Astronomers Use Slime Mould to Map the Universe’s Largest Structures

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Map of the Cosmic Web Generated from Slime Mould Algorithm

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The Cosmic Web (Artist’s Impression)

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Zooming Through the Cosmic Web (Artist’s Impression)

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The behaviour of one of nature’s humblest creatures and archival data from the NASA/ESA Hubble Space Telescope are helping astronomers probe the largest structures in the Universe.

The single-cell organism known as slime mould (Physarum polycephalum) builds complex web-like filamentary networks in search of food, always finding near-optimal pathways to connect different locations.

In shaping the Universe, gravity builds a vast cobweb-like structure of filaments tying galaxies and clusters of galaxies together along invisible bridges of gas and dark matter hundreds of millions of light-years long. There is an uncanny resemblance between the two networks, one crafted by biological evolution, the other by the primordial force of gravity.

The cosmic web is the large-scale backbone of the cosmos, consisting primarily of dark matter and laced with gas, upon which galaxies are built. Even though dark matter cannot be seen, it makes up the bulk of the Universe’s material. Astronomers have had a difficult time finding these elusive strands, because the gas within them is too dim to be detected.

The existence of a web-like structure to the Universe was first hinted at in galaxy surveys in the 1980s. Since those studies, the grand scale of this filamentary structure has been revealed by subsequent sky surveys. The filaments form the boundaries between large voids in the Universe. Now a team of researchers has turned to slime mould to help them build a map of the filaments in the local Universe (within 100 million light-years of Earth) and find the gas within them.

They designed a computer algorithm, inspired by the behaviour of slime mould, and tested it against a computer simulation of the growth of dark matter filaments in the Universe. A computer algorithm is essentially a recipe that tells a computer precisely what steps to take to solve a problem.

The researchers then applied the slime mould algorithm to data containing the locations of over 37 000 galaxies mapped by the Sloan Digital Sky Survey. The algorithm produced a three-dimensional map of the underlying cosmic web structure.

They then analysed the light from 350 faraway quasars catalogued in the Hubble Spectroscopic Legacy Archive. These distant cosmic flashlights are the brilliant black-hole-powered cores of active galaxies, whose light shines across space and through the foreground cosmic web. Imprinted on that light was the telltale signature of otherwise invisible hydrogen gas that the team analysed at specific points along the filaments. These target locations are far from the galaxies, which allowed the research team to link the gas to the Universe’s large-scale structure.

“It’s really fascinating that one of the simplest forms of life actually enables insights into the very largest-scale structures in the Universe,” said lead researcher Joseph Burchett of the University of California (UC), U.S.A. “By using the slime mould simulation to find the location of the cosmic web filaments, including those far from galaxies, we could then use the Hubble Space Telescope’s archival data to detect and determine the density of the cool gas on the very outskirts of those invisible filaments. Scientists have detected signatures of this gas for over half a century, and we have now proven the theoretical expectation that this gas comprises the cosmic web.”

The survey further validates research that indicates intergalactic gas is organised into filaments and also reveals how far away gas is detected from the galaxies. Team members were surprised to find gas associated with the cosmic web filaments more than 10 million light-years away from the galaxies.

But that wasn’t the only surprise. They also discovered that the ultraviolet signature of the gas gets stronger in the filaments’ denser regions, but then disappears. “We think this discovery is telling us about the violent interactions that galaxies have in dense pockets of the intergalactic medium, where the gas becomes too hot to detect,” Burchett said.

The researchers turned to slime mould simulations when they were searching for a way to visualise the theorised connection between the cosmic web structure and the cool gas, detected in previous Hubble spectroscopic studies.

Then team member Oskar Elek, a computer scientist at UC Santa Cruz, discovered online the work of Sage Jenson, a Berlin-based media artist. Among Jenson’s works were mesmerizing artistic visualisations showing the growth of a slime mould’s tentacle-like network of structures moving from one food source to another. Jenson’s art was based on scientific work from 2010 by Jeff Jones of the University of the West of England in Bristol, which detailed an algorithm for simulating the growth of slime mould.

The research team was inspired by how the slime mould builds complex filaments to capture new food, and how this mapping could be applied to how gravity shapes the Universe, as the cosmic web constructs the strands between galaxies and galaxy clusters. Based on the simulation outlined in Jones’s paper, Elek developed a three-dimensional computer model of the buildup of slime mould to estimate the location of the cosmic web’s filamentary structure.

This analysis of the cosmic web in the local Universe also dovetails with observations published last autumn in the journal Science of the Universe’s filamentary structure much farther away, about 12 billion light-years from Earth, near the Universe’s beginning. In that study, astronomers analysed the energetic light from a young galaxy cluster illuminating the filaments of hydrogen gas connecting it.

The team’s paper will appear in the Astrophysical Journal Letters.

Source: ESA/Hubble/News

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More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of J. Burchett, O. Elek, N. Tejos, J. X. Prochaska, T. M. Tripp, R. Bordoloi, and A. G. Forbes

Image Credit: NASA, ESA, and J. Burchett and O. Elek (UC Santa Cruz)

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Links

• Images of Hubble
• HubbleSite release
• Science paper
• Link to SpaceScoop

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Contacts

Joseph N. Burchett
University of California
Santa Cruz, USA
Email: burchett@ucolick.org

Oskar Elek
University of California
Santa Cruz, USA
Email: oelek@ucsc.edu

Bethany Downer
ESA/Hubble, Public Information Officer
Garching, Germany
Email: bethany.downer@partner.eso.org

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Astronomers Catch Rare Eclipse Of A Double Brown Dwarf System

An artist's view of one of de Speculoos Telescopes, with the eclipsing binary brown dwarf in the sky. The third red dot is a third nearby brown dwarf, whick is also part of the same system. The book on the side shows the data that led to discovery. On the left page is the eclipse captured by Speculoos while the right page show the data form Keck Observatory and VLT. The illustration's copyright is University of Birminghan/Amanda J. Smith

Maunakea, Hawaii – Astronomers working on “first light” data from a newly commissioned telescope in Chile made a chance discovery that led to the identification of a rare eclipse of two brown dwarfs. The result, which includes data taken from W. M. Keck Observatory on Maunakea in Hawaii to help confirm the discovery, published today in the journal Nature Astronomy.

Sometimes called “failed stars,” brown dwarfs occupy a grey zone between stars and giant planets. They are unable to sustain the fusion of hydrogen into helium, a process that powers the light from normal stars like the sun; yet they appear to form like stars, only with less mass. They provide a critical link in scientists’ understanding of star and planet formation.

