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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Gemini South Telescope Captures Exquisite Planetary Nebula

The international Gemini Observatory composite color image of the planetary nebula CVMP 1 imaged by the Gemini Multi-Object Spectrograph on the Gemini South telescope on Cerro Pachón in Chile. Credit: The international Gemini Observatory/NSF’s National Optical-Infrared Astronomy Research Laboratory/AURA. download JPG | TIFF

20-Second zoom out from the core of the planetary nebula CVMP 1. Credit: The international Gemini Observatory/NSF’s National Optical-Infrared Astronomy Research Laboratory/AURA.

The latest image from the international Gemini Observatory showcases the striking planetary nebula CVMP 1. This object is the result of the death throes of a giant star and is a glorious but relatively short-lived astronomical spectacle. As the progenitor star of this planetary nebula slowly cools, this celestial hourglass will run out of time and will slowly fade from view over many thousands of years.

Located roughly 6500 light-years away in the southern constellation of Circinus (The Compass) this astronomical beauty formed during the final death throes of a massive star. CVMP 1 is a planetary nebula; it emerged when an old red giant star blew off its outer layers in the form of a tempestuous stellar wind [1]. As this cast-aside stellar atmosphere sped outwards into interstellar space, the hot, exposed core of the progenitor star began to energize the ejected gases and cause them to glow. This formed the beautiful hourglass shape captured in this observation from the international Gemini Observatory, a program of NSF’s National Optical-Infrared Astronomy Research Laboratory.

Planetary nebulae like CVMP 1 are formed by only certain stars — those with a mass somewhere between 0.8 and 8 times that of our own Sun [2]. Less massive stars will gently fizzle out, transitioning into white dwarfs at the end of their long lives, whereas more massive stars live fast and die young, ending their lives in gargantuan explosions known as supernovae. For stars lying between these extremes, however, the final stretch of their lives results in a striking astronomical display such as the one seen in this image. Unfortunately, the spectacle provided by a planetary nebula is as brief as it is glorious; these objects typically persist for only 10,000 years — a tiny stretch of time compared to the lifespan of most stars, which lasts billions of years.

These short-lived planetary nebulae come in myriad shapes and sizes, and several particularly striking forms are well known, such as the Helix Nebula which is captured in this image from 2003 which combined OIR Lab facilities at  Kitt Peak National Observatory with the Hubble Space Telescope. The great diversity of shapes stems from the diversity of progenitor star systems, whose characteristics can greatly influence the ensuing planetary nebula. The presence of companion stars, orbiting planets, or even the rotation of the original red giant star can help determine the shape of a planetary nebula, but we don’t yet have a detailed understanding of the processes sculpting these beautiful astronomical fireworks displays.

But CVMP 1 is intriguing for more than just its aesthetic value. Astronomers have found that the gases making up the hourglass are highly enriched with helium and nitrogen, and that CVMP 1 is one of the largest planetary nebulae known. These clues together suggest that CVMP 1 is highly evolved, making it an ideal object to help astronomers understand the later lives of planetary nebulae.

Astronomical measurements have revealed the characteristics of CVMP 1’s central star. By measuring the light emitted from the gas in the planetary nebula, astronomers infer that the temperature of the central star is at least 130,000 degrees C (230,000 degrees F). Despite this scorching temperature, the star is doomed to steadily cool over thousands of years. Eventually, the light it emits will have too little energy to ionize gas in the planetary nebula, causing the striking hourglass shown in this image to fade from view.

The international Gemini Observatory, comprises telescopes in the northern and southern hemispheres, which together can access the entire night sky. Similar to many large observatories, a small fraction of the observing time of the Gemini telescopes is set aside for the creation of color images that can share the beauty of the Universe with the public. Objects are chosen for their aesthetic appeal — such as this striking celestial hourglass.

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Notes

[1] Despite their name, planetary nebulae have nothing to do with planets. This misnomer originates from the round, planet-like appearance of these objects when viewed through early telescopes. As telescopes improved, the striking beauty and stellar origin of planetary nebulae became more obvious, but their original name has persisted.

[2] Which in turn implies that our own Sun will form a planetary nebula after burning through its hydrogen fuel, around 5 billion years from now.

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More information

NSF’s National Optical-Infrared Astronomy Research Laboratory, the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a program of NSF, NRC–Canada, CONICYT–Chile, MCTI–Brazil, MCTIP–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and the Vera C. Rubin Observatory. It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai’i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

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Contact:

Peter Michaud
NewsTeam Manager
NSF’s National Optical-Infrared Astronomy Research Laboratory
Gemini Observatory, Hilo HI
Desk: +1 808-974-2510
Cell: +1 808-936-6643
Email: pmichaud@gemini.edu

Source: Gemini Observatory

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LIGO-Virgo Network Catches Another Neutron Star Collision

GW190425 : Artist's impression of the binary neutron star merger observed by LIGO Livingston on April 25, 2019. Image credit: National Science FounGW190425 : Artist's impression of the binary neutron star merger observed by LIGO Livingston on April 25, 2019. Image credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet. dation/LIGO/Sonoma State University/A. Simonnet.

