Betelgeuse – a giant with blemishes

An artist's impression of the Red Supergiant Betelgeuse. Its surface is covered by large star spots, which reduce its brightness. During their pulsations, such stars regularly release gas into their surroundings, which condenses into dust. Image: MPIA graphics department.

These high-resolution images of Betelgeuse show the distribution of brightness in visible light on its surface before and during its darkening. Due to the asymmetry, the authors conclude that there are huge stars pots. The images were taken by the SPHERE camera of the European Southern Observatory (ESO). Image: ESO/M. Montargès et al.

Gigantic star spots are probably the reason for the recent drop in brightness of the red giant star

Betelgeuse, the bright star in the constellation of Orion, has been fascinating astronomers in the recent months because of its unusually strong decline in brightness. Scientists have been discussing a number of scenarios trying to explain its behaviour. Now a team led by Thavisha Dharmawardena of the Max Planck Institute for Astronomy have shown that most likely unusually large star spots on the surface of Betelgeuse have caused the dimming. Their results rule out the previous conjecture that it was dust, recently ejected by Betelgeuse, which obscured the star. The results are published today in the journal The Astrophysical Journal Letters.

Red giant stars like Betelgeuse undergo frequent brightness variations. However, the striking drop in Betelgeuse's luminosity to about 40% of its normal value between October 2019 and April 2020 came as a surprise to astronomers. Scientists have developed various scenarios to explain this change in the brightness of the star, which is visible to the naked eye and almost 500 light years away. Some astronomers even speculated about an imminent supernova. An international team of astronomers led by Thavisha Dharmawardena from the Max Planck Institute for Astronomy (MPIA) in Heidelberg have now demonstrated that temperature variations in the photosphere, i.e. the luminous surface of the star, caused the brightness to drop. The most plausible source for such temperature changes are gigantic cool star spots, similar to sunspots, which, however, cover 50 to 70% of the star’s surface.

“Towards the end of their lives, stars become red giants,” Dharmawardena explains. “As their fuel supply runs out, the processes change by which the stars release energy. As a result, they bloat, become unstable and pulsate with periods of hundreds or even thousands of days, which we see as a fluctuation in brightness.” Betelgeuse is a so-called Red Supergiant, a star which, compared to our Sun, is about 20 more massive and roughly 1000 times larger. If placed in the centre of the solar system, it would almost reach the orbit of Jupiter.

Because of its size, the gravitational pull on the surface of the star is less than on a star of the same mass but with a smaller radius. Therefore, pulsations can eject the outer layers of such a star relatively easily. The released gas cools down and develops into compounds that astronomers call dust. This is why red giant stars are an important source of heavy elements in the Universe, from which planets and living organisms eventually evolve. Astronomers have previously considered the production of light absorbing dust as the most likely cause of the steep decline in brightness.

To test this hypothesis, Thavisha Dharmawardena and her collaborators evaluated new and archival data from the Atacama Pathfinder Experiment (APEX) and the James Clerk Maxwell telescope (JCMT). These telescopes measure radiation from the spectral range of submillimetre waves (terahertz radiation), whose wavelength is a thousand times greater than that of visible light. Invisible to the eye, astronomers have been using them for some time to study interstellar dust. Cool dust in particular glows at these wavelengths.

“What surprised us was that Betelgeuse turned 20% darker even in the submillimetre wave range,” reports Steve Mairs from the East Asian Observatory, who collaborated on the study. Experience shows that such behaviour is not compatible with the presence of dust. For a more precise evaluation, she and her collaborators calculated what influence dust would have on measurements in this spectral range. It turned out that indeed a reduction in brightness in the sub-millimetre range cannot be attributed to an increase in dust production. Instead, the star itself must have caused the brightness change the astronomers measured.

Physical laws tell us that the luminosity of a star depends on its diameter and especially on its surface temperature. If only the size of the star decreases, the luminosity diminishes equally in all wavelengths. However, temperature changes affect the radiation emitted along the electromagnetic spectrum differently. According to the scientists, the measured darkening in visible light and submillimeter waves is therefore evidence of a reduction in the mean surface temperature of Betelgeuse, which they quantify at 200 K (or 200 °C).

“However, an asymmetric temperature distribution is more likely,” explains co-author Peter Scicluna from the European Southern Observatory (ESO). “Corresponding high-resolution images of Betelgeuse from December 2019 show areas of varying brightness. Together with our result, this is a clear indication of huge star spots covering between 50 and 70% of the visible surface and having a lower temperature than the brighter photosphere.” Star spots are common in giant stars, but not on this scale. Not much is known about their lifetimes. However, theoretical model calculations seem to be compatible with the duration of Betelgeuse's dip in brightness.

We know from the Sun that the amount of spots increases and decreases in an 11-year cycle. Whether giant stars have a similar mechanism is uncertain. An indication for this could be the previous brightness minimum, which was also much more pronounced than those in previous years. “Observations in the coming years will tell us whether the sharp decrease in Betelgeuse's brightness is related to a spot cycle. In any case, Betelgeuse will remain an exciting object for future studies,” Dharmawardena concludes.

Background information

This study was published in an article titled “Betelgeuse fainter in the sub-millimetre too: an analysis of JCMT and APEX monitoring during the recent optical minimum” in The Astrophysical Journal Letters (DOI: 10.3847/2041-8213/ab9ca6). Besides the main author, seven scientists from five research institutes in four countries are involved in the publication.

The scientists used data from the following observatories: James Clerk Maxwell Telescope (JCMT) operated by the East Asian Observatory on Hawaii, USA; Atacama Pathfinder Experiment (APEX) operated in conjunction of Max Planck Institute for Radio Astronomy in Bonn, Germany , Onsala Space Observatory, Sweden, and the European Southern Observatory (ESO)

Source: Max Planck Institute for Astronomy

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Contacts

Thavisha Dharmawardena
Phone:+49 6221 528-451
Max Planck Institute for Astronomy, Heidelberg
Max Planck Institute for Astronomy

Markus Nielbock
Press and public relations officer
Phone:+49 6221 528-134
Max Planck Institute for Astronomy, Heidelberg
Max Planck Institute for Astronomy
Mobile: +49 15678 747326

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Original publication

1. Thavisha E. Dharmawardena, Steve Mairs, Peter Scicluna, et al.

Betelgeuse fainter in the sub-millimetre too: an analysis of JCMT and APEX monitoring during the recent optical minimum

The Astrophysical Journal Letters (2020), Vol. 897, p. 1

Source / DOI

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Download

High-resolution version of the image of Betelgeuse

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Hubble Sees Cosmic Flapping ‘Bat Shadow’

Astronomers using Hubble previously captured a remarkable image of a young star's unseen, planet-forming disk casting a huge shadow across a more distant cloud in a star-forming region. The star is called HBC 672, and the shadow feature was nicknamed the "Bat Shadow" because it resembles a pair of wings. The nickname turned out to be unexpectedly appropriate, because now those "wings" appear to be flapping! Credits: NASA, ESA, and STScI.  Hi-res image

This illustration shows a fledgling star surrounded by a warped, saddle-shaped disk with two peaks and two dips. A planet embedded in the disk, inclined to the disk's plane, may be causing the warping. As the disk rotates around the young star, it is thought to block the light from that star and cast a varying, flapping shadow on a distant cloud. Credits: NASA, ESA, and A. James and G. Bacon (STScI)

Download this video in HD formats from NASA Goddard's Scientific Visualization Studio

Credits: NASA's Goddard Space Flight Center

Sometimes nicknames turn out to be closer to reality than you might imagine.

