giant planet (or planets) at some 4-12 times the Earth-Sun distance (approximately between Jupiter and Uranus, if orbiting our Sun)."This is perhaps the best such evidence yet for planet formation so close to a binary system," says Rapson. Analysis of the data also indicates that the dust grains orbiting the star are sorted by particle size, as predicted by recent planet formation models. The result is published in The Astrophysical Journal Letters and the preprint is at http://arxiv.org/abs/1503.06192, see abstract below.
We report the presence of scattered light from dust grains located in the giant planet formation region of the circumbinary disk orbiting the ∼20-Myr-old close (∼0.045 AU separation) binary system V4046 Sgr AB based on observations with the new Gemini Planet Imager (GPI) instrument. These GPI images probe to within ∼7 AU of the central binary with linear spatial resolution of ∼3 AU, and are thereby capable of revealing dust disk structure within a region corresponding to the giant planets in our solar system. The GPI imaging reveals a relatively narrow (FWHM ∼10 AU) ring of polarized near-infrared flux whose brightness peaks at ∼14 AU. This ∼14 AU radius ring is surrounded by a fainter outer halo of scattered light extending to ∼45 AU, which coincides with previously detected mm-wave thermal dust emission. The presence of small grains that efficiently scatter starlight well inside the mm-wavelength disk cavity supports current models of planet formation that suggest planet-disk interactions can generate pressure traps that impose strong radial variations in the particle size distribution throughout the disk.
The region of Re50 and Re50N observed in 2006 with SuprimeCam at the Subaru telescope, and in 2014 with the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope. A [SII] filter was used for both images. The seeing was in both cases 0.5 arcsec. Each image is about 3 arcmin wide. North is up and east is left.
Changes in the universe don’t often happen on human timescales.
In the cosmic “blink of an eye,” astronomers have detected rapid changes in brightness and appearance of a restless stellar nursery in Orion. The luminous cloud of gas, going by the designation Re50, first appeared about half a century ago in the constellation of Orion. Now, astronomers using the Gemini South telescope, and other telescopes around the world, have discovered that the chaotic caldron has once again brightened further. According to team member Bo Reipurth, of the University of Hawaii’s Institute for Astronomy, “This most recent brightening, happened, I believe in 2014, when unfortunately we weren’t able to look since Orion was in the Sun’s glare.” Reipurth adds that areas of stellar birth, in this case called a Class I protostar, are extremely dynamic places and change on human timescales, “… while we missed the initial brightening event, we can still study the changes going on and learn a lot about what’s happening.” Based on the team’s observations, they conclude that curtains of obscuring material are likely casting patterns of illumination and shadows onto the molecular cloud that envelopes the nursery, “…which gives us a spectacular stellar light show!” says Reipurth.
Learn more in the team’s paper, which is accepted for publication in The Astrophysical Journal, at: http://arxiv.org/abs/1503.04241.
The luminous Class I protostar HBC 494, embedded in the Orion A cloud, is associated with a pair of reflection nebulae, Re50 and Re50N, which appeared sometime between 1955 and 1979. We have found that a dramatic brightening of Re50N has taken place sometime between 2006 and 2014. This could result if the embedded source is undergoing a FUor eruption. However, the near-infrared spectrum shows a featureless very red continuum, in contrast to the strong CO bandhead absorption displayed by FUors. Such heavy veiling, and the high luminosity of the protostar, is indicative of strong accretion but seemingly not in the manner of typical FUors. We favor the alternative explanation that the major brightening of Re50N and the simultaneous fading of Re50 is caused by curtains of obscuring material that cast patterns of illumination and shadows across the surface of the molecular cloud. This is likely occurring as an outflow cavity surrounding the embedded protostar breaks through to the surface of the molecular cloud. Several Herbig-Haro objects are found in the region.
A wide-field image showing the OMC1 outflow in H2 with proper motions of the BN object, radio source I, and radio source n superimposed. The lengths of the red-solid vectors are proportional to the motions measured by Gomez et al. (2008) with the the lengths of the vectors in arcseconds equal to the motion in km s-1 (e.g. 1000 corresponds to a motion of 10 km s-1). The ejection center as determined by radio proper motions is shown by a cross.
The Orion Nebula, probably the most well-known deep sky object in the night sky, also offers rare glimpses into catastrophic episodes in the lives of stars. Widespread, high-velocity outflow points to an explosive origin of the region known as the “Orion Fingers.” With new observations using adaptive optics imaging from Gemini South, John Bally of the University of Colorado and colleagues find over 120 high-velocity outflows in this region. Direct comparisons with earlier observations reveal the motion of these fingers. Measurements of their properties, and comparison with simulations, are evidence that an explosive event drives the outflows, which may be connected to the birth of “runaway,” massive stars.
Aims. Adaptive optics images are used to test the hypothesis that the explosive BN/KL outflow from the Orion OMC1 cloud core was powered by the dynamical decay of a non-hierarchical system of massive stars.
Methods. Narrow-band H2, [Fe II], and broad-band Ks obtained with the Gemini South multi-conjugate adaptive optics (AO) system GeMS and near-infrared imager GSAOI are presented. The images reach resolutions of 0.08 to 0.10”, close to the 0.07” diffraction limit of the 8-meter telescope at 2.12µm. Comparison with previous AO-assisted observations of sub-fields and other ground-based observations enable measurements of proper motions and the investigation of morphological changes in H2 and [Fe II] features with unprecedented precision. The images are compared with numerical simulations of compact, high-density clumps moving ~ 103 times their own diameter through a lower density medium at Mach 103.
Results. Several sub-arcsecond H2 features and many [FeII] ‘fingertips’ on the projected outskirts of the flow show proper motions of ~ 300 km/sec. High-velocity, subarcsecond H2 knots (‘bullets’) are seen as far as 140” from their suspected ejection site. If these knots propagated through the dense Orion A cloud, their survival sets a lower bound on their densities of order 107 cm3, consistent with an origin within a few au of a massive star and accelerated by a final multi-body dynamic encounter that ejected the BN object and radio source I from OMC1 about 500 years ago.
Conclusions. Over 120 high-velocity bow-shocks propagating in nearly all directions from the OMC1 cloud core provide evidence for an explosive origin for the BN/KL outflow triggered by the dynamic decay of a non-hierarchical system of massive stars. Such events may be linked to the origin of runaway, massive stars.
The research is accepted for publication in Astronomy and Astrophysics and the preprint can be accessed at http://arxiv.org/abs/1502.04711.
GMOS image of Kim 2, in g band. The image is 4 arcminutes across.
Like the lost little puppy that wanders too far from home, astronomers have found an unusually small and distant group of stars that seems oddly out of place. The cluster, made of only a handful of stars, is located far away, in the Milky Way’s “suburbs.” It is located where astronomers have never spotted such a small cluster of stars before.
The new star cluster was discovered by Dongwon Kim, a PhD student at the Australian National University (ANU), together with a team of astronomers (Helmut Jerjen, Antonino Milone, Dougal Mackey, and Gary Da Costa) who are conducting the Stromlo Milky Way Satellite Survey* at ANU.
“This cluster is faint, very faint, and truly in the suburbs of our Milky Way,” said Kim. “In fact, this group of stars is about ten times more distant than the average globular star cluster in the halo of our galaxy -- it's a lost puppy,” Mackey adds. Globular clusters are spherical cities of stars that form a vast, extended halo around the core of our galaxy, the brightest of which are easily seen in amateur telescopes or even binoculars. However, this new discovery required one of the world’s largest telescopes to confirm, “it’s definitely a diminutive oddball,” says Milone.
The oddly small, far-flung, cluster was discovered using the Dark Energy Camera (DECam) on the 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. “This discovery sheds new light on the formation and evolution of the Milky Way,” said Daniel Evans, National Science Foundation program director for Gemini Observatory. “It's great to see so many telescopes come together to produce this result, not the least being Gemini Observatory with its incredible light-gathering power.”
The team’s first evidence of the unusually remote star cluster came when they ran detection algorithms on a 500 square-degree imaging data field obtained with DECam. “Such objects are too faint and optically elusive to be seen by eye. The cluster stars are sprinkled so thinly over the image, you look right through them without noticing (see image on electronic release, URL above). They are hiding in the sea of stars from the Milky Way. Sophisticated computer programs are our tools to find them,” said Jerjen.
Because it is so faint, ultra-deep follow-up observations using the Gemini Multi-Object Spectrograph (in imaging mode) confirmed that the new globular cluster is among the faintest Milky Way globular clusters ever found. Seven out of 150 known Milky Way globular clusters are comparably faint but none are located as far out toward the edge of the Milky Way. This new globular cluster has 10-20 times fewer stars than any of the other outer halo globular clusters. Also, its star density is less than half of that of other Milky Way globular clusters in the same luminosity (brightness) range.
The new star cluster, named Kim 2, also shows evidence of significant mass loss over its history. Computer simulations predict that, as a consequence of their evolution over many billions of years, including the slow loss of member stars due to the gravitational pull of the Milky Way, star clusters ought to be arranged such that their more massive stars are concentrated toward their centers. “This ‘mass segregation’ has been difficult to observe, particularly in low mass clusters, but the excellent Gemini data reveal that Kim 2 appears to be mass segregated and has therefore likely lost much of its original mass,” said Da Costa. The finding suggests that a substantial number of low-luminosity globular clusters must have existed in the halo when the Milky Way was younger, but most of them might have evaporated due to internal dynamical processes.
The observed properties of the new star cluster also raise the question about how such a low luminosity system could have survived until today. One possible scenario is that Kim 2 is not actually a genuine member of the Milky Way globular cluster family, but a star cluster originally located in a satellite dwarf galaxy and was accreted into the Milky Way’s halo. This picture is also supported by the fact that the stars in Kim 2 appear to be more chemically enriched with heavier elements than the other outer halo globular clusters and are young relative to the oldest globular clusters in the Milky Way. As a consequence of spending much of its life in a dwarf galaxy Kim 2 could have largely escaped the destructive influence of tidal forces, thus helping it to survive until the present epoch.