On April 25, 2019, the LIGO Livingston Observatory picked up what appeared to be gravitational ripples from a collision of two neutron stars. LIGO Livingston is part of a gravitational-wave network that includes LIGO (the Laser Interferometer Gravitational-wave Observatory), funded by the National Science Foundation (NSF), and the European Virgo detector. Now, a new study confirms that this event was indeed likely the result of a merger of two neutron stars. This would be only the second time this type of event has ever been observed in gravitational waves.

The first such observation, which took place in August of 2017, made history as the first joint observation of the same cosmic event in both gravitational waves and light. The April 25 merger, by contrast, did not result in any light being detected. However, through an analysis of the gravitational-wave data alone, researchers have learned that the objects involved in this collision were unusually massive given the expectations for neutron star binaries.

"From conventional observations with light, we already knew of 17 binary neutron star systems in our own galaxy and we have estimated the masses of these stars", says Ben Farr, a LIGO team member based at the University of Oregon. "What's surprising is that the combined mass of this binary is much higher than what was expected."

"We have detected a second event consistent with a binary neutron star system and this is an important confirmation of the August 2017 event that marked an exciting new beginning for multi-messenger astronomy two years ago", says Jo van den Brand, Virgo Spokesperson and professor at Maastricht University, and Nikhef and VU University Amsterdam in the Netherlands. Multi-messenger astronomy occurs when different types of signals are witnessed simultaneously, such as those based on gravitational waves and light.

The study, accepted for publication in The Astrophysical Journal Letters, is authored by an international team comprised of the LIGO Scientific Collaboration and the Virgo Collaboration, the latter of which is associated with the Virgo gravitational-wave detector in Italy.

Neutron stars are the remnants of dying stars that undergo catastrophic explosions as they collapse at the end of their lives. When two neutron stars spiral together, they undergo a violent merger that sends gravitational shudders through the fabric of space and time.

LIGO became the first observatory to directly detect gravitational waves in 2015; in that instance, the waves were generated by the violent collision of two black holes. Since then, LIGO and Virgo have registered dozens of additional candidate black hole mergers.

“Just as the first gravitational wave detection revealed a binary of unexpectedly massive black holes, this detection again reveals an unexpected member of the ‘cosmological ecosystem’ ”, says Nathan Johnson-McDaniel from the Department of Applied Mathematics and Theoretical Physics (DAMTP) at the University of Cambridge. “It is yet another illustration of the great discovery potential of gravitational wave observations.”

GW190425 FactSheet

Hi-res image

The April 2019 event was first identified in data from the LIGO Livingston detector alone. The LIGO Hanford detector was temporarily offline at the time, and, at a distance of more than 500 million light-years, the event was extremely faint in Virgo's data. Using the Livingston data, combined with information derived from Virgo’s data, the team narrowed the location of the event to a patch of sky more than 8,200 square degrees in size, or about 20 percent of the sky. For comparison, the August 2017 event was narrowed to a region of just 16 square degrees, or 0.04 percent of the sky.

“But what was the fate of this merger, what type of remnant did it leave behind?”, wonders Michalis Agathos, researcher at DAMTP and the Kavli Institute for Cosmology in Cambridge. “To answer this we can make use of information on the properties of neutron-star matter, that we had gained from the first event back in 2017. And we infer that the binary of this second event seems to be massive enough to immediately collapse upon merger, forming a black hole. Hence we should not expect a strong electromagnetic afterglow.”

The LIGO data reveal that the combined mass of the merged bodies is about 3.4 times the mass of our Sun. In our galaxy, known binary neutron star systems have combined masses up to only 2.9 times that of the Sun. One possibility for the unusually high mass is that the collision took place not between two neutron stars, but a neutron star and a black hole (black holes can be heavier than neutron stars). In this case, however, the black hole would be too light to match astrophysical observations and theoretical expectations. Therefore, the scientists believe it is much more likely that LIGO witnessed a merger of two neutron stars.

“When you look at the black holes and neutron stars observed so far, however, there is a gap in their mass distributions”, says Ulrich Sperhake head of the Cambridge LIGO group at DAMTP. “You have the black holes on the heavy end, the neutron stars on the light end and seemingly no objects in between with about 2.5 to 5 solar masses. This detection may give us the first clues whether and how this gap is filled.”

“This second event was consistent with matter properties extracted from the first binary neutron star observation, GW170817, but was not as loud”, said Charalampos Markakis from the University of Cambridge. “Future events and detector upgrades will allow us to measure properties of matter at extreme densities, beyond the reach of terrestrial laboratories, expanding our understanding of high-energy physics.”

Neutron star pairs are thought to form in two possible ways. They might form from binary systems of massive stars that each end their lives as neutron stars, or they might arise when two separately formed neutron stars come together within a dense stellar environment. The LIGO data for the April 25 event do not indicate which of these scenarios is more likely, but they do suggest that more data and new models are needed to explain the merger’s unexpectedly high mass.

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Additional information about the gravitational-wave observatories:

LIGO is funded by the NSF and operated by Caltech and MIT, which conceived of LIGO and lead the project. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. Approximately 1,300 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

The Virgo Collaboration is currently composed of approximately 520 members from 99 institutes in 11 different countries including Belgium, France, Germany, Hungary, Italy, the Netherlands, Poland, and Spain. The European Gravitational Observatory (EGO) hosts the Virgo detector near Pisa in Italy, and is funded by Centre National de la Recherche Scientifique (CNRS) in France, the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and Nikhef in the Netherlands. A list of the Virgo Collaboration groups can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu.

