Thursday, December 23, 2021

ESO telescopes help uncover largest group of rogue planets yet

Artist’s impression of a rogue planet in Rho Ophiuchi 
 
The faint red glow of a rogue planet
 
PR Image eso2120c
Locations of the rogue planets found


Videos

Rogue planets uncovered (ESOcast 249 Light)
Rogue planets uncovered (ESOcast 249 Light) 
 
Artist’s animation of a rogue planet in Rho Ophiuchi
Artist’s animation of a rogue planet in Rho Ophiuchi 
 
Zooming into a rogue planet
Zooming into a rogue planet



Rogue planets are elusive cosmic objects that have masses comparable to those of the planets in our Solar System but do not orbit a star, instead roaming freely on their own. Not many were known until now, but a team of astronomers, using data from several European Southern Observatory (ESO) telescopes and other facilities, have just discovered at least 70 new rogue planets in our galaxy. This is the largest group of rogue planets ever discovered, an important step towards understanding the origins and features of these mysterious galactic nomads.

“We did not know how many to expect and are excited to have found so many,” says Núria Miret-Roig, an astronomer at the Laboratoire d’Astrophysique de Bordeaux, France and the University of Vienna, Austria, and the first author of the new study published today in Nature Astronomy.

Rogue planets, lurking far away from any star illuminating them, would normally be impossible to image. However, Miret-Roig and her team took advantage of the fact that, in the few million years after their formation, these planets are still hot enough to glow, making them directly detectable by sensitive cameras on large telescopes. They found at least 70 new rogue planets with masses comparable to Jupiter’s in a star-forming region close to our Sun, located within the Scorpius and Ophiuchus constellations [1].

To spot so many rogue planets, the team used data spanning about 20 years from a number of telescopes on the ground and in space. “We measured the tiny motions, the colours and luminosities of tens of millions of sources in a large area of the sky,” explains Miret-Roig. “These measurements allowed us to securely identify the faintest objects in this region, the rogue planets.”

The team used observations from ESO’s Very Large Telescope (VLT), the Visible and Infrared Survey Telescope for Astronomy (VISTA), the VLT Survey Telescope (VST) and the MPG/ESO 2.2-metre telescope located in Chile, along with other facilities. “The vast majority of our data come from ESO observatories, which were absolutely critical for this study. Their wide field of view and unique sensitivity were keys to our success,” explains Hervé Bouy, an astronomer at the Laboratoire d’Astrophysique de Bordeaux, France, and project leader of the new research. “We used tens of thousands of wide-field images from ESO facilities, corresponding to hundreds of hours of observations, and literally tens of terabytes of data.”

The team also used data from the European Space Agency’s Gaia satellite, marking a huge success for the collaboration of ground- and space-based telescopes in the exploration and understanding of our Universe.

The study suggests there could be many more of these elusive, starless planets that we have yet to discover. “There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star,” Bouy explains.

By studying the newly found rogue planets, astronomers may find clues to how these mysterious objects form. Some scientists believe rogue planets can form from the collapse of a gas cloud that is too small to lead to the formation of a star, or that they could have been kicked out from their parent system. But which mechanism is more likely remains unknown.

Further advances in technology will be key to unlocking the mystery of these nomadic planets. The team hopes to continue to study them in greater detail with ESO’s forthcoming Extremely Large Telescope (ELT), currently under construction in the Chilean Atacama Desert and due to start observations later this decade. “These objects are extremely faint and little can be done to study them with current facilities,” says Bouy. “The ELT will be absolutely crucial to gathering more information about most of the rogue planets we have found.”


Notes

[1] The exact number of rogue planets found by the team is hard to pin down because the observations don’t allow the researchers to measure the masses of the probed objects. Objects with masses higher than about 13 times the mass of Jupiter are most likely not planets, so they cannot be included in the count. However, since the team didn’t have values for the mass, they had to rely on studying the planets’ brightness to provide an upper limit to the number of rogue planets observed. The brightness is, in turn, related to the age of the planets themselves, as the older the planet, the longer it has been cooling down and reducing in brightness. If the studied region is old, then the brightest objects in the sample are likely above 13 Jupiter masses, and below if the region is on the younger side. Given the uncertainty in the age of the study region, this method gives a rogue planet count of between 70 and 170. 

 

More Information

This research was presented in the paper “A rich population of free-floating planets in the Upper Scorpius young stellar association” to appear in Nature Astronomy (DOI: 10.1038/s41550-021-01513-x). It has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 682903, P.I. H. Bouy), and from the French State in the framework of the ”Investments for the Future” Program, IdEx Bordeaux, reference ANR-10-IDEX-03-02.

The team is composed of Núria Miret-Roig (Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, France [LAB]; University of Vienna, Department of Astrophysics, Austria), Hervé Bouy (LAB), Sean N. Raymond (LAB), Motohide Tamura (Department of Astronomy, Graduate School of Science, The University of Tokyo, Japan; Astrobiology Center, National Institutes of Natural Sciences, Tokyo, Japan [ABC-NINS]), Emmanuel Bertin (CNRS, UMR 7095, Institut d’Astrophysique de Paris,France [IAP]; Sorbonne Université, IAP, France) David Barrado (Centro de Astrobiología [CSIC-INTA], Depto. de Astrofísica, ESAC Campus, Spain), Javier Olivares (LAB), Phillip Galli (LAB), Jean-Charles Cuillandre (AIM, CEA, CNRS, Université Paris-Saclay, Université de Paris, France), Luis Manuel Sarro (Depto. de Inteligencia Artificial, UNED, Spain) Angel Berihuete (Depto. Estadística e Investigación Operativa, Universidad de Cádiz, Spain) & Nuria Huélamo (CSIC-INTA).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration in astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 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’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its 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. Together with international partners, ESO operates APEX and ALMA on Chajnantor, two facilities that observe the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.