There are many Milky Way globular clusters formerly and currently associated with satellite dwarf galaxies. It is possible that a significant fraction of the ancient satellite dwarf galaxies were completely disrupted by the tidal field of the Milky Way while the high density of the globular clusters allowed them to survive in our galaxy’s halo. Indeed, Kim 2 is found close to the vast polar structure of Milky Way satellite galaxies, a disc-like region surrounding the Milky Way where satellite galaxies and young halo clusters preferentially congregate. A similar distribution of satellite galaxies is also found in the neighbouring Andromeda Galaxy.
A large fraction of the Milky Way’s halo is thought to be populated with optically elusive satellite galaxies and star clusters. New discoveries of satellite galaxies and globular clusters will therefore provide valuable information about the formation and the structure of the Milky Way. Previous surveys like the Sloan Digital Sky Survey have contributed to many new discoveries in the northern sky. However, most of the southern sky still remains unexplored to date. The detection of Kim 2 suggests that there are a substantial number of interesting astronomical objects waiting to be discovered in the southern hemisphere and the Stromlo Milky Way Satellite Survey team plans to continue searching for them.
The team's paper, accepted for publication in the Astrophysical Journal, is available as a preprint at http://arxiv.org/abs/1502.03952.
* The Stromlo Milky Way Satellite Survey is led by Australian National University’s Associate Professor Helmut Jerjen. The research team includes Dongwon Kim, Antonino Milone, Dougal Mackey, and Gary Da Costa (all from the Australian National University). See project website at: http://www.mso.anu.edu.au/~jerjen/SMS_Survey.html
The spectrum obtained using the Gemini Near-Infrared Spectrograph (GNIRS) combined with observations from the Magellan Telescope appears in red; gaps are regions of low sky transparency. The optical spectrum (from the Large Binocular Telescope; black) and noise (magenta) are also plotted. The inset shows the three components of the fit to a portion of the near-infrared emission. The ionized magnesium (Mg II; blue) is used to estimate the extremely large black hole mass mass, of 12 billion times the mass of the Sun. Figure credit: Nature.
Infrared observations with the Gemini North telescope have confirmed a 12 billion solar mass black hole in an exceptionally bright quasar in the very early universe. The finding, led by a Chinese team, used Gemini, as well as telescopes from around the world, to discover and characterize an extremely massive black hole from a period when the universe was very young (about 900 million years after the Big Bang). This observation requires extremely rapid growth of the black hole. While black holes of comparable mass have been observed after they have had billions of years to gradually gain mass over cosmic history this quasar challenges astronomers to figure out how such a huge object could exist so early in the history of the universe.
The research is published in the February 26th issue of Nature, led by Xue-Bing Wu at Peking University in Beijing, China.
Abstract: So far, roughly 40 quasars with redshifts greater than z=6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses. The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultraluminous quasar, SDSSJ010013.021280225.8, at redshift z=6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z>6 quasars. On the basis of the deep absorption trough on the blue side of the Lyman-a emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z>6.1 quasars with lower luminosities. We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of ~1.2 x 1010 solar masses, which is consistent with the 1.3 x 1010 solar masses derived by assuming an Eddington-limited accretion rate.
Reviewers for the Fast Turnaround program must declare that they are able to provide an unbiased review of each proposal, before being given access to the proposal itself.
As of January 2nd, 2015, Gemini’s Fast Turnaround (FT) program is open for business. Following the first proposal deadline on January 31st, the Gemini community is now able to submit proposals every month for the duration of this open-ended trial.
The intent of the FT scheme - which is initially being run as a pilot at Gemini North only - is to greatly shorten the time between having an idea and acquiring the supporting data. Proposals will be reviewed in the 14 days following each deadline, and principal investigators (PIs) will be notified of the outcome by the 21st of the month. A small support team at Gemini will work with successful PIs to quickly prepare their observations, which will then be available for execution on three dedicated nights each month for the following three months.
The proposal review process differs from anything that Gemini (or, as far as we are aware, any astronomical observatory) has done before. To meet the 14-day review requirement, the scientific merit of the proposals will be judged by the PIs (or designated co-investigators) of other proposals submitted during the same round. After a set of manual checks performed by the support team shortly after the proposal deadline, reviewers are notified of their proposal assignments. They must agree to ethical participation in the assessment process; that is, they must consent to keep the proposals confidential and use their contents only for the purpose of the review. Upon doing so, they are shown the titles, abstract, and investigator lists of the proposals that have been selected for them. At this stage, reviewers are asked to declare whether or not they are able to provide an unbiased review of each proposal (Figure 1). Only then are they given access to the proposals themselves, and to the form on which they provide their assessments.
The assessors must supply a grade for each proposal, a brief written review, and an indication of their level of expertise in the proposal’s field. On the 14th of the month, the review forms are closed (and if any reviewer has not completed their assessments by this date, their own proposal is automatically excluded from the rest of the process!). The software generates a ranked list that is passed to the FT support team, which then performs technical assessments on the highest-rated proposals and constructs the set of the highest-ranked, technically-feasible proposals that will fit in the available time. This is probably the most difficult part of the process from the staff point of view, because it involves finding a balance between accepting proposals that have a realistic chance of being observed (not accepting several programs all requiring exceptional image quality, for example), while remaining as true to the scientific ranking as possible.
Much more information about the FT scheme is available on the program’s web pages. The FT program is rather experimental, and designing the system has been a very interesting exercise. The monthly cycle will allow us to make adjustments as we see how the scheme works in practice, and we certainly expect that adjustments will be necessary. Feedback from users and potential users of the system will also be invaluable (and encouraged) as the pilot project proceeds. If you have something to say, feel free to get in touch at fast.turnaround at gemini.edu.
Figure 1. GPI imaging of the planetary system HR 8799 in K band, showing 3 of the 4 planets. (Planet b is outside the field of view shown here, off to the left.) These data were obtained on November 17, 2013 during the first week of operation of GPI and in relatively challenging weather conditions, but with GPI’s advanced adaptive optics system and coronagraph the planets can still be clearly seen and their spectra measured (see Figure 2). Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team.
Figure 2. GPI spectroscopy of planets c and d in the HR 8799 system. While earlier work showed that the planets have similar overall brightness and colors, these newly-measured spectra show surprisingly large differences. The spectrum of planet d increases smoothly from 1.9-2.2 microns while planet c’s spectrum shows a sharper kink upwards just beyond 2 microns. These new GPI results indicate that these similar-mass and equal-age planets nonetheless have significant differences in atmospheric properties, for in-stance more open spaces between patchy cloud cover on planet c versus uniform cloud cover on planet d, or perhaps differences in atmospheric chemistry. These data are helping refine and improve a new generation of atmospheric models to explain these effects. Image credit: Patrick Ingraham (Stanford University), Mark Marley (NASA Ames), Didier Saumon (Los Alamos National Laboratory) and the GPI Team.
Figure 3. GPI imaging polarimetry of the circumstellar disk around HR 4796A, a ring of dust and planetesimals similar in some ways to a scaled up version of the solar system’s Kuiper Belt. These GPI observations reveal a complex pattern of variations in brightness and polarization around the HR 4796A disk. The western side (tilted closer to the Earth) appears brighter in polarized light, while in total intensity the eastern side appears slightly brighter, particularly just to the east of the widest apparent separation points of the disk. Reconciling this complex and apparently-contradictory pattern of brighter and darker regions required a major overhaul of our understanding of this circumstellar disk. Image credit: Marshall Perrin (Space Telescope Science Institute), Gaspard Duchene (UC Berkeley), Max Millar-Blanchaer (University of Toronto), and the GPI Team.
Figure 4. Diagram depicting the GPI team's revised model for the orientation and composition of the HR 4796A ring. To explain the observed polarization levels, the disk must consist of relatively large (> 5 µm) silicate dust particles, which scatter light most strongly and polarize it more for forward scattering. To explain the relative faintness of the east side in total intensity, the disk must be dense enough to be slightly opaque, comparable to Saturn’s optically thick rings, such that on the near side of the disk our view of its brightly illuminated inner portion is partially obscured. This revised model requires the disk to be much narrower and flatter than expected, and poses a new challenge for theories of disk dynamics to explain. GPI’s high contrast imaging and polarimetry capabilities together were essential for this new synthesis. Image credit: Marshall Perrin (Space Telescope Science Institute).
See the AAS press conference featuring Marshall Perrin speaking about Gemini Planet Imager results at:
Click on the “Exoplanet & Host Stars II” session, Perrin is the final speaker in the session.
Stunning exoplanet images and spectra from the first year of science operations with the Gemini Planet Imager (GPI) were featured today in a press conference at the 225th meeting of the American Astronomical Society (AAS) in Seattle, Washington. The Gemini Planet Imager GPI is an advanced instrument designed to observe the environments close to bright stars to detect and study Jupiter-like exoplanets (planets around other stars) and see protostellar material (disk, rings) that might be lurking next to the star.
Marshall Perrin (Space Telescope Science Institute), one of the instrument’s team leaders, presented a pair of recent and promising results at the press conference. He revealed some of the most detailed images and spectra ever of the multiple planet system HR 8799. His presentation also included never-seen details in the dusty ring of the young star HR 4796A. “GPI’s advanced imaging capabilities have delivered exquisite images and data,” said Perrin. “These improved views are helping us piece together what’s going on around these stars, yet also posing many new questions.”