The chance discovery was led by an international team of researchers, including scientists at UC San Diego, working on a project called SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars), which aims to find planets orbiting the smallest stars, including brown dwarfs. SPECULOOS finds planets by detecting periodic dips in a star’s brightness as a planet passes in front of it, an event called a planetary transit. Astronomers predict that the smallest stars and brown dwarfs could host large populations of close-in, potentially habitable rocky planets, like the famous seven-planet system TRAPPIST-1 that was discovered in 2017 by members of the same team.

“This is a great example of scientific serendipity,” explained Adam Burgasser, professor of physics at UC San Diego and co-leading author on the study. “While searching for planets, we found an eclipsing brown dwarf binary, a system that is uniquely suited for studying the fundamental physics of these faint celestial objects.”

Soon after the construction of the first SPECULOOS telescopes in Chile, and during early testing observations, the team targeted the brown dwarf “2MASSW J1510478-281817,” also known as 2M1510, in the constellation Libra. In this case, the SPECULOOS observations picked up a distinct signal that led the researchers to speculate that 2M1510 might be two brown dwarfs instead of one, in orbit around each other.

“Among the first test observations we performed, we turned one of our telescopes to a known brown dwarf. But suddenly the object appeared to get dimmer for about 90 minutes, which indicated an eclipse just took place,” reported Michaël Gillon, principal investigator of the SPECULOOS project.

Artem Burdanov, a postdoctoral researcher at Massachusetts Institute of Technology and co-author on the study concurred, adding, “We rapidly realized that we were probably looking at two eclipsing brown dwarfs, one passing in front of the other, a configuration which is much rarer than planetary systems.”

The researchers were able to confirm their hypothesis using two powerful telescopes – the 10-meter Keck II telescope and the 8-meter Very Large Telescope (VLT) on Cerro Paranal in Chile, the same site as the SPECULOOS telescopes. Keck Observatory and VLT are each equipped with sensitive spectrometers (the Near-Infrared Spectrograph, or NIRSPEC, at Keck Observatory and VLT’s UV-Visual Échelle Spectrograph, or UVES) that can measure the velocities of celestial objects. In the case of 2M1510, the astronomers detected the velocities of both brown dwarfs as they orbit one another.

“From the very first spectrum we obtained, we could tell we had an exciting binary discovery,” said Burgasser, who led the spectroscopic analysis with current and former graduate students at UC San Diego’s Cool Star Lab. “It was thrilling to see the absorption lines move back and forth in perfect synchronicity, which allowed us to measure the mass of the binary.”

The detection of an eclipsing brown dwarf binary is extremely rare because the system needs to be precisely aligned with our line-of-sight to move in front of each other. Only one other such system has been identified to date. These systems allow astronomers to measure both the radii and masses of the brown dwarfs directly. 2M1510 is also unique in that it is among the few brown dwarfs that have a known age, due to its membership in a nearby cluster of young stars called the Argus moving group. The eclipsing binary is also part of a brown dwarf triple system—another rarity—with a third component orbiting at a much wider separation.

“Collecting a combination of mass, radius, and age is really rare for a star, let alone for a brown dwarf,” explained Amaury Triaud, Birmingham Fellow at the University of Birmingham in the UK who was the primary author of the study. “Usually one or more of these measurements is missing. By drawing all these elements together, we were able to verify theoretical models for how brown dwarfs cool, models which are over 30 years old. We found the models match remarkably well with the observations, a testament to human ingenuity.”

Source: W. M. Keck Observatory/News

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About NIRSPEC

The Near-Infrared Spectrograph (NIRSPEC) is a unique, cross-dispersed echelle spectrograph that captures spectra of objects over a large range of infrared wavelengths at high spectral resolution. Built at the UCLA Infrared Laboratory by a team led by Prof. Ian McLean, the instrument is used for radial velocity studies of cool stars, abundance measurements of stars and their environs, planetary science, and many other scientific programs. A second mode provides low spectral resolution but high sensitivity and is popular for studies of distant galaxies and very cool low-mass stars. NIRSPEC can also be used with Keck II’s adaptive optics (AO)system to combine the powers of the high spatial resolution of AO with the high spectral resolution of NIRSPEC. Support for this project was provided by the Heising-Simons Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two, 10-meter optical/infrared telescopes on the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems.

Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Catastrophic Collisions in Protoplanetary Disks

Striking images of protoplanetary disks with unique arced and spiral features, captured by the SPHERE instrument on ESO’s Very Large Telescope. [ESO]

Some of the most spectacular images to come out of observatories like the Atacama Large Millimeter/submillimeter Array (ALMA) or the Very Large Telescope (VLT) are detailed views of protoplanetary disks. These disks of gas and dust around young stars aren’t just smooth and featureless; instead, they exhibit arcs, rings, gaps, and spirals. What causes this impressive array of structure? 

Scientists have primarily focused on two explanations:

1. The structures are caused by the perturbations of massive baby planets interacting with the disk as they orbit.
2. The structures are generated by various instabilities within the disk that cause the gas and dust to clump.

A new study has now put forward an alternative explanation: the structures are the result of catastrophic, destructive collisions of planetesimals within the disk. Scientists Tatiana Demidova (Crimean Astrophysical Observatory) and Vladimir Grinin (Pulkovo Observatory of the Russian Academy of Sciences; St. Petersburg University, Russia) lay out their scenario of destruction in a recent publication.

This ALMA image of the protoplanetary disk surrounding the star HL Tauri reveals the detailed substructure of the disk. [ALMA (ESO/NAOJ/NRAO)]

Outcome of a Crash

Collisions of large bodies — planetesimals and planetary embryos — are likely common during the formation of planetary systems around young stars. Some gentle collisions may help build up the mass of these bodies as they grow into planets. But objects that smash together at high enough velocities will be completely destroyed in the process, generating an expanding cloud of many smaller bodies and particles.

This cloud won’t remain stationary, however; instead, it will continue to orbit within the protoplanetary disk. Due to the different speeds of the various particles, the initial debris clump should be sheared out into arced structures that might persist for multiple disk orbits.

Could this process faithfully reproduce the disk structures that we’ve observed with ALMA or the VLT? Demidova and Grinin conduct simulations to find out.

Simulated 1.3-mm observations of the evolution of an expanding debris cloud over 40 orbital periods of the cloud center. Time steps advance from top left to bottom right panel. Click to enlarge. [Demidova & Grinin 2019]

Dragging Debris in a Disk

By modeling an expanding debris cloud within a disk that starts at a distance of 30 AU from its solar-mass star, the authors show how the dust and gas will evolve over several disk orbits. They then produce simulated observations of the results at a wavelength of 1.3 mm.

The result? Demidova and Grinin find that as the dust cloud stretches, it successively reproduces all three structures we’ve seen in protoplanetary disks — first, it shapes into an arc, then a tightly wound spiral, and eventually into a ring. The simulated observations at 1.3 mm look very similar to various disk images we’ve captured.