NASA’s Hubble Space Telescope captured a striking image of a fledgling star’s unseen, planet-forming disk casting a huge shadow across a more distant cloud in a star-forming region – like a fly wandering into the beam of a flashlight shining on a wall.

The young star is called HBC 672, and the shadow feature was nicknamed the “Bat Shadow” because it resembles a pair of wings. The nickname turned out to be surprisingly appropriate: Now, the team reports that they see the Bat Shadow flapping!

“The shadow moves. It’s flapping like the wings of a bird!” described lead author Klaus Pontoppidan, an astronomer at the Space Telescope Science Institute (STScI) in Baltimore. The phenomenon may be caused by a planet pulling on the disk and warping it. The team witnessed the flapping over 404 days.

But what created the Bat Shadow in the first place?

“You have a star that is surrounded by a disk, and the disk is not like Saturn’s rings – it’s not flat. It’s puffed up. And so that means that if the light from the star goes straight up, it can continue straight up – it’s not blocked by anything. But if it tries to go along the plane of the disk, it doesn’t get out, and it casts a shadow,” explained Pontoppidan.

He suggests imagining a lamp with a shade that casts a shadow on the wall. In this case, the lightbulb is the star, the lampshade is the disk, and the cloud is the wall. Based on the shadow’s shape, the disk must be flared, with an angle that increases with distance – like bell-bottom pants, or a trumpet.

The disk – a circling structure of gas, dust, and rock – might be roughly saddle-shaped, with two peaks and two dips, which would explain the “flapping” of the shadow. The team speculates that a planet is embedded in the disk, with an orbit inclined to the disk’s plane. This planet would be the cause of the doubly warped shape of the orbiting disk and the resulting movement in its shadow.

“If there were just a simple bump in the disk, we'd expect both sides of the shadow to tilt in opposite directions, like airplane wings during a turn,” said team member Colette Salyk of Vassar College in Poughkeepsie, New York.

The shadow, extending from the star across the surrounding cloud, is so large – about 200 times the length of our solar system – that light doesn’t travel instantaneously across it. In fact, the time it takes for the light to travel from the star out to the perceivable edge of the shadow is about 40 to 45 days. Pontoppidan and his team calculate a planet warping the disk would orbit its star in no fewer than 180 days. They estimate that this planet would be about the same distance from its star as Earth is from the Sun.

If not a planet, an alternative explanation for the shadow motion is a lower-mass stellar companion orbiting HBC 672 outside the plane of the disk, causing HBC 672 to “wobble” relative to its shadowing disk. But Pontoppidan and his team doubt this is the case, based on the thickness of the disk. There is also no current evidence for a binary companion.

The disk is too small and too distant to be seen, even by Hubble. The star HBC 672 resides in a stellar nursery called the Serpens Nebula, about 1,400 light-years away. It is only one or two million years old, which is young in cosmic terms.

This finding was serendipitous. The first image of the Bat Shadow was taken by another team. Later, the image was slated for use in NASA’s Universe of Learning, a program that creates materials and experiences to enable learners to explore the universe for themselves. The goal was to illustrate how shadows can convey information about phenomena invisible to us. However, the original team only observed the Bat Shadow in one light filter, which did not provide enough data for the color image desired by NASA’s Universe of Learning.

To get the color image, Pontoppidan and his team had to observe the shadow in additional filters. When they combined the old and new images, the shadow appeared to have moved. At first, they thought the problem was in the image processing, but they quickly realized the images were properly aligned and the phenomenon was real.

The team’s paper will appear in an upcoming edition of the Astrophysical Journal.

NASA’s Universe of Learning materials are based upon work supported by NASA under award number NNX16AC65A. For more information about NASA’s Universe of Learning, see: https://www.universe-of-learning.org/

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 conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

For images, video, and more information about this study and Hubble, visit:

https://hubblesite.org/contents/news-releases/2020/news-2020-22 - https://www.nasa.gov/hubble

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Contacts

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

Ann Jenkins / Ray Villard
Space Telescope Science Institute, Baltimore
410-338-4488 / 410-338-4514
jenkins@stsci.edu / villard@stsci.edu

Klaus Pontoppidan
Space Telescope Science Institute, Baltimore
pontoppi@stsci.edu

Colette Salyk
Vassar College, Poughkeepsie, New York
cosalyk@vassar.edu

Editor: Rob Garner

Source: NASA/Hubble

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Researchers find the origin and the maximum mass of massive black holes observed by gravitational wave detectors

Figure 1: Schematic diagram of the binary black hole formation path for GW170729. A star below 80 solar mass evolves and develops into a core-collapse supernova. The star does not experience pair-instability, so there is no significant mass ejection by pulsation. After the star forms a massive iron core, it collapses by its own gravity and forms a black hole with a mass below 38 solar mass. A star between 80 and 140 solar mass evolves and develops into a pulsational pair-instability supernova. After the star forms a massive carbon-oxygen core, the core experiences catastrophic electron-positron pair-creation. This excites strong pulsation and partial ejection of the stellar materials. The ejected materials form the circumstellar matter surrounding the star. After that, the star continues to evolve and forms a massive iron core, which collapses in a fashion similar to the ordinary core-collapse supernova, but with a higher final black hole mass between 38 - 52 solar mass. These two paths could explain the origin of the detected binary black hole masses of the gravitational wave event GW170729. (Credit：Shing-Chi Leung et al./Kavli IPMU)

Simulation: Pulsational pair-instability supernova evolutionary process

Credit: Shing-Chi Leung et al.

Figure 2: The red line shows the time evolution of the temperature and density at the center of the initially 120 solar mass star (PPISN: pulsational pair-instability supernova). The arrows show the direction of time. The star pulsates (i.e., contraction and expansion twice) by making bounces at #1 and #2 and finally collapses along a line similar to that of a 25 solar mass star (thin blue line: CCSN (core-collapse supernova)). The thick blue line shows the contraction and final expansion of the 200 solar mass star which is disrupted completely with no black hole left behind (PISN: pair-instability supernova). Top left area enclosed by the black solid line is the region where a star is dynamically unstable. (Credit：Shing-Chi Leung et al.)

Figure 3: The red line (that connects the red simulation points) shows the mass of the black hole left after the pulsational pair-instability supernova (PPISN) against the initial stellar mass. The red and black dashed lines show the mass of the helium core left in the binary system. The red line is lower than the dashed line because some amount of mass is lost from the core by pulsational mass loss. (Pair-instability supernova, PISN, explodes completely with no remnant left.) The peak of the red line gives the maximum mass, 52 solar mass, of the black hole to be observed by gravitational waves. (Credit：Shing-Chi Leung et al.)