The GPI spectra obtained for two of the planetary members of the HR 8799 system presents a challenge for astronomers. GPI team member Patrick Ingraham (Stanford University), lead the paper on HR 8799. Ingraham reports that the shape of the spectra for the two planets differ more profoundly than expected based on their similar colors, indicating significant differences between the companions. “Current atmospheric models of exoplanets cannot fully explain the subtle differences in color that GPI has revealed. We infer that it may be differences in the coverage of the clouds or their composition.” Ingraham adds, "The fact that GPI was able to extract new knowledge from these planets on the first commissioning run in such a short amount of time, and in conditions that it was not even designed to work, is a real testament to how revolutionary GPI will be to the field of exoplanets."
Perrin, who is working to understand the dusty ring around the young star HR 4796A, said that the new GPI data present an unprecedented level of detail in studies of the ring’s polarized light. “GPI not only sees the disk more clearly than previous instruments, it can also measure how polarized its light appears, which has proven crucial in under-standing its physical properties.” Specifically, the GPI measurements of the ring show it must be partially opaque, implying it is far denser and more tightly compressed than similar dust found in the outskirts of our own Solar System, which is more diffuse. The ring circling HR 4796A is about twice the diameter of the planetary orbits in our Solar System and its star about twice our Sun’s mass. “These data taken during GPI commissioning show how exquisitely well its polarization mode works for studying disks. Such observations are critical in advancing our understanding of all types and sizes of planetary systems – and ultimately how unique our own solar system might be,” said Perrin.
During the commissioning phase, the GPI team observed a variety of targets, ranging from asteroids in our solar system, to an old star near its death. Other teams of scientists have been using GPI as well and already astronomers around the world have published eight papers in peer-reviewed journals using GPI data. “This might be the most productive new instrument Gemini has ever had,” said Professor James Graham of the University of California, who leads the GPI science team and who will describe the GPI exoplanet survey (see below) in a talk scheduled at the AAS meeting on Thursday, January 8th.
The Gemini Observatory staff integrated the complex instrument into the telescope’s software and helped to characterize GPI’s performance. “Even though it’s so complicated, GPI now operates almost automatically,” said Gemini’s instrument scientist for GPI Fredrik Rantakyro. “This allows us to start routine science operations.” The instrument is now available to astronomers and their proposals are scheduled to start ob-serving in early 2015. In addition, “shared risk” observations are already underway, starting in November 2014.
The one thing GPI hasn’t done yet is discovered a new planet. “For the early tests, we concentrated on known planets or disks” said GPI PI Bruce Macintosh. Now that GPI is fully operational, the search for new planets has begun. In addition to observations by astronomers world-wide, the Gemini Planet Imager Exoplanet Survey (GPIES) will look at 600 carefully selected stars over the next few years. GPI ‘sees’ planets through the infrared light they emit when they’re young, so the GPIES team has assembled a list of the youngest and closest stars. So far the team has observed 50 stars, and analysis of the data is ongoing. Discovering a planet requires confirmation observations to distinguish a true planet orbiting the target star from a distant star that happens to sneak into GPI’s field of view - a process that could take years with previous instruments. The GPIES team found one such object in their first survey run, but GPI observations were sensitive enough to almost immediately rule it out. Macintosh said, “With GPI, we can tell almost instantly that something isn’t a planet – rather than months of uncertainty, we can get over our disappointment almost immediately. Now it’s time to find some real planets!”
The Gemini Planet Imager (GPI) instrument was constructed by an international collaboration led by Lawrence Livermore National Laboratory under Gemini’s supervision. The GPI Exoplanet Survey (GPIES) is the core science program to be carried out with it. GPIES is led by Bruce Macintosh, now a professor at Stanford University and James Graham, professor at the University of California at Berkeley and is designed to find young, Jupiter-like exoplanets. They survey will observe 600 young nearby stars in 890 hours over three years. Targets have been carefully selected by team members at Arizona State University, the University of Georgia, and UCLA. The core of the data processing architecture is led by Marshall Perrin of the Space Telescope Science Institute, with the core software originally written by University of Montreal, data management infrastructure from UC Berkeley and Cornell University, and contributions from all the other team institutions. The SETI institute located in California manages GPIES’s communications and public out-reach. Several teams located at the Dunlap Institute, the University of Western Ontario, the University of Chicago, the Lowell Observatory, NASA Ames, the American Museum of Natural History, University of Arizona and the University of California at San Diego and at Santa Cruz also contribute to the survey. The GPI Exoplanet Survey is supported by the NASA Origins Program NNX14AG80, the NSF AAG pro-gram, and grants from other institutions including the University of California Office of the President. Dropbox Inc. has generously provided storage space for the entire survey's archive.
Gemini Legacy image of the galaxy group VV 166, obtained using the Gemini Multi-Object Spectrograph (GMOS), at the Gemini North telescope located on Mauna Kea, Hawai‘i. In this image, north is up, east left, and the field of view is 5.2 x 5.2 arcminutes. Composite color image produced by Travis Rector, University of Alaska Anchorage. Image credit: Gemini Observatory/AURA
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A compelling new image from Gemini Observatory peers into the heart of a group of galaxies (VV166) traveling through space together. The variety of galactic forms range from a perfect spiral, to featureless blobs and present, at a glance, a sampling of the diversity and evolution of galaxies.
Galaxy groups are the most evident structures in the nearby universe. They are important laboratories for studying how galaxies form and evolve beyond our own Local Group of galaxies, which includes the Milky Way and the Great Spiral in Andromeda. Exploring the nature of these extragalactic “herds” may help to unlock the secrets to the overall structure of the universe.
Unlike animal herds, which are generally the same species traveling together, most galaxies move through space in associations comprised of myriad types, shapes, and sizes. Galaxy groups differ in their richness, size, and internal structure as well as the ages of their members. Some group galaxies are composed mainly of ancient stars, while others radiate with the power and splendor of youth.
These facts raise important questions for astronomers: Do all the galaxies in a group share a common origin? Are some just chance alignments? Or do galaxy groups pick up “strays” along the way and amalgamate them into the group?
The new Gemini image, of a grouping called VV 166, after its position in the catalog by B. Vorontsov-Vel’yaminov, provides clarity and definition to the group’s different morphological types despite its great distance of about 300 million light-years – some 30 times farther away than the closest galaxy groups to our Local Group. One of its most fascinating features is a perfect alignment of three disparate galaxies in a precise equilateral triangle: blue-armed spiral NGC 70 at top, elliptical galaxy NGC 68 to its lower right, and lenticular galaxy NGC 71 to its lower left.
The blue spiral (NGC 70) looks like an elephant among lions. This massive galaxy is impressive as it spans 180,000 light-years or nearly twice the extent of the Milky Way’s reach. Its spiral arms appear blue because they are dominated by active regions of star formation. Here, young hot stars burn with an intense blue light that overpowers that from any older red and yellow stars that might populate the galaxy.
The opposite is true in the galaxy’s central bulge, where the extinction of star formation has left it to glow with the warm light of ancient red giant and supergiant suns. The galaxy’s sharp star-like core is a telltale sign of an active galactic nucleus powered by a centrally located supermassive black hole feasting on a disk of interstellar gas only a few light-days across.
In contrast, NGC 68 (lower right) is a much older system known as an elliptical galaxy. NGC 68 is about half the size of the blue spiral and hosts little dust and gas, so star formation is all but absent, as is any spiral structure; the galaxy’s overall yellowish hue reveals that most of its stars are old and red. If there’s an outlier in the image, it might be NGC 68, given that it is about 20 million light-years closer to us than NGC 70. In fact, some researchers have argued that NGC 68 is nothing but a chance alignment. Indeed, while small galaxy groups prevail in the nearby universe, many may not be real gravitationally bound systems at all. But this does not appear to be the case with VV 166, for most of these galaxies are indeed bound as a group.
Although NGC 71 looks much like NGC 68 (a smooth featureless glow, below and to the left of NGC 68) it is actually a lens-shaped galaxy seen face on, so it appears more like a sphere. Lenticular galaxies are mysterious creatures, as they appear to be trapped between classifications: like a spiral galaxy it has a bulge and a disk but no spiral arms; but, like an elliptical galaxy, it is largely devoid of dust and gas. Possibly galaxies like NGC 71 were originally spiral systems and have either consumed, or somehow lost their interstellar material through other galactic interactions.
The image also shows possible evidence for such a dynamic interaction. Careful inspection reveals that blue spiral’s arms appear distorted between NGC 68 and NGC 71, indicating a possible tidal interaction with one or more of the galaxies. These graceful interactions are choreographed as the group whizzes collectively through space at about 6,500 kilometers per second. The image also sharply resolves a flurry of starlight around the elliptical and lenticular systems. Often the brightest cluster galaxy has an extraordinarily diffuse and extended outer halo.
Just beyond the triangle to the lower left is the Group’s fourth brightest member, a barred spiral galaxy known as NGC 72. Its prominent bar slices across its nucleus. Dusty arms wind out from either end of the bar and form a distinct nuclear ring – the result of recent star formation. Our own Milky Way Galaxy has a similar bar component spanning nearly 30,000 light-years from end to end, as well as a circumnuclear ring. But we have evidence that our Milky Way is a “Grand-design” spiral with more splendid and numerous arms.
Despite the apparent diversity of galaxy types in VV 166, the relative proportions of morphologies that we see here may provide a representative sample of galactic types found throughout the universe. It’s possible that some members of VV166 may have grown by drawing in smaller galaxies from the local environment and consuming them. Or, perhaps, like some herds of animals, galaxy groups may be joined by other “species” – sometimes passively, sometimes violently; this would help to explain the observed mix of morphological types in these groups.
On the larger cosmological scale, galaxy groups are like beads in the long filamentary structures that make up the skeleton of our universe. These filaments are made up of isolated galaxies, groups, clusters, and superclusters. In time, the isolated galaxies may merge with the groups, which will themselves merge with other groups to form larger clusters of galaxies. As with the animal kingdom, the universe has its hierarchy and includes all things great, and even greater.
Figure 1. All of the images shown in Figure 2 were “stacked” in this image of Comet 67P. Background stars are expanded and fuzzy due to the use of a “median” filter when stacking the images while keeping the comet centered.