Source: Kavli Institute for Cosmology, Cambridge (KICC)/News

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Beyond the Brim, Sombrero Galaxy's Halo Suggests a Turbulent Past

Halo of the Sombrero Galaxy

Copyright NASA , ESA , and R. Cohen and P. Goudfrooij (STScI )

Surprising new data from NASA's Hubble Space Telescope suggests the smooth, settled "brim" of the Sombrero galaxy's disk may be concealing a turbulent past. Hubble's sharpness and sensitivity resolves tens of thousands of individual stars in the Sombrero's vast, extended halo, the region beyond a galaxy's central portion, typically made of older stars. These latest observations of the Sombrero are turning conventional theory on its head, showing only a tiny fraction of older, metal-poor stars in the halo, plus an unexpected abundance of metal-rich stars typically found only in a galaxy's disk, and the central bulge. Past major galaxy mergers are a possible explanation, though the stately Sombrero shows none of the messy evidence of a recent merger of massive galaxies. 

"The Sombrero has always been a bit of a weird galaxy, which is what makes it so interesting," said Paul Goudfrooij of the Space Telescope Science Institute (STScI), Baltimore, Maryland. "Hubble's metallicity measurements (i.e.: the abundance of heavy elements in the stars) are another indication that the Sombrero has a lot to teach us about galaxy assembly and evolution."

"Hubble's observations of the Sombrero's halo are turning our generally accepted understanding of galaxy makeup and metallicity on its head," added co-investigator Roger Cohen of STScI.

Long a favorite of astronomers and amateur sky watchers alike for its bright beauty and curious structure, the Sombrero Galaxy (M104) now has a new chapter in its strange story — an extended halo of metal-rich stars with barely a sign of the expected metal-poor stars that have been observed in the halos of other galaxies. Researchers, puzzling over the data from Hubble, turned to sophisticated computer models to suggest explanations for the perplexing inversion of conventional galactic theory. 

Those results suggest the equally surprising possibility of major mergers in the galaxy's past, though the Sombrero's majestic structure bears no evidence of recent disruption. The unusual findings and possible explanations are published in the Astrophysical Journal

"The absence of metal-poor stars was a big surprise," said Goudfrooij, "and the abundance of metal-rich stars only added to the mystery."

In a galaxy's halo astronomers expect to find earlier generations of stars with less heavy elements, called metals, as compared to the crowded stellar cities in the main disk of a galaxy. Elements are created through the stellar "lifecycle" process, and the longer a galaxy has had stars going through this cycle, the more element-rich the gas and the higher-metallicity the stars that form from that gas. These younger, high-metallicity stars are typically found in the main disk of the galaxy where the stellar population is denser — or so goes the conventional wisdom.

Complicating the facts is the presence of many old, metal-poor globular clusters of stars. These older, metal-poor stars are expected to eventually move out of their clusters and become part of the general stellar halo, but that process seems to have been inefficient in the Sombrero galaxy. The team compared their results with recent computer simulations to see what could be the origin of such unexpected metallicity measurements in the galaxy's halo.

The results also defied expectations, indicating that the unperturbed Sombrero had undergone major accretion, or merger, events billions of years ago. Unlike our Milky Way galaxy, which is thought to have swallowed up many small satellite galaxies in so-called "minor" accretions over billions of years, a major accretion is the merger of two or more similarly massive galaxies that are rich in later-generation, higher-metallicity stars.

The satellite galaxies only contained low metallicity stars that were largely hydrogen and helium from the big bang. Heavier elements had to be cooked up in stellar interiors through nucleosynthesis and incorporated into later generation stars. This process was rather ineffective in dwarf galaxies such as those around our Milky Way, and more effective in larger, more evolved galaxies.

The results for the Sombrero are surprising because its smooth disk shows no sign.s of disruption. By comparison, numerous interacting galaxies, like the iconic Antennae galaxies, get their name from the distorted appearance of their spiral arms due to the tidal forces of their interaction. Mergers of similarly massive galaxies typically coalesce into large, smooth elliptical galaxies with extended halos — a process that takes billions of years. But the Sombrero has never quite fit the traditional definition of either a spiral or an elliptical galaxy. It is somewhere in between — a hybrid.

For this particular project, the team chose the Sombrero mainly for its unique morphology. They wanted to find out how such "hybrid" galaxies might have formed and assembled over time. Follow-up studies for halo metallicity distributions will be done with several galaxies at distances similar to that of the Sombrero.

The research team looks forward to future observatories continuing the investigation into the Sombrero's unexpected properties. The Wide Field Infrared Survey Telescope (WFIRST), with a field of view 100 times that of Hubble, will be capable of capturing a continuous image of the galaxy's halo while picking up more stars in infrared light. The James Webb Space Telescope will also be valuable for its Hubble-like resolution and deeper infrared sensitivity.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Source: HubbleSite

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Contact:

Leah Ramsay/ Ray Villard 
Space Telescope Science Institute, Baltimore, Maryland 
667-218-6439 / 410-338-4514 
lramsay@stsci.edu / villard@stsci.edu

Roger Cohen / Paul Goudfrooij 
Space Telescope Science Institute, Baltimore, Maryland 
rcohen@stsci.edu / goudfroo@stsci.edu

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Related Links:

