Astronomy Cmarchesin: September 2019

Monday, September 30, 2019

Oldest Galaxy Protocluster forms "Queen's Court"

Figure 1: The most distant protocluster discovered by the Subaru Telescope. The blue shading shows the calculated extent of the protocluster, and the bluer color indicates higher density of galaxies in the protocluster. The red objects in zoom-in figures are the 12 galaxies found in it. This figure shows a square field-of-view 24 arcminutes along each side (corresponding to 198 million light-years along each side at a distance of 13.0 billion light-years). Each zoom-in figure is 16 arcseconds along each side (corresponding to 2.2 million light-years). (Credit: NAOJ/Harikane et al.)

Using the Subaru, Keck, and Gemini Telescopes, an international team of astronomers has discovered a collection of 12 galaxies in the constellation Cetus which existed about 13.0 billion years ago. This is the earliest protocluster ever found. One of the 12 galaxies is a giant object, known as Himiko, which was discovered a decade ago by the Subaru Telescope and named for a legendary queen in ancient Japan. This discovery suggests that large structures such as protoclusters already existed when the Universe was only about 800 million years old, 6 percent of its present age.

In the present Universe, galaxy clusters can contain thousands of members, but how these clusters form is a big question in astronomy. To understand the formation of clusters, astronomers search for possible progenitors in the ancient Universe, known as protoclusters. A protocluster is a dense system of dozens of galaxies in the early Universe, growing into a cluster. The previous record holder was the SDF protocluster, discovered by the Subaru Telescope in the Subaru Deep Field (SDF) near the constellation Coma Berenices.

Yuichi Harikane, a JSPS fellow at the National Astronomical Observatory of Japan who led the team of astronomers explains, "A protocluster is a rare and special system with an extremely high density, and not easy to find. To overcome this problem, we used the wide field of view of the Subaru Telescope to map a large area of the sky and look for protoclusters."

In the map of the Universe made by the Subaru Telescope, the team discovered a protocluster candidate, z66OD, where galaxies are 15 times more concentrated than normal for that era. The team then conducted follow-up spectroscopic observations using the W.M. Keck Observatory and Gemini North telescope, and confirmed 12 galaxies which existed 13.0 billion years ago, making it the earliest protocluster known to date. Yoshiaki Ono at the University of Tokyo, Japan, who conducted the spectroscopic observations, explains, "The z66OD protocluster is the earliest protoclutser, breaking the record set by the SDF protocluster by 100 million years."

Figure 2: Three-dimensional map of galaxies obtained in this research. The black points indicate locations of galaxies, and bluer color means higher density. The red arrow indicates the most distant protocluster discovered in this research. (Credit: NAOJ/Harikane et al.)

Interestingly, one of the 12 galaxies in z66OD was a giant object with a huge body of gas, known as Himiko, which was found previously by the Subaru Telescope in 2009. "It is reasonable to find a protocluster near a massive object, such as Himiko. However, we're surprised to see that Himiko was located not in the center of the protocluster, but on the edge 500 million light-years away from the center." said Masami Ouchi, a team member at the National Astronomical Observatory of Japan and the University of Tokyo, who discovered Himiko in 2009. Ironically, the legendary queen Himiko is also said to have lived cloistered away from her people. Ouchi continues, "It is still not understood why Himiko is not located in the center. These results will be a key for understanding the relationship between clusters and massive galaxies."

Another surprise was that the team found very active star formation in the z66OD protocluster using observational results from the Subaru Telescope, United Kingdom Infra-Red Telescope, and Spitzer Space Telescope. "The total amount of stars forming in the galaxies in z660D is five times larger than in other galaxies with similar masses in the same age of the Universe. The galaxies in z66OD form stars very efficiently, probably because the large mass of the system helps it to collect a large amount of gas, the material for stars." explained Darko Donevski, a team member at SISSA Institute, Trieste, Italy.

Team member Seiji Fujimoto at Waseda University, Japan, comments, "Recent observations are revealing that protoclusters can also contain massive galaxies obscured by dust. Although we didn't find any such galaxies in z66OD, future observations, such as by ALMA (Atacama Large Millimeter/submillimeter Array), may find some, and reveal the entire structure of z66OD."

This research will be published on September 30, 2019 in The Astrophysical Journal as Yuichi Harikane, et al. "SILVERRUSH. VIII. Spectroscopic Identifications of Early Large Scale Structures with Protoclusters Over 200 Mpc at z~6-7: Strong Associations of Dusty Star-Forming Galaxies". This work was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and the Japan Society for the Promotion of Science.

Source: Subaru Telescope

Links:

Sunday, September 29, 2019

High value for Hubble constant from two gravitational lenses

Images of the two lensing systems used in this study, B1608+656 and RXJ1131. Labels A to D denote images of the background quasar, G1 and G2 are lens galaxies on the left, G is the lens galaxy on the right with a satellite galaxy S. © MPA

The expansion rate of the Universe today is described by the so-called Hubble constant and different techniques have come to inconsistent results about how fast our Universe actually does expand. An international team led by the Max Planck Institute for Astrophysics (MPA) has now used two gravitational lenses as new tools to calibrate the distances to hundreds of observed supernovae and thus measure a fairly high value for the Hubble constant. While the uncertainty is still relatively large, this is higher than that inferred from the cosmic microwave background.

Gravitational lensing describes the fact that light is deflected by large masses in the Universe, just like a glass lens will bend a light right on Earth. In recent years, cosmologists have increasingly used this effect to measure distances by exploiting the fact that, in a multiple image system, an observer will see photons arriving from different directions at different times due to the difference in optical path lengths for the various images. This measurement thus gives a physical size of the lens, and comparing it to an observed size in the sky gives a geometric distance estimate called the “angular diameter distance”. Such distance measurements in astronomy are the basis for measurements of the Hubble constant, named after the astronomer Edwin Hubble, who found a linear relationship between the redshifts (and thus the expansion velocity of the Universe) and the distances of galaxies (which was also independently found by Georges Lemaître).