Figure 4: The masses of a pair of the black holes (indicated by the same color) whose merging produced gravitational waves (GW) detected by advanced LIGO and VIRGO (merger event names GW150914 to GW170823 indicate year-month-day). The box enclosed by 38 - 52 solar mass is the remnant mass range produced by PPISNe. Black hole masses falling inside this box must have an origin of PPISN before collapse. Below 38 solar mass is the black hole formed by a massive star undergoing CCSN. In addition to GW170729, GW170823 is a candidate of a PPISN in the lower mass limit side. (Credit：Shing-Chi Leung et al.)

Through simulations of a dying star, a team of theoretical physics researchers have found the evolutionary origin and the maximum mass of black holes which are discovered by the detection of gravitational waves as shown in Figure 1.

The exciting detection of gravitational waves with LIGO (laser interferometer gravitational-wave observatory) and VIRGO (Virgo interferometric gravitational-wave antenna) have shown the presence of merging black holes in close binary systems.

The masses of the observed black holes before merging have been measured and turned out to have a much larger than previously expected mass of about 10 times the mass of the Sun (solar mass). In one of such event, GW170729, the observed mass of a black hole before merging is actually as large as about 50 solar mass. But it is not clear which star can form such a massive black hole, or what the maximum of black holes which will be observed by the gravitational wave detectors is.

To answer this question, a research team at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) consisting of Project Researcher at the time Shing-Chi Leung (currently at the California Institute of Technology), Senior Scientist Ken’ichi Nomoto, and Visiting Senior Scientist Sergei Blinnikov (professor at the Institute for Theoretical and Experimental Physics in Mosow) have investigated the final stage of the evolution of very massive stars, in particular 80 to 130 solar mass stars in close binary systems. Their finding are shown in Illustrations (a - e) and Figures (1 - 4).

In close binary systems, initially 80 to 130 solar mass stars lose their hydrogen-rich envelope and become helium stars of 40 to 65 solar mass. When the initially 80 to 130 solar mass stars form oxygen-rich cores, the stars undergo dynamical pulsation (Illustrations a - b and Figure 2), because the temperature in the stellar interior becomes high enough for photons to be converted into electron-positron pairs. Such “pair-creation” makes the core unstable and accelerates contraction to collapse (Illustration b).

In the over-compressed star, oxygen burns explosively. This triggers a bounce of collapse and then rapid expansion of the star. A part of the stellar outer layer is ejected, while the inner part cools down and collapses again (Illustration c). The pulsation (collapse and expansion) repeats until oxygen is exhausted (Illustration d). This process is called “pulsational pair-instability”(PPI). The star forms an iron core and finally collapses into a black hole, which would trigger the supernova explosion (Illustration e), being called PPI-supernova (PPISN).

By calculating several such pulsations and associated mass ejection until the star collapses to form a black hole, the team found that the maximum mass of the black hole formed from pulsational pair-instability supernova is 52 solar mass (Figure 3).

Stars initially more massive than 130 solar mass (which form helium stars more massive than 65 solar mass) undergo “pair instability supernova” due to explosive oxygen burning, which disrupts the star completely with no black hole remnant. Stars above 300 solar mass collapse and may form a black hole more massive than about 150 solar mass.

The above results predict that there exists a “mass-gap” in the black hole mass between 52 and about 150 solar mass. The results mean that the 50 solar mass black hole in GW170729 is most likely a remnant of a pulsational pair-instability supernova as shown in Figures 3 and 4.

The result also predicts that a massive circumstellar medium is formed by the pulsational mass loss, so that the supernova explosion associated with the black hole formation will induce collision of the ejected material with the circumstellar matter to become a super-luminous supernovae. Future gravitational wave signals will provide a base upon which their theoretical prediction will be tested.

Source: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)

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Paper details:

Journal: The Astrophysical Journal

Title: Pulsational Pair-instability Supernovae. I. Pre-collapse Evolution and Pulsational Mass Ejection

Authors: Shing-Chi Leung (1, 2), Ken'ichi Nomoto (1) and Sergei Blinnikov (1, 3, 4)

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Author affiliations:

1. Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan.
2. Walter Burke Institute for Theoretical Physics, California Institute of Technology (TAPIR at Caltech), Pasadena, CA 91125, USA.
3. National Research Center, “Kurchatov Institute,” Institute for Theoretical and Experimental Physics (ITEP), B. Cheremushkinkaya 25, 117218 Moscow, Russia.

4. Automatics Research Institute (VNIIA), Suschevskaya 22, 127055 Moscow, Russia.

DOI: https://doi.org/10.3847/1538-4357/ab4fe5 (Published 10 December, 2019)

Images All images can be downloaded from here

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Research contact

Ken'ichi Nomoto
Senior Scientist
Kavli Institute for the Physics and Mathematics for the Universe,
University of Tokyo
E-mail: nomoto@stron.s.u-tokyo.ac.jp
Phone: +81-4-7136-5940

Media Contact

John Amari
Press officer
Kavli Institute for the Physics and Mathematics of the Universe
The University of Tokyo
E-mail: press_at_ipmu.jp
Tel: 080-4056- 2767

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Black Hole Collision May Have Exploded with Light

Artist's concept of a supermassive black hole and its surrounding disk of gas. Embedded within this disk are two smaller black holes orbiting one another. Using data from the Zwicky Transient Facility (ZTF) at Palomar Observatory, researchers have identified a flare of light suspected to have come from one such binary pair soon after they merged into a larger black hole. The merger of the black holes would have caused them to move in one direction within the disk, plowing through the gas in such a way to create a light flare. The finding, while not confirmed, could amount to the first time that light has been seen from a coalescing pair of black holes. These merging black holes were first spotted on May 21, 2019, by the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector, which picked up gravitational waves generated by the merger. Credit: Caltech/R. Hurt (IPAC)

Possible light flare observed from small black holes within the disk of a massive black hole

When two black holes spiral around each other and ultimately collide, they send out ripples in space and time called gravitational waves. Because black holes do not give off light, these events are not expected to shine with any light waves, or electromagnetic radiation. But some theorists have come up with ways in which a black hole merger might explode with light. Now, for the first time, astronomers have seen evidence for one of these light-producing scenarios.

With the help of Caltech's Zwicky Transient Facility (ZTF), funded by the National Science Foundation (NSF) and located at Palomar Observatory near San Diego, the scientists have spotted what might be a flare of light from a pair of coalescing black holes. The black hole merger was first witnessed by the NSF's Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector on May 21, 2019, in an event called S190521g. As the black holes merged, jiggling space and time, they sent out gravitational waves.

While this was happening, ZTF was performing its robotic survey of the sky that captured all kinds of objects that flare, erupt, or otherwise vary in the night sky. One flare the survey caught, generated by a distant active supermassive black hole, or quasar, called J1249+3449, was pinpointed to the region of the gravitational-wave event S190521g.

"This supermassive black hole was burbling along for years before this more abrupt flare," says Matthew Graham, a research professor of astronomy at Caltech and the project scientist for ZTF. "The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event. In our study, we conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities." Graham is lead author of the new study, published today, June 25, in the journal Physical Review Letters.