• The science paper by R. Cohen et al. (ApJ)  
• NASA's Hubble Portal

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A Cosmic Jekyll and Hyde

Terzan 5

Credit: X-ray: NASA/CXC/Univ. of Amsterdam/N.Degenaar, et al.; Optical: NASA, ESA

JPEG (455.9 kb) - Large JPEG (4.8 MB) - Tiff (30.3 MB) - More Images 
A Tour of a Cosmic Jekyll and Hyde - More Animations

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A double star system has been flipping between two alter egos, according to observations with NASA's Chandra X-ray Observatory and the National Science Foundation's Karl F. Jansky Very Large Array (VLA). Using nearly a decade and a half worth of Chandra data, researchers noticed that a stellar duo behaved like one type of object before switching its identity, and then returning to its original state after a few years. This is a rare example of a star system changing its behavior in this way.

Astronomers found this volatile double, or binary, system in a dense collection of stars, the globular cluster Terzan 5, which is located about 19,000 light years from Earth in the Milky Way galaxy. This stellar duo, known as Terzan 5 CX1, has a neutron star (the extremely dense remnant left behind by a supernova explosion) in close orbit around a star similar to the Sun, but with less mass. 

In this new image of Terzan 5 (right), low, medium and high-energy X-rays detected by Chandra are colored red, green and blue respectively. On the left, an image from the Hubble Space Telescope shows the same field of view in optical light. Terzan 5 CX1 is labeled as CX1 in the Chandra image.

In binary systems like Terzan 5 CX1, the heavier neutron star pulls material from the lower-mass companion into a surrounding disk. Astronomers can detect these so-called accretion disks by their bright X-ray light, and refer to these objects as "low-mass X-ray binaries." 

Spinning material in the disk falls onto the surface of the neutron star, increasing its rotation rate. The neutron star can spin faster and faster until the roughly 10-mile-wide sphere, packed with more mass than the Sun, is rotating hundreds of times per second. Eventually, the transfer of matter slows down and the remaining material is swept away by the whirling magnetic field of the neutron star, which becomes a millisecond pulsar. Astronomers detect pulses of radio waves from these millisecond pulsars as the neutron star's beam of radio emission sweeps over the Earth during each rotation. 

While scientists expect the complete evolution of a low-mass X-ray binary into a millisecond pulsar should happen over several billion years, there is a period of time when the system can switch rapidly between these two states. Chandra observations of Terzan 5 CX1 show that it was acting like a low-mass X-ray binary in 2003, because it was brighter in X-rays than any of the dozens of other sources in the globular cluster. This was a sign that the neutron star was likely accumulating matter.

Terzan 5, Labeled

Credit: NASA/CXC/Univ. of Amsterdam/N.Degenaar, et al.

In Chandra data taken from 2009 to 2014, Terzan 5 CX1 had become about ten times fainter in X-rays. Astronomers also detected it as a radio source with the VLA in 2012 and 2014. The amount of radio and X-ray emission and the corresponding spectra (the amount of emission at different wavelengths) agree with expectations for a millisecond pulsar. Although the radio data used did not allow a search for millisecond pulses, these results imply that Terzan 5 CX1 underwent a transformation into behaving like a millisecond pulsar and was blowing material outwards. By the time Chandra had observed Terzan 5 CX1 again in 2016, it had become brighter in X-rays and changed back to acting like a low-mass X-ray binary again.

To confirm this pattern of "Jekyll and Hyde" behavior, astronomers need to detect radio pulses while Terzan 5 CX1 is faint in X-rays. More radio and X-ray observations are planned to search for this behavior, along with sensitive searches for pulses in existing data. Only three confirmed examples of these identity-changing systems are known, with the first discovered in 2013 using Chandra and several other X-ray and radio telescopes.

The study of this binary was led by Arash Bahramian of the International Centre for Radio Astronomy Research (ICRAR), Australia and was published in the September 1st, 2018 issue of The Astrophysical Journal. A preprint is available here.

Two other recent studies have used Chandra observations of Terzan 5 to study how neutron stars in two different low-mass X-ray binaries recover after having had large amounts of material dumped on their surface by a companion star. Such studies are important for understanding the structure of a neutron star's outer layer, known as its crust.

In one of these studies, of the low-mass X-ray binary Swift J174805.3–244637 (T5 X-3 for short), material dumped onto the neutron star during an X-ray outburst detected by Chandra in 2012 heated up the star's crust. The crust of the neutron star then cooled down, taking about a hundred days to fall back to the temperature seen before the outburst. The rate of cooling agrees with a computer model for such a process.

In a separate Chandra study of a different low-mass X-ray binary in Terzan 5, IGR J17480–2446 (T5 X-2 for short) the neutron star was still cooling when its temperature was taken five and a half years after it was known to have an outburst. These results show this neutron star's crust ability to transfer, or conduct, heat may be lower than what astronomers have found in other cooling neutron stars in low-mass X-ray binaries. This difference in the ability to conduct heat may be related to T5 X-2 having a higher magnetic field compared to other cooling neutron stars, or being much younger than T5 X-3. 

Both T5 X-3 and T5 X-2 are labeled in the image.

The work on the rapidly cooling neutron star, led by Nathalie Degenaar of the University of Amsterdam in the Netherlands, was published in the June 2015 issue of the Monthly Notices of the Royal Astronomical Society and a preprint is available here. The study of the slowly cooling neutron star, led by Laura Ootes, then of the University of Amsterdam, was published in the July 2019 issue of the Monthly Notices of the Royal Astronomical Society and a preprint is available here.