Figure 2. Fifteen consecutive sixty-second exposures of Comet 67P obtained on single night using an r' band filter with the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile. Images run left to right, top to bottom, with the initial and final positions of the comet indicated by arrow. The changes in apparent brightness of the comet are due to varying sky brightness since the comet was positioned close to the Sun as viewed from the Earth.
QuickTime video of time-lapse sequence from the images shown in Figure 2. The motion of Comet 67P is apparent over the duration of the sequence.
New Gemini Observatory images show an Earth-based perspective of the comet targeted by the Rosetta spacecraft. The images capture the comet about nine hours before the Philae probe landed on the “dirty snowball’s” surface.
A series of images released today by the Gemini Observatory reveal Comet 67P/Churyumov-Gerasimenko (67P, the comet currently being explored by the European Space Agency’s Rosetta spacecraft) as it glides against a starry background. The images were obtained over a 26-minute period -- and only nine hours prior to the successful landing of the washing-machine sized probe, called Philae, which bounced to a safe landing on the comet’s surface.
Images, like these from Gemini, and other telescopes, allow the Rosetta team to monitor the total activity level of the comet. In addition, they provide scientists with the data needed to study how the large-scale coma (the comet’s atmosphere) and its tails develop. Meanwhile, Rosetta's instruments concentrate on the nucleus and innermost tens-of-kilometers of the coma. "Through this scientists can simultaneously investigate the whole comet at all distance scales," says team member Colin Snodgrass.
The images, obtained with the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile, reveals the extent of the comet's coma, which extends at least 12,000 kilometers in diameter. Rosetta and the comet's nucleus, with Philae on it, are all hidden within the central pixel in images seen from Earth - each pixel spans an area 400 kilometers wide at the Earth-comet distance. The nucleus itself occupies only 1/10,000th of a pixel, and the spacecraft are much smaller, highlighting just how difficult the landing of Philae was (as directed from Earth).
Team lead Matthew Knight points out that these observations from the ground are also challenging. "Since the comet is very low on the horizon and sets very soon after sunset, as well as being set against myriad Milky Way stars, this makes it a challenging task for even the best of the world’s telescopes."
67P is currently 3.4 Astronomical Units (AU) from Earth (approximately 500 million kilometers) and 3 AU from the Sun, between the orbits of Mars and Jupiter, at the same distance as the outer edge of the asteroid belt. Rosetta is currently orbiting the comet at a distance between 30 and 50 kilometers from the surface of the nucleus, which is estimated to be about four kilometers wide.
The team responsible for the Gemini images of Comet 67P is led by Matthew Knight (Lowell Observatory), and includes Colin Snodgrass (Open University, UK), and Blair Conn (Gemini Observatory). Observational data were obtained by Pascale Hibon and Andrew Cardwell.
Figure 1. Images of P/2013 P2 (left) obtained using the Gemini North telescope on September 4, 2013 when it was 3.2 AU from the sun, and of P/2014 S3 obtained using the CFHT telescope in late September 2014 when it was 2.1 AU from the sun. Both images have been processed to remove most of the background stars and galaxies to enhance the visibility of the faint dust tails.
Figure 2. Spectrum of C/2013 P2 (Pan STARRS) from the visible (blue points) to near infrared (red points) compared to other solar system small bodies: comets (represented by comet 6P/d’Arrest), Trojan asteroids, outer asteroid belt red D-type asteroids, and ultra-red Kuiper belt objects (TNOs). This shows that C/2013 P2 looks very different from other small body surfaces.
Astronomers are announcing today the discovery of two unusual objects in comet-like orbits that originate in the Oort cloud but with almost no activity, giving scientists a first look at their surfaces. These results, presented today at the annual meeting of the Division of Planetary Sciences of the American Astronomical Society in Tucson, Arizona, are particularly intriguing because the surfaces are different from what astronomers expected, and they give us clues about the movement of material in the early solar system as the planets were assembled.
On August 4, 2013 an apparently asteroidal object, C/2013 P2 Pan-STARRS, was discovered by the Pan STARRS1 survey telescope (PS1) on Haleakala, Maui, Hawaii. What made this object unique is its orbit – that of a comet coming from the Oort cloud, with an orbital period greater than 51 million years, yet no cometary activity was seen. The Oort cloud is a spherical halo of comet nuclei in the outer solar system that extends to about 100,000 times the Earth-sun distance, which is known as 1 astronomical unit, or 1 AU.
“Objects on long-period orbits like this usually exhibit cometary tails, for example comet ISON and comet Hale Bopp, so we immediately knew this object was unusual,” explained team leader Dr. Karen Meech. “I wondered if this could be the first evidence of movement of solar system building blocks from the inner solar system to the Oort cloud.”
Follow-up observations in September 2013 with the 8-meter Gemini North telescope on Mauna Kea, Hawaii, hinted at faint, low-level light reflected off a dusty tail. This tail remained through the object’s closest approach to the sun (2.8 times the Earth-sun distance, within the outer asteroid belt) in February 2014, but the object didn’t get much brighter.
When the object was observable again in the spring, the team used the Gemini North telescope to obtain a spectrum of the surface, which showed that it was very red, completely different from comet or asteroid surfaces, and more like the surface of an ultra-red Kuiper belt object.
“We had never seen a naked (inactive) Oort cloud comet, but Jan Oort hypothesized their existence back in 1950 when he inferred the existence of what we now call the Oort Cloud. Oort suggested that these bodies might have a layer of “volatile frosting” left over from 4.5 billion years of space radiation that disappears after their first pass through the inner solar system. Maybe we are seeing the first evidence of this,” said Dr. Olivier Hainaut of the European Southern Observatory.
While the team analyzed their observations of comet C/2013 P2 Pan-STARRS, a second object was discovered. C/2014 S3 Pan-STARRS was discovered through the NASA-sponsored Near Earth Object survey on the PS1 telescope on September 22, 2014. Like C/2013 P2 Pan-STARRS, it was on the same type of cometary orbit and also showed minimal activity. Team member Dr. Richard Wainscoat (IfA, University of Hawaii) commented, “With PS1 now exclusively involved in surveying the solar system for Near Earth Objects (NEOs), we expect to find many fascinating objects. This will help revolutionize our understanding of the early solar system”.
The team immediately followed up this second object with the Canada-France-Hawaii Telescope on Mauna Kea, to obtain data on the object’s colors, and to their surprise, this one has colors similar to inner solar system asteroid material.
“While the orbit of C/2014 S3 is similar to objects in the so-called Damocloid class, which are believed to be extinct comets, the surface of this object looks nothing like previously observed Damocloids. This is the first outer solar system object which matches inner asteroid belt material,” said team member Henry Hsieh (Academia Sinica, Taipei, Taiwan). “Damocloids typically have moderately red surfaces, but this is much more blue. These may be the first of a new class of objects,” noted team member Bin Yang (ESO Santiago, Chile).
While the orbit of C/2014 S3 Pan-STARRS took it closer to the sun than C/2013 P2 in mid August 2014 (2.0 AU—between the asteroid belt and the orbit of Mars), it also barely had a tail.
“I’ll be thrilled if this object turns out to have a surface composition similar to asteroids in the inner part of the asteroid belt. If this is the case, it will be remarkable for a body found so far out in the Solar System, especially since it exhibited a tail that may be due to volatile outgassing,” commented team leader Karen Meech. “There are several models that try to explain how the planets grew in the early solar system, and some of these predict that material formed close to the sun could have been thrown outward into the outer Solar System and Oort cloud, where it remains today. Maybe we are finally seeing that evidence.”
The report is being presented by Drs. Karen Meech, Jan Kleyna, Jacqueline Keane, Richard Wainscoat of the University of Hawaii at Manoa’s Institute for Astronomy (Honolulu, Hawaii), Bin Yang (Santiago, Chile) and Olivier Hainaut (Garching, Germany) from the European Southern Observatory, Henry Hsieh from Academia Sinica (Taipei, Taiwan), Ryan Park and James Bauer from the Jet Propulsion Laboratory (Pasadena, California), Peter Veres from Comenius University (Bratislava, Slovakia), and Bhuwan Bhatt and Devendra Sahu from the Indian Institute of Astrophysics (Bangalore, India).
Based in part on observations obtained at the Pan-STARRS1 Survey telescope, made possible through the Pan STARRS science consortium, in part at the Gemini Observatory which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership; in part on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The observations are also based in part from the Himalayan Chandra Telescope, operated by the Indian Institute of Astrophysics, Bangalore, and through the use of the 72-inch Perkins telescope at Lowell Observatory in Arizona.
This work was supported by NASA through the NASA Astrobiology Institute under Cooperative Agreement No. NNA09DA77A issued through the Office of Space Science, and in part based upon work supported by the National Aeronautics and Space Administration under Grant No. NNX12AR65G and Grant No. NNX14AM74G issued through the NEO Observation Program.
Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.
Left panel: the velocity vs. clustercentric radius phase space of galaxies in the nine GCLASS clusters. The velocities are in units relative to the individual cluster velocity dispersions and the radii are relative to the position of the brightest cluster galaxy scaled by the R200 of the cluster. The shaded regions are arbitrarily defined but are indicative of increasing time since infall (see text). Quiescent galaxies (red triangles), star forming galaxies (blue triangles), and poststarburst galaxies (green stars) all occupy distinct locations in phase space. Right panels: the ratio of quiescent and poststarburst galaxies compared to star-forming galaxies separated into the three radial bins marked by the dotted lines (top panel), and the three phase space bins marked by the shaded regions (bottom panel). The error bars are 1σ Poisson errors. Poststarburst galaxies are distributed fairly uniformly in the cluster by radius (top panel), with a peak in the middle bin; however, in phase space they are most prevalent in the middle bin and completely absent in the inner bin (bottom panel).