There are still many open questions about the structure of the disks around young stars, but this work shows that there are also many potential answers. As planetary systems form, collisions may both grow planetary embryos and destroy them, possibly causing some of the disk features that we’ve observed. One thing is for certain: the environment around young stars is certainly dramatic!

Citation

“Catastrophic Events in Protoplanetary Disks and Their Observational Manifestations,” Tatiana V. Demidova and Vladimir P. Grinin 2019 ApJL 887 L15. doi:10.3847/2041-8213/ab59e0

 Source:  American Astronomical Society (AAS)

By Susanna Kohler

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ALMA Spots Metamorphosing Aged Star

ALMA image of the old star system W43A. The high velocity bipolar jets ejected from the central aged star are seen in blue, low velocity outflow is shown in green, and dusty clouds entrained by the jets are shown in orange. Credit: ALMA (ESO/NAOJ/NRAO), Tafoya et al.

Artist’s impression of W43A based on the ALMA observation results. Diffuse spherical gas was emitted from the star in the past. W43A has just started ejecting bipolar jets which entrain the surrounding material. Bright spots in radio emissions from water molecules are distributed around the interface of the jets and the diffuse gas. Credit: NAOJ.

An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) captured the very moment when an old star first starts to alter its environment. The star has ejected high-speed bipolar gas jets which are now colliding with the surrounding material; the age of the observed jet is estimated to be less than 60 years. These are key features to understand how the complex shapes of planetary nebulae are formed.

Sun-like stars evolve to puffed-up Red Giants in the final stage of their lives. Then, the star expels gas to form a remnant called a planetary nebula. There is a wide variety in the shapes of planetary nebulae; some are spherical, but others are bipolar or show complicated structures. Astronomers are interested in the origins of this variety, but the thick dust and gas expelled by an old star obscure the system and make it difficult to investigate the inner-workings of the process.

To tackle this problem, a team of astronomers led by Daniel Tafoya in Chalmers University of Technology, Sweden, pointed ALMA at W43A, an old star system in the constellation Aquila, the Eagle.

Thanks to ALMA’s high resolution, the team obtained a very detailed view of the space around W43A. “The most notable structures are its small bipolar jets,” says Tafoya, the lead author of the research paper published by the Astrophysical Journal Letters. The team found that the velocity of the jets is as high as 175 km per second, which is much higher than previous estimations. Based on this speed and the size of the jets, the team calculated the age of the jets to be less than a human life-span.

“Considering the youth of the jets compared to the overall lifetime of a star, it is safe to say we are witnessing the ‘exact moment’ that the jets have just started to shove through the surrounding gas,” explains Tafoya. “When the jets carve through the surrounding material in some 60 years, a single person can watch the progress in their life.”

In fact, the ALMA image clearly maps the distribution of dusty clouds entrained by the jets, which is telltale evidence that it is impacting on the surroundings.

The team assumes that this entrainment is the key to form a bipolar-shaped planetary nebula. In their scenario, the aged star originally ejects gas spherically and the core of the star loses its envelope. If the star has a companion, gas from the companion pours onto the core of the dying star, and a portion of this new gas forms the jets. Therefore, whether or not the old star has a companion is an important factor to determine the structure of the resulting planetary nebula.

“W43A is one of the peculiar so called ‘water fountain’ objects,” says Hiroshi Imai at Kagoshima University, Japan, a member of the team. “Some old stars show characteristic radio emissions from water molecules. We suppose that spots of these water emissions indicate the interface region between the jets and the surrounding material. We named them ‘water fountains,’ and it could be a sign that the central source is a binarity system launching a new jet.”

“There are only 15 ‘water fountain’ objects identified to date, despite the fact that more than 100 billion stars are included in our Milky Way Galaxy,” explains José Francisco Gómez at Instituto de Astrofísica de Andalucía, Spain. “This is probably because the lifetime of the jets is quite short, so we are very lucky to see such rare objects.”

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Additional Information

These observation results were presented in D. Tafoya et al. “Shaping the envelope of the asymptotic giant branch star W43A with a collimated fast jet” published by the Astrophysical Journal Letters on February 13, 2020.

The research team members are Daniel Tafoya (Calmers University of Technology), Hiroshi Imai (Kagoshima University), José F. Gómez (Instituto de Astrofísica de Andalucía, CSIC), Jun-ichi Nakashima (Sun Yat-sen University), Gabor Orosz (University of Tasmania/Xinjiang Astronomical Observatory), and Bosco H. K. Yung (Nicolaus Copernicus Astronomical Center)

This research was supported by MEXT KAKENHI (No. 16H02167), the Invitation Program for Foreign Researchers of the Japan Society for Promotion of Science (JSPS grant S14128), MINECO (Spain) Grant AYA2017-84390-C2-R (co-funded by FEDER), State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofisica de Andalucía (SEV-2017-0709), Australian Research Council Discovery project DP180101061 of the Australian government, CAS LCWR 2018-XBQNXZ-B-021, and National Key R&D Program 2018YFA0404602 of China.

The original press release was published by the National Astronomical Observatory of Japan (NAOJ), an ALMA partner on behalf of East Asia.

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) 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.

Scientific Paper

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Contacts

Nicolás Lira
Education and Public Outreach Coordinator
Joint ALMA Observatory, Santiago - Chile
Phone: +56 2 2467 6519
Cell phone: +56 9 9445 7726
Email: nicolas.lira@alma.cl

Masaaki Hiramatsu
Education and Public Outreach Officer, NAOJ Chile
Observatory
, Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: pio@eso.org

Iris Nijman
News and Public Information Manager
National Radio Astronomy Observatory Charlottesville, Virginia - USA
Cell phone: +1 (434) 249 3423
Email: inijman@nrao.edu

Source: Atacama Large Millimeter/submillimeter Array (ALMA)

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New ESO Study Evaluates Impact of Satellite Constellations on Astronomical Observations

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Areas of the sky most affected by satellite constellations

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Schematic showing the satellites that would be visible at a given time and place

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The sky above the ELT site

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Astronomers have recently raised concerns about the impact of satellite mega-constellations on scientific research. To better understand the effect these constellations could have on astronomical observations, ESO commissioned a scientific study of their impact, focusing on observations with ESO telescopes in the visible and infrared but also considering other observatories. The study, which considers a total of 18 representative satellite constellations under development by SpaceX, Amazon, OneWeb and others, together amounting to over 26 thousand satellites [1], has now been accepted for publication in Astronomy & Astrophysics.