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. Source: NASA’s Chandra X-ray Observatory

A Quick Look at a Cosmic Jekyll and Hyde

Source: NASA’s handra X-ray Observatory

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Fast Facts for Terzan 5:

Scale: Each panel is about 3.1 arcmin (17 light years) across.
Category: Normal Stars & Star Clusters
Coordinates: (J2000): RA 17h 48m 4.8s | Dec -24° 46´ 45"
Constellation: Sagittarius
Observation Date: 17 observations from July 13, 2003 through July 20, 2014
Observation Time: 171 hours 37 minutes (7 days 3 hours 37 minutes)
Obs. ID: 3798, 10059, 12454, 13225, 13252, 13705, 13706, 14339, 14475-14479, 14625, 15615, 15750, 16638
Instrument: ACIS
References: Bahramian, A. et al., 2018, ApJ, 864, 28; arXiv:1807.11589v Degenaar, N. et al., 2015, MNRAS, 451, 2071; arXiv:1505.01862. Ootes, L.S. et al., 2019, MNRAS, 487, 1447; arXiv:1805.00610
Color Code: X-ray: Red: 0.3-1.2 keV Green: 1.2-2.0 keV Blue: 2.0-6.0 keV

Distance Estimate: About 19,000 light years

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How Newborn Stars Prepare for the Birth of Planets

VANDAM survey

ALMA and the VLA observed more than 300 protostars and their young protoplanetary disks in Orion. This image shows a subset of stars, including a few binaries. The ALMA and VLA data compliment each other: ALMA sees the outer disk structure (visualized in blue), and the VLA observes the inner disks and star cores (orange). Credit: ALMA (ESO/NAOJ/NRAO), J. Tobin; NRAO/AUI/NSF, S. Dagnello. Hi-Res File

Observed protostars in Orion Molecular Clouds 

This image shows the Orion Molecular Clouds, the target of the VANDAM survey. Yellow dots are the locations of the observed protostars on a blue background image made by Herschel. Side panels show nine young protostars imaged by ALMA (blue) and the VLA (orange). Credit: ALMA (ESO/NAOJ/NRAO), J. Tobin; NRAO/AUI/NSF, S. Dagnello; Herschel/ESA. Hi-Res File

Schematic showing the formation of protostars 

This schematic shows a proposed pathway (top row) for the formation of protostars, based on four very young protostars (bottom row) observed by VLA (orange) and ALMA (blue). Step 1 represents the collapsing fragment of gas and dust. In step 2, an opaque region starts to form in the cloud. In step 3, a hydrostatic core starts to form due to an increase in pressure and temperature, surrounded by a disk-like structure and the beginning of an outflow. Step 4 depicts the formation of a class 0 protostar inside the opaque region, that may have a rotationally supported disk and more well-defined outflows. Step 5 is a typical class 0 protostar with outflows that have broken through the envelope (making it optically visible), an actively accreting, rotationally supported disk. In the bottom row, white contours are the protostar outflows as seen with ALMA. Credit: ALMA (ESO/NAOJ/NRAO), N. Karnath; NRAO/AUI/NSF, B. Saxton and S. Dagnello. Hi-Res File

Star chart of constellation Orion and observed protostars

The Orion Molecular Clouds (blue, as seen with Herschel) are located in the constellation Orion. Red dots show the locations of the observed protostars in the VANDAM survey. Credit: IAU; Sky & Telescope magazine; NRAO/AUI/NSF, S. Dagnello; Herschel/ESA; ALMA (ESO/NAOJ/NRAO), J. Tobin. Hi-Res File

ALMA and VLA observe hundreds of planet-forming disks around infant stars 

An international team of astronomers used two of the most powerful radio telescopes in the world to create more than three hundred images of planet-forming disks around very young stars in the Orion Clouds. These images reveal new details about the birthplaces of planets and the earliest stages of star formation.

Most of the stars in the universe are accompanied by planets. These planets are born in rings of dust and gas, called protoplanetary disks. Even very young stars are surrounded by these disks. Astronomers want to know exactly when these disks start to form, and what they look like. But young stars are very faint, and there are dense clouds of dust and gas surrounding them in stellar nurseries. Only highly sensitive radio telescope arrays can spot the tiny disks around these infant stars amidst the densely packed material in these clouds.

For this new research, astronomers pointed both the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) to a region in space where many stars are born: the Orion Molecular Clouds. This survey, called VLA/ALMA Nascent Disk and Multiplicity (VANDAM), is the largest survey of young stars and their disks to date.

Very young stars, also called protostars, form in clouds of gas and dust in space. The first step in the formation of a star is when these dense clouds collapse due to gravity. As the cloud collapses, it begins to spin – forming a flattened disk around the protostar. Material from the disk continues to feed the star and make it grow. Eventually, the left-over material in the disk is expected to form planets.

Many aspects about these first stages of star formation, and how the disk forms, are still unclear. But this new survey provides some missing clues as the VLA and ALMA peered through the dense clouds and observed hundreds of protostars and their disks in various stages of their formation.