"ZTF was specifically designed to identify new, rare, and variable types of astronomical activity like this," says NSF Division of Astronomical Science Director Ralph Gaume. "NSF support of new technology continues to expand how we can track such events."

How do two merging black holes erupt with light? In the scenario outlined by Graham and his colleagues, two partner black holes were nestled within a disk surrounding a much larger black hole.

"At the center of most galaxies lurks a supermassive black hole. It's surrounded by a swarm of stars and dead stars, including black holes," says co-author K. E. Saavik Ford of the City University of New York (CUNY) Graduate Center, the Borough of Manhattan Community College (BMCC), and the American Museum of Natural History (AMNH). "These objects swarm like angry bees around the monstrous queen bee at the center. They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole's disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up," she says.

Once the black holes merge, the new, now-larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the disk. "It is the reaction of the gas to this speeding bullet that creates a bright flare, visible with telescopes," says co-author Barry McKernan, also of the CUNY Graduate Center, BMCC, and AMNH.

Such a flare is predicted to begin days to weeks after the initial splash of gravitational waves produced during the merger. In this case, ZTF did not catch the event right away, but when the scientists went back and looked through archival ZTF images months later, they found a signal that started days after the May 2019 gravitational-wave event. ZTF observed the flare slowly fade over the period of a month.

The scientists attempted to get a more detailed look at the light of the supermassive black hole, called a spectrum, but by the time they looked, the flare had already faded. A spectrum would have offered more support for the idea that the flare came from merging black holes within the disk of the supermassive black hole. However, the researchers say they were able to largely rule out other possible causes for the observed flare, including a supernova or a tidal disruption event, which occurs when a black hole essentially eats a star.

What is more, the team says it is not likely that the flare came from the usual rumblings of the supermassive black hole, which regularly feeds off its surrounding disk. Using the Catalina Real-Time Transient Survey, led by Caltech, they were able to assess the behavior of the black hole over the past 15 years, and found that its activity was relatively normal until May of 2019, when it suddenly intensified.

"Supermassive black holes like this one have flares all the time. They are not quiet objects, but the timing, size, and location of this flare was spectacular," says co-author Mansi Kasliwal (MS '07, PhD '11), an assistant professor of astronomy at Caltech. "The reason looking for flares like this is so important is that it helps enormously with astrophysics and cosmology questions. If we can do this again and detect light from the mergers of other black holes, then we can nail down the homes of these black holes and learn more about their origins."

The newly formed black hole should cause another flare in the next few years. The process of merging gave the object a kick that should cause it to enter the supermassive black hole's disk again, producing another flash of light that ZTF should be able to see.

The Physical Review Letters paper, titled, "A Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational Wave Event GW190521g," was funded by the NSF, NASA, the Heising-Simons Foundation, and the GROWTH (Global Relay of Observatories Watching Transients Happen) program. Other co-authors include: K. Burdge, S.G. Djorgovski, A.J. Drake, D. Duev, A.A. Mahabal, J. Belecki, R. Burruss, G. Helou, S.R. Kulkarni, F.J. Masci, T. Prince, D. Reiley, H. Rodriguez, B. Rusholme, R.M. Smith, all from Caltech; N.P. Ross of the University of Edinburgh; Daniel Stern of the Jet Propulsion Laboratory, managed by Caltech for NASA; M. Coughlin of the University of Minnesota; S. van Velzen of University of Maryland, College Park and New York University; E.C. Bellm of the University of Washington; S.B. Cenko of NASA Goddard Space Flight Center; V. Cunningham of University of Maryland, College Park; and M.T. Soumagnac of the Lawrence Berkeley National Laboratory and the Weizmann Institute of Science.

In addition to the NSF, ZTF is funded by an international collaboration of partners, with additional support from NASA, the Heising-Simons Foundation, members of the Space Innovation Council at Caltech, and Caltech itself.

Written by Whitney Clavin

Contact:

Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

Source: Caltech/News

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Monster Black Hole Found in the Early Universe

Astronomers discovered this, the second most distant quasar ever found, using the international Gemini Observatory and Cerro Tololo Inter-American Observatory (CTIO), Programs of NSF’s NOIRLab. It is the first quasar to receive an indigenous Hawaiian name. In honor of its discovery from Maunakea, a sacred mountain revered in the Hawaiian culture, the quasar J1007+2115 was given the Hawaiian name Pōniuāʻena, meaning “unseen spinning source of creation, surrounded with brilliance" in the Hawaiian language. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld. download TIFF | JPEG

An artist’s impression of the formation of quasar Pōniuāʻena, starting with a seed black hole, 100 million years after the Big Bang. Astronomers discovered this, the second most distant quasar ever found, using the international Gemini Observatory and Cerro Tololo Inter-American Observatory (CTIO), Programs of NSF’s NOIRLab. It is the first quasar to receive an indigenous Hawaiian name. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld.  download TIFF | JPEG

An artist’s impression of the quasar Pōniuāʻena. Astronomers discovered this, the second most distant quasar ever found, using the international Gemini Observatory and Cerro Tololo Inter-American Observatory (CTIO), Programs of NSF’s NOIRLab. It is the first quasar to receive an indigenous Hawaiian name. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld.  download TIFF | JPEG

Astronomers have discovered the second most distant quasar ever found, using the international Gemini Observatory and Cerro Tololo Inter-American Observatory (CTIO). It is also the first quasar to receive an indigenous Hawaiian name, Pōniuāʻena. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Pete Marenfeld, ESA/Hubble, NASA, M. Kornmesser. A Special Thanks to A Hua He Inoa and the ‘Imiloa Astronomy Center of Hawaiʻi. Music: zero-project — The Lower Dungeons (zero-project.gr).  Video

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The second most distant quasar ever discovered now has a Hawaiian name

Astronomers have discovered the second most distant quasar ever found, using the international Gemini Observatory and Cerro Tololo Inter-American Observatory (CTIO), Programs of NSF’s NOIRLab. It is also the first quasar to receive an indigenous Hawaiian name, Pōniuāʻena. The quasar contains a monster black hole, twice the mass of the black hole in the only other quasar found at the same epoch, challenging the current theories of supermassive black hole formation and growth in the early Universe.

After more than a decade of searching for the first quasars, a team of astronomers used the NOIRLab’s Gemini Observatory and CTIO to discover the most massive quasar known in the early Universe — detected from a time only 700 million years after the Big Bang [1]. Quasars are the most energetic objects in the Universe, powered by their supermassive black holes, and since their discovery astronomers have been keen to determine when they first appeared in our cosmic history.

Systematic searches for these objects have led to the discovery of the most distant quasar (J1342+0928) in 2018 and now the second most distant, J1007+2115 [2]. The A Hua He Inoa program named J1007+2115 Pōniuāʻena, meaning “unseen spinning source of creation, surrounded with brilliance" in the Hawaiian language [3]. The supermassive black hole powering Pōniuāʻena is 1.5 billion times more massive than our Sun.