The study finds that large telescopes like ESO's Very Large Telescope (VLT) and ESO's upcoming Extremely Large Telescope (ELT) will be "moderately affected" by the constellations under development. The effect is more pronounced for long exposures (of about 1000 s), up to 3% of which could be ruined during twilight, the time between dawn and sunrise and between sunset and dusk. Shorter exposures would be less impacted, with fewer than 0.5% of observations of this type affected. Observations conducted at other times during the night would also be less affected, as the satellites would be in the shadow of the Earth and therefore not illuminated. Depending on the science case, the impacts could be lessened by making changes to the operating schedules of ESO telescopes, though these changes come at a cost [2]. On the industry side, an effective step to mitigate impacts would be to darken the satellites.

The study also finds that the greatest impact could be on wide-field surveys, in particular those done with large telescopes. For example, up to 30% to 50% of exposures with the US National Science Foundation's Vera C. Rubin Observatory (not an ESO facility) would be "severely affected”, depending on the time of year, the time of night, and the simplifying assumptions of the study. Mitigation techniques that could be applied on ESO telescopes would not work for this observatory although other strategies are being actively explored. Further studies are required to fully understand the scientific implications of this loss of observational data and complexities in their analysis. Wide-field survey telescopes like the Rubin Observatory can scan large parts of the sky quickly, making them crucial to spot short-lived phenomena like supernovae or potentially dangerous asteroids. Because of their unique capability to generate very large data sets and to find observation targets for many other observatories, astronomy communities and funding agencies in Europe and elsewhere have ranked wide-field survey telescopes as a top priority for future developments in astronomy.

Professional and amateur astronomers alike have also raised concerns about how satellite mega-constellations could impact the pristine views of the night sky. The study shows that about 1600 satellites from the constellations will be above the horizon of an observatory at mid-latitude, most of which will be low in the sky — within 30 degrees of the horizon. Above this — the part of the sky where most astronomical observations take place — there will be about 250 constellation satellites at any given time. While they are all illuminated by the Sun at sunset and sunrise, more and more get into the shadow of the Earth toward the middle of the night. The ESO study assumes a brightness for all of these satellites. With this assumption, up to about 100 satellites could be bright enough to be visible with the naked eye during twilight hours, about 10 of which would be higher than 30 degrees of elevation. All these numbers plummet as the night gets darker and the satellites fall into the shadow of the Earth. Overall, these new satellite constellations would about double the number of satellites visible in the night sky to the naked eye above 30 degrees [3].

These numbers do not include the trains of satellites visible immediately after launch. Whilst spectacular and bright, they are short lived and visible only briefly after sunset or before sunrise, and — at any given time — only from a very limited area on Earth.

The ESO study uses simplifications and assumptions to obtain conservative estimates of the effects, which may be smaller in reality than calculated in the paper. More sophisticated modelling will be necessary to more precisely quantify the actual impacts. While the focus is on ESO telescopes, the results apply to similar non-ESO telescopes that also operate in the visible and infrared, with similar instrumentation and science cases.

Satellite constellations will also have an impact on radio, millimetre and submillimetre observatories, including the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX). This impact will be considered in further studies.

ESO, together with other observatories, the International Astronomical Union (IAU), the American Astronomical Society (AAS), the UK Royal Astronomical Society (RAS), and other societies, is taking measures to raise the awareness of this issue in global fora such as the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) and the European Committee on Radio Astronomy Frequencies (CRAF). This is being done while exploring with the space companies practical solutions that can safeguard the large-scale investments made in cutting-edge ground-based astronomy facilities. ESO supports the development of regulatory frameworks that will ultimately ensure the harmonious coexistence of highly promising technological advancements in low Earth orbit with the conditions that enable humankind to continue its observation and understanding of the Universe.

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Notes

[1] Many of the parameters characterising satellite constellations, including the total number of satellites, are changing on a frequent basis. The study assumes 26,000 constellation satellites in total will be orbiting the Earth, but this number could be higher.

[2] Examples of mitigation measures include: computing the position of the satellites to avoid observing where one will pass; closing the telescope shutter at the precise moment when a satellite crosses the field of view; and constraining observations to areas of the sky that are in Earth’s shadow, where satellites are not illuminated by the sun. These methods, however, are not suitable for all science cases.

[3]  It is estimated that about 34 000 objects greater than 10 cm in size are currently orbiting the Earth. Of these, about 5500 are satellites, including about 2300 functional ones. The remainder are space debris, including rocket upper stages and satellite launch adapters. About 2000 of these objects are above the horizon at any given place at any one time. During twilight hours, about 5–10 of them are illuminated by the Sun and bright enough to be seen with the naked eye.

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More information

The study, “On the impact of Satellite Constellations on Astronomical Observations with ESO Telescopes in the Visible and Infrared Domains”, by O. Hainaut and A. Williams, will appear in Astronomy and Astrophysics, and is available here and on ArXiv.

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Links

• Science paper
• ESO announcement "Satellite Constellations and their Impact on Astronomy"
• IAU press release "Understanding the Impact of Satellite Constellations on Astronomy"
• AAS post "AAS Works to Mitigate Impact of Satellite Constellations on Ground-Based Observing"
• Rubin Observatory Legacy Survey of Space and Time (LSST) "Impact on Optical Astronomy of LEO Satellite Constellations"

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Contacts

Olivier R. Hainaut
Garching bei München, Germany
Tel: +49 89 3200 6752
Cell: +49 151 2262 0554
Email: ohainaut@eso.org

Andrew Williams
ESO External Relations Officer
Garching bei München, Germany
Tel: +49 89 320 062 78
Email: awilliam@eso.org

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: pio@eso.org

Source: ESO/News

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Detection of the relativistic cocoon structure around the ultra-relativistic Jet

Imaginary picture of GRB jet

Credit: Yuji Urata

Using the combined power of the Submillimeter Array (SMA) and NASA’s and JAXA’s satellite missions, a team led by Mr. Wei Ju Chen, Prof. Urata and Dr. Asada (ASIAA) in Taiwan has confirmed the shocked jet cocoon afterglow of a Gamma-Ray Burst (1) through the observation of an energetic GRB, GRB160623A. The team utilizes multi-frequency observations including long-term monitoring in a submillimeter range to characterize the two components of jets. For both the two populations of the GRBs, short and long GRBs, understanding of the jet and its structure is essential. Although the structured jet of short GRB has not yet observationally confirmed, numerous theoretical models are trying to use the off-axis viewing of the short GRB jet including its structures to explain the unusual weak short GRB170817 associated with the gravitational wave transient GW170817 caused by binary neutron star merger. Therefore, this result would be feedback to the multi-messenger (2) astrophysics.