Understanding the behaviors of galaxies in clusters is a large and complex problem that has not daunted Adam Muzzin of the Leiden Observatory at Leiden University in The Netherlands. Muzzin led an international team using data from the Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS) in order to explore galaxies that have recently stopped (quenched) the formation of stars. Their findings reveal that these galaxies are very different from other cluster galaxies, and for the first time show that these quenched galaxies tend to be closer to the cluster’s center and moving especially fast. As a critical part of their results, the team established unprecedented constraints on how long this quenching takes, and where it happens. It’s quick, by astrophysical timescales – between 100-500 million years, and happens roughly halfway out from the center of the cluster.
Scientific Abstract (from the paper):
We investigate the velocity versus position phase space of z ∼ 1 cluster galaxies using a set of 424 spectroscopic redshifts in nine clusters drawn from the GCLASS survey. Dividing the galaxy population into three categories: quiescent, star-forming, and poststarburst, we find that these populations have distinct distributions in phase space. Most striking are the poststarburst galaxies, which are commonly found at small clustercentric radii with high clustercentric velocities, and appear to trace a coherent “ring” in phase space. Using several zoom simulations of clusters we show that the coherent distribution of the poststarbursts can be reasonably well-reproduced using a simple quenching scenario. Specifically, the phase space is best reproduced if these galaxies are quenched with a rapid timescale (0.1 < τQ < 0.5 Gyr) after they make their first passage of R ∼ 0.5 R200 , a process that takes a total time of ∼ 1 Gyr after first infall. The poststarburst phase space is not well-reproduced using long quenching timescales (τQ > 0.5 Gyr), or by quenching galaxies at larger radii (R∼R200 ).We compare this quenching timescale to the timescale implied by the stellar populations of the poststarburst galaxies and find that the poststarburst spectra are well-fit by a rapid quenching (τQ = 0.4+0.3−0.4 Gyr) of a typical star-forming galaxy. The similarity between the quenching timescales derived from these independent indicators is a strong consistency check of the quenching model. Given that the model implies satellite quenching is rapid, and occurs well within R200 , this would suggest that ram-pressure stripping of either the hot or cold gas component of galaxies are the most plausible candidates for the physical mechanism. The high cold gas consumption rates at z ∼ 1 make it difficult to determine if hot or cold gas stripping is dominant; however, measurements of the redshift evolution of the satellite quenching timescale and location may be capable of distinguishing between the two.
The GMOS-North light curve (top panel) and Fourier transform (bottom panel) for the optical companion to PSR J1738+0333. A comparison star is shown in blue, offset by -7%. We mark the 4 sigma and 3 sigma significance level as dashed green and blue lines, respectively. The three significant pulsations are marked with red lines in the bottom panel and the frequency solution is illustrated in the top panel.
The universe is a place of extremes, but rarely do astronomers get a chance to observe two so closely associated as in this recent finding based on Gemini data. The observations, led by Mukremin Kilic of the University of Oklahoma, reveal a unique, very close pairing of stellar corpses that have different evolutionary histories: one is the extremely dense, mountain-sized remains of a supernova explosion (called a pulsar, a rapidly rotating neutron star spinning (in this case) at over 10,000 times per minute), and the other is a Neptune-sized cooling ember of a deceased Sun-like star (a white dwarf) that pulsates about every 30 minutes. Together, this orbiting pair provides a unique laboratory for the understanding, and testing of theoretical models on the mass, internal structure, and characteristics of neutron stars and white dwarfs – the evolutionary end-states of many, if not most, stars.
The paper is accepted for publication in the Monthly Notices of the Royal Astronomical Society Letters and can be accessed at http://arxiv.org/abs/1410.4898.
Scientific Abstract (from the paper):
We report the discovery of the first millisecond pulsar with a pulsating white dwarf companion. Following the recent discoveries of pulsations in extremely low-mass (ELM, <0. 3 M⊙ ) white dwarfs (WDs), we targeted ELM WD companions to two millisecond pulsars with high-speed Gemini photometry. We find significant optical variability in PSR J1738+0333 with periods between roughly 1790− 3060 s, consistent in timescale with theoretical and empirical observations of pulsations in ≈ 0.17 M⊙ He-core ELM WDs. We additionally put stringent limits on a lack of variability in PSR J1909− 3744, showing this ELM WD is not variable to < 0.1 per cent amplitude. Thanks to the accurate distance and radius estimates from radio timing measurements, PSR J1738+0333 becomes a benchmark for low mass, pulsating WDs. Future, more extensive time-series photometry of this system offers an unprecedented opportunity to constrain the physical parameters (including the cooling age) and interior structure of this ELM WD, and in turn, the mass and spin-down age of its pulsar companion.
Here you can find the full videos to give you just a taste of what happened:
Figure 1. Bill (left) and Steve (right) relate exoplanet chemistry to the preserving of blueberry puree.
Figure 2. Steve shows a very engaged nine year old how to create slime.
Figure 3. Steve and Bill create an exotic foam column, demonstrating the use of foam in the kitchen.
Figure 4. Bill and Steve create fruit spheres and provide tasty treats for the audience.
Figure 5. The team's "anti-gravity machine" keeps frozen bubbles aloft.
Figure 6. Bill (right) and Steve (second from right) share their ideas and exoplanet-inspired cooking with Hale Pohaku cook Jason Hashimoto (second from left) as they prepare food for observatory staff at the Mauna Kea mid-level facilities. Also shown is Charlie Fabella (left) who is assisting the team in the kitchen.
On Saturday evening, July 19th, Gemini Observatory, in a partnership with the ‘Imiloa Astronomy Center shared with Hawai'i residents "The Adventures of gAstronomy!" Dr. Steve Howell, Project Scientist for NASA's Kepler Planet Finding Mission, and Chef Bill Yosses, former White House Executive Pastry Chef, wowed the audience with their speculation about the conditions on selected exoplanets -- which inspire recipes for chefs like Yosses.
Numerous samples of exoplanet-inspired culinary delights, from mango spheres, to exotic foams, and polymers, titillated audience's taste buds throughout the evening. “The excitement of discovering thousands of exoplanets can be brought right into your kitchen,” said Howell, who added that, “The same science principles astronomers use to understand alien worlds are used to create marvels of culinary delight.” Together, Howell and Yosses have combined modern molecular gastronomy methods, and basic physics, to teach a little of both, and provide exotic taste treats.
“We believe the enthusiasm we have for cooking and science is contagious and this event at the ‘Imiloa Planetarium proves that new discoveries in one field can generate waves of new ideas in others. We want to thank the Gemini and ‘Imiloa teams, the volunteers, and the Hilo community for their support,” Chef Yosses noted.
We hope these photos capture some of the event’s “flavor!”
Dr. Howell and his research/observing team are in Hilo/Hawai'i Island to observe with the Gemini North telescope on Mauna Kea. Using their visiting instrument -- DSSI (Differential Speckle Survey Instrument) – they will confirm and explore dozens of Kepler discovered exoplanet candidates.
UPDATE: Here are two "recipies" you can use to re-create either Oxygen Foam or Slime as seen during the event.
Procedure for making a long-lasting Oxygen Foam
The basic science here is that you have hydrogen peroxide, which could be called hydrogen dioxide, since it is just a water molecule with an extra oxygen atom attached. Hydrogen peroxide is H2O2, water is of course H2O. By adding another chemical, called a catalyst, to the peroxide, you start a chemical reaction that releases the extra oxygen attached to the water molecule. If you mix in a little dish soap you can capture the released oxygen gas in the form of bubbles.
You will need…
• an empty 16 oz. plastic soda or water bottle or simply a plastic glass
• 1/2 cup 3% hydrogen peroxide (the kind you buy in a drug store). Hydrogen peroxide is simply water with an extra O atom attached. H2O + O = H2O2. This extra O atom is what we will be releasing during the reaction.
• Dish detergent, such as Dawn liquid – this will capture the O2 into bubbles
• Food coloring – for fun
• 1 teaspoon (or half a packet) of yeast dissolved in warm water
What to do:
Fill your soda bottle (or glass) with the 1/2 cup of peroxide. Add a squirt or two of dish detergent. Add a squirt or two of your favorite food coloring (or a combination) to make things a bit festive. Note: The food coloring is only for fun and is not needed.
Now you need to prepare your yeast. The yeast acts as a catalyst to release an oxygen atom from the hydrogen peroxide. These free O atoms will combine to form O2 resulting in the reaction H2O2 à H2O + O2. Add the teaspoon of yeast to a few tablespoons of warm water, stir and let sit for 30 seconds. This yeast solution will give you a rich creamy foam of tiny bubbles.
Add the yeast solution to the hydrogen peroxide solution. You will get quite a surge of tiny soapy bubbles. The long lasting foam will be warm because this reaction is exothermic, that is it produces heat.
Procedure for making Slime, a cross-linked polymer
You will need…
• 1 cup hot water
• 1.5 tsp. Borax (non-toxic/available by laundry detergents, sodium borate)
• 2 cups clear school glue – note this has to be polyvinyl alcohol (PVA). Do not be confused with the PVA polyvinyl acetate, it will not work in the experiment.
• 2 cups warm water
• 1 tsp. some coloring, food colors work fine. For a “glow in the dark” slime, use yellow high-lite marker dye (Fluorscen). See below.
What to do:
1. Mix 1 cup hot water and 1.5 tsp. of Borax until dissolved. Set aside.
2. Mix 2 cups of clear polyvinyl alcohol glue and 2 cups of warm water together in a plastic bowl.
3. Add food coloring or “glow in the dark” coloring.
4. Using a metal spoon (much more fun to use your fingers), slowly pour Borax mixture into the glue mixture while stirring quickly. Stir and the mixture will begin to thicken, become sticky and slimy. For a thicker slime, add more Borax solution. Play with the slime.