“There are multiple ways to measure distances in the Universe, based on our knowledge of the object whose distance is being measured,” explains Sherry Suyu (MPA/TUM), who is a world expert in using gravitational lensing for determining the Hubble constant. “A well-known technique is the luminosity distance using supernovae explosions; however, they must adopt an external calibrator of the absolute distance scale. With our analysis of gravitational lens systems we can provide a completely new, independent anchor for this method.”

Derived Hubble diagram, using the two lens systems (red and yellow dots) as anchors for the 740 supernovae in the JLA dataset. © MPA

The team used two strong gravitational lens systems B1608+656 and RXJ1131 (see Figure 1). In each of these systems, there are four images of a background galaxy with one or two foreground galaxies acting as lenses. This relatively simple configuration allowed the scientists to produce an accurate lensing model and thus measure the angular diameter distances to a precision of 12 to 20% per lens. These distances were then applied as anchors to 740 supernovae in a public catalogue (Joint Light-curve Analysis dataset).

“By construction, our method is insensitive to the details of the assumed cosmological model,” states Inh Jee (MPA), who did the statistical analysis and combined the supernova data with the lensing distances. “We get a fairly high result for the Hubble constant and although our measurement has a larger uncertainty than other direct methods, this is dominated by statistical uncertainty because we use only two lens systems.”

The value for the Hubble constant based on this new analysis is about 82 +/- 8 km/s/Mpc. This is consistent with values derived from the distance ladder method, which uses different anchors for the supernova data, as well as with values from time-delay distances, where other gravitational lensing systems were used to determine the Hubble constant directly.

“Again this new measurement confirms that there seems to be a systematic difference in values for the Hubble constant derived directly from local or intermediate sources and indirectly from the cosmic microwave background,” states Eiichiro Komatsu, director at MPA, who oversaw this project. “If confirmed by further measurements, this discrepancy would call for a revision of the standard model of cosmology.”

Variability in B1608+656

Variability observed in the lens system B1608+656, the labels are the same as in Figure 1. The arrows denote a flare seen at different times in the four images.

Source: Max Planck Institute for Astrophysics

Contacts

Inh Jee
jee1213@MPA-Garching.mpg.de

Sherry Suyu
Scientific Staff 2015
suyu@mpa-garching.mpg.de

Hannelore Hämmerle
Press officer 3980
hanne@mpa-garching.mpg.de

Original publication

1. I. Jee, S.H. Suyu, E. Komatsu, et al.
A measurement of the Hubble constant from angular diameter distances to two gravitational lenses Science, 13.9.2019
Source / DOI

Saturday, September 28, 2019

Enigmatic radio burst illuminates a galaxy’s tranquil halo

PR Image eso1915a

Artist’s impression of a fast radio burst traveling through space and reaching Earth

PR Image eso1915b

Infographic showing the path of FRB 18112 passing through the halo of an intervening galaxy

PR Image eso1915c

VLT image of the location of FRB 181112

Videos

Astronomers using ESO’s Very Large Telescope have for the first time observed that a fast radio burst passed through a galactic halo. Lasting less than a millisecond, this enigmatic blast of cosmic radio waves came through almost undisturbed, suggesting that the halo has surprisingly low density and weak magnetic field. This new technique could be used to explore the elusive halos of other galaxies.

Using one cosmic mystery to probe another, astronomers analysed the signal from a fast radio burst to shed light on the diffuse gas in the halo of a massive galaxy [1]. In November 2018 the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope pinpointed a fast radio burst, named FRB 181112. Follow-up observations with ESO’s Very Large Telescope (VLT) and other telescopes revealed that the radio pulses have passed through the halo of a massive galaxy on their way toward Earth. This finding allowed astronomers to analyse the radio signal for clues about the nature of the halo gas.

“The signal from the fast radio burst exposed the nature of the magnetic field around the galaxy and the structure of the halo gas. The study proves a new and transformative technique for exploring the nature of galaxy halos,” said J. Xavier Prochaska, professor of astronomy and astrophysics at the University of California Santa Cruz and lead author of a paper presenting the new findings published today in the journal Science.

Astronomers still don’t know what causes fast radio bursts and only recently have been able to trace some of these very short, very bright radio signals back to the galaxies in which they originated. “When we overlaid the radio and optical images, we could see straight away that the fast radio burst pierced the halo of this coincident foreground galaxy and, for the first time, we had a direct way of investigating the otherwise invisible matter surrounding this galaxy,” said coauthor Cherie Day, a PhD student at Swinburne University of Technology, Australia.

A galactic halo contains both dark and ordinary—or baryonic—matter that is primarily in the form of a hot ionised gas. While the luminous part of a massive galaxy might be around 30 000 light years across, its roughly spherical halo is ten times larger in diameter. Halo gas fuels star formation as it falls towards the centre of the galaxy, while other processes, such as supernova explosions, can eject material out of the star-forming regions and into the galactic halo. One reason astronomers want to study the halo gas is to better understand these ejection processes which can shut down star formation.

“This galaxy’s halo is surprisingly tranquil,” Prochaska said. “The radio signal was largely unperturbed by the galaxy, which is in stark contrast to what previous models predict would have happened to the burst.”

The signal of FRB 181112 was comprised of a few pulses, each lasting less than 40 microseconds (10 000 times shorter than the blink of an eye). The short duration of the pulses puts an upper limit on the density of the halo gas because passage through a denser medium would broaden the duration of the radio signal. The researchers calculated that the density of the halo gas must be less than 0.1 atoms per cubic centimeter (equivalent to several hundred atoms in a volume the size of a child’s balloon) [2].