GRB is believed to be stellar explosions accompanied with relativistic outflows and narrowly-collimated jets. Since direct imaging of GRB jets is impossible unlike AGN jets, studying the GRB jet collimation and its structure have been made by the multi-frequency monitoring observations. Based on the past observations, the typical value of GRB jet opening-angles is 3.5 deg, which is in the same order with that of AGN jets (1.5 deg). In this time, the team made use of the submillimeter-observations using SMA, which has been playing an essential role in revealing new insights of the GRB afterglows (3) and relativistic transients (4). Their observations revealed that the temporal and spectral evolutions of the radio afterglow agree with those expected from a synchrotron radiation modelling with typical physical parameters except for the fact that the observed wide jet opening angle (~30 deg) for the submillimeter emission is significantly larger than the theoretical maximum opening angle. By contrast, the opening angle ( less  then 4.5 deg) of the X-ray afterglow is consistent with the typical value of GRB jets. Since the theory of the relativistic cocoon afterglow emission is similar to that of the regular afterglow with the jet opening angle wider than that of regular afterglow, the observed radio emission can be interpreted as the shocked jet cocoon emission. This result therefore indicates that the two components of the jets observed in the GRB 160623A afterglow is caused by the jet and the shocked jet cocoon afterglows.

Prof. Urata emphasizes that “the jet structure and unification of various relativistic transients with viewing angle are crucial for multi-messenger astrophysics and submillimeter observations become the critical part of the transient sciences. On the other hand, the unification could be also revealed with the wide-field optical surveys such as ongoing Subaru/Hyper-Suprime-Cam.”

Dr. Asada (ASIAA) also mentions that “The Greenland Telescope (ASIAA has been preparing for the further black hole imaging as the EHT collaboration) would also enrich the astrophysical jet sciences like this result on GRBs.”.

Finally, the research team deeply thanks for the staffs of SMA for various supports for this observing project.  

Source: Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)

Copyright (2020) ASIAA/Lauren Huang

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Notes:

(1) Gamma-Ray Bursts (GRBs):

Gamma-Ray Bursts (GRBs) are highly energetic explosions in the universe, and are currently being exploited as probes of first-generation stars and gravitational wave transients. In fact, the distant events at the cosmic reionization epoch and short GRB coincident with a gravitational wave transient have both already been observed, respectively.

(2) Multi-messenger astronomy:

Multi-messenger astronomy is astronomy based on the coordinated observation and interpretation of disparate “messenger” signals, which are electromagnetic radiation, gravitational waves, neutrinos, and cosmic rays.

(3) Astronomers Study Mysterious New Type of Cosmic Blast (Press Release of ALMA)

(4) ALMA Reveals Origin of Mysterious Blast: AT2018cow originated from supernova in a strongly-magnetized, dense environmentPaper and Research Team (Press Release of ALMA-Japan)

These observation results were published as Chen, W. J, Urata, Y. et al. “Two Component Jets of GRB160623A as Shocked Jet cocoon afterglow” in Astrophysical Journal Letters 891: L 15.

The research team members are: Wei Ju Chen (NCU), Yuji Urata (NCU), Kuiyun Huang (CYCU), Satoko Takahashi(JAO/NAOJ/SOKENDAI), Glen Petitpas (Harvard-Smithsonian Center for Astrophysics), and Keiichi Asada (ASIAA)

This work is supported by the Ministry of Science and Technology of Taiwan grants MOST 105-2112-M-008-013-MY3 and 106-2119-M-001-027.

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Globular cluster billowing in the Galactic wind

Globular cluster 47 Tuc (upper right) and the Small Magellanic Cloud in the same field-of-view. The inset is a close-up of the cluster showing the detected magnetic field in a colour scale. The lines indicate the effect of the Galactic wind on the magnetic field. © ESO/VISTA VMC (background image); F. Abbate et al., Nature Astronomy (inset)

Investigation of pulsars in 47 Tuc provides constraints on the magnetic field in the halo of the Milky Way

March 02, 2020. The Galactic magnetic field plays an important role in the evolution of our Galaxy, but its small-scale behaviour is still poorly known. It is also unknown whether it permeates the halo of the Galaxy or not. By using observations of pulsars in the halo globular cluster 47 Tuc, an international research team led by Federico Abbate from the Max Planck Institute for Radio Astronomy in Bonn, Germany who started this work at University of Milano Bicocca and INAF-Astronomical Observatory of Cagliari, could probe the Galactic magnetic field at scales of a few light years for the first time. They discovered an unexpected strong magnetic field in the direction of the cluster. This magnetic field points perpendicularly to the Galactic disk and could be explained by an interaction with the Galactic wind. This is a magnetized outflow that extends from the Galactic disk into the surrounding halo and its existence has never been proven before.

47 Tucanae, or 47 Tuc as it is usually called, is a spectacular globular cluster visible with the naked eye in the constellation “Tucana” in the southern sky close to the Small Magellanic Cloud. The first pulsar in this cluster was discovered in 1990 with the Parkes 64-m radio telescope in Australia, and soon more were found with the same telescope. Currently there are 25 pulsars known in 47 Tuc. For this reason, this very well-studied globular cluster became one of the most important for pulsar astronomers as well.

Pulsars are periodic sources that allow astronomers to measure the so-called dispersion measure which is a delay of the arrival time of the single pulses at different frequencies. This delay is proportional to the density of free electrons along the path from the pulsar to the Earth. “In 2001, we noticed that the pulsars in the far side of the cluster had a higher dispersion measure than those in the near side, which implied the presence of gas in the cluster”, says Paulo Freire from the Max Planck Institute for Radio Astronomy (MPIfR) who led a number of research projects on 47 Tuc.

What makes 47 Tuc even more interesting is that the cluster is at a distance of about 15,000 light years, located in a relatively undisturbed area in the Galactic halo. The halo surrounds the Galactic disk and hosts very few stars and very small quantities of gas. “The pulsars in this cluster can give us a unique and unprecedented insight into the large-scale geometry of the magnetic field in the Galactic halo.” says Federico Abbate, lead author of the paper and now working at MPIfR, who performed the analysis during his PhD at the University of Milano-Bicocca and at INAF - Cagliari Astronomical Observatory.

Understanding the geometry and strength of Galactic magnetic fields is essential to draw a complete picture of our Galaxy. The magnetic fields can affect star formation, regulate the propagation of high-energy particles and help establish the presence of a Galactic scale outflow of gas from the disk to the surrounding halo. Despite their importance, the large-scale geometry of the magnetic fields in the Galactic halo is not fully known.

Magnetic fields are not observable directly, but scientists make use of the effects they have on the low-density plasma that permeates the Galactic disk. In this plasma, the electrons are separated from the atomic nuclei and they behave like small magnets. The electrons are attracted by the magnetic field and are forced to orbit the magnetic field lines, emitting radiation known as synchrotron radiation. Other than emitting their own radiation, the free electrons also leave a peculiar signature on the polarized radiation that travels through the plasma. The electromagnetic field of the polarized radiation oscillates always in the same direction and the electrons in a magnetized medium will rotate this direction by different amounts at different frequencies. This effect is called Faraday rotation and is measurable only at radio frequencies.