“Pōniuāʻena is the most distant object known in the Universe hosting a black hole exceeding one billion solar masses” said Jinyi Yang, a Postdoctoral Research Associate at the Steward Observatory of the University of Arizona.

For a black hole of this size to form this early in the Universe, it would need to start as a 10,000 solar mass “seed” black hole about 100 million years after the Big Bang, rather than growing from a much smaller black hole formed by the collapse of a single star.

“How can the Universe produce such a massive black hole so early in its history?” wondered Xiaohui Fan, Regents’ professor and associate department head of the Department of Astronomy at the University of Arizona. “This discovery presents the biggest challenge yet for the theory of black hole formation and growth in the early Universe.”

Current theory suggests that at the beginning of the Universe following the Big Bang, atoms were too distant from one another to interact and form stars and galaxies. The birth of stars and galaxies as we know them happened during the Epoch of Reionization, beginning about 400 hundred million years after the Big Bang. The discovery of quasars like Pōniuāʻena, deep into the reionization epoch, is a big step towards understanding this process of reionization and the formation of early supermassive black holes and massive galaxies. Pōniuāʻena has placed new and important constraints on the evolution of the matter between galaxies (the intergalactic medium) in the reionization epoch.

The search for distant quasars began with the research team combing through large area surveys such as the DECaLS imaging survey which uses the Dark Energy Camera (DECam) on the Víctor M. Blanco 4-meter Telescope, located at CTIO in Chile. The team uncovered a possible quasar in the data, and in 2019 they observed it with telescopes including the Gemini North telescope and the W. M. Keck Observatory both on Maunakea on Hawai‘i Island. Gemini’s GNIRS instrument confirmed the existence of Pōniuāʻena.

“Observations with Gemini were critical for obtaining high-quality near-infrared spectra which provided us with the measurement of the black hole’s astounding mass,” said Feige Wang, a NASA NHFP fellow at the Steward Observatory of the University of Arizona.

In honor of its discovery from Maunakea, this quasar was given the Hawaiian name Pōniuāʻena. The name was created by thirty Hawaiian immersion school teachers during a workshop led by the A Hua He Inoa group, a Hawaiian naming program led by the ‘Imiloa Astronomy Center of Hawai‘i. Pōniuāʻena is the first quasar to receive an indigenous name.

“In addition to the teamwork of the telescopes of NOIRLab that made this discovery possible, it is exciting to see the collaboration of science and culture in local communities, highlighted by this new name,” said Chris Davis, Program Officer at the National Science Foundation.

“I am extremely grateful to be a part of this educational experience — it is a rare learning opportunity,” said Kauʻi Kaina, a High School Hawaiian Immersion Teacher from Kahuku, Oʻahu who was involved in the naming workshop. “Today it is relevant to apply these cultural values in order to further the wellbeing of the Hawaiian language beyond ordinary contexts, such as in school, but also so that the language lives throughout the Universe.”

Source: Gemini Observatory

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Notes

[1] This corresponds to a redshift of 7.52 or a lookback time of 13.02 billion years.

[2] The full name of the quasar is J100758.264+211529.207.

[3] Pronounced: POH-knee-ew-aah-EH-na.

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More information

This research was presented in a paper to appear in The Astrophysical Journal Letters.

The team is composed of Jinyi Yang (University of Arizona), Feige Wang (University of Arizona), Xiaohui Fan (University of Arizona), Joseph F. Hennawai (University of California, Santa Barbara), Frederick B. Davis (University of California, Santa Barbara), Minghao Yue (University of Arizona), Eduardo Banados (Max Planck Institute for Astronomy), Xue-Bing Wu (Peking University), Bran Venemans (Max Planck Institute for Astronomy), Aaron J. Barth (University of California, Irvine), Fuyan Bian (European Southern Observatory), Roberto Decalari (INAF), Emanuele Paolo Farina (Max Planck Institute for Astrophysics), Richard Green (University of Arizona), Linhua Jiang (Peking University), Jiang-Tao Li (University of Michigan), Chiara Mazzucchelli (European Southern Observatory), and Fabian Walter (Max Planck Institute for Astronomy).

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Links

• Research paper
  
• Interview on the naming process
• Photos of the Gemini Telescope

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Contacts:

Jinyi Yang
University of Arizona
Phone: +1 520 360 3966
Email: jinyiyang@email.arizona.edu

Xiaohui Fan
University of Arizona
Phone: +1 520 626 7558
Email: fan@as.arizona.edu

Peter Michaud
NewsTeam Manager
NSF’s NOIRLab
Gemini Observatory, Hilo HI
Cell: +1 808 936 6643
Email: pmichaud@gemini.edu

Amanda Kocz
Press and Internal Communications Officer
NSF’s NOIRLab
Cell: +1 626 524 5884
Email: akocz@aura-astronomy.org

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Young Planets Bite the Dust

noirlab2014a/noirlab2014b (Labeled) – GPI Circumstellar Disks

Six circumstellar disks selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). These images highlight the diversity of shapes and sizes that these disks can take and show the outer reaches of star systems in their formative years. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley). Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin. 3906 × 2642 jpg  -  3906 × 2642 jpg  (Labeled)

noirlab2014c – HD 129590

A circumstellar disk around star HD 129590 selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI).  Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley).  Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin. 1200 × 1200 jpg

noirlab2014d – HD 117214

A circumstellar disk around star HD 117214 selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin. noirlab2014e – HD 111520 A circumstellar disk around star HD 111520 selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin. 1200 × 1200 jpg

noirlab2014e – HD 111520

A circumstellar disk around star HD 111520 selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.  1200 × 1200 jpg

noirlab2014f – HR 4796 A

A circumstellar disk around star HR 4796 A selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.  1200 × 1200 jpg

noirlab2014g – TWA 7

A circumstellar disk around star TWA 7 selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.  1200 × 1200 jpg

noirlab2014h – HD 32297

A circumstellar disk around star HD 32297 selected from the larger sample of 26 disks obtained with the Gemini South telescope in Chile using the Gemini Planet Imager (GPI). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Esposito (UC Berkeley) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.  1200 × 1200 jpg

noirlab2014a – Images of Dusty Star Systems Revealed by the Gemini Planet Imager Animation of the Solar System and moving outward to indicate stars observed with the Gemini Planet Imager (GPI) mounted on the Gemini South telescope in Chile. Highlighted are the images of the dusty rings encircling some of these young stars. More than 100 researchers have contributed to GPI and the GPI Exoplanet Survey, whose work is highlighted in this video. The work was supported by the National Science Foundation (NSF) and NASA. Created by Jenny Patience and Ric Alling, Arizona State University, with scientific input from Justin Hom (ASU), Paul Kalas (UC Berkeley), Tom Esposito (UC Berkeley) and Franck Marchis (SETI Institute). Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. Patience & R. Alling (Arizona State University)/T. Esposito (UC Berkeley) noirlab2014a mp4

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Astronomers unveil new collection of planet-forming dusty star systems

These orange swirls of dust are snapshots from the largest collection of sharp, detailed images of dusty debris disks around young stars — published this week by an international group of astronomers. The images — captured by the 8-meter Gemini South telescope using the Gemini Planet Imager — illustrate the variety of shapes and sizes that stellar systems can take during their infancy. Unexpectedly, the majority of these systems display evidence of planet formation.