Links


Contacts:

Núria Miret-Roig
Department of Astrophysics, University of Vienna
Vienna, Austria
Tel: +43 1427753845
Email: nuria.miret.roig@univie.ac.at

Hervé Bouy
Laboratoire d'Astrophysique de Bordeaux, Université de Bordeaux
Pessac, France
Tel: +33 5 40 00 32 94
Email: herve.bouy@u-bordeaux.fr

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org


Source: ESO/News

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Wednesday, December 22, 2021

RBS 797: Astronomers Spy Quartet of Cavities From Giant Black Holes


RBS 797 is a galaxy cluster located about 3.9 billion light years from Earth. Four enormous cavities, or bubbles, have been found at the center of the RBS 797 galaxy cluster using Chandra. Hot gas that envelopes the individual galaxies is invisible in optical light, but it is detected in X-rays by Chandra. Scientists have seen many pairs of X-ray cavities before in other galaxy clusters, but four in the same cluster is very rare. The researchers think the quartet of cavities represents the essentially simultaneous explosive activity of a pair of supermassive black holes at the center of the galaxy cluster.Credit: X-ray: NASA/CXC/Univ. of Bologna/F. Ubertosi; Optical: NASA/STScl/M.Calzadilla; Radio: NSF/NRAO/ALMA)
Four enormous cavities, or bubbles, have been found at the center of a galaxy cluster using NASA's Chandra X-ray Observatory, as described in our latest press release. The left panel of this graphic shows an optical image of the galaxy cluster called RBS 797, from NASA's Hubble Space Telescope. Hot gas that envelopes the individual galaxies is invisible in optical light, but it is detected in X-rays by Chandra (right). One pair of cavities can be seen towards the left and right of center in the Chandra image as black oval-shaped regions. The other pair is less distinct, but can be found above and below the center of the image.

Credit: NASA/CXC/Univ. of Bologna/F. Ubertosi

Scientists have seen these X-ray cavities before in other galaxy clusters. A pair of cavities is thought to be a byproduct of eruptions from a giant black hole in a large galaxy at the center of a cluster. The eruptions power jets in opposite directions, which push gas away to create a pair of cavities. However, to produce four cavities each roughly pointing 90 degrees away from one another, a more complex phenomenon must be at play.

A team of astronomers studying RBS 797 think the most likely answer is that the galaxy cluster contains a pair of supermassive black holes, each of which has launched jets in perpendicular directions at almost the same time. Another possible explanation for the four cavities seen in RBS 797 is that there is only one supermassive black hole — with jets that somehow manage to flip around in direction quite quickly. Analysis of the Chandra data shows that the age difference for the east-west and north-south cavities is less than 10 million years.

Previously, astronomers observed the pair of cavities in the east-west direction in RBS 797, but the pair in the north-south direction was only detected in a new, much longer Chandra observation. The deeper image uses almost five days of Chandra observing time, compared to about 14 hours for the original observation. The NSF's Karl G. Jansky Very Large Array had already observed evidence for two pairs of jets as radio emission, which line up with the cavities.

A paper describing these results, led by Francesco Ubertosi (University of Bologna in Italy) appears in The Astrophysical Journal Letters as is available online: https://arxiv.org/abs/2111.03679 The other authors include Myriam Gitti (Univ. of Bologna), Fabrizio Brighenti (Univ. of Bologna), Gianfranco Brunetti (INAF), Michael McDonald (Massachusetts Insitute of Technology), Paul Nulsen (Center for Astrophysics | Harvard & Smithsonian), Brian McNamara (Perimeter Institute), Scott Randall (CfA), William Forman (CfA), Megan Donahue (Michigan State University), Alessandro Ignesti (INAF), Massimo Gaspari (INAF), Steffano Ettori (INAF), Luigina Feretti (INAF), Elizabeth L. Blanton (Boston University), Christine Jones (CfA), and Michael S. Calzadilla (MIT).

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




Fast Facts for RBS 797:

Scale: X-ray & optical images are about 1 arcmin (1.1 million light years) across.
Category: Groups & Clusters of Galaxies, Black Holes
Constellation: Draco
Observation Date: 13 pointings between May 24, 2020 and Dec 6, 2020
Observation Time: 113 hours 33 minutes (4 days, 17 hours, 33 minutes)
Obs. ID: 22636-22638, 22931-22935, 23332, 24631-24632, 24852, 24865
Instrument: ACIS
References: Ubertosi, F. et al, 2021. ApJL paper
Color Code: X-ray: blue; Optical: orange and blue
Distance Estimate: About 3.9 billion light years (z=0.354)



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Tuesday, December 21, 2021

A gigantic lane made of raw material for new stars


This image shows a section of the side view of the Milky Way as measured by ESA’s Gaia satellite. The dark band consists of gas and dust, which dims the light from the embedded stars. The Galactic Centre of the Milky Way is indicated on the right of the image, shining brightly below the dark zone. The box to the left of the middle marks the location of the “Maggie” filament. It shows the distribution of atomic hydrogen. The colours indicate different velocities of the gas. Image: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO & T. Müller/J. Syed/MPIA


This false-colour image shows the distribution of atomic hydrogen measured at a wavelength of 21 cm. The red dashed line traces the “Maggie” filament. Image: J. Syed/MPIA


This image corresponds to the box in the figure with the overview of the Milky Way. In addition to the distribution of atomic hydrogen, the colours indicate different velocity ranges of the gas as measured by the observations of the THOR survey. The “Maggie” filament is visible in the lower area. Image: T. Müller/J. Syed/MPIA

This animation begins with a schematic top view of the Milky Way with “Maggie’s” location marked by a red line. Then it rotates to a side view of the Milky Way and moves towards the filament. Finally, we see the distribution of atomic hydrogen, with the measured velocities represented by different colours.Credit: NASA/JPL-Caltech/ESO/R. Hurt & ESA/Gaia/DPAC, CC BY-SA 3.0 IGO & T. Müller/J. Syed/MPIA


Astronomers discover a huge filament of atomic hydrogen, a possible precursor to star-forming clouds

A group of astronomers, led by researchers from the Max Planck Institute for Astronomy (MPIA), have identified one of the longest known structures in the Milky Way. It stretches some 3900 light-years and consists almost entirely of atomic hydrogen gas. This filament, called “Maggie”, could represent a link in the matter cycle of the stars. Analysing the measurements suggests that the atomic gas in this lane converges locally to form molecular hydrogen. When compressed in large clouds, this is the material from which stars eventually form.