Observations of polarized radio emission work well to constrain the magnetic field in the Galactic disk where the plasma is dense enough. In the Galactic halo, however, the plasma density is too low to directly observe the effects. For this reason, the geometry and strength of the magnetic field in the halo is unknown and models predict that it could either be parallel or perpendicular to the disk. The presence of a magnetized outflow from the disk to the halo has been suggested following observations in other galaxies. It can also explain the diffuse X-ray emission in the Galaxy.

Recent observations of the pulsars in 47 Tuc, also performed with the Parkes radio telescope in Australia, were able to measure their polarized radio emission and their Faraday rotation. These reveal the presence of a magnetic field in the globular cluster that is surprisingly strong - so strong, in fact, that it cannot be maintained by the globular cluster itself but requires an external source located in the Galactic halo. The direction of the magnetic field is compatible with that of the Galactic wind, perpendicular to the Galactic disk. The interaction of the Galactic wind and the cluster forms a shock that amplifies the magnetic field to the values observed.

This work reveals a new technique to study the magnetic field in the Galactic halo. This cluster is a perfect target for observations with the innovative MeerKAT radio telescope in South Africa. “In the near future, the MeerKAT telescope will greatly improve the polarization measurements and possibly not only confirm the presence of the Galactic wind but also constrain its properties,” says Andrea Possenti from the INAF – Cagliari Astronomical Observatory who is involved in the globular cluster pulsars efforts with MeerKAT together with the MPIfR. Moreover, this powerful telescope in particular with its further development towards the Square Kilometre Array (SKA) has the capabilities to observe other globular clusters in the halo and corroborate the results.

The results are published in this week’s issue of „Nature Astronomy“.

Source: Max Planck Institute for Radio Astronomy/News

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The research team consists of Federico Abbate, Andrea Possenti, Caterina Tiburzi, Ewan Barr, Willem van Straten, Alessandro Ridolfi and Paulo Freire. The first author, Federico Abbate, is now at the MPIfR. Co-authors Ewan Barr and Paulo Freire are both affiliated with the MPIfR.

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Original Paper

Constraints on the magnetic field in the Galactic halo from globular cluster pulsars 

F. Abbate et al., Nature Astronomy, 02 March 2020. DOI: 10.1038/s41550-020-1030-6.

The URL will become valid after the embargo expires on Monday, March 02, 19:00 CET (13:00 US EST).

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Links

Fundamental Physics in Radio Astronomy
Research Department "Fundamental Physics in Radio Astronomy" at MPIfR, Bonn, Germany

Parkes
CSIRO Parkes Observatory

Millisecond Pulsars in 47 Tuc 
Information on millisecond pulsars in globular cluster 47 Tuc (Website Paulo Freire)

MeerKAT
South African MeerKAT radio telescope

SKA Observatory 
Square Kilometre Array Observatory

Pulsar Dispersion Measure 
Website "Pulsar Dispersion Measure" at Swinburne University, Australia

Cosmic Magnetism
Website "Cosmic Magnetism" at Square Kilometre Array (SKA)

Galactic Magnetic Fields
Scholarpedia article "Galactic Magnetic Fields" by Rainer Beck/MPIfR

Pulsars in 47 Tuc (Movie)

Ensemble of pulsars in 47 Tuc: movie simulation with pulsar sounds (Jodrell Bank; Andrew Lyne & Michael Kramer; 40 MB)

Pulsars in 47 Tuc (Audio file)

Sounds of an ensemble of millisecond pulsars in 47 Tuc. Audio file (Jodrell Bank; Andrew Lyne & Michael Kramer)

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NASA Approves Development of Universe-Studying, Planet-Finding Mission

This graphic shows a simulation of a WFIRST observation of M31, also known as the Andromeda galaxy. Hubble used more than 650 hours to image areas outlined in blue. Using WFIRST, covering the entire galaxy would take only three hours.Credits: DSS, R. Gendle, NASA, GSFC, ASU, STScI, B. F. Williams

NASA’s Wide Field Infrared Survey Telescope (WFIRST) project has passed a critical programmatic and technical milestone, giving the mission the official green light to begin hardware development and testing.

The WFIRST space telescope will have a viewing area 100 times larger than that of NASA’s Hubble Space Telescope, which will enable it to detect faint infrared signals from across the cosmos while also generating enormous panoramas of the universe, revealing secrets of dark energy, discovering planets outside our solar system (exoplanets), and addressing a host of other astrophysics and planetary science topics.

WFIRST’s design already is at an advanced stage, using components with mature technologies. These include heritage hardware --primarily Hubble-quality telescope assets transferred to NASA from another federal agency -- and lessons learned from NASA’s James Webb Space Telescope – the agency’s flagship infrared observatory, targeted for launch next year.

With the passage of this latest key milestone, the team will begin finalizing the WFIRST mission design by building engineering test units and models to ensure the design will hold up under the extreme conditions during launch and while in space.

WFIRST has an expected development cost of $3.2 billion. Including the cost of five years of operations and science, and a ride-along technology demonstration instrument capable of imaging planets around other stars, brings the maximum cost of WFIRST to $3.934 billion.

The FY2020 Consolidated Appropriations Act funds the WFIRST program through September 2020.  The FY2021 budget request proposes to terminate funding for the WFIRST mission and focus on the completion of the James Webb Space Telescope, now planned for launch in March 2021. The Administration is not ready to proceed with another multi-billion-dollar telescope until Webb has been successfully launched and deployed.

WFIRST is managed at Goddard, with participation by the Jet Propulsion Laboratory (JPL) in Pasadena, California, the Space Telescope Science Institute in Baltimore, the Infrared Processing and Analysis Center, also in Pasadena, and a science team comprised of members from U.S. research institutions across the country.

For more information about NASA’s WFIRST mission, visit:  https://www.nasa.gov/wfirst

Editor: Sean Potter

Source: NASA/WFIRST

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Examining the Ice Giants with NASA's Webb Telescope

The Hubble Space Telescope captured these images of the mysterious ice giants Uranus, left, and Neptune, right. Shortly after launch in 2021, the James Webb Space Telescope will unlock secrets of the atmospheres of both planets. Credits: Left: NASA, ESA, and M. Showalter (SETI Institute), Right: NASA, ESA , and A. Simon (NASA Goddard Space Flight Center), and M. Wong and A. Hsu (University of California, Berkeley)

Scientists will study the circulation patterns, chemistry and weather of Uranus and Neptune

Shortly after its launch in 2021, a team of scientists will train NASA’s James Webb Space Telescope on the upper atmospheres of our solar system’s mysterious ice giants, Uranus and Neptune. They plan to map the atmospheric temperature and chemical structure of both planets to study their circulation patterns, chemistry and weather. All the gases in the upper atmospheres of Uranus and Neptune have unique chemical fingerprints that Webb can detect. Crucially, Webb can distinguish one chemical from another. Scientists think that the weather and climate of the ice giants are going to be very different from the gas giants, Jupiter and Saturn.