**Making “glow in the dark” slime dye. Take a yellow high-lite marker and break it open. Inside is a yellow colored cartridge soaked with Fluorscen, a compound that absorbs very blue and ultraviolet light and re-emits it as yellow-green light. Place the cartridge in a glass of water and let it sit for a few hours. The water will turn yellow as the water-soluble dye is absorbed into the water. Use the water as you would food coloring to color the slime.
Figure 1. Stellar Kinematic Maps of M60-UCD1 showing clear rotation and a dispersion peak.
Panels a and b show the measured radial velocities (bulk motions towards & away from us) and
velocity dispersions (random motions) of the stars in M60-UCD1 with typical errors of 6 km/s.
Black contours show isophotes in the K band stellar continuum. Kinematics are determined in
each individual pixel near the center, but at larger radii the data were binned to increase signal-tonoise
and enable kinematic measurements. Panels b and c show the best fit dynamical model; a
black hole is required to replicate the central dispersion peak.
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Figure 2. The Gemini North telescope on Hawaii’s Mauna Kea propagates a laser beam into the night sky to create an “artificial star” that astronomers use to adjust images made by the telescope to remove the blurring effects of Earth’s atmosphere. Gemini North utilized this technology in a new University of Utah-led study that discovered the smallest galaxy yet known to harbor a supermassive black hole. More images of Gemini are available at www.gemini.edu/images. Credit: Gemini Observatory/Association of Universities for Research in Astronomy.
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The following is duplicated from the University of Utah media release, distributed on September 17, 2014.
A University of Utah astronomer and his colleagues discovered that an ultracompact dwarf galaxy harbors a supermassive black hole – the smallest galaxy known to contain such a massive light-sucking object. The finding suggests huge black holes may be more common than previously believed.
“It is the smallest and lightest object that we know of that has a supermassive black hole,” says Anil Seth, lead author of an international study of the dwarf galaxy published in Thursday’s issue of the journal Nature. “It’s also one of the most black hole-dominated galaxies known.”
The astronomers used the Gemini North 8-meter optical/infrared telescope on Hawai`i’s Mauna Kea and photos taken by the Hubble Space Telescope to discover that a small galaxy named M60-UCD1 has a black hole with a mass equal to 21 million suns.
Their finding suggests plenty of other ultracompact dwarf galaxies likely also contain supermassive black holes – and those dwarfs may be the stripped remnants of larger galaxies that were torn apart during collisions with yet other galaxies.
“We don’t know of any other way you could make a black hole so big in an object this small,” says Seth, an assistant professor of physics and astronomy at the University of Utah. “There are a lot of similar ultracompact dwarf galaxies, and together they may contain as many supermassive black holes as there are at the centers of normal galaxies.”
Black holes are collapsed stars and collections of stars with such strong gravity that even light is pulled into them, although material around them sometimes can spew jets of X-rays and other forms of radiation. Supermassive black holes – those with the mass of at least 1 million stars like our sun – are thought to be at the centers of many galaxies.
The central, supermassive black hole at the center of our Milky Way galaxy has the mass of 4 million suns, but as heavy as that is, it is less than 0.01 percent of the galaxy’s total mass, estimated at some 50 billion solar masses.
By comparison, the supermassive black hole at the center of ultracompact dwarf galaxy M60-UCD1 is five times larger than the Milky Way’s, with a mass of 21 million suns, and is a stunning 15 percent of the small galaxy’s total mass of 140 million suns.
“That is pretty amazing, given that the Milky Way is 500 times larger and more than 1,000 times heavier than the dwarf galaxy M60-UCD1,” Seth says.
“We believe this once was a very big galaxy with maybe 10 billion stars in it, but then it passed very close to the center of an even larger galaxy, M60, and in that process all the stars and dark matter in the outer part of the galaxy got torn away and became part of M60,” he says. “That was maybe as much as 10 billion years ago. We don’t know.”
Seth says ultracompact dwarf galaxy M60-UCD1 may be doomed, although he cannot say when because the dwarf galaxy’s orbit around M60 isn’t known. M60 is among the largest galaxies in what astronomers refer to as “the local universe.”
“Eventually, this thing may merge with the center of M60, which has a monster black hole in it, with 4.5 billion solar masses – more than 1,000 times bigger than the supermassive black hole in our galaxy. When that happens, the black hole we found in M60-UCD1 will merge with that monster black hole.”
Galaxy M60 also is pulling in another galaxy, named NGC4647. M60 is about 25 times more massive than NGC4647.
Ultracompact Dwarf Galaxies and Supermassive Black Holes
The study – conducted by Seth and 13 other astronomers – was funded in the United States by the National Science Foundation, the German Research Foundation and the Gemini Observatory partnership, which includes the US NSF and scientific agencies in Canada, Chile, Australia, Brazil and Argentina.
Ultracompact dwarf galaxies are among the densest star systems in the universe. M60-UCD1 is the most massive of these systems now known, with a total of 140 million solar masses.
These dwarf galaxies range are less than a few hundred light years across (about 1,700 trillion miles wide), compared with our Milky Way’s 100,000-light-year diameter.
M60-UCD1 is roughly 54 million light years from Earth or about 320 billion billion miles. But the dwarf galaxy is only 22,000 light years from the center of galaxy M60, which “is closer than the sun is to the center of the Milky Way,” Seth says.
Astronomers have debated whether these dwarf galaxies are the stripped centers or nuclei of larger galaxies that were ripped away during collisions with other galaxies, or whether they formed like globular clusters – groups of perhaps 100,000 stars, all born together. There are about 200 globular clusters in our Milky Way, and some galaxies have thousands, Seth says.
The astronomers estimated the mass of the dwarf galaxy’s supermassive black hole by using the Gemini North telescope to measure the speed and motion of stars in orbit around it, and they showed the galaxy contains more mass than would be expected by the amount of starlight it emits. The stars at the center of M60-UCD1 move at about 230,000 mph – faster than stars would be expected to move without the black hole.
An alternate theory is that M60-UCD1 doesn’t have a supermassive black hole, but instead is populated by a lot of massive, dim stars.
But Seth says the research team’s observations with the Gemini North telescope and analysis of archival photos by the Hubble Space Telescope revealed that mass was concentrated in the galaxy’s center, indicating the presence of a supermassive black hole. That suggests that M60-UCD1 is the stripped nucleus of what once was a much larger galaxy, and that other ultracompact dwarf galaxies also may harbor huge black holes, Seth says.
The galaxy that was stripped and left M60-UCD1 as a remnant was about 10 billion solar masses, or about one-fifth the mass of the Milky Way, Seth says.
The astronomers studied M60-UCD1 because they had published a paper last year showing the galaxy was an X-ray source and was extremely dense. The X-ray emissions suggest gas is being sucked into the black hole at a rate typical of supermassive black holes in much larger galaxies.
The Research Facilities and Team
The Gemini Observatory is an international collaboration with two identical 8-meter telescopes: Gemini North on the island of Hawai‘i and Gemini South on Cerro Pachón in central Chile. Together, the telescopes cover both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin and actively controlled mirrors to collect and focus infrared light from space, eliminating the blurring effects of the atmosphere and enabling the observations for the new study. The observatory is managed by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation.
The Hubble Space Telescope was built by NASA and the European Space Agency and is operated by the Space Telescope Science Institute.
Seth conducted the study with University of Utah physics and astronomy postdoctoral researcher Mark den Brok and with astronomers Remco van den Bosch of the Max Planck Institute for Astronomy, Germany; Steffen Mieske of the European Southern Observatory, Santiago, Chile; Holger Baumgardt of the University of Queensland, Australia; Jay Strader of Michigan State University; Nadine Neumayer and Michel Hilker of the European Southern Observatory, Garching, Germany; Igor Chilingarian of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, and Moscow State University; Richard McDermid and Lee Spitler of Asutralia’s Macquarie University; Jean Brodie of the University of California, Santa Cruz; Matthias J. Frank of the University of Heidelberg, Germany; and Jonelle Walsh of the University of Texas, Austin.
A video simulation of galaxy M60’s gravity stripping M60-UCD1’s outer parts is here: http://vimeo.com/105370891.
Figure 1. Part of MACS J0416-2403 seen by GSAOI. The average angular resolution is about 80 milliarcseconds, the full field-of-view of the data released is nearly twice as large as shown here.
Figure 2. Comparison of the Ks-band (2.2 micron) image taken with GSAOI (left) and the H-band (1.6 micron) image as observed with HST/WFC3. While not as deep as HST data, the new GeMS/GSAOI dataset offers twice the resolution on the distant universe.
The first data from the Gemini Frontier Fields are now available for astronomers. This dataset features wide-field adaptive optics images of a strong lensing galaxy cluster obtained with the GeMS adaptive optics system and GSAOI on the Gemini South telescope.
Massive clusters of galaxies provide astronomers with a unique view of the very distant Universe behind them as well as revealing their galaxies themselves. The deep gravitational potential of clusters distorts and amplifies the background galaxies - an effect known as strong gravitational lensing. In this way, galaxies that are otherwise unobservable with existing telescopes, are acquirable. This circumstance allows astronomers to study these distant galaxies in great detail, shedding light on how the very young universe looked, and pushing the frontiers of our knowledge.
In the course of the Frontier Fields campaign, the Hubble Space Telescope (HST) observed six galaxy clusters, selected for their strong lensing effects. Deep optical and near-infrared images are already included in the HST dataset, augmented by additional X-ray and far-infrared observations with the Chandra and Spitzer space telescopes, respectively. However, one limitation of the HST data is its sensitivity cut-off at wavelengths longer than 1.7 microns.
A Director's Discretionary Time program at Gemini has helped to fill the gap at 2.2 microns (Ks-band), utilizing Gemini's advanced multi-conjugated adaptive optics system, GeMS with the Gemini South Adaptive Optics Imager (GSAOI). Staff astronomer Rodrigo Carrasco led the observations, and the first of three targets visible from Gemini South in Chile is MACS J0416.1-2403, which is available now. Observations of the galaxy cluster Abell 2744 have started recently, and Abell 370 is slated for observation at Gemini South over the next year.