Hydrogen is the most widespread substance in the Universe and the main ingredient in the formation of stars. Unfortunately, detecting individual clouds of hydrogen gas is a demanding task, which makes research into the early phases of star formation challenging. That is why the recent discovery of a surprisingly long structure, a filament, of atomic hydrogen gas by an international research group led by astronomers from the Max Planck Institute for Astronomy (MPIA) in Heidelberg is all the more exciting.

“The location of this filament has contributed to this success,” says Jonas Syed, a PhD student at MPIA and first author of the paper published today in the journal Astronomy & Astrophysics. “We don’t yet know exactly how it got there. But the filament extends about 1600 light-years below the Milky Way plane.” As a result, the radiation from the hydrogen, which is at a wavelength of 21 centimetres, stands out clearly against the background, making the filament visible.

“The observations also allowed us to determine the velocity of the hydrogen gas,” explains Henrik Beuther. He is a co-author of the study and heads the THOR (The HI/OH/Recombination line survey of the Milky Way) observing programme at MPIA, on which the data are based. “This allowed us to show that the velocities along the filament barely differ.” Therefore, the researchers conclude, it is indeed a coherent structure.

Its mean velocity is determined mainly by the rotation of the Milky Way disk. “With this information and a new method for analysing data, we managed to determine the size and distance of the filament,” says Sümeyye Suri. She is another co-author and former MPIA astronomer who now works at the University of Vienna. “It is about 3900 light-years long and 130 light-years wide.” At a distance of around 55,000 light-years, it is on the far side of the Milky Way. In contrast, the largest known clouds of molecular gas typically extend “only” about 800 light-years across.

Hydrogen occurs in the Universe in various states. Astronomers find it in the form of atoms and molecules, in which two atoms are joined together. Only molecular gas condenses to relatively compact clouds, which develop frosty regions where new stars finally emerge. But exactly how the transition from atomic to molecular hydrogen happens is still largely unknown. That makes the opportunity to study this extraordinarily long filament all the more exciting.

Co-author Juan D. Soler already found the first clue to this object a year ago. He named the filament “Maggie” after the longest river in his home country of Colombia, called the Río Magdalena. “Maggie was already recognizable in earlier evaluations of the data. But only the current study proves beyond doubt that it is a coherent structure,” explains Soler, who recently moved from MPIA to the Istituto Nazionale di Astrofisica (INAF) in Rome.

On closer inspection, the team noticed that the gas converges at some points along the filament. They conclude that the hydrogen gas accumulates at those locations and condenses into large clouds. The researchers also suspect that those are the environments where the atomic gas gradually changes into a molecular form.

In previously published data, they indeed found evidence of Maggie containing molecular hydrogen at a mass fraction of about 8 %. We may be looking at a region in the Milky Way where the immediate raw material for new stars is being produced. Hence, new stars could form here in the distant future. “However, many questions remain unanswered,” Syed points out. “Additional data, which we hope will give us more clues about the fraction of molecular gas, are already waiting to be analysed.”

Additional information

The team consists of Jonas Syed (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), Juan D. Soler (MPIA; Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Rome, Italy), Henrik Beuther (MPIA), Yuan Wang (MPIA), Sümeyye Suri (MPIA; Astrophysical Institute, University of Vienna, Austria), Jonathan D. Henshaw (MPIA), Manuel Riener (MPIA), Shmuel Bialy (Harvard Smithsonian Center, Cambridge, USA), Sara Rezaei Khoshbakht (MPIA; Chalmers tekniska högskola, Gothenburg, Sweden), Jeroen M. Stil (Department of Physics and Astronomy, The University of Calgary, Canada), Paul F. Goldsmith (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA), Michael R. Rugel (Max Planck Institute for Radio Astronomy, Bonn, Germany), Simon C. O. Glover (Centre for Astronomy, Institute for Theoretical Astrophysics, University of Heidelberg, Germany [ZAH/ITA]), Ralf S. Klessen (ZAH/ITA; Interdisciplinary Centre for Scientific Computing, University of Heidelberg, Germany), Jürgen Kerp (Argelander Institute for Astronomy, University of Bonn, Germany), James S. Urquhart (Centre for Astrophysics and Planetary Science, University of Kent, UK), Jürgen Ott (National Radio Astronomy Observatory, Socorro, USA), Nirupam Roy (Department of Physics, Indian Institute of Science, Begaluru, India), Nicola Schneider (I. Phyikalisches Institut, University of Cologne, Germany), Rowan J. Smith (Jodrell Bank Centre for Astrophysics, University of Manchester, UK), Steven N. Longmore (Astrophysics Research Institute, Liverpool John Moores University, Liverpool, UK), Hendrik Linz (MPIA)


Contact

Dr. Markus Nielbock
Press and public relations officer
tel:+49 6221 528-134
Max Planck Institute for Astronomy, Heidelberg

Jonas Syed
tel:+49 6221 528-124
Max Planck Institute for Astronomy, Heidelberg

Prof. Dr. Henrik Beuther
tel:+49 6221 528-447
Max Planck Institute for Astronomy, Heidelberg

Original publication

1. J. Syed, J. D. Soler, H. Beuther, et al.
The “Maggie” filament: Physical properties of a giant atomic cloud
Astronomy & Astrophysics (2021)
Source / DOI


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Monday, December 20, 2021

Our Milky Way may be more fluffy, less wiry


In a map of the Milky Way, the neighboring spiral arm just beyond the Sun is known as the Perseus arm. Astronomers created this map by measuring the locations of natural radio sources known as masers (pink dots in pullouts at right) and dust clouds (blue dots). At upper right, a shaded region shows the previously believed shape of the Perseus arm, demarcated by a combination of masers and dust clouds. New measurements (middle right) show that some of these dust clouds are much closer or farther from the Sun than originally thought. As a result, the Perseus arm may be much clumpier and less well-defined (lower right). Credits: Science: Joshua Peek (STScI) - Illustration: Robert L. Hurt (Caltech, IPAC), Leah Hustak (STScI). Release images

Our Milky Way has long been known to be a spiral galaxy, shaped much like a fried egg with a bulbous central bulge and a thin, flat disk of stars. For decades, astronomers have struggled to map the Milky Way’s disk and its associated spiral arms. As the old saying goes, you can’t see the forest for the trees, and if you’re in the middle of the forest, how can you map its groves without a bird’s-eye view?