Young planet-forming disks

“This survey revealed the average mass and size of these very young protoplanetary disks,” said John Tobin of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, and leader of the survey team. “We can now compare them to older disks that have been studied intensively with ALMA as well.”

What Tobin and his team found, is that very young disks can be similar in size, but are on average much more massive than older disks. “When a star grows, it eats away more and more material from the disk. This means that younger disks have a lot more raw material from which planets could form. Possibly bigger planets already start to form around very young stars.”

Four special protostars

Among hundreds of survey images, four protostars looked different than the rest and caught the scientists’ attention. “These newborn stars looked very irregular and blobby,” said team member Nicole Karnath of the University of Toledo, Ohio (now at SOFIA Science Center). “We think that they are in one of the earliest stages of star formation and some may not even have formed into protostars yet.”

It is special that the scientists found four of these objects. “We rarely find more than one such irregular object in one observation,” added Karnath, who used these four infant stars to propose a schematic pathway for the earliest stages of star formation. “We are not entirely sure how old they are, but they are probably younger than ten thousand years.”

To be defined as a typical (class 0) protostar, stars should not only have a flattened rotating disk surrounding them, but also an outflow – spewing away material in opposite directions – that clears the dense cloud surrounding the stars and makes them optically visible. This outflow is important, because it prevents stars from spinning out of control while they grow. But when exactly these outflows start to happen, is an open question in astronomy.

One of the infant stars in this study, called HOPS 404, has an outflow of only two kilometers (1.2 miles) per second (a typical protostar-outflow of 10-100 km/s or 6-62 miles/s). “It is a big puffy sun that is still gathering a lot of mass, but just started its outflow to lose angular momentum to be able to keep growing,” explained Karnath. “This is one of the smallest outflows that we have seen and it supports our theory of what the first step in forming a protostar looks like.”

Combining ALMA and VLA

The exquisite resolution and sensitivity provided by both ALMA and the VLA were crucial to understand both the outer and inner regions of protostars and their disks in this survey. While ALMA can examine the dense dusty material around protostars in great detail, the images from the VLA made at longer wavelengths were essential to understand the inner structures of the youngest protostars at scales smaller than our solar system.

“The combined use of ALMA and the VLA has given us the best of both worlds,” said Tobin. “Thanks to these telescopes, we start to understand how planet formation begins.”

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

Source:  National Radio Astronomy Observatory (NRAO)/News

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Media contact:

Iris Nijman
News and Public Information Manager
National Radio Astronomy Observatory (NRAO)
inijman@nrao.edu
+1 (434) 296-0314

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This research was presented in two papers:

• The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. A Statistical Characterization of Class 0 and I Protostellar Disks,” by J. Tobin et al., The Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab6f64


• “Detection of Irregular, Sub-mm Opaque Structures in the Orion Molecular Clouds: Protostars within 10000 years of formation?,” by N. Karnath et al., The Astrophysical Journal. https://doi.org/10.3847/1538-4357/ab659e

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.

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Dramatic Starbursts Hidden in Protoclusters at 12 Billion Years Ago

Figure 1: A schematic view of the image analysis in this work. First, the team selected protocluster candidates at 12 billion years ago from the deep and wide extragalactic survey with HSC. Then they used the archival full sky survey images at mid-far infrared taken by infrared space telescopes like Planck to investigate the infrared properties of galaxies in protoclusters. The spatial resolution and sensitivity of these images are too low to resolve distant galaxies individually, however, by stacking the images of the 180 protocluster candidates selected with HSC, the team successfully constrained the average total infrared flux of a protocluster. (Credit: NAOJ)

A team of astronomers from the National Astronomical Observatory of Japan (NAOJ) and the University of Tokyo has detected the strong infrared emissions from protoclusters at 12 billion years ago by using the deep and wide extragalactic survey with Hyper Suprime-Cam (HSC) on the Subaru Telescope and archival infrared data taken by various space telescopes. The detected infrared emissions were brighter than that which was expected from the galaxy population observed in the visible. These results indicate dramatic star formation and super massive black hole growth which are not observable in the optical but luminous in the infrared.

There are many galaxies in our Universe. There is an environmental dependence of galaxy type in that giant elliptical galaxies dominate galaxy overdense regions (clusters of galaxies) while spiral galaxies dominate general fields. To investigate how the environmental dependence of galaxies developed, the team studied progenitors of modern clusters of galaxies, called protoclusters. 

To constrain the typical properties of protoclusters, they needed to observe many protoclusters statistically. However, the surface number density of protoclusters is too low to search for them easily. Therefore, only a small number of protoclusters which existed over 10 billion years ago have been known. 

HSC on the Subaru Telescope enables an effective search for protoclusters. HSC is an optical camera with an extremely wide field of view (about 1.8 square degrees, equivalent to the area of nine full moons) and high sensitivity. Now, a deep and wide extragalactic survey is on-going with HSC (HSC-SSP). From the 120 square degree survey of the first HSC-SSP results, the team selected about 180 protocluster candidates. This is the largest catalog of protoclusters ever (March 4, 2018, Press Release from Subaru Telescope).