“Like the shimmering air on a hot summer’s day, the tenuous atmosphere in this massive galaxy should warp the signal of the fast radio burst. Instead we received a pulse so pristine and sharp that there is no signature of this gas at all,” said coauthor Jean-Pierre Macquart, an astronomer at the International Center for Radio Astronomy Research at Curtin University, Australia.

The study found no evidence of cold turbulent clouds or small dense clumps of cool halo gas. The fast radio burst signal also yielded information about the magnetic field in the halo, which is very weak—a billion times weaker than that of a refrigerator magnet.

At this point, with results from only one galactic halo, the researchers cannot say whether the low density and low magnetic field strength they measured are unusual or if previous studies of galactic halos have overestimated these properties. Prochaska said he expects that ASKAP and other radio telescopes will use fast radio bursts to study many more galactic halos and resolve their properties.

“This galaxy may be special,” he said. “We will need to use fast radio bursts to study tens or hundreds of galaxies over a range of masses and ages to assess the full population.” Optical telescopes like ESO’s VLT play an important role by revealing how far away the galaxy that played host to each burst is, as well as whether the burst would have passed through the halo of any galaxy in the foreground.

Notes

[1] A vast halo of low-density gas extends far beyond the luminous part of a galaxy where the stars are concentrated. Although this hot, diffuse gas makes up more of a galaxy’s mass than stars do, it is very difficult to study.

[2] The density constraints also limit the possibility of turbulence or clouds of cool gas within the halo. Cool here is a relative term, referring to temperatures around 10 000°C, versus the hot halo gas at around 1 million degrees.

More Information

This research was presented in a paper published on 26 September 2019 in the journal Science.

The team is composed of J. Xavier Prochaska (University of California Observatories-Lick Observatory, University of California, USA and Kavli Institute for the Physics and Mathematics of the Universe, Japan), Jean-Pierre Macquart (International Centre for Radio Astronomy Research, Curtin University, Australia), Matthew McQuinn (Astronomy Department, University of Washington, USA), Sunil Simha (University of California Observatories-Lick Observatory, University of California, USA), Ryan M. Shannon (Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Australia), Cherie K. Day (Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Australia and Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia), Lachlan Marnoch (Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia and Department of Physics and Astronomy, Macquarie University, Australia), Stuart Ryder (Department of Physics and Astronomy, Macquarie University, Australia), Adam Deller (Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Australia), Keith W. Bannister (Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia), Shivani Bhandari (Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia), Rongmon Bordoloi (North Carolina State University, Department of Physics, USA), John Bunton (Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia), Hyerin Cho (School of Physics and Chemistry, Gwangju Institute of Science and Technology, Korea), Chris Flynn (Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Australia), Elizabeth Mahony (Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia), Chris Phillips (Commonwealth Science and Industrial Research Organisation, Australia Telescope National Facility, Australia), Hao Qiu (Sydney Institute for Astronomy, School of Physics, University of Sydney, Australia), Nicolas Tejos (Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Chile).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

Link

Contact

J. Xavier Prochaska
UCO/Lick Observatory — UC Santa Cruz
USA
Tel: +1 (831) 295-0111
Email: xavier@ucolick.org

Cherie Day
Centre for Astrophysics and Supercomputing — Swinburne University of Technology
Australia
Tel: +61 4 5946 3110
Email: cday@swin.edu.au

Mariya Lyubenova
ESO Head of Media Relations
Garching bei München, Germany
Tel: +49 89 3200 6188
Email: pio@eso.org

Source: ESO/News

Friday, September 27, 2019

NASA’s TESS Mission Spots Its 1st Star-shredding Black Hole

This illustration shows a tidal disruption, which occurs when a passing star gets too close to a black hole and is torn apart into a stream of gas. Some of the gas eventually settles into a structure around the black hole called an accretion disk. Credit: NASA's Goddard Space Flight Center

For the first time, NASA’s planet-hunting Transiting Exoplanet Survey Satellite (TESS) watched a black hole tear apart a star in a cataclysmic phenomenon called a tidal disruption event. Follow-up observations by NASA’s Neil Gehrels Swift Observatory and other facilities have produced the most detailed look yet at the early moments of one of these star-destroying occurrences.

“TESS data let us see exactly when this destructive event, named ASASSN-19bt, started to get brighter, which we’ve never been able to do before,” said Thomas Holoien, a Carnegie Fellow at the Carnegie Observatories in Pasadena, California. “Because we identified the tidal disruption quickly with the ground-based All-Sky Automated Survey for Supernovae (ASAS-SN), we were able to trigger multiwavelength follow-up observations in the first few days. The early data will be incredibly helpful for modeling the physics of these outbursts.”

A paper describing the findings, led by Holoien, was published in the Sept. 27, 2019, issue of The Astrophysical Journal and is now available online.

TESS Catches its First Star-destroying Black Hole

When a star strays too close to a black hole, intense tides break it apart into a stream of gas. The tail of the stream escapes the system, while the rest of it swings back around, surrounding the black hole with a disk of debris. This video includes images of a tidal disruption event called ASASSN-19bt taken by NASA’s Transiting Exoplanet Survey Satellite (TESS) and Swift missions, as well as an animation showing how the event unfolded. Credits: NASA's Goddard Space Flight Center. Download this video in HD formats from NASA Goddard's Scientific Visualization Studio

ASAS-SN, a worldwide network of 20 robotic telescopes headquartered at Ohio State University (OSU) in Columbus, discovered the event on Jan. 29. Holoien was working at the Las Campanas Observatory in Chile when he received the alert from the project’s South Africa instrument. Holoien quickly trained two Las Campanas telescopes on ASASSN-19bt and then requested follow-up observations by Swift, ESA’s (European Space Agency’s) XMM-Newton and ground-based 1-meter telescopes in the global Las Cumbres Observatory network.