Previous work has suggested that the Milky Way is what’s known as a “grand design” spiral, with long, narrow, well-defined spiral arms. However, new research finds that at least one portion of the outer Milky Way (beyond the Sun’s location) is much more clumpy and chaotic.

“We have long had a picture of the galaxy in our minds, based on a combination of measurements and inference,” said Josh Peek of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “This work calls that picture into question. We don’t see evidence that pieces we’ve been connecting up are actually connected.”

Distances are Key

When mapping our galaxy, the biggest challenge is finding the distance to any given star, star cluster, or gas clump. The gold standard is to use parallax measurements of naturally occurring radio sources called masers, some of which are found in high-mass star-forming regions. However, this technique inevitably leaves gaps.

To fill those gaps, astronomers switch from examining star-forming regions to gas clouds, and more specifically, the motions of those gas clouds. In an ideal situation, the line-of-sight motion we measure for a gas cloud is directly related to its distance due to the overall rotation of the Milky Way. As a result, by measuring gas velocities, we can determine distances and hence the underlying structure of the galaxy.

The question then becomes, what about a non-ideal situation? While the motion of any given gas cloud might be dominated by its rotation around the galactic center, it undoubtedly has some additional, more random motions as well. Can those extra motions throw off our maps?

Chunky and Lumpy

To investigate this question, Peek and his colleagues examined not the gas, but the dust. In general within our galaxy, gas and dust are closely associated, so if you can map one, you also map the other.)

3D dust maps can be created by examining the colors of large collections of stars spread across the sky. The more dust that is between the star and our telescope, the redder the star will appear compared to its natural color.)

Peek and his team examined a region of space known as the Perseus spiral arm, which is beyond our Sun in the Milky Way’s disk. They compared the distances measured via dust reddening to those determined by the velocity relationship. They found that many of the clouds do not, in fact, lie at the distance of the Perseus arm, but instead stretch along a distance of some 10,000 light-years.)

“We don’t have long, skinny spiral arms after all, at least in this section of the galaxy. There are chunks and lumps that don’t look like anything,” explained Peek. “It’s a good possibility that the outer disk of the Milky Way resembles the nearby galaxy Messier 83, with shorter, chopped-up pieces of arms.”

Revising Our Map
While this latest research focused on the outer Milky Way, Hubble Fellow Catherine Zucker, a member of Peek’s team at STScI, is planning to extend that work to the inner Milky Way. The region interior to the Sun’s orbit is where the spiral arms that are most actively forming stars reside.

Zucker plans to create 3D dust maps using existing large-scale infrared surveys to measure the reddening of some 1 to 2 billion stars. By linking those new dust maps with existing gas velocity surveys, astronomers can refine our map of the inner Milky Way much as they have already done with the outer galaxy.

“Previous 3D dust mapping efforts have largely relied on data at wavelengths visible to the human eye. No one has used deep infrared data to create a 3D dust map,” said Zucker. “We may find that this region, like the Perseus arm, is more chaotic and less well defined.”

Even more insights may come from the upcoming Nancy Grace Roman Space Telescope and Vera Rubin Observatory. The Roman Space Telescope will have the capability to map the entire galactic plane in a few hundred hours. Also, its infrared measurements will cut through the dust.

“We could see clear to the other side of the galaxy for the first time. If a survey like this is selected for Roman, it would be stunning,” said Peek.)

Rubin, on the other hand, will be able to make deep observations of faint objects at a variety of optical wavelengths. By combining Roman’s infrared view of the sky with Rubin’s deep, multi-wavelength optical data, we may finally map our own cosmic “forest.”

This work is accepted for publication in The Astrophysical Journal.

The Space Telescope Science Institute is expanding the frontiers of space astronomy by hosting the science operations center of the Hubble Space Telescope, the science and mission operations centers for the James Webb Space Telescope, and the science operations center for the Nancy Grace Roman Space Telescope. STScI also houses the Barbara A. Mikulski Archive for Space Telescopes (MAST) which is a NASA-funded project to support and provide to the astronomical community a variety of astronomical data archives, and is the data repository for the Hubble, Webb, Roman, Kepler, K2, TESS missions and more. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.


Media Contact:

Christine Pulliam[
Space Telescope Science Institute, Baltimore, Maryland

Contact us: Direct inquiries to the News Team.

Related links and documents:

Science Paper: The science paper by J. Peek et al., PDF (9.64 MB)


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Saturday, December 18, 2021

Super-bright stellar explosion is likely a dying star giving birth to a black hole or neutron star

An artist’s impression of the mysterious burst AT2018cow.
Credits:Credit: National Astronomical Observatory of Japan

The discovery, based on an unusual event dubbed “the Cow,” may offer astronomers a new way to spot infant compact objects.

In June of 2018, telescopes around the world picked up a brilliant blue flash from the spiral arm of a galaxy 200 million light years away. The powerful burst appeared at first to be a supernova, though it was much faster and far brighter than any stellar explosion scientists had yet seen. The signal, procedurally labeled AT2018cow, has since been dubbed simply “the Cow,” and astronomers have catalogued it as a fast blue optical transient, or FBOT — a bright, short-lived event of unknown origin.

Now an MIT-led team has found strong evidence for the signal’s source. In addition to a bright optical flash, the scientists detected a strobe-like pulse of high-energy X-rays. They traced hundreds of millions of such X-ray pulses back to the Cow, and found the pulses occurred like clockwork, every 4.4 milliseconds, over a span of 60 days.

Based on the frequency of the pulses, the team calculated that the X-rays must have come from an object measuring no more than 1,000 kilometers wide, with a mass smaller than 800 suns. By astrophysical standards, such an object would be considered compact, much like a small black hole or a neutron star.