The Subaru Telescope is an optical telescope, but to study galaxy properties in more detail, observations at various wavelengths are needed. In the case of a rapidly star forming galaxy, most of the light from its young stars, which is an indicator of the star formation rate, is absorbed by its surrounding dust. The team needed to observe the infrared/radio emissions re-emitted from the dust to evaluate the star formation rate of a galaxy correctly. However, it is hard to observe in the infrared with ground-based telescopes because most of the infrared emissions are absorbed by water vapor in the atmosphere. There is no working space telescope with the sensitivity required to observe galaxies at 12 billion years ago in the infrared. ALMA can observe distant galaxies at radio wavelengths, however, its available wavelength range is limited and it is impractical to observe over 100 protoclusters.

To investigate the infrared properties of galaxies in protoclusters, the science team focused on the infrared data in public archives freely accessible to everyone. They used the archival full sky survey images at mid-far infrared taken by five (one is not a full sky survey) infrared space telescopes like Planck (Note 1). The spatial resolution and sensitivity of these images are too low to resolve distant galaxies individually, however, by stacking the images of the 180 protocluster candidates selected with HSC, they successfully constrained the average total infrared flux of a protocluster. Especially, the mid-far infrared flux (30-200 microns) of galaxies at 12 billion years ago has been unknown.

Figure 2: The derived average total infrared flux of a protocluster at 12 billion years ago. The red circles show the total fluxes from all the galaxies in a protocluster. Black points and the dotted line show the fluxes from a galaxy that was detected by HSC. The gray curve shows the infrared flux of a protocluster expected from the optical measurements by HSC. The dark gray region shows the difference in the flux between the actual infrared observations and the expectation from the HSC measurements. This difference implies that there are galaxies which are not observable in the optical but which are luminous in the infrared. (Credit: NAOJ)

Surprisingly, the average total infrared flux of a protocluster is brighter than that which was expected from the galaxy population found by HSC. This implies that there are galaxies which are not observable in the optical but which are luminous in the infrared.

What is the origin of this strong infrared emission? The team investigated the flux to wavelength distribution in the infrared and found that the average dust temperature of the protoclusters is warmer than that of a typical star forming galaxy. That implies that there are not only typical star forming galaxies but also growing super massive black holes at the centers of the galaxies (so called active galactic nuclei) and/or young hot dusty starburst galaxies which heat dust to higher temperatures. This study demonstrates the need to study protoclusters at wavelengths outside of the wavelength coverage of ground-based large telescopes like the Subaru Telescope and ALMA. 

To study the galaxies in protoclusters in more detail, individual protocluster galaxies need to be resolved in the mid to far-infrared, however, there is no telescope capable of such observations at this point. The leader of the team, Mariko Kubo (postdoctoral fellow at NAOJ) says, "In the future, SPICA, the future space telescope planned by Japan and ESA, will reveal the mid-far infrared forms of distant galaxies. On the other hand, unlike HSC, SPICA will not be made for wide field surveys. Our results partly complement SPICA's science."

This study was published in The Astrophysical Journal on December 20, 2019 (Mariko Kubo, Jun Toshikawa, Nobunari Kashikawa, Yi-Kuan Chiang, Roderik Overzier, Hisakazu Uchiyama, David L. Clements, David M. Alexander, Yuichi Matsuda, Tadayuki Kodama, Yoshiaki Ono, Tomotsugu Goto, Tai-An Cheng, and Kei Ito, 2019, ApJ 887, 214, "Planck Far-infrared Detection of Hyper Suprime-Cam Protoclusters at z∼4: Hidden AGN and Star Formation Activity"). This work was funded, in part, by the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (JP15H03645, JP17H04831, JP17KK0098, JP19H00697).

Source: Subaru Telescope

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Note 1: 

The science team used the data archived by the Planck, IRAS, WISE, Herschel, and AKARI space telescopes. These telescopes finished their missions a long time ago, but the data taken by them is in public data archives. Infrared space telescopes generally finish their lives within a few years because they have to load coolant (which should be exhausted) and operate in a harsh environment. For mid-infrared wavelength observations, the James Webb Space Telescope will be launched next year. However, there is no far-infrared observatory for distant galaxies between the Herschel space telescope, which finished its mission in 2013, and SPICA (planned to be launched in around 2030).

Links

• Double or Nothing: Astronomers Rethink Quasar Environment (March 4, 2018, Subaru Telescope Press Release)

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ESO Telescope Sees Surface of Dim Betelgeuse

PR Image eso2003a

SPHERE’s view of Betelgeuse in December 2019

PR Image eso2003b

SPHERE’s view of Betelgeuse in January 2019

PR Image eso2003c

Betelgeuse before and after dimming

PR Image eso2003d

Betelgeuse’s dust plumes seen by VISIR image

PR Image eso2003e

A plume on Betelgeuse (artist’s impression with annotations)

PR Image eso2003f

The star Betelgeuse in the constellation of Orion

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Videos

PR Video eso2003a

ESOcast 217 Light: ESO Telescope Sees Surface of Dim Betelgeuse

PR Video eso2003b

Zooming in on Betelgeuse

PR Video eso2003c

Betelgeuse before and after dimming (animated)

PR Video eso2003d
From Betelgeuse’s surroundings to its surface

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Using ESO’s Very Large Telescope (VLT), astronomers have captured the unprecedented dimming of Betelgeuse, a red supergiant star in the constellation of Orion. The stunning new images of the star’s surface show not only the fading red supergiant but also how its apparent shape is changing.