Far-flung Uranus and Neptune—the ice giants of our solar system—are as mysterious as they are distant. Soon after its launch in 2021, NASA’s James Webb Space Telescope will change that by unlocking secrets of the atmospheres of both planets

The cold and remote giant planets Uranus and Neptune are nicknamed the “ice giants” because their interiors are compositionally different from Jupiter and Saturn, which are richer in hydrogen and helium, and are known as the “gas giants.” The ice giants are also much smaller than their gaseous cousins, being intermediate in size between terrestrial planets and the gas giants. They represent the least-explored category of planet in our solar system. Scientists using Webb plan to study the circulation patterns, chemistry and weather of Uranus and Neptune in a way only Webb can.

“The key thing that Webb can do that is very, very difficult to accomplish from any other facility is map their atmospheric temperature and chemical structure,” explained the studies’ leader, Leigh Fletcher, an associate professor of planetary science at the University of Leicester in the United Kingdom. “We think that the weather and climate of the ice giants are going to have a fundamentally different character compared to the gas giants. That’s partly because they’re so far away from the Sun, they’re smaller in size and rotate faster on their axes, but also because the blend of gases and the amount of atmospheric mixing is very different compared with Jupiter and Saturn.”

All the gases in the upper atmospheres of Uranus and Neptune have unique chemical fingerprints that Webb can detect. Crucially, Webb can distinguish one chemical from another. If these chemicals are being produced by sunlight interacting with the atmosphere, or if they’re being redistributed from place to place by large-scale circulation patterns, Webb will be able to see that.

These studies will be conducted through a Guaranteed Time Observations (GTO) program of the solar system led by Heidi Hammel, a planetary scientist and Webb Interdisciplinary Scientist. She is also Vice President for Science at the Association of Universities for Research in Astronomy (AURA) in Washington, D.C. Hammel’s program will demonstrate the capabilities of Webb for observing solar system objects and exercise some of Webb’s specific techniques for objects that are bright and/or are moving in the sky.

Uranus: The Tilted Planet

Unlike the other planets in our solar system, Uranus—along with its rings and moons—is tipped on its side, rotating at roughly a 90-degree angle from the plane of its orbit. This makes the planet appear to roll like a ball around the Sun. That weird orientation—which may be the result of a gargantuan collision with another massive protoplanet early in the formation of the solar system—gives rise to extreme seasons on Uranus.

When NASA’s Voyager 2 spacecraft flew by Uranus in 1986, one pole was pointing directly at the Sun. “No matter how much Uranus would spin,” Hammel explained, “one half was in complete sunlight all the time, and the other half was in total darkness. It’s the craziest thing you can imagine.”

Disappointingly, Voyager 2 saw only a billiard-ball smooth planet covered in haze, with only a scant handful of clouds. But when Hubble viewed Uranus in the early 2000s, the planet had traveled a quarter of the way around in its orbit. Now the equator was pointed at the Sun, and the entire planet was illuminated over the course of a Uranian day.

“Theory told us nothing would change,” said Hammel, “But the reality was that Uranus started sprouting up all kinds of bright clouds, and a dark spot was discovered by Hubble. The clouds seemed to be changing dramatically in response to the immediate change in sunlight as the planet traveled around the Sun.”

As the planet continues its slow orbital trek, it will point its other pole at the Sun in 2028.

Webb will give insight into the powerful seasonal forces driving the formation of its clouds and weather, and how this is changing with time. It will help determine how energy flows and is transported through the Uranian atmosphere. Scientists want to watch Uranus throughout Webb’s life, to build up a timeline of how the atmosphere responds to the extreme seasons. That will help them understand why this planet’s atmosphere seems to go through periods of intense activity punctuated by moments of calm.

Neptune: A World of Supersonic Winds

Neptune is a dark, cold world, yet it is whipped by supersonic winds that can reach up 1,500 miles per hour. More than 30 times as far from the Sun as Earth, Neptune is the only planet in our solar system not visible to the naked eye. Its existence was predicted by mathematics before its discovery in 1846. In 2011, Neptune completed its first 165-year orbit since its discovery.

Like Uranus, this ice giant’s very deep atmosphere is made of a thick soup of water, ammonia, hydrogen sulfide and methane over an unknown and inaccessible interior. The accessible upper layers of the atmosphere are made of hydrogen, helium and methane. As with Uranus, the methane gives Neptune its blue color, but some still-mysterious atmospheric chemistry makes Neptune’s blue a bit more striking than that of Uranus.

“It’s the same question here: How does energy flow and how is it transported through a planetary atmosphere?” explained Fletcher. “But in this case, unlike Uranus, the planet has a strong internal heat source. That heat source generates some of the most powerful winds and the most short-lived atmospheric vortices and cloud features of anywhere in the solar system. If we look at Neptune from night to night, its face is always shifting and changing as these clouds are stretched and pulled and manipulated by the underlying wind field.”

Following the 1989 Voyager 2 flyby of Neptune, scientists discovered a bright, hot vortex—a storm—at the planet’s south pole. Because the temperature there is higher than everywhere else in the atmosphere, this region is likely associated with some unique chemistry. Webb’s sensitivity will allow scientists to understand the unusual chemical environment within that polar vortex.

Just the Beginning

Fletcher advises to be prepared for seeing phenomena on Uranus and Neptune that are totally unlike what we’ve witnessed in the past. “Webb really has the capability to see the ice giants in a whole new light. But to understand the continual atmospheric processes that are shaping these giant planets, you really need more than just a couple of samples,” he said. “So we compare Jupiter to Saturn to Uranus to Neptune, and by that, we build up a wider picture of how atmospheres work in general. This is the beginning of understanding how these worlds are changing with time.”

Hammel added, “We now know of hundreds of exoplanets—planets around other stars—of the size of our local ice giants. Uranus and Neptune provide us ground truth for studies of these newly discovered worlds.”

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.

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

Source: James Webb Space Telescope/News

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Ophiuchus Galaxy Cluster: Record-Breaking Explosion by Black Hole Spotted

Ophiuchus Galaxy Cluster
 Credit: X-ray: Chandra: NASA/CXC/NRL/S. Giacintucci, et al., XMM: ESA/XMM;
Radio: NCRA/TIFR/GMRT; 

Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF

JPEG (309 kb) - Large JPEG (1.1 MB) - Tiff (51.5 MB)

A Tour of the Biggest Explosion Ever Seen in the Universe - More Animations

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Evidence for the biggest explosion seen in the Universe is contained in these composite images. This discovery, covered in our latest press release, combines data from NASA's Chandra X-ray Observatory, ESA's XMM-Newton, the Murchison Widefield Array, and the Giant Metrewave Telescope.