Their findings, published today in the journal Nature Astronomy, strongly suggest that AT2018cow was likely a product of a dying star that, in collapsing, gave birth to a compact object in the form of a black hole or neutron star. The newborn object continued to devour surrounding material, eating the star from the inside — a process that released an enormous burst of energy.

“We have likely discovered the birth of a compact object in a supernova,” says lead author Dheeraj “DJ” Pasham, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “This happens in normal supernovae, but we haven’t seen it before because it’s such a messy process. We think this new evidence opens possibilities for finding baby black holes or baby neutron stars.”



“The core of the Cow”

AT2018cow is one of many “astronomical transients” discovered in 2018. The “cow” in its name is a random coincidence of the astronomical naming process (for instance, “aaa” refers to the very first astronomical transient discovered in 2018). The signal is among a few dozen known FBOTs, and it is one of only a few such signals that have been observed in real-time. Its powerful flash — up to 100 times brighter than a typical supernova — was detected by a survey in Hawaii, which immediately sent out alerts to observatories around the world.

“It was exciting because loads of data started piling up,” Pasham says. “The amount of energy was orders of magnitude more than the typical core collapse supernova. And the question was, what could produce this additional source of energy?”

Astronomers have proposed various scenarios to explain the super-bright signal. For instance, it could have been a product of a black hole born in a supernova. Or it could have resulted from a middle-weight black hole stripping away material from a passing star. However, the data collected by optical telescopes haven’t resolved the source of the signal in any definitive way. Pasham wondered whether an answer could be found in X-ray data.

“This signal was close and also bright in X-rays, which is what got my attention,” Pasham says. “To me, the first thing that comes to mind is, some really energetic phenomenon is going on to generate X-rays. So, I wanted to test out the idea that there is a black hole or compact object at the core of the Cow.”

Finding a pulse

The team looked to X-ray data collected by NASA’s Neutron Star Interior Composition Explorer (NICER), an X-ray-monitoring telescope aboard the International Space Station. NICER started observing the Cow about five days after its initial detection by optical telescopes, monitoring the signal over the next 60 days. This data was recorded in a publicly available archive, which Pasham and his colleagues downloaded and analyzed.

The team looked through the data to identify X-ray signals emanating near AT2018cow, and confirmed that the emissions were not from other sources such as instrument noise or cosmic background phenomena. They focused on the X-rays and found that the Cow appeared to be giving off bursts at a frequency of 225 hertz, or once every 4.4 milliseconds.

Pasham seized on this pulse, recognizing that its frequency could be used to directly calculate the size of whatever was pulsing. In this case, the size of the pulsing object cannot be larger than the distance that the speed of light can cover in 4.4 milliseconds. By this reasoning, he calculated that the size of the object must be no larger than 1.3x108 centimeters, or roughly 1,000 kilometers wide.

“The only thing that can be that small is a compact object — either a neutron star or black hole,” Pasham says.

The team further calculated that, based on the energy emitted by AT2018cow, it must amount to no more than 800 solar masses.

“This rules out the idea that the signal is from an intermediate black hole,” Pasham says.

Apart from pinning down the source for this particular signal, Pasham says the study demonstrates that X-ray analyses of FBOTs and other ultrabright phenomena could be a new tool for studying infant black holes.

“Whenever there’s a new phenomenon, there’s excitement that it could tell something new about the universe,” Pasham says. “For FBOTs, we have shown we can study their pulsations in detail, in a way that’s not possible in the optical. So, this is a new way to understand these newborn compact objects.”

This research was supported, in part, by NASA.

Jennifer Chu | MIT News Office


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Friday, December 17, 2021

Astronomers just got better at finding "bright" Black Holes

A spiral galaxy named NGC 4051 — about 45 million light-years from Earth
Credit: ESA/Hubble & NASA, D. Crenshaw and O. Fox

One of the galaxies involved in the study
Credit: GAMA Survey Team-ICRAR/UWA, and the KiDS and VIKING Teams

Astronomers have a new way of detecting active black holes in the Universe and measuring how much matter they are sucking in.

The technique can be applied to millions of galaxies, searching for bright, supermassive black holes at the centre of the galaxies.

Lead author Jessica Thorne, a PhD student at the University of Western Australia node of the International Centre for Radio Astronomy Research, said active black holes are typically found in the largest galaxies in the Universe.


“The black holes we’re looking for are between a million and a billion times more massive than our Sun,” she said.

“As they suck in matter from around them, the matter gets super-heated because of friction and becomes very, very luminous.

“And when they’re active, these black holes can outshine the rest of the galaxy.”

Until now, identifying bright black holes has been challenging, with astronomers having to specifically look for them using complex methods unique to different types of telescopes.

Instead, the new technique works on typical telescope observations that already exist for millions of galaxies.

“We can identify these active black holes and look at how much light they’re emitting, but also measure the properties of the galaxy it is in at the same time,” Thorne said.

“By doing both at once, we can have a better idea of exactly how the black hole is impacting its host galaxy.”

The researchers developed the new technique by using an algorithm called ProSpect to model emission from galaxies and black holes at different wavelengths of light.

They then applied the method to almost half a million galaxies from Anglo-Australian Telescope’s DEVILS survey.

They also applied it to more than 200,000 galaxies from the GAMA survey, which brings together observations from six of the world’s best ground and space-based telescopes.

A mosaic of some of the galaxies involved in the study
Credit: GAMA Survey Team-ICRAR/UWA, and the KiDS and VIKING Teams

“One of the reasons we’ve ignored them in the past is because it’s hard to find them all,” she said.

“We don’t really understand these bright black holes to incorporate them into our modelling with sufficient detail.”


Galaxy NGC 5548. At its heart, though not visible here, is a supermassive black hole behaving in a strange and unexpected manner. Researchers detected a clumpy gas stream flowing quickly outwards and blocking 90 percent of the X-rays emitted by the black hole. This activity could provide insights into how supermassive black holes interact with their host galaxies. Credit: ESA/Hubble, A. Riess et al., J. Greene

Dr Bellstedt said the new technique is easier, more consistent and more thorough.

“It suddenly means we can look for active black holes in so many more places than we were able to before,” she said.