TESS, however, didn’t need a call to action because it was already looking at the same area. The planet hunter monitors large swaths of the sky, called sectors, for 27 days at a time. This lengthy view allows TESS to observe transits, periodic dips in a star’s brightness that may indicate orbiting planets.

ASAS-SN began spending more time looking at TESS sectors when the satellite started science operations in July 2018. Astronomers anticipated TESS could catch the earliest light from short-lived stellar outbursts, including supernovae and tidal disruptions. TESS first saw ASASSN-19bt on Jan. 21, over a week before the event was bright enough for ASAS-SN to detect it. However, the satellite only transmits data to Earth every two weeks, and once received they must be processed at NASA’s Ames Research Center in Silicon Valley, California. So the first TESS data on the tidal disruption were not available until March 13. This is why obtaining early follow-up observations of these events depends on coordination by ground-based surveys like ASAS-SN.

Fortunately, the disruption also occurred in TESS’s southern continuous viewing zone, which was always in sight of one of the satellite’s four cameras. (TESS shifted to monitoring the northern sky at the end of July.) ASASSN-19bt’s location allowed Holoien and his colleagues to follow the event across several sectors. If it had occurred outside this zone, TESS might have missed the beginning of the outburst.

“The early TESS data allow us to see light very close to the black hole, much closer than we’ve been able to see before,” said Patrick Vallely, a co-author and National Science Foundation Graduate Research Fellow at OSU. “They also show us that ASASSN-19bt’s rise in brightness was very smooth, which helps us tell that the event was a tidal disruption and not another type of outburst, like from the center of a galaxy or a supernova.”

Holoien’s team used UV data from Swift — the earliest yet seen from a tidal disruption — to determine that the temperature dropped by about 50%, from around 71,500 to 35,500 degrees Fahrenheit (40,000 to 20,000 degrees Celsius), over a few days. It’s the first time such an early temperature decrease has been seen in a tidal disruption before, although a few theories have predicted it, Holoien said.

More typical for these kinds of events was the low level of X-ray emission seen by both Swift and XMM-Newton. Scientists don’t fully understand why tidal disruptions produce so much UV emission and so few X-rays.

“People have suggested multiple theories — perhaps the light bounces through the newly created debris and loses energy, or maybe the disk forms further from the black hole than we originally thought and the light isn’t so affected by the object’s extreme gravity,” said S. Bradley Cenko, Swift’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “More early-time observations of these events may help us answer some of these lingering questions.”

Astronomers think the supermassive black hole that generated ASASSN-19bt weighs around 6 million times the Sun’s mass. It sits at the center of a galaxy called 2MASX J07001137-6602251 located around 375 million light-years away in the constellation Volans. The destroyed star may have been similar in size to our Sun.

Tidal disruptions are incredibly rare, occurring once every 10,000 to 100,000 years in a galaxy the size of our own Milky Way. Supernovae, by comparison, happen every 100 years or so. In total, astronomers have observed only about 40 tidal disruptions so far, and scientists predicted TESS would see only one or two in its initial two-year mission.

“For TESS to observe ASASSN-19bt so early in its tenure, and in the continuous viewing zone where we could watch it for so long, is really quite extraordinary,” said Padi Boyd, the TESS project scientist at Goddard. “Future collaborations with observatories around the world and in orbit will help us learn even more about the different outbursts that light up the cosmos.”

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA's Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes and observatories worldwide are participants in the mission.

NASA's Goddard Space Flight Center manages the Swift mission in collaboration with Penn State in University Park, the Los Alamos National Laboratory in New Mexico and Northrop Grumman Innovation Systems in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory of the University College London in the United Kingdom, Brera Observatory and ASI.

By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Press Contacts

Claire Andreoli
claire.andreoli@nasa.gov, (301) 286-1940
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Natasha Metzler
nmetzler@carnegiescience.edu, (202) 939-1142
Carnegie Institution, Strategic Communications

Laura Arenschield
Arenschield.2@osu.edu
The Ohio State University, Research Communications

Editor: Rob Garner

Source: NASA/TESS

Thursday, September 26, 2019

Found: Three Black Holes On Collision Course

SDSS J084905.51+111447.2

Credit X-ray: NASA/CXC/George Mason Univ./R. Pfeifle et al.; Optical: SDSS & NASA/STScI

JPEG (257.7 kb) - Large JPEG (1.6 MB) - Tiff (62.3 MB) - More Images

A Tour of Triplet Black Holes - More Animations

A new study using data from NASA's Chandra X-ray Observatory and other telescopes provides the strongest evidence yet for a system of three supermassive black holes, as described in our latest press release. Astronomers think these triplet collisions, while extremely rare, play a critical role in how the biggest black holes grow over time.

The system is known as SDSS J084905.51+111447.2 (SDSS J0849+1114 for short) and is located a billion light years from Earth. In this graphic, X-rays from Chandra (purple) are shown in the pull-out in comparison with optical light from the Hubble Space Telescope and the Sloan Digital Sky Survey (red, green, and blue) in the main panel.

The Chandra data revealed three X-ray sources — a tell-tale sign of material being consumed by the black holes — at the bright centers of each galaxy in the merger, exactly where scientists expect supermassive black holes to reside. The separations between the black holes range between about 10,000 and 30,000 light years. Chandra and NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) satellite also found evidence for large amounts of gas and dust around one of the black holes, typical for a merging black hole system.

SDSS J0849+1114 was first flagged as a potential system of colliding black holes by SDSS with the help of citizen scientists across the globe as part of the Galaxy Zoo Project.