GeMS/GSAOI delivers near diffraction-limited images in the near infrared (0.9-2.5 microns), over a field nearly as large as HST's Wide Field Camera 3 (WFC3). Using five artificial laser guide stars, and up to three natural guide stars, GeMS/GSAOI can correct for atmospheric turbulence at an unprecedented level, making it the most powerful wide-field adaptive optics system currently available to astronomers. This system is also the only multi-conjugated adaptive optics system currently operational at an 8-meter-class telescope. "We have achieved an angular resolution of 70-100 milliarcseconds with these data, which is a factor of two better than HST/WFC3, even though we did not go as deep as HST. These are truly spectacular data!" says Mischa Schirmer, a staff astronomer at Gemini who led the data processing effort.
The fully calibrated and co-added images of MACS J0416.1-2403 are now available to the scientific community in order to maximize scientific return.
The associated paper is available from http://arxiv.org/abs/1409.1820.
Figure 1. The surface plot of Kepler-14, one of the first Kepler stars to be shown to both host a planet and have a stellar companion (seen here) using speckle imaging.
Figure 2. A false-color image of Kepler-14. The projected separation between the stars is estimated to be about 250 times the distance between the Sun and the Earth.
The following is duplicated from the National Optical Astronomy Observatory press release, distributed on September 3, 2014.
Imagine living on an exoplanet with two suns. One, you orbit and the other is a very bright, nearby neighbor looming large in your sky. With this “second sun” in the sky, nightfall might be a rare event, perhaps only coming seasonally to your planet. A new study suggests that this could be far more common than we realized.
The NASA Kepler Space Telescope has confirmed about 1000 exoplanets, as well as thousands more stars considered “Kepler objects of interest”, dubbed KOIs – stars that could possibly host planets. Until now, there has been an unanswered question about exoplanet host stars; how many host stars are binaries? Binary stars have long been known to be commonplace – about half the stars in the sky are believed to consist of two stars orbiting each other. So, are stars with planets equally likely to have a companion star, or do companion stars affect the formation of planets? A team of astronomers, led by Dr. Elliott Horch, Southern Connecticut State University, have shown that stars with exoplanets are just as likely to have a binary companion: that is, 40% to 50% of the host stars are actually binary stars. As Dr. Horch said, “It’s interesting and exciting that exoplanet systems with stellar companions turn out to be much more common than was believed even just a few years ago.”
Their study makes use of very high spatial resolution observations that were carried out on the WIYN telescope located on Kitt Peak in southern Arizona and the Gemini North telescope located on Mauna Kea in Hawaii.
The technique used by the team is called speckle imaging and consists of obtaining digital images of a small portion of the sky surrounding a star of interest, 15 to 25 times a second. The images are then combined in software using a complex set of algorithms, yielding a final picture of the star with a resolution better that that of the Hubble space telescope.
By using this technique, the team can detect companion stars that are up to 125 times fainter than the target, but only 0.05 arcseconds away. For the majority of the Kepler stars, this means companion stars with a true separation of a few to about 100 times the Sun-Earth distance (termed the astronomical distance, or AU). By noting the occurrence rate of these true binary companion stars, the discoveries can be extended to show that half of the stars that host exoplanets are probably binaries.
Co-author of the study, Dr. Steve B. Howell (NASA Ames Research Center), commented, “An interesting consequence of this finding is that in the half of the exoplanet host stars that are binary we can not, in general, say which star in the system the planet actually orbits.”
Kepler has discovered a number of circumbinary planets, that is, a planet that orbits both stars in very close binary systems. There also exist exoplanets that are known to orbit one of the stars in very wide binary systems. If the two stars are very close to each other and the planet far away, a circumbinary planet will be reminiscent of Tatooine in Star Wars. If instead the exoplanet orbits one of the stars in a very wide pair, the companion star might appear simply as a bright star among others in the night sky. “Somewhere there will be a transition between these two scenarios,” Howell said,” but we are far from knowing where.”
The accompanying figure shows the Kepler field of view, located between two bright stars in the summer triangle, rising over the WIYN telescope in southern Arizona.
In a study like this, it is critical to rule out faint companions that are only in the line of sight with the KOI star. To allow for these possibilities, the team performed a model simulation that relied on known statistical properties of binary star systems and line of sight companions. The results suggest that the large majority of the stellar companions to KOIs are true bound companions, not line of sight stars unconnected with the system.
This work has been accepted for publication in the Astrophysical Journal. The additional authors are Dr. Mark E. Everett, National Optical Astronomy Observatory and Dr. David R. Ciardi, NASA Exoplanet Science Institute, California Institute of Technology.
The WIYN telescope is operated by the WIYN Consortium, which consists of the University of Wisconsin, Indiana University and the National Optical Astronomy Observatory (NOAO). Kitt Peak National Observatory is a division of NOAO, which is operated by the Association of Universities for Research in Astronomy Inc. under a cooperative agreement with the National Science Foundation.
A four-stage sequence (left to right) showing the possible extreme temperature evolution for WISE J0304-2705. For about 20 million years, the object was as hot as a star, shining with a temperature of at least 5,100 degrees Fahrenheit (2800 degrees Celsius). After about 100 million years it had cooled to about 2,700 degrees Fahrenheit (1500 degrees Celsius), and by a billion years its temperature was about 1,800 degrees Fahrenheit (1000 degrees Celsius). The final stage is billions of years later, when WISE J0304-2705 has cooled to its current planetary temperature of 100-150 C. Artwork credit: John Pinfield
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The following is duplicated from the Carnegie Institution for Science press release, distributed on August 5, 2014.
Astronomers have discovered an extremely cool object that could have a particularly diverse history—although it is now as cool as a planet, it may have spent much of its youth as hot as a star.
The current temperature of the object is 200 to 300 degrees Fahrenheit (100 to 150 degrees Celsius), which is intermediate between that of the Earth and of Venus. However, the object shows evidence of a possible ancient origin, implying that a large change in temperature has taken place. In the past this object would have been as hot as a star for many millions of years.
Called WISE J0304-2705, the object is a member of the recently established "Y dwarf" class—the coolest stellar temperature class yet defined, following the other classes O, B, A, F, G, K, M, L, and T. Although the temperature is similar to that of the planets, the object is dissimilar to the rocky Earth-like planets, and instead is a giant ball of gas like Jupiter.
The international discovery team, led by David Pinfield from the University of Hertfordshire and including Carnegie’s Yuri Beletsky, identified the Y dwarf using the WISE observatory—a NASA space telescope that has imaged the entire sky in the mid-infrared. The team also measured the spectrum of light emitted by the Y dwarf, which allowed them to determine its current temperature and better understand its history. Their work is published by Monthly Notices of the Royal Astronomical Society.
Only 20 other Y dwarfs have been discovered to-date, and amongst these WISE J0304-2705 is defined as “peculiar” due to unusual features in its emitted light spectrum.
"Our measurements suggest that this Y dwarf may have a composition and/or age characteristic of one of the Galaxy's older members,” Pinfield explained. "This would mean its temperature evolution could have been rather extreme."
The reason that WISE J0304-2705 undergoes such extensive evolutionary cooling is because it is "sub-stellar,” meaning its interior never gets hot enough for hydrogen fusion, the process that has kept our Sun hot for billions of years, and without an energy source maintaining a stable temperature, cooling and fading is inevitable.
If WISE J0304-2705 is an ancient object, then its temperature evolution would have followed through an understood series of stages (as depicted below in the illustration): During its first approximately 20 million years it would have a temperature of at least 5,100 degrees Fahrenheit (2800 degrees Celsius), the same as red dwarf stars like Proxima Centauri (the nearest star to the Sun). After 100 million years it would have cooled to about 2,700 degrees Fahrenheit (1,500 degrees Celsius), with silicate clouds condensing out in its atmosphere. At a billion years of age it would have cooled to about 1,800 degrees Fahrenheit (1,000 degrees Celsius), so cool that methane gas and water vapor would dominate its appearance. And since then it would have continued to cool to its current temperature, barely enough to boil water for a cup of tea.
WISE J0304-2705 is as massive as 20-30 Jupiters combined, which is intermediate between the more massive stars and typical planets. But in terms of temperature it may have actually "taken the journey" from star-like to planet-like conditions.
Having identified WISE 0304-2705, Pinfield's team made crucial ground-based observations with some of the world's largest telescopes—the 8-meter Gemini South Telescope, the 6.5-meter Magellan Telescope and the European Southern Observatory's 3.6-meter New Technology Telescope, all located in the Chilean Andes.
Team member Mariusz Gromadzki said: "The ground based measurements were very challenging, even with the largest telescopes. It was exciting when the results showed just how cool this object was, and that it was unusual".
"The discovery of WISE J0304-2705, with its peculiar light spectrum, poses ongoing challenges for the most powerful modern telescopes that are being used for its detailed study" remarked Maria Teresa Ruiz, team member from the Universidad de Chile.
WISE J0304-2705 is located in the Fornax (Furnace) constellation, belying its cool temperature.
There is currently no lower limit for Y dwarf temperatures, and there could be many even cooler and more diverse objects un-detected in the solar neighborhood. WISE went into hibernation in February 2011 after carrying out its main survey mission. However, by popular demand it was revived in December 2013, and is continuing to observe as part of a three-year mission extension.
"WISE gives us wonderful sensitivity to the coolest objects" said Pinfield, "and with three more years of observations we will be able to search the sky for more Y dwarfs, and more diverse Y dwarfs."
The paper, to be published by Monthly Notices of the Royal Astronomical Society, is available on astro-ph.