“It’s going to help us search more galaxies, and look further back in time to the distant Universe.”

Supermassive black holes are thought to have a huge impact on how galaxies evolve.

“We think that an active black hole in a galaxy is able to decrease the amount of star formation really quickly and stop the galaxy from growing any further,” Thorne said. “It can effectively kill it.”

With observations from new telescopes such as the James Webb Space Telescope, the Vera C. Rubin Observatory in Chile, and the Square Kilometre Array in Australia and South Africa, astronomers may be able to apply the technique to millions of galaxies at once.

“It’s exciting to think about how many doors this has unlocked for the future,” Thorne said.

Publication

‘Deep Extragalactic VIsible Legacy Survey (DEVILS): Identification of AGN through SED Fitting and the Evolution of the Bolometric AGN Luminosity Function’, published in Monthly Notices of the Royal Astronomical Society on December 14th, 2021.

Research Paper
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Thursday, December 16, 2021

Watch stars move around the Milky Way’s supermassive black hole in deepest images yet

ESO’s VLTI images of stars at the centre of the Milky Way
 
Stars around Sgr A* in March 2021
 
Stars around Sgr A* in May 2021
 
Stars around Sgr A* in June 2021

Stars around Sgr A* in July 2021
 
Wide-field view of the centre of the Milky Way
 
Sagittarius A* in the constellation of Sagittarius



Videos

Watch Stars Move Around our Galaxy’s Central Black Hole (ESOcast 248 Light)
Watch Stars Move Around our Galaxy’s Central Black Hole (ESOcast 248 Light) 
 
Animated sequence of the VLTI images of stars around the Milky Way’s central black hole
Animated sequence of the VLTI images of stars around the Milky Way’s central black hole 
 
Zooming into the black hole at the centre of our galaxy
Zooming into the black hole at the centre of our galaxy 
 



The European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI) has obtained the deepest and sharpest images to date of the region around the supermassive black hole at the centre of our galaxy. The new images zoom in 20 times more than what was possible before the VLTI and have helped astronomers find a never-before-seen star close to the black hole. By tracking the orbits of stars at the centre of our Milky Way, the team has made the most precise measurement yet of the black hole’s mass.

“We want to learn more about the black hole at the centre of the Milky Way, Sagittarius A*: How massive is it exactly? Does it rotate? Do stars around it behave exactly as we expect from Einstein’s general theory of relativity? The best way to answer these questions is to follow stars on orbits close to the supermassive black hole. And here we demonstrate that we can do that to a higher precision than ever before,” explains Reinhard Genzel, a director at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany who was awarded a Nobel Prize in 2020 for Sagittarius A* research. Genzel and his team’s latest results, which expand on their three-decade-long study of stars orbiting the Milky Way's supermassive black hole, are published today in two papers in Astronomy & Astrophysics.

On a quest to find even more stars close to the black hole, the team, known as the GRAVITY collaboration, developed a new analysis technique that has allowed them to obtain the deepest and sharpest images yet of our Galactic Centre. “The VLTI gives us this incredible spatial resolution and with the new images we reach deeper than ever before. We are stunned by their amount of detail, and by the action and number of stars they reveal around the black hole,” explains Julia Stadler, a researcher at the Max Planck Institute for Astrophysics in Garching who led the team’s imaging efforts during her time at MPE. Remarkably, they found a star, called S300, which had not been seen previously, showing how powerful this method is when it comes to spotting very faint objects close to Sagittarius A*.

With their latest observations, conducted between March and July 2021, the team focused on making precise measurements of stars as they approached the black hole. This includes the record-holder star S29, which made its nearest approach to the black hole in late May 2021. It passed it at a distance of just 13 billion kilometres, about 90 times the Sun-Earth distance, at the stunning speed of 8740 kilometres per second. No other star has ever been observed to pass that close to, or travel that fast around, the black hole.

The team’s measurements and images were made possible thanks to GRAVITY, a unique instrument that the collaboration developed for ESO’s VLTI, located in Chile. GRAVITY combines the light of all four 8.2-metre telescopes of ESO’s Very Large Telescope (VLT) using a technique called interferometry. This technique is complex, “but in the end you arrive at images 20 times sharper than those from the individual VLT telescopes alone, revealing the secrets of the Galactic Centre,” says Frank Eisenhauer from MPE, principal investigator of GRAVITY.

“Following stars on close orbits around Sagittarius A* allows us to precisely probe the gravitational field around the closest massive black hole to Earth, to test General Relativity, and to determine the properties of the black hole,” explains Genzel. The new observations, combined with the team’s previous data, confirm that the stars follow paths exactly as predicted by General Relativity for objects moving around a black hole of mass 4.30 million times that of the Sun. This is the most precise estimate of the mass of the Milky Way’s central black hole to date. The researchers also managed to fine-tune the distance to Sagittarius A*, finding it to be 27 000 light-years away.

To obtain the new images, the astronomers used a machine-learning technique, called Information Field Theory. They made a model of how the real sources may look, simulated how GRAVITY would see them, and compared this simulation with GRAVITY observations. This allowed them to find and track stars around Sagittarius A* with unparalleled depth and accuracy. In addition to the GRAVITY observations, the team also used data from NACO and SINFONI, two former VLT instruments, as well as measurements from the Keck Observatory and NOIRLab’s Gemini Observatory in the US.

GRAVITY will be updated later this decade to GRAVITY+, which will also be installed on ESO’s VLTI and will push the sensitivity further to reveal fainter stars even closer to the black hole. The team aims to eventually find stars so close that their orbits would feel the gravitational effects caused by the black hole’s rotation. ESO’s upcoming Extremely Large Telescope (ELT), under construction in the Chilean Atacama Desert, will further allow the team to measure the velocity of these stars with very high precision. “With GRAVITY+’s and the ELT’s powers combined, we will be able to find out how fast the black hole spins,” says Eisenhauer. “Nobody has been able to do that so far.”


More Information

This research was presented in two GRAVITY Collaboration papers to appear in Astronomy & Astrophysics.