Then infrared imaging data from NASA's WISE mission revealed that the system was glowing intensely in the infrared during a phase in the galaxy merger when more than one of the black holes is expected to be feeding rapidly. To follow up on these clues, astronomers then turned to Chandra and the Large Binocular Telescope (LBT) in Arizona.

One reason it is difficult to find a triplet of supermassive black holes is that they are likely to be shrouded in gas and dust, blocking much of their light. The infrared images of WISE, the infrared spectra from LBT and the X-ray images from Chandra bypass this issue, because infrared and X-ray light pierce clouds of gas much more easily than optical light.

The paper, led by Ryan Pfeifle of George Mason University in Fairfax, Virginia, describing these results appears in the latest issue of The Astrophysical Journal and a preprint is also available.

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge, Massachusetts.

A Quick Look at Triplet Black Holes

Fast Facts for SDSS J0849+1114:

Scale: The optical image is about 36 arcsec (172,000 light years) across. The inset X-ray image is about 9 arcsec (43,000 light years) across.

Category: Black Holes, Quasars & Active Galaxies
Coordinates (J2000): RA 08h 49m 05.51s | Dec 11° 14´ 47.2"
Constellation: Cancer
Observation Date: March 3, 2016
Observation Time: 5 hours 48 minutes
Obs. ID: 18196
Instrument: ACIS
References: Pfeifle R. et. al, 2019, ApJ, accepted. arXiv:1908.01732
Color Code: X-ray: Blue/Purple; Optical: Red/Green/Blue
Distance Estimate: About 1 Billion light years (z=0.077)

Source: NASA’s Chandra X-ray Observatory

Wednesday, September 25, 2019

NASA's Webb to Unlock the Mysteries of Comets and the Early Solar System

Comet Hale-Bopp

Credits: E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria (http://www.sternwarte.at). Available under Creative Commons CC-by-SA 3.0.

Nucleus of Comet 19P/Borrelly

Credits: NASA/JPL

Release images

Astronomers to study three different types of comets

Though no longer thought of as harbingers of doom, comets are still mysterious. Scientists using NASA’s James Webb Space Telescope plan to unlock some of those mysteries when they study three different types of comets to learn more about them and about the early solar system. Astronomers are already somewhat familiar with two of the comets—Read and Borrelly. The third is a “target-of-opportunity,” one that is not yet known but is expected to be discovered in the first year of Webb’s mission. If they are lucky, perhaps they will capture an interstellar comet. Or perhaps they will train Webb on a comet from the Oort Cloud, a spherical cloud of icy bodies surrounding our solar system.

Since ancient times, comets have fascinated sky-watchers, who often considered them divine omens. A Chinese historian recorded an apparition of Comet Halley as far back as 240 B.C., describing it as a “broom star.” The Babylonians and Romans also referenced the comet’s appearance, but perhaps its most famous depiction is in the Bayeux Tapestry, which commemorates the Norman Conquest of England in 1066. The tapestry shows King Harold and a crowd of fearful Englishmen pointing to Comet Halley as it looms in the sky.

We now know that comets — which are clumps of rock, dirt, dust, and ice in space — are not harbingers of doom, but there is still much we don’t know about them. Because comets have changed very little in the solar system's 4.6-billion-year history, they are among the most primitive bodies scientists can study.

Shortly after its launch in 2021, NASA’s James Webb Space Telescope will observe three different types of comets in infrared light, which is invisible to human eyes. By learning more about comets, scientists can gain new insights into what the solar system was like billions of years ago.

Webb, A Powerful Tool

These three comet studies will be conducted through Webb's Guaranteed Time Observations (GTO) program of the solar system led by Heidi Hammel, a planetary scientist who was selected by NASA as a Webb Interdisciplinary Scientist in 2002. She is also executive vice president of the Association of Universities for Research in Astronomy (AURA) in Washington, D.C. Hammel’s program will demonstrate Webb's capabilities for tracking moving targets and looking at bright objects in the solar system.

“We want to study comets with Webb because of the telescope’s very powerful capabilities in the near- and mid-infrared,” Hammel says. “What makes those wavelengths of light particularly powerful for cometary studies is that they allow us to study the chemical makeup of this dust and gas that’s come off of the comet’s nucleus and figure out what it is."

Molecules of gas and dust emit and absorb infrared wavelengths of light, so by analyzing this light, Webb can determine which chemicals are present. "If this is primitive material, it will give us some clues to the makeup of the early solar system,” Hammel says.

Comparing Different Comet Families

When comets venture close to the Sun, some of their ice turns into vapor. This vapor forms an envelope, or coma, of gases and dust around the central body, or nucleus. The Sun’s solar wind and radiation pressure from sunlight stream this coma away from the nucleus, creating comet tails. The word “comet” comes from the Greek "kome,” which means "hair." In ancient times, comets were thought to be stars with hair streaming off them.

Scientists using time from Hammel’s program plan to map the inner comae of three different types of comets, one of which has not yet been discovered:

A Jupiter-Family Comet (proposed target: Comet Borrelly): With an orbit strongly affected by the gravity of the giant planet Jupiter, Comet Borrelly is classified as a Jupiter-family comet. A science team led by Michael Kelley of the University of Maryland plans to study how the relatively bright comet’s gases and dust escape the nucleus, and what happens to them after they leave. The team will map individual types of gas and study the composition of the comet’s dust, which will help them understand how a comet works.

A Main-Belt Comet (proposed target: Comet Read): The second target to be studied, Comet Read, is fainter and smaller than Borrelly. It is a Main-Belt comet, meaning it orbits within the asteroid belt, even though it acts like a comet for part of its orbit. Kelley and his team will try to detect the gas—and particularly water—around this comet. This has never been done for a Main-Belt comet; until now, scientists have only been able to detect their dust.