This extremely powerful eruption occurred in the Ophiuchus galaxy cluster, which is located about 390 million light years from Earth. Galaxy clusters are the largest structures in the Universe held together by gravity, containing thousands of individual galaxies, dark matter, and hot gas.

The hot gas that pervades clusters like Ophiuchus gives off much of its light as X-rays. The main panel contains X-rays from XMM-Newton (pink) along with radio data from GMRT (blue), and infrared data from 2MASS (white). In the inset, Chandra's X-ray data are pink.

In the center of the Ophiuchus cluster is a large galaxy containing a supermassive black hole. Researchers have traced the source of this gigantic eruption to jets that blasted away from the black hole and carved out a large cavity in the hot gas. (A labeled version includes a dashed line showing the edge of the cavity in the hot gas seen in X-rays from both Chandra and XMM-Newton.) Radio emission from electrons accelerated to almost the speed of light fills this cavity, providing evidence that an eruption of unprecedented size took place.

A cross in the labeled version gives the location of the central galaxy. The publicly-available infrared data, which show the stars and galaxies in the field of view, are not sensitive enough to reveal the galaxy. (Even with higher quality data the galaxy would still not be visible in this composite image because it overlaps with bright X-ray and radio emission surrounding it.)

One interesting aspect of the Ophiuchus observations is that the densest and coolest gas seen in X-rays is located about 6,500 light years to the north of the central galaxy. This corresponds to a distance on the image that is smaller than the size of the cross. If this gas shifted away from the galaxy it would have deprived the black hole of fuel for its growth, turning off the jets. This gas displacement is likely caused by "sloshing" of the gas around the middle of the cluster, like wine sloshing around in a glass. Usually the merger of two galaxy clusters triggers such sloshing, but here it could have been set off by the eruption.

A paper describing these results appears online on February 27th in The Astrophysical Journal, and a preprint is available here. The authors of this paper are Simona Giancintucci (Naval Research Laboratory, Washington, DC), Maxim Markevitch (Goddard Space Flight Center, Greenbelt, Maryland), Melanie Johnston-Hollitt (International Centre for Radio Astronomy, Australia), Daniel Wik (University of Utah), Qian Wang (University of Utah), and Tracy Clarke (Naval Research Laboratory). The 2016 paper by Norbert Werner was published in the Monthly Notices of the Royal Astronomical Society.

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 and Burlington, Massachusetts.

A Quick Look at the Biggest Explosion Ever Seen in the Universe

Source: NASA’s Chandra X-ray Observatory

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Fast Facts for Ophiuchus Galaxy Cluster:

Scale: Main image is about 25.2 arcmin (2.8 million light years) across. The inset image is about 6.5 arcmin (720,000 light years) across.

Category: Groups & Clusters of Galaxies, Black Holes
Coordinates (J2000): RA 17h 12m 27.82s | Dec -23° 22´ 11"
Constellation: Ophiuchus
Observation Date: 9 pointings from July 1, 2014 to Aug 9, 2014
Observation Time: 63 hours 9 minutes (2 days 15 hours 9 minutes)
Obs. ID: 16142-16143,16464,16626-16627, 16633-16635,16645
Instrument: ACIS
References: Giacintucci, S., et al., 2020, ApJ in press; arXiv:2002.01291
Color Code: X-ray: Pink; Radio: Blue; Infrared: White
Distance Estimate: About 390 million light years

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Help to find the location of newly discovered black holes in the LOFAR Radio Galaxy Zoo project

As an example, take the case of the famous radio source 3C236. The upper image is the radio source, the middle one an optical image showing many stars and galaxies and the lower image an overlay of the radio and the optical image. In this case, for the human eye the origin of the radio emission is clear, it is the bright point-like radio source at the center of the radio image. This is the location of the massive black hole that is driving all the radio activity. From the overlay with the optical images the galaxy that hosts the black hole can then be identified. Image credit: Aleksandar Shulevski, Erik Osinga & The LOFAR surveys team. Hi-res image

Scientists are asking for the public’s help to find the origin of hundreds of thousands of galaxies that have been discovered by the largest radio telescope ever built: LOFAR. Where do these mysterious objects that extend for thousands of light-years come from? A new citizen science project, LOFAR Radio Galaxy Zoo, gives anyone with a computer the exciting possibility to join the quest to find out where the black holes at the centre of these galaxies are located.

Astronomers use radio telescopes to make images of the radio sky, much like optical telescopes like the Hubble space telescope make maps of stars and galaxies. The difference is that the images made with a radio telescope show a sky that is very different from the sky that an optical telescope sees. In the radio sky, stars and galaxies are not directly seen but instead an abundance of complex structures linked to massive black holes at the centres of galaxies are detected. Most dust and gas surrounding a supermassive black hole gets consumed by the black hole, but part of the material will escape and gets ejected into deep space. This material forms large plumes of extremely hot gas, it is this gas that forms large structures that is observed by radio telescopes.

The Low Frequency Array (LOFAR) telescope, operated by the Netherlands Institute for Radio Astronomy (ASTRON), is continuing its huge survey of the radio sky and 4 million radio sources have now been discovered. A few hundred thousand of these have very complicated structures. So complicated that it is difficult to determine which galaxies belong to which radio source, or in other words, which black hole belongs to which galaxy?

While the international LOFAR team consists of more than 200 astronomers from 18 countries, it is simply too small to take on this daunting task of identifying which radio structures belong to which host galaxy. Therefore, LOFAR astronomers are asking the public to help. In the context of the citizen science project ‘LOFAR Radio Galaxy Zoo’, the public is asked to look at images from LOFAR and images of galaxies and then associate radio sources with galaxies.

“LOFAR’s new survey has revealed millions of previously undetected radio sources. With the help of the public we can investigate the nature of these sources: Where are their black holes? In what kind of galaxies are the black holes located?’’ says Huub Röttgering from Leiden University (The Netherlands).

Tim Shimwell, ASTRON and Leiden University, explains why this is significant: “Your task is to match the radio sources with the right galaxy. This will help researchers understand how radio sources are formed, how black holes evolve, and how vast quantities of material can be ejected into deep space with such unprecedented amounts of energy”, he says.

Radio Galaxy Zoo: LOFAR is part of the Zooniverse project, the world’s largest and most popular platform for people-powered research. This research is made possible by volunteers — more than a million people around the world who come together to assist professional researchers.

Images

• More images can be found here
• The Radio Galaxy Zoo: LOFAR page is accessible here
• The tutorial video can be viewed here

Source: ASTRON-Netherlands Institute for Radio Astronomy/News

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