Figure 1. Image of Io taken in the near-infrared with adaptive optics at the Gemini North telescope on August 29. In addition to the extremely bright eruption on the upper right limb of the satellite, the lava lake Loki is visible in the middle of Io’s disk, as well as the fading eruption that was detected earlier in the month by de Pater on the southern (bottom) limb. Io is about one arcsecond across. Image credit: Katherine de Kleer/UC Berkeley/Gemini Observatory/AURA
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Figure 2. Images of Io taken in the near-infrared with adaptive optics at the Gemini North telescope tracking the evolution of the eruption as it decreased in intensity over 12 days. Due to Io’s rapid rotation, a different area of the surface is viewed on each night; the outburst is visible with diminishing brightness on August 29 & 30 and September 1, 3, & 10. Image credit: Katherine de Kleer/UC Berkeley/Gemini Observatory/AURA
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During the middle of 2013, Jupiter’s moon Io came alive with volcanism. Now, an image from the Gemini Observatory captures what is one of the brightest volcanoes ever seen in our solar system. The image, obtained on August 29, reveals the magnitude of the eruption that was the “grand finale” in a series of eruptions on the distant moon. Io’s volcanism is caused by the tidal push-and-pull of massive Jupiter, which heats the satellite’s interior – making it our Solar System’s most volcanically active known body.
According to University of California Berkeley (UCB) astronomer Katherine de Kleer, the Gemini observations, “… represent the best day-by-day coverage of such an eruption – thanks to Gemini’s rapid and flexible scheduling capabilities.” De Kleer, who led one of a pair of two papers published today in the journal Icarus, adds that the Gemini data allowed the team to monitor the evolution of the extreme volcanic activity over nearly the first two weeks of the eruption – which provided a critical new perspective on the outburst events.
De Kleer’s paper examines the powerful late-August eruption in detail, concluding that the energy emitted was about 20 Terawatts and expelled many cubic kilometers of lava. “At the time we observed the event, an area of newly-exposed lava on the order of tens of square kilometers was visible” says de Kleer. “We believe that it erupted in fountains from long fissures on Io’s surface, which were over ten-thousand-times more powerful than the lava fountains during the 2010 eruption of Eyjafjallajokull, Iceland, for example.”
The original detection of the volcano was made simultaneously at Gemini and NASA’s Infrared Telescope Facility (IRTF), and was the first of a series of observations monitoring Io at both facilities over the following year. These particular observations were timed to follow up on a different outburst eruption that was detected earlier in the month by Imke de Pater, also of UCB.
This record of the spate of activity began when de Pater first spotted a hotspot using the W.M. Keck Observatory in mid-August (see UCB press release, also released today at: http://newscenter.berkeley.edu/2014/08/04/a-hellacious-two-weeks-on-jupiters-moon-io/), which the team followed with further observations from Mauna Kea. The late August Gemini observations of the most extreme outburst (see Figure 1) used adaptive optics on the Gemini North telescope to produce this super-sharp near-infrared image. Gemini also recorded a series of images chronicling the massive eruption’s evolution as it faded over the next 12 days (see Figure 2).
In addition to de Kleer and de Pater, the lead authors on the two publications discussing these events, the research team included Máté Ádámkovics of UCB, Ashley Davies from the Jet Propulsion Laboratory and David Ciardi of Caltech's NASA Exoplanet Science Institute. The work is funded by the National Science Foundation and NASA’s Outer Planets Research and Planetary Geology and Geophysics Program.
The papers are available in the journal Icarus (subscription required).
Figure 1. Artist's rendition of the future evolution of the WD 0931+444 system. Credit: David A. Aguilar (Harvard-Smithsonian Center for Astrophysics).
Figure 2. Gemini time-resolved spectroscopy of H-gamma (top) and H-beta lines (bottom) over 45 minutes. Both lines clearly show a 20 minute periodicity.
Figure 3. The radial velocities of the Balmer lines in WD 0931+444. The bottom panel shows all of these data points phased with the best-fit period. The dotted line represents the best-fit model for a circular orbit with a period of 19.8 minutes.
Figure 4. Gemini time-resolved spectroscopy of the Na I doublet (top) and the H-alpha line (bottom) over 90 minutes. The Na I lines and the H-alpha line from the M dwarf are stationary, whereas the H-alpha line from the WD clearly shows a 20 minute periodicity.
Einstein's Theory of General Relativity predicts that accelerated masses emit gravitational waves, or ripples in space-time. Even though gravitational waves have yet to be detected directly, we expect that there are more than hundred million gravitational wave sources in our own galaxy. However, as of today, we know of only a few such sources.
A team of researchers, led by Dr. Mukremin Kilic of the University of Oklahoma and Dr. Warren Brown of the Smithsonian Astrophysical Observatory, have recently identified one of the best (and perhaps the most powerful) gravitational wave sources currently known using the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope and the Blue Channel spectrograph on the 6.5-meter MMT Telescope. Known as WD 0931+444, the object was first identified in 1982, and classified as a white dwarf with a low-mass M-dwarf stellar companion.
This new data from Gemini and MMT reveal that the white dwarf in this system is not in a binary with the M dwarf. Instead, it is orbiting another invisible white dwarf every 20 minutes. Thanks to the large collecting area of the Gemini and MMT telescopes, the team was able to obtain high quality optical spectroscopy of this system every 2 minutes and resolve the 20 minute orbital period.
The orbital separation of the two stars is only 20 percent of the size of the Sun. These two stars will lose angular momentum through gravitational wave radiation and merge in less than nine Million years. Depending on the inclination angle (which is currently unknown) the pair may merge even faster, in only a few million years. This previously unknown source is believed to be stretching everything around us (due to gravity waves) by a factor of 10-22 (or more) every 10 minutes!
The discovery of the true nature of WD 0931+444 indicates that there are likely many other strong gravitational wave sources hiding in plain sight. Some of these hidden sources can be identified through further optical follow-up observations as in this work. However, the direct detection of gravitational waves from these sources has to wait for a space-based gravitational wave mission like the evolved Laser Interferometer Space Antenna, which will likely not be operational until 2034 as currently envisioned.”
The paper can be accessed at: http://arxiv.org/abs/1406.3346
Figure 1. Artist’s impression of a galaxy with a large-scale outflow. Credit: ESA/ATG medialab.
Figure 2. An example object from the GMOS observations. The background image is from the Sloan Digital Sky Survey. The cyan rectangle shows the GMOS field of view. The red/yellow contours show the distribution of high-‐velocity ionized gas. The inset shows an example oxygen emission-‐line profile ([O III]5007) that was used to trace the velocity of the gas.
Figure 3. Left: Distribution of the emission-line widths (a proxy for gas velocity) of both the overall population of luminous quasars (yellow histogram) and the sample studied here (red histogram). Around half the luminous quasars in the parent population show very high gas velocities (> 700 kilometers per second). The 16 objects studied here were selected from this population. Right: Similar histograms show that the radio luminosities of the quasars studied here are representative of the parent population.
Observations using the Gemini Multi-Object Spectrograph on Gemini South reveal that galaxy-wide high-velocity outflows are extremely common among galaxies that host luminous quasars. These outflows may represent a crucial stage in a galaxy’s evolution when the supermassive black hole at its center begins injecting vast amounts of mass and energy into the galaxy.
Supermassive black holes reside at the center of all massive galaxies and they grow through mass accretion, taking on material from their surroundings. During the most active periods they become luminous quasars. The most successful models of galaxy evolution predict that quasars play an integral role in the formation and evolution of massive galaxies by injecting mass and energy into their host galaxies. Without such feedback mechanisms, models are unable to accurately reproduce the properties of local massive galaxies such as the distributions of colors, star formation rates and stellar masses.
A popular idea for a feedback mechanism is that extremely powerful and high-velocity outflows of gas are launched by quasars and consequently propagate throughout the galaxy (see Figure 1). These outflows could sweep up and heat material, reducing the star formation rates of the host galaxies and add material to the larger scale environment. While earlier observations have shown that high-velocity outflows exist in some quasars, it has remained unclear what the spatial extent of these outflows are and how often they occur.
Using the Gemini Multi-Object Spectrograph (GMOS) on Gemini South, astronomers at Durham University, led by Chris Harrison, have begun to answer these questions and show the properties and frequency of outflows in quasars. Using GMOS’s integral field spectrograph, they traced the properties of the gas across the host galaxies of 16 quasars. Critically, GMOS on Gemini South enabled the astronomers to trace the velocity of the gas over the full spatial extent of the quasars’ host galaxies. By using emission lines produced by ionized hydrogen and oxygen to trace the gas velocities the observations revealed that outflows, reaching velocities of >1000 kilometers/second, were found over the full spatial extent of the host galaxies of all of the quasars observed (e.g., see Figure 2). Estimates of the masses involved in these outflows indicate that they are removing significant amounts of gas from the galaxies and their overall properties are in line with model predictions.
A key aspect of this work is the quasars that were observed with GMOS were initially selected from a parent sample of several thousand objects with optical spectra (Figure 3). These observations can thus be placed in the context of the overall population and reveal properties of quasars generally. For example, these observations imply that at least 70% of the most luminous quasars (those predicted by models to drive the feedback mechanisms) exhibit galaxy-wide outflows of this type. Further work now needs to be done to pin-down exactly how the central black holes are able to launch such large-scale outflows. Furthermore, while models predict that outflows, such as those observed here, have a dramatic impact upon the star formation in their host galaxies the current observational evidence for these effects remains only indirect. Astronomers continue to search for direct observational proof that these outflows can have a profound influence the evolution of massive galaxies.
This research is presented in the paper: Kiloparsec-scale outflows are prevalent among luminous AGN: outflows and feedback in the context of the overall AGN population by C. M. Harrison, D. M. Alexander, J. R. Mullaney and A. M. Swinbank. The paper is published in the Monthly Notices of the Royal Astronomical Society (2014 441 3306) and is available on astro-ph.