A Target-of-Opportunity Comet: In a study led by Stefanie Milam of NASA’s Goddard Space Flight Center, scientists will investigate a target comet that is not yet known, but is expected to be discovered shortly after Webb’s launch. This third type of comet might come from the Oort Cloud, a spherical cloud surrounding our solar system very far from the planets. The outer Oort Cloud is only loosely bound to the solar system, and it is subject to gravitational forces that occasionally dislodge comets from within the cloud and send them toward the inner solar system. Alternatively, this opportunistic comet might be an interstellar interloper. To date, just two interstellar objects have been detected passing through our solar system: ‘Oumuamua in 2017, and the newly detected object called C/2019 Q4 (Borisov). “Oort Cloud comets are really long-period comets that approach the Sun very rarely, and they tend to have a lot more ice in them and a lot more volatile material,” explains Milam. “So they make these big, beautiful, bright comae. They’re usually huge apparitions on the sky, and that’s what the focus would be for that comet.” Hammel notes that we aren’t quite sure what Webb would see for an interstellar object. “One of Webb’s strengths is its ability to sense faint objects, and that makes it a great tool to study these very rare and very faint interstellar interlopers. If we could glean compositional information about its surface, that might open a whole new field of study.”

Astronomers are not limited to just these objects.

“Ultimately, these are just individual examples, but over Webb’s lifetime, we’ll eventually observe many comets, and we’ll have lots of examples from these different classes, and we can compare them all to each other,” says Kelley. “With time — and in conjunction with all the ground-based data that we’ve had and will continue to obtain — we’ll have a better understanding of where these comets come from."

Among the questions that scientists hope to answer with Webb: Are all solar system comets derived from a uniform population, and they’ve all just evolved differently? Or are they really chemically distinct from the start, and we’re just seeing that today? And, how do interstellar comets compare with local comets?

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Source: NASA's James Webb Space Telescope/News Release

Contact:

Ann Jenkins / Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4366
jenkins@stsci.edu / cpulliam@stsci.edu

Related Links: NASA's Webb Portal

Saturday, September 21, 2019

First Canadian-led ALMA Survey to Investigate the Impact of Galaxy Environment on Star Formation

Optical image of the spiral galaxy NGC 4330, located in the Virgo Cluster. Ionised gas is shown in red. The blue overlay shows the expected ALMA observations of CO gas. Dr Brown and his colleagues will use the Atacama Compact Array (ACA) to study the influence of galaxy environment on star formation in the Virgo Cluster. Credit: T. Brown; Fossati et al., 2018. Hi-res image

The first-ever Canadian-led Atacama Large Millimeter/submillimeter Array (ALMA) Large Program has been announced and it will be led by Dr Toby Brown, a former ICRAR PhD student who is now based at McMaster University in Canada.

Where galaxies live in the Universe, how they interact with their surroundings (the intergalactic medium), and with each other is a major influence on star formation over cosmic time. But exactly how the so-called environment dictates the life and death of galaxies is a major focus of the astronomy community.

Dr Brown and his colleagues will use the Atacama Compact Array (ACA) to study the influence of galaxy environment on star formation in the Virgo Cluster. Galaxy clusters are the most extreme environments in the Universe, with huge gravitational forces acting on their member galaxies and super-heated plasma in the intergalactic medium.

Dr Brown said that the Virgo Cluster is an ideal location for detailed studies of the environment.

“It is our nearest massive galaxy cluster and is in the process of forming, which means that we can get a snapshot of galaxies in different stages of their lifecycle,” he said.

“This allows us to understand how star formation is shut off in cluster galaxies.”

Virgo has been studied at almost every wavelength, but a millimetre data set with the required sensitivity and resolution does not exist yet. Therefore, Dr Brown and his colleagues will use ALMA to map the star-forming gas, the fuel from which stars are born, at high resolution in 51 Virgo spiral galaxies.

With the new data, the team will study how the Virgo Cluster environment influences the molecular star-forming gas.

“One of the ways in which star formation can be stopped is gas removal or stripping,” Brown explains.

“When galaxies pass through the intracluster medium, hot plasma can sweep gas from the galaxies like a huge cosmic broom.”

Another environmental mechanism is starvation: when molecular gas used in star formation is not replenished and new stars cannot be formed.

“This ALMA Large Program allows us to better understand these mechanisms,” he said.

ALMA Large Programs are designed to address strategic scientific issues that will lead to a major advance or breakthrough in the field.

Dr Toby Brown

Source: International Centre for Radio Astronomy Research (ICRAR)

More Information

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Extreme Cosmos

Tuesday, September 17, 2019

Most Massive Neutron Star Ever Detected, Almost too Massive to Exist

Artist impression of the pulse from a massive neutron star being delayed by the passage of a white dwarf star between the neutron star and Earth. Credit: BSaxton, NRAO/AUI/NSF

Astronomers using the GBT have discovered the most massive neutron star to date, a rapidly spinning pulsar approximately 4,600 light-years from Earth. This record-breaking object is teetering on the edge of existence, approaching the theoretical maximum mass possible for a neutron star.

Neutron stars – the compressed remains of massive stars gone supernova – are the densest “normal” objects in the known universe. (Black holes are technically denser, but far from normal.) Just a single sugar-cube worth of neutron-star material would weigh 100 million tons here on Earth, or about the same as the entire human population. Though astronomers and physicists have studied and marveled at these objects for decades, many mysteries remain about the nature of their interiors: Do crushed neutrons become “superfluid” and flow freely? Do they breakdown into a soup of subatomic quarks or other exotic particles? What is the tipping point when gravity wins out over matter and forms a black hole?