These remarkable portraits of dusty disks are a selection from 26 new images of debris disks obtained by the Gemini Planet Imager (GPI) at the international Gemini Observatory, a Program of NSF’s NOIRLab. These images highlight the diversity of shapes and sizes that these disks can take and show the outer reaches of exoplanetary systems in their formative years. The young stars imaged, which range from tens of millions to a few hundred million years old, are at the ideal age to settle down and raise planets. The forming planets sculpt the dust disk and leave behind gaps and warps that are indirect clues to their existence and motion.

While debris disks have been imaged before, this new cohort of 26 disks represents one of the largest samples to be imaged with highly uniform data quality. This enables detailed comparison of the observations, a unique breakthrough in debris disk surveys. Thirteen of the disks form a perfect natural laboratory, all belonging to the Scorpius–Centaurus stellar association, roughly 400 light-years from Earth. The group of stars, which were born in the same region at roughly the same time, enables astronomers to compare the architectures of a variety of young planetary systems developing under different conditions.

GPI was able to capture these dusty disks with the help of some ingenious astronomical engineering.

GPI is sensitive to the polarization of light, allowing it to distinguish dust-scattered light, which is polarized, from the unpolarized light emanating from the stars. This gives GPI the impressive ability to improve the contrast of images and capture disks that are 10 million times fainter than their parent stars.

Measuring polarization is only one of GPI’s tricks, however — the instrument also exploits a coronagraph and adaptive optics to get the most from its observations [1][2].

GPI’s precision is in large part due to its perch on the 8-meter Gemini South telescope on Cerro Pachón in Chile. The dry conditions, high altitude, and dark skies are perfect for cutting-edge astronomical research. By combining this exquisite location with some engineering ingenuity, GPI is able to capture images as sharp as those from the Hubble Space Telescope — and detect objects up to three times closer to the host stars [3].

GPI’s first-rate observing abilities enabled this work, part of the Gemini Planet Imager Exoplanet Survey (GPIES), a 4-year search for light emitted by giant gas planets orbiting more than 500 of the youngest stars near the Sun. As well as doubling the number of debris disks imaged at this high resolution, the survey uncovered six giant exoplanets and four brown dwarfs. Surveys such as GPIES are a perfect way to screen targets for the next generation of space- and ground-based telescopes.

“The Gemini instrument program continues to provide unique science opportunities. This combination of GPI mounted upon a large ground-based telescope is delivering exciting new details about the process of how planets form,” said Martin Still, NSF Program Manager for the Gemini Observatory partnership.

The GPIES survey concluded in 2019, but the investment and technical capability of the Gemini Planet Imager will continue with an upgrade to GPI’s hardware to improve its resolution and sensitivity [4].

The new “GPI 2.0,” is slated for a future installation at Gemini North atop Maunakea in Hawai‘i, where it will search the less-observed northern hemisphere skies for more exoplanets and debris disks. GPI 2.0 will also continue the work of scouting out targets for the next generation of exoplanet missions, setting the scene for new insights into the mystery of planet formation.

Source:  NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)

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Notes

[1] Coronagraphs are devices which block light coming directly from a central star, allowing the faint disk to be seen. The presence of GPI’s coronagraph can be inferred from the conspicuous black circle at the center of these images.

[2] Adaptive Optics is a cutting-edge astronomical technique that uses deformable mirrors to correct blurring and distortions caused by turbulence in Earth’s atmosphere.

[3] GPI’s coronagraph blocks a smaller region around the star and better suppresses noise at small angular separations from the star, compared to HST’s coronagraph.

[4] The upgrade to GPI is funded by the NSF and by the Heising-Simons Foundation.

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More information

This research was presented in the paper Debris Disk Results from the Gemini Planet Imager Exoplanet Survey’s Polarimetric Imaging Campaign in The Astronomical Journal.

The team is composed of Thomas M. Esposito (University of California, Berkeley), Paul Kalas, (University of California, Berkeley, SETI Institute, and Foundation for Research and Technology – Hellas), Michael P. Fitzgerald (University of California, Los Angeles), Maxwell A. Millar-Blanchaer (NASA Hubble Fellow at NASA Jet Propulsion Laboratory), Gaspard Duchêne (University of California,Berkeley and Université Grenoble Alpes), Jennifer Patience (Arizona State University), Justin Hom (Arizona State University), Marshall D. Perrin (Space Telescope Science Institute), Robert J. De Rosa (Kavli Institute for Particle Astrophysics and Cosmology), Eugene Chiang (University of California, Berkeley), Ian Czekala (NASA Hubble Fellowship Program Sagan Fellow at the University of California, Berkeley), Bruce Macintosh (Kavli Institute for Particle Astrophysics and Cosmology), James R. Graham (University of California, Berkeley), Megan Ansdell (University of California, Berkeley), Pauline Arriaga (University of California, Los Angeles), Sebastian Bruzzone (The University of Western Ontario), Joanna Bulger (Pan-STARRS Observatory), Christine H. Chen (Space Telescope Science Institute), Tara Cotton (University of Georgia), Ruobing Dong (University of Victoria), Zachary H. Draper (University of Victoria and National Research Council of Canada), Katherine B. Follette (Amherst College), Li-Wei Hung (University of California, Los Angeles), Ronald Lopez (University of California, Los Angeles), Brenda C. Matthews (National Research Council of Canada and University of Victoria), Johan Mazoyer (NASA Hubble Fellow at NASA Jet Propulsion Laboratory), Stan Metchev (The University of Western Ontario and Stony Brook University), Julien Rameau (Université de Montréal), Bin Ren (Johns Hopkins University and Space Telescope Science Institute), Malena Rice (Yale University), Inseok Song (University of Georgia), Kevin Stahl (University of California, Los Angeles), Jason Wang (California Institute of Technology and University of California, Berkeley), Schuyler Wolff (Leiden University), Ben Zuckerman (University of California, Los Angeles), S. Mark Ammons (Lawrence Livermore National Laboratory), Vanessa P. Bailey (NASA Jet Propulsion Laboratory), Travis Barman (University of Arizona), Jeffrey Chilcote (Kavli Institute for Particle Astrophysics and Cosmology and University of Notre Dame), Rene Doyon (Université de Montréal), Benjamin L. Gerard (University of Victoria and National Research Council of Canada), Stephen J. Goodsell (Gemini Observatory), Alexandra Z. Greenbaum (University of Michigan), Pascale Hibon (Gemini Observatory), Sasha Hinkley (University of Exeter), Patrick Ingraham (Vera C. Rubin Observatory), Quinn Konopacky (University of California San Diego), Jérôme Maire (University of California San Diego), Franck Marchis (SETI Institute), Mark S. Marley (NASA Ames Research Center), Christian Marois (University of Victoria and National Research Council of Canada), Eric L. Nielsen (SETI Institute and Kavli Institute for Particle Astrophysics and Cosmology), Rebecca Oppenheimer (American Museum of Natural History), David Palmer (Lawrence Livermore National Laboratory), Lisa Poyneer (Lawrence Livermore National Laboratory), Laurent Pueyo (Space Telescope Science Institute), Abhijith Rajan (Space Telescope Science Institute), Fredrik T. Rantakyrö (Gemini Observatory), Jean-Baptiste Ruffio (Kavli Institute for Particle Astrophysics and Cosmology), Dmitry Savransky (Cornell University), Adam C. Schneider (Arizona State University), Anand Sivaramakrishnan (Space Telescope Science Institute), Rémi Soummer (Space Telescope Science Institute), Sandrine Thomas (Vera C. Rubin Observatory), and Kimberly Ward-Duong (Amherst College).

NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–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 Hawaiʻi, 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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Links

• University of California, Berkeley release
• Video by Arizona State University
• Research paper
• Photos of the Gemini telescope
• The Gemini Planet Imager Web Page

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Contacts

Peter Michaud
NewsTeam Manager
NSF’s NOIRLab
Gemini Observatory, Hilo HI
Cell: +1 808-936-6643
Email: pmichaud@gemini.edu

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LIGO-Virgo Finds Mystery Object in "Mass Gap"

In August of 2019, the LIGO-Virgo gravitational-wave network witnessed the merger of a black hole with 23 times the mass of our sun and a mystery object 2.6 times the mass of the sun. Scientists do not know if the mystery object was a neutron star or black hole, but either way it set a record as being either the heaviest known neutron star or the lightest known black hole. Image credit: LIGO/Caltech/MIT/R. Hurt (IPAC)

When the most massive stars die, they collapse under their own gravity and leave behind black holes; when stars that are a bit less massive die, they explode in a supernova and leave behind dense, dead remnants of stars called neutron stars. For decades, astronomers have been puzzled by a gap that lies between neutron stars and black holes: the heaviest known neutron star is no more than 2.5 times the mass of our sun, or 2.5 solar masses, and the lightest known black hole is about 5 solar masses. The question remained: does anything lie in this so-called mass gap?

Now, in a new study from the National Science Foundation's Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap. The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. A paper about the detection has been accepted for publication in The Astrophysical Journal Letters.

"We've been waiting decades to solve this mystery," says co-author Vicky Kalogera, a professor at Northwestern University. "We don't know if this object is the heaviest known neutron star, or the lightest known black hole, but either way it breaks a record."

"This is going to change how scientists talk about neutron stars and black holes," says co-author Patrick Brady, a professor at the University of Wisconsin, Milwaukee, and the LIGO Scientific Collaboration spokesperson. "The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities. Time and more observations will tell."

The cosmic merger described in the study, an event dubbed GW190814, resulted in a final black hole about 25 times the mass of the sun (some of the merged mass was converted to a blast of energy in the form of gravitational waves). The newly formed black hole lies about 800 million light-years away from Earth.

Before the two objects merged, their masses differed by a factor of 9, making this the most extreme mass ratio known for a gravitational-wave event. Another recently reported LIGO-Virgo event, called GW190412, occurred between two black holes with a mass ratio of about 4:1.

"It's a challenge for current theoretical models to form merging pairs of compact objects with such a large mass ratio in which the low-mass partner resides in the mass gap. This discovery implies these events occur much more often than we predicted, making this a really intriguing low-mass object," explains Kalogera. "The mystery object may be a neutron star merging with a black hole, an exciting possibility expected theoretically but not yet confirmed observationally. However, at 2.6 times the mass of our sun, it exceeds modern predictions for the maximum mass of neutron stars, and may instead be the lightest black hole ever detected."

When the LIGO and Virgo scientists spotted this merger, they immediately sent out an alert to the astronomical community. Dozens of ground- and space-based telescopes followed up in search of light waves generated in the event, but none picked up any signals. So far, such light counterparts to gravitational-wave signals have been seen only once, in an event called GW170817. The event, discovered by the LIGO-Virgo network in August of 2017, involved a fiery collision between two neutron stars that was subsequently witnessed by dozens of telescopes on Earth and in space. Neutron star collisions are messy affairs with matter flung outward in all directions and are thus expected to shine with light. Conversely, black hole mergers, in most circumstances, are thought not to produce light.

According to the LIGO and Virgo scientists, the August 2019 event was not seen by light-based telescopes for a few possible reasons. First, this event was six times farther away than the merger observed in 2017, making it harder to pick up any light signals. Secondly, if the collision involved two black holes, it likely would have not shone with any light. Thirdly, if the object was in fact a neutron star, its 9-fold more massive black-hole partner might have swallowed it whole; a neutron star consumed whole by a black hole would not give off any light.

"I think of Pac-Man eating a little dot," says Kalogera. "When the masses are highly asymmetric, the smaller neutron star can be eaten in one bite."

How will researchers ever know if the mystery object was a neutron star or black hole? Future observations with LIGO, Virgo, and possibly other telescopes may catch similar events that would help reveal whether additional objects exist in the mass gap.

"This is the first glimpse of what could be a whole new population of compact binary objects," says Charlie Hoy, a member of the LIGO Scientific Collaboration and a graduate student at Cardiff University. "What is really exciting is that this is just the start. As the detectors get more and more sensitive, we will observe even more of these signals, and we will be able to pinpoint the populations of neutron stars and black holes in the universe."

"The mass gap has been an interesting puzzle for decades, and now we've detected an object that fits just inside it," says Pedro Marronetti, program director for gravitational physics at the National Science Foundation (NSF). "That cannot be explained without defying our understanding of extremely dense matter or what we know about the evolution of stars. This observation is yet another example of the transformative potential of the field of gravitational-wave astronomy, which brings novel insights to light with every new detection."

Source:  LIGO Caltech

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Webinar Series

For those wishing for a deeper dive into these LIGO-Virgo results and other research from the latest observing run, the team has scheduled a webinar intended for a scientific audience. Called the LIGO-Virgo-KAGRA Webinar Series, this will be the first in a series of webinars discussing the gravitational-wave network’s results in-depth. The one-hour Zoom webinar will be on June 25 at 14:00 Universal Time Coordinated (7:00am Pacific Daylight Time; 10:00am Eastern Daylight Time; 16:00 Central European Summer Time; 23:00 Japan Standard Time).

To register, visit:  https://zoom.us/webinar/register/3315925939436/WN_rsJximZ8R36WqZnMH16IrA

The Zoom webinar will also be live streamed and a recording will be available upon request.

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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 550 members from 106 institutes in 12 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.