Betelgeuse has been a beacon in the night sky for stellar observers but it began to dim late last year. At the time of writing Betelgeuse is at about 36% of its normal brightness, a change noticeable even to the naked eye. Astronomy enthusiasts and scientists alike were excitedly hoping to find out more about this unprecedented dimming.

A team led by Miguel Montargès, an astronomer at KU Leuven in Belgium, has been observing the star with ESO's Very Large Telescope since December, aiming to understand why it’s becoming fainter. Among the first observations to come out of their campaign is a stunning new image of Betelgeuse’s surface, taken late last year with the SPHERE instrument.

The team also happened to observe the star with SPHERE in January 2019, before it began to dim, giving us a before-and-after picture of Betelgeuse. Taken in visible light, the images highlight the changes occurring to the star both in brightness and in apparent shape.

Many astronomy enthusiasts wondered if Betelgeuse’s dimming meant it was about to explode. Like all red supergiants, Betelgeuse will one day go supernova, but astronomers don’t think this is happening now. They have other hypotheses to explain what exactly is causing the shift in shape and brightness seen in the SPHERE images. “The two scenarios we are working on are a cooling of the surface due to exceptional stellar activity or dust ejection towards us,” says Montargès [1]. “Of course, our knowledge of red supergiants remains incomplete, and this is still a work in progress, so a surprise can still happen.”

Montargès and his team needed the VLT at Cerro Paranal in Chile to study the star, which is over 700 light-years away, and gather clues on its dimming. “ESO's Paranal Observatory is one of few facilities capable of imaging the surface of Betelgeuse,” he says. Instruments on ESO’s VLT allow observations from the visible to the mid-infrared, meaning astronomers can see both the surface of Betelgeuse and the material around it. “This is the only way we can understand what is happening to the star.”

Another new image, obtained with the VISIR instrument on the VLT, shows the infrared light being emitted by the dust surrounding Betelgeuse in December 2019. These observations were made by a team led by Pierre Kervella from the Observatory of Paris in France who explained that the wavelength of the image is similar to that detected by heat cameras. The clouds of dust, which resemble flames in the VISIR image, are formed when the star sheds its material back into space.

“The phrase ‘we are all made of stardust’ is one we hear a lot in popular astronomy, but where exactly does this dust come from?” says Emily Cannon, a PhD student at KU Leuven working with SPHERE images of red supergiants. “Over their lifetimes, red supergiants like Betelgeuse create and eject vast amounts of material even before they explode as supernovae. Modern technology has enabled us to study these objects, hundreds of light-years away, in unprecedented detail giving us the opportunity to unravel the mystery of what triggers their mass loss.”

Souce: ESO/News

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Notes

[1] Betelgeuse's irregular surface is made up of giant convective cells that move, shrink and swell. The star also pulsates, like a beating heart, periodically changing in brightness. These convection and pulsation changes in Betelgeuse are referred to as stellar activity. 

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More Information

The team is composed of Miguel Montargès (Institute of Astronomy, KU Leuven, Belgium), Emily Cannon (Institute of Astronomy, KU Leuven, Belgium), Pierre Kervella (LESIA, Observatoire de Paris - PSL, France), Eric Lagadec (Laboratoire Lagrange, Observatoire de la Côte d'Azur, France), Faustine Cantalloube (Max-Planck-Institut für Astronomie, Heidelberg, Germany), Joel Sánchez Bermúdez (Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico and Max-Planck-Institut für Astronomie, Heidelberg, Germany), Andrea Dupree (Center for Astrophysics | Harvard & Smithsonian, USA), Elsa Huby (LESIA, Observatoire de Paris - PSL, France), Ryan Norris (Georgia State University, USA), Benjamin Tessore (IPAG, France), Andrea Chiavassa (Laboratoire Lagrange, Observatoire de la Côte d'Azur, France), Claudia Paladini (ESO, Chile), Agnès Lèbre (Université de Montpellier, France), Leen Decin (Institute of Astronomy, KU Leuven, Belgium), Markus Wittkowski (ESO, Germany), Gioia Rau (NASA/GSFC, USA), Arturo López Ariste (IRAP, France), Stephen Ridgway (NSF’s National Optical-Infrared Astronomy Research Laboratory, USA), Guy Perrin (LESIA, Observatoire de Paris - PSL, France), Alex de Koter (Astronomical Institute Anton Pannekoek, Amsterdam University, The Netherlands & Institute of Astronomy, KU Leuven, Belgium), Xavier Haubois (ESO, Chile), Eric Pantin (CEA, France), Ralf Siebenmorgen (ESO, Germany).

The VISIR image was obtained as part of the NEAR science demonstration observations. NEAR (Near Earths in the AlphaCen Region) is an upgrade of VISIR, which was implemented as a time-limited experiment.

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

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Links

• Photos of the VLT

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Contacts

Miguel Montargès
FWO [PEGASUS]² Marie Skłodowska-Curie Fellow / Institute of Astronomy, KU Leuven
Leuven, Belgium
Tel: +32 16 32 74 67
Email: miguel.montarges@kuleuven.be

Emily Cannon
Institute of Astronomy, KU Leuven
Leuven, Belgium
Tel: +32 16 32 88 92
Email: emily.cannon@kuleuven.be

Pierre Kervella
LESIA, Observatoire de Paris - PSL
Paris, France
Tel: +33 0145077966
Email: pierre.kervella@observatoiredeparis.psl.eu

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

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