A team of astronomers using the National Science Foundation’s (NSF) Green Bank Telescope (GBT) has brought us closer to finding the answers.

The researchers, members of the NANOGrav Physics Frontiers Center, discovered that a rapidly rotating millisecond pulsar, called J0740+6620, is the most massive neutron star ever measured, packing 2.17 times the mass of our Sun into a sphere only 30 kilometers across. This measurement approaches the limits of how massive and compact a single object can become without crushing itself down into a black hole. Recent work involving gravitational waves observed from colliding neutron stars by LIGO suggests that 2.17 solar masses might be very near that limit.

“Neutron stars are as mysterious as they are fascinating,” said Thankful Cromartie, a graduate student at the University of Virginia and Grote Reber pre-doctoral fellow at the National Radio Astronomy Observatory in Charlottesville, Virginia. “These city-sized objects are essentially ginormous atomic nuclei. They are so massive that their interiors take on weird properties. Finding the maximum mass that physics and nature will allow can teach us a great deal about this otherwise inaccessible realm in astrophysics.”

Pulsars get their name because of the twin beams of radio waves they emit from their magnetic poles. These beams sweep across space in a lighthouse-like fashion. Some rotate hundreds of times each second. Since pulsars spin with such phenomenal speed and regularity, astronomers can use them as the cosmic equivalent of atomic clocks. Such precise timekeeping helps astronomers study the nature of spacetime, measure the masses of stellar objects, and improve their understanding of general relativity.

In the case of this binary system, which is nearly edge-on in relation to Earth, this cosmic precision provided a pathway for astronomers to calculate the mass of the two stars.

Artist impression and animation of the Shapiro Delay. As the neutron star sends a steady pulse towards the Earth, the passage of its companion white dwarf star warps the space surrounding it, creating the subtle delay in the pulse signal. Animation: BSaxton, NRAO/AUI/NSF

As the ticking pulsar passes behind its white dwarf companion, there is a subtle (on the order of 10 millionths of a second) delay in the arrival time of the signals. This phenomenon is known as “Shapiro Delay.” In essence, gravity from the white dwarf star slightly warps the space surrounding it, in accordance with Einstein’s general theory of relativity. This warping means the pulses from the rotating neutron star have to travel just a little bit farther as they wend their way around the distortions of spacetime caused by the white dwarf.

Astronomers can use the amount of that delay to calculate the mass of the white dwarf. Once the mass of one of the co-orbiting bodies is known, it is a relatively straightforward process to accurately determine the mass of the other.

Cromartie is the principal author on a paper accepted for publication in Nature Astronomy. The GBT observations were research related to her doctoral thesis, which proposed observing this system at two special points in their mutual orbits to accurately calculate the mass of the neutron star.

“The orientation of this binary star system created a fantastic cosmic laboratory,” said Scott Ransom, an astronomer at NRAO and coauthor on the paper. “Neutron stars have this tipping point where their interior densities get so extreme that the force of gravity overwhelms even the ability of neutrons to resist further collapse. Each “most massive” neutron star we find brings us closer to identifying that tipping point and helping us to understand the physics of matter at these mindboggling densities.”

These observation were also part of a larger observing campaign known as NANOGrav, short for the North American Nanohertz Observatory for Gravitational Waves, which is a Physics Frontiers Center funded by the NSF.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

The Green Bank Observatory is supported by the National Science Foundation, and is operated under cooperative agreement by Associated Universities, Inc. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.

Media Contact

Jill Malusky
Public Relations Specialist
Green Bank Observatory
304-456-2236

Scientific Contacts

Karen O’Neill
Site Director
Green Bank Observatory
304-456-2130

Ryan Lynch
Staff Scientist
Green Bank Observatory
304-456-2357

Source: Green Bank Observatory

Monday, September 16, 2019

Gemini Observatory Captures Multicolor Image of First-ever Interstellar Comet

Gemini Observatory two-color composite image of C/2019 Q4 (Borisov) which is the first interstellar comet ever identified. This image was obtained using the Gemini North Multi-Object Spectrograph (GMOS) from Hawaii’s Maunakea. The image was obtained with four 60-second exposures in bands (filters) r and g. Blue and red dashes are images of background stars which appear to streak due to the motion of the comet. Composite image by Travis Rector. Image Credit: Gemini Observatory/NSF/AURA. download JPG 230 KB | TIFF 23 MB

The first-ever comet from beyond our Solar System has been successfully imaged by the Gemini Observatory in multiple colors. The image of the newly discovered object, denoted C/2019 Q4 (Borisov), was obtained on the night of 9-10 September using the Gemini Multi-Object Spectrograph on the Gemini North Telescope on Hawaii’s Maunakea.

“This image was possible because of Gemini’s ability to rapidly adjust observations and observe objects like this, which have very short windows of visibility,” said Andrew Stephens of Gemini Observatory who coordinated the observations. “However, we really had to scramble for this one since we got the final details at 3:00 am and were observing it by 4:45!”

The image shows a very pronounced tail, indicative of outgassing, which is what defines a cometary object. This is the first time an interstellar visitor to our Solar System has clearly shown a tail due to outgassing. The only other interstellar visitor studied in our Solar System was ‘Oumuamua which was a very elongated asteroid-like object with no obvious outgassing.

The Gemini observations used for this image were obtained in two color bands (filters) and combined to produce a color image. The observations were obtained as part of a target of opportunity program led by Piotr Guzik and Michal Drahus at the Jagiellonian University in Krakow (Poland). The research team has submitted a paper for publication.

C/2019 Q4 is currently close to the apparent position of the Sun in our sky and is consequently difficult to observe due to the glow of twilight. The comet’s hyperbolic path, which is evidence of its origin beyond our Solar System, will bring it to more favorable observing conditions over the next few months.