The team who authored the paper “The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits” (doi:10.1051/0004-6361/202142465) is composed of: R. Abuter (European Southern Observatory, Garching, Germany [ESO]), A. Amorim (Universidade de Lisboa - Faculdade de Ciências, Portugal and Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Portugal [CENTRA]),  M. Bauböck (Max Planck Institute for Extraterrestrial Physics, Garching, Germany [MPE] and Department of Physics, University of Illinois, USA), J. P. Berger (Univ. Grenoble Alpes, CNRS, Grenoble, France [IPAG] and ESO), H. Bonnet (ESO), G. Bourdarot (IPAG and MPE), W. Brandner (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), V. Cardoso (CENTRA and CERN, Genève, Switzerland), Y. Clénet (Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, Meudon, France [LESIA]), Y. Dallilar (MPE), R. Davies (MPE), P. T. de Zeeuw (Sterrewacht Leiden, Leiden University [Leiden], The Netherlands and MPE), J. Dexter (Department of Astrophysical & Planetary Sciences, JILA, Duane Physics Bldg.,University of Colorado [Colorado], Boulder, USA), A. Drescher (MPE), A. Eckart (1st Institute of Physics, University of Cologne, Germany [Cologne] and Max Planck Institute for Radio Astronomy, Bonn, Germany), F. Eisenhauer (MPE), N. M. Förster Schreiber (MPE), P. Garcia (Faculdade de Engenharia, Universidade do Porto, Portugal and CENTRA), F. Gao (Hamburger Sternwarte, Universität Hamburg, Germany and MPE), E. Gendron (LESIA), R. Genzel (MPE and Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, USA), S. Gillessen (MPE), M. Habibi (MPE), X. Haubois (European Southern Observatory, Santiago, Chile [ESO Chile]), G. Heißel (LESIA), T. Henning (MPIA), S. Hippler (MPIA), M. Horrobin (Cologne), L. Jochum (ESO Chile), L. Jocou (IPAG), A. Kaufer (ESO Chile), P. Kervella (LESIA), S. Lacour (LESIA), V. Lapeyrère (LLESIA), J.-B. Le Bouquin (IPAG), P. Léna (LESIA), D. Lutz (MPE), T. Ott (MPE), T. Paumard (LESIA), K. Perraut (IPAG), G. Perrin (LESIA), O. Pfuhl (ESO and MPE), S. Rabien (MPE), G. Rodríguez-Coira (LESIA), J. Shangguan (MPE), T. Shimizu (MPE), S. Scheithauer (MPIA), J. Stadler (MPE), O. Straub (MPE), C. Straubmeier (Cologne), E. Sturm (MPE), L. J. Tacconi (MPE), K. R. W. Tristram (ESO Chile), F. Vincent (LESIA), S. von Fellenberg (MPE), F. Widmann (MPE), E. Wieprecht (MPE), E. Wiezorrek (MPE), J. Woillez (ESO), S. Yazici MPE and Cologne), and A. Young (MPE). 

The team who authored the paper “Deep images of the Galactic Center with GRAVITY” (doi:10.1051/0004-6361/202142459)is composed of: R. Abuter (ESO), P. Arras (Max Planck Institute for Astrophysics [MPA], Garching, Germany and Department of Physics, Technical University Munich [TUM], Garching, Germany), M. Bauböck (MPE and Department of Physics, University of Illinois, USA), H. Bonnet (ESO), W. Brandner (MPIA), G. Bourdarot (IPAG and MPE), V. Cardoso (CENTRA and CERN), Y. Clénet (LESIA), P. T. de Zeeuw (Leiden and MPE), J. Dexter (Colorado and MPE), Y. Dallilar (MPE), A. Drescher (MPE), A. Eckart (Cologne and Max Planck Institute for Radio Astronomy, Bonn, Germany), F. Eisenhauer (MPE), T. Enßlin (MPA), N. M. Förster Schreiber (MPE), P. Garcia (Faculdade de Engenharia, Universidade do Porto, Portugal and CENTRA), F. Gao (Hamburger Sternwarte, Universität Hamburg, Germany and MPE),  E. Gendron (LESIA), R. Genzel (MPE and Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, USA), S. Gillessen (MPE), M. Habibi (MPE), X. Haubois (ESO Chile), G. Heißel (LESIA), T. Henning (MPIA), S. Hippler (MPIA), M. Horrobin (Cologne), A. Jiménez-Rosales (MPE), L. Jochum (ESO Chile), L. Jocou (IPAG), A. Kaufer (ESO Chile), P. Kervella (LESIA), S. Lacour (LESIA), V. Lapeyrère (LESIA), J.-B. Le Bouquin (IPAG), P. Léna (LESIA), D. Lutz (MPE), T. Ott (MPE) , T. Paumard (LESIA) , K. Perraut (IPAG) , G. Perrin (LESIA) , O. Pfuhl (ESO and MPE), S. Rabien (MPE), J. Shangguan (MPE), T. Shimizu (MPE), S. Scheithauer (MPIA), J. Stadler (MPE , O. Straub (MPE), C. Straubmeier (Cologne), E. Sturm (MPE), L.J. Tacconi (MPE), K. R. W. Tristram (ESO Chile), F. Vincent (LESIA), S. von Fellenberg (MPE), I. Waisberg (Department of Particle Physics & Astrophysics, Weizmann Institute of Science, Israel and MPE), F. Widmann (MPE), E. Wieprecht (MPE), E. Wiezorrek (MPE), J. Woillez (ESO), S. Yazici (MPE and Cologne), A. Young (MPE) and G. Zins (ESO).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration in astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 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’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its 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. Together with international partners, ESO operates APEX and ALMA on Chajnantor, two facilities that observe the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.