C/2019 Q4 was discovered by Russian amateur astronomer Gennady Borisov on 30 August, 2019.

Contacts:

Peter Michaud
Gemini Observatory, Hilo HI
Email: pmichaud@gemini.edu
Cell: (808) 936-6643
Desk: (808) 974-2510

Michal Drahus
Jagiellonian University, Krakow (Poland)
Email: drahus@oa.uj.edu.pl

Andy Stephens
Gemini Observatory
Email: astephens@gemini.edu

Source: Gemini Observatory

Saturday, September 14, 2019

VISTA unveils a new image of the Large Magellanic Cloud

PR Image eso1914a

The Large Magellanic Cloud revealed by VISTA

PR Image eso1914b

Highlights of the Large Magellanic Cloud

PR Image eso1914c

Large Magellanic Cloud

Videos

PR Video eso1914a

ESOcast 206 Light: VISTA Unveils the Large Magellanic Cloud (4K UHD)

PR Video eso1914b

Zooming on the Large Magellanic Cloud

PR Video eso1914c

Comparison of the Large Magellanic Cloud in infrared and visible light

PR Video eso1914d

Comparison of the Tarantula nebula in infrared and visible light

PR Video eso1914e

Panning across the Large Magellanic Cloud

ESO’s VISTA telescope reveals a remarkable image of the Large Magellanic Cloud, one of our nearest galactic neighbours. VISTA has been surveying this galaxy and its sibling the Small Magellanic Cloud, as well as their surroundings, in unprecedented detail. This survey allows astronomers to observe a large number of stars, opening up new opportunities to study stellar evolution, galactic dynamics, and variable stars.

The Large Magellanic Cloud, or LMC, is one of our nearest galactic neighbors, at only 163 000 light years from Earth. With its sibling the Small Magellanic Cloud, these are among the nearest dwarf satellite galaxies to the Milky Way. The LMC is also the home of various stellar conglomerates and is an ideal laboratory for astronomers to study the processes that shape galaxies.

ESO’s VISTA telescope, has been observing these two galaxies for the last decade. The image presented today is the result of one of the many surveys that astronomers have performed with this telescope. The main goal of the VISTA Magellanic Clouds (VMC) Survey has been to map the star formation history of the Large and Small Magellanic Clouds, as well as their three-dimensional structures.

VISTA was key to this image because it observes the sky in near-infrared wavelengths of light. This allows it to see through clouds of dust that obscure parts of the galaxy. These clouds block a large portion of visible light but are transparent at the longer wavelengths VISTA was built to observe. As a result, many more of the individual stars populating the centre of the galaxy are clearly visible. Astronomers analysed about 10 million individual stars in the Large Magellanic Cloud in detail and determined their ages using cutting-edge stellar models[1]. They found that younger stars trace multiple spiral arms in this galaxy.

For millennia, the Magellanic Clouds have fascinated people in the Southern Hemisphere, but they were largely unknown to Europeans until the Age of Discovery. The name we use today harkens back to the explorer Ferdinand Magellan, who 500 years ago began the first circumnavigation of the Earth. The records the expedition brought back to Europe revealed many places and things to Europeans for the first time. The spirit of exploration and discovery is ever more live today in the work of astronomers around the world, including the VMC Survey team whose observations led to this stunning image of the LMC.

Notes

[1] Stellar models allow astronomers to predict the life and death of stars, providing insights into properties like their ages, mass, and temperature.

More information

The stars revealed by this image were discussed in the paper “The VMC Survey - XXXIV. Morphology of Stellar Populations in the Magellanic Clouds” to appear in the journal Monthly Notices of the Royal Astronomical Society.

Links

Contacts

Maria-Rosa Cioni
Leibniz-Institut für Astrophysik Potsdam (AIP)
Potsdam, Germany
Tel: +49 331 7499 651
Email: mcioni@aip.de

Mariya Lyubenova
ESO Head of Media Relations
Garching bei München, Germany
Tel: +49 89 3200 6188
Email: pio@eso.org

Source: ESO/News

Friday, September 13, 2019

Saturn's Rings Shine in New Hubble Portrait

Saturn's Rings

Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), M.H. Wong (University of California, Berkeley), and the OPAL Team. Release Images - Release Videos

Saturn is so beautiful that astronomers cannot resist using the Hubble Space Telescope to take yearly snapshots of the ringed world when it is at its closest distance to Earth.

These images, however, are more than just beauty shots. They reveal a planet with a turbulent, dynamic atmosphere. This year's Hubble offering, for example, shows that a large storm visible in the 2018 Hubble image in the north polar region has vanished. Smaller storms pop into view like popcorn kernels popping in a microwave oven before disappearing just as quickly. Even the planet's banded structure reveals subtle changes in color.

But the latest image shows plenty that hasn't changed. The mysterious six-sided pattern, called the "hexagon," still exists on the north pole. Caused by a high-speed jet stream, the hexagon was first discovered in 1981 by NASA's Voyager 1 spacecraft.

Saturn's signature rings are still as stunning as ever. The image reveals that the ring system is tilted toward Earth, giving viewers a magnificent look at the bright, icy structure. Hubble resolves numerous ringlets and the fainter inner rings.

This image reveals an unprecedented clarity only seen previously in snapshots taken by NASA spacecraft visiting the distant planet. Astronomers will continue their yearly monitoring of the planet to track shifting weather patterns and identify other changes. The second in the yearly series, this image is part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system's gas giant planets.

Source: HubbleSite\News

Contact:

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Amy Simon
Goddard Space Flight Center, Greenbelt, Maryland
amy.simon@nasa.gov

Mike Wong
University of California, Berkeley, California
mikewong@astro.berkeley.edu

Related Links:

Astronomy Cmarchesin