Links



Contacts

Reinhard Genzel
Director, Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3281
Email: genzel@mpe.mpg.de

Julia Stadler
Max Planck Institute for Astrophysics
Garching bei München, Germany
Tel: +49 89 30000 2205
Email: jstadler@mpe.mpg.de

Frank Eisenhauer
Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3563
Email: eisenhau@mpe.mpg.de

Stefan Gillessen
Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3839
Cell: +49 176 99 66 41 39
Email: ste@mpe.mpg.de

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

Source: ESO/News

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Wednesday, December 15, 2021

Gaia finds fossil spiral arms in Milky Way


All-sky map of the Milky Way in motion using the Gaia data. Areas with significant motion are shown in black/purple and those with relatively low motion in yellow. A number of large scale filamentary disc structures are evident about the midplane. The map also shows the Magellanic Clouds and their connecting stellar bridge to left, while the Sgr dwarf galaxy currently being torn apart can be seen on the right (main body). Credit: Laporte et al. Licence type Attribution (CC BY 4.0)

An international team of astronomers, led by researcher Chervin Laporte of the Institute of Cosmos Sciences of the University of Barcelona (ICCUB-IEEC), has used data from the Gaia space mission to create a new map of the Milky Way’s outer disc. Intriguingly, newly found structures include evidence for fossil spiral arms. The team published the new work in a paper in Monthly Notices of the Royal Astronomical Society: Letters.

The team analysed the Gaia motion data, available from December 2020, to identify coherent structures. Their resulting map revealed the existence of many previously unknown spinning filamentary structures at the edge of the disc. It also gave a sharper overall view of previously known structures. Numerical simulations predict such filamentary structures to form in the outer disc from past satellite interactions, but the sheer quantity of substructure revealed by this map was not expected and remains a mystery.

What could these structures possibly be? One possibility is that they are the remains of tidal arms from the Milky Way disc which were excited at different times by various satellite galaxies. Our Galaxy is now surrounded by 50 of these satellites and has engulfed numerous other galaxies in its past. At present, the Milky Way is thought to be being perturbed by the Sagittarius dwarf galaxy, But in its more distant past it interacted with another intruder, the Gaia Sausage, which has now dispersed its debris into the outskirts of our galaxy.

In an earlier study, the same team showed that one of the filamentary structures in the outer disc, the Anticenter Stream, had stars which were predominantly more than 8 billion years old. This makes it potentially too old to have been excited by Sagittarius alone and instead points to the Gaia Sausage.

Another possibility is that not all these structures are actual genuine fossil spiral arms but instead form the crests of large scale vertical distortions in the Milky Way disc. “We believe that discs respond to satellite impacts which set up vertical waves that propagate like ripples on a pond" says Laporte.

To try to distinguish between the two explanations, the team has now secured a dedicated follow-up programme with the William Herschel Telescope on the Canary Islands in order to study the properties of the stellar populations in each substructure. Future surveys will help shed light on the nature and origin of these heavenly wispy structures.

Laporte comments on their findings: “Typically this region of the Milky Way has remained poorly explored due to the intervening dust which severely obscures most of the Galactic midplane”. He adds, “While dust affects the luminosity of a star, its motion remains unaffected. We were certainly very excited to see that the Gaia motions data helped us uncover these filamentary structures! Now the challenge remains to figure what these things exactly are, how they came to be, why in such large numbers, and what they can tell us about the Milky Way, its formation and evolution."




Media Contacts:

Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)7802 877 699
press@ras.ac.uk

Gurjeet Kahlon
Royal Astronomical Society
Mob: +44 (0) 7802 877 700
press@ras.ac.uk

Science Contacts:

Dr Chervin F. P. Laporte
Distinguished Researcher / ERC Group Leader
Institute of Cosmos Sciences, University of Barcelona
chervin.laporte@icc.ub.edu

Professor Sergey E. Koposov
Reader in Observational Astronomy, University of Edinburgh
Affiliated Associate Professor, University of Cambridge
Royal Observatory, Edinburgh
sergey.koposov@ed.ac.uk

Professor Vasily Belokurov
Professor of Astronomy
Institute of Astronomy, University of Cambridge
vasily@ast.cam.ac.uk


Further information

The research appears in ‘Kinematics beats dust: unveiling nested substructure in the perturbed outer disc of the Milky Way’, Monthly Notices of the Royal Astronomical Society: Letters, C. F. P. Laporte, S. E. Koposov, V. Belokurov


Notes for Editors

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognises outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

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Tuesday, December 14, 2021

Stellar “Ashfall” Could Help Distant Planets Grow


Artist’s impression of the “Ashfall” in a protoplanetary disk. The dust particles swept up by the bipolar outflow from the center of the protoplanetary disk are piled up on the outer edge of the disk. (Credit: Kagoshima University) Original size (2.9MB)

The world’s first 3D simulation simultaneously considering dust motion and growth in a disk around a young star has shown that large dust from the central region can be entrained by and then ejected by gas outflows, and eventually fall back onto the outer regions of the disk where it may enable planetesimal formation. This process can be likened to volcanic “ashfall” where ash carried up by gas during an eruption falls back on the area around the volcano. These results help to explain observed dust structures around young protostars.

Observations by ALMA (Atacama Large Millimeter/submillimeter Array) have revealed gaps in protoplanetary disks of gas and dust around young stars. The gravitational effects of planets are thought to be one of the reasons for the formation of these rings. However, some rings are seen even further out than the position of Neptune in the Solar System. At these distances, dust, a vital component to planet formation, should be scarce. Furthermore, the dust is expected to move in towards the central region of the disk as it grows. So how planets can form in the outer regions has been a mystery.

A research team led by Yusuke Tsukamoto at Kagoshima University used ATERUI II, the world’s most powerful supercomputer dedicated to astronomy calculations at the National Astronomical Observatory of Japan, to perform the world’s first 3D simulation of dust motion and growth in a protoplanetary disk. The team found that large dust particles grown in the central region can be carried out perpendicular to the disk by streams of gas, called bipolar outflow, erupting out from the disk. This dust then drifts out from the outflow and gravity pulls it back down to the outer part of the disk. Tsukamoto comments, “Living in Kagoshima, in the shadow of the active volcano Mt. Sakurajima, I naturally thought of volcanic ashfall when I saw the simulation results.”

The simulation shows that this “stellar ashfall” can enrich large dust in the outer region of the protoplanetary disk and facilitate planetesimal formation, which may eventually cause planet formation.

These results appeared as Yusuke Tsukamoto et al. Yusuke Tsukamoto et al. ““Ashfall” induced by molecular outflow in protostar evolution” in the Astrophysical Journal Letters on October 15, 2021.


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