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Related:

GW190814 detection paper

Virgo press release on GW190814

GW190814 announcement on the LSC website

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Media Contacts

Caltech
Whitney Clavin
wclavin@caltech.edu
626-390-9601

MIT
Abigail Abazorius
abbya@mit.edu
617-253-2709

Virgo
Livia Conti
livia.conti@pd.infn.it

EGO
Vincenzo Napolano
napolano@ego-gw.it
+393472994985

NSF
Josh Chamot
jchamot@nsf.gov
703-292-4489

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Our deepest view of the X-ray sky

The energetic universe as seen with the eROSITA X-ray telescope. The first eROSITA all-sky survey was conducted over a period of six months by letting the telescope rotate continuously, thus providing a uniform exposure of about 150-200 seconds over most of the sky, with the ecliptic poles being visited more deeply. As eROSITA scans the sky, the energy of the collected photons is measured with an accuracy ranging from 2% - 6%. To generate this image, in which the whole sky is projected onto an ellipse (so-called Aitoff projection) with the centre of the Milky Way in the middle and the body of the Galaxy running horizontally, photons have been colour-coded according to their energy (red for energies 0.3-0.6 keV, green for 0.6-1 keV, blue for 1-2.3 keV). The original image, with a resolution of about 10”, and a corresponding dynamic range of more than one billion, is then smoothed (with a 10’ FWHM Gaussian) in order to generate the above picture.The red diffuse glow away from the galactic plane is the emission of the hot gas in the vicinity of the solar system (the Local Bubble). Along the plane itself, dust and gas absorb the lowest energy X-ray photons, so that only high-energy emitting sources can be seen, and their colour appears blue in the image. The hotter gas close to the galactic centre, shown in green and yellow, carries imprinted the history of the most energetic processes in the life of the Milky Way, such as supernova explosions, driving fountains of gas out of the plane, and, possibly, past outburst from the now dormant supermassive black hole in the centre of the galaxy. Piercing through this turbulent, hot diffuse medium, are hundreds of thousands of X-ray sources, which appear mostly white in the image, and uniformly distributed over the sky. Among them, distant active galactic nuclei (including a few emitting at a time when the Universe was less than one tenth of its current age) are visible as point sources, while clusters of galaxies reveal themselves as extended X-ray nebulosities. In total, about one million X-ray sources have been detected in the eROSITA all-sky image, a treasure trove that will keep the teams busy for the coming years. Credit: Jeremy Sanders, Hermann Brunner and the eSASS team (MPE); Eugene Churazov, Marat Gilfanov (on behalf of IKI). Additional Images

The eROSITA telescope has provided a new, sharp view of hot and energetic processes across the Universe

Over the course of 182 days, the eROSITA X-ray telescope onboard SRG has completed its first full sweep of the sky. This new map of the hot, energetic universe contains more than one million objects, roughly doubling the number of known X-ray sources discovered over the 60-year history of X-ray astronomy. Most of the new sources are active galactic nuclei at cosmological distances, marking the growth of gigantic black holes over cosmic time. Clusters of galaxies in the new map will be used to track the growth of cosmic structures and constrain cosmological parameters. Closer to home, stars with hot coronae, binaries and supernova remnants dot our Galaxy, and we now have a complete map of the hot baryons in the Milky Way, something that can only be achieved with the 360-degree view provided by the eROSITA survey.

A million X-ray sources revealing the nature of the hot universe – this is the impressive harvest of the first scan of the entire sky with the eROSITA telescope onboard SRG. “This all-sky image completely changes the way we look at the energetic universe,” says Peter Predehl, the Principal Investigator of eROSITA at the Max Planck Institute for Extraterrestrial Physics (MPE). “We see such a wealth of detail - the beauty of the images is really stunning.”

This first complete sky image from eROSITA is about 4 times deeper than the previous all-sky survey by the ROSAT telescope 30 years ago, and has yielded around 10 times more sources: about as many as have been discovered by all past X-ray telescopes combined. And while most classes of astronomical objects emit in X-rays, the hot and energetic Universe looks quite different to the one seen by optical or radio telescopes. Looking outside the body of our Galaxy, most of the eROSITA sources are active galactic nuclei, accreting supermassive black holes at cosmological distances, interspersed with clusters of galaxies, which appear as extended X-ray haloes shining thanks to the hot gas confined by their huge concentrations of dark matter. The all-sky image reveals in exquisite detail the structure of the hot gas in the Milky Way itself, and the circum-galactic medium, which surrounds it, whose properties are key to understanding the formation history of our Galaxy. The eROSITA X-ray map also reveals stars with strong, magnetically active hot coronae, X-ray binary stars containing neutron stars, black holes or white dwarves, and spectacular supernova remnants in our own and other nearby galaxies such as the Magellanic clouds.

Due to its size and close distance to Earth, the "Vela supernova remnant" which is shown in this picture is one of the most prominent objects in the X-ray sky. The Vela supernova exploded about 12000 years ago at a distance of 800 light-years and overlaps with at least two other supernova remnants, Vela Junior (in the picture seen as bluish ring at the bottom left) and Puppis-A (top right). Vela Junior was discovered just 20 years ago, although this object is so close to Earth that remains of this explosion were found in polar ice cores. All three supernova explosions produced both the X-ray-bright supernova remnants and neutron stars, which shine as intense X-ray point sources near the centres of the remnants. The quality of the new eROSITA data of this "stellar cemetery" will give astronomers many exciting new insights into the physical processes operating in the hot supernova plasma as well as for exploring the exotic neutron stars. Credit: Peter Predehl, Werner Becker (MPE), Davide Mella

We were all eagerly awaiting the first all-sky map from eROSITA,” says Mara Salvato, the scientist at MPE who leads the effort to combine eROSITA observations with other telescopes across the electromagnetic spectrum. “Large sky areas have already been covered at many other wavelengths, and now we have the X-ray data to match. We need these other surveys to identify the X-ray sources and understand their nature.” The survey is also a treasure trove of rare and exotic phenomena, including numerous types of transients and variables, such as flares from compact objects, merging neutron stars, and stars being swallowed by black holes. “eROSITA often sees unexpected bursts of X-rays from the sky,” continues Salvato. “We need to alert ground-based telescopes immediately to understand what’s producing them.”  

Assembling the image has been a mammoth task. So far, the operations team has received and processed about 165 GB of data collected by eROSITA’s seven cameras. While relatively small by “big-data” standards on the ground, operating this complex instrument in space provided its own special challenges. “We check and monitor the health of the instrument on a daily basis, in cooperation with our colleagues in Moscow who operate the SRG spacecraft” explains Miriam Ramos-Ceja, a member of the eROSITA operations team at MPE. “This means we can respond quickly to any anomalies. We’ve been able to react to these immediately to keep the instrument safe, while collecting data at ~97% efficiency. It’s amazing to be able to communicate in real time with an instrument located 1.5 million kilometres away!” The data downlink occurs daily. “We perform immediate quality checks on the data”, she continues, “before it is being processed and analysed by the teams in Germany and Russia.”

While the team is now busy analysing this first all-sky map and using the images and catalogues to deepen our understanding of cosmology and high-energy astrophysical processes, the telescope continues its sweep of the X-ray sky. “The SRG Observatory is now starting its second all-sky survey, which will be completed by the end of this year“, says Rashid Sunyaev, Lead Scientist of the Russian SRG team. “Overall, during the next 3.5 years, we plan to get 7 maps similar to the one seen in this beautiful image. Their combined sensitivity will be a factor of 5 better and will be used by astrophysicists and cosmologists for decades.“

Kirpal Nandra, head of the high-energy astrophysics group at MPE, adds “With a million sources in just six months, eROSITA has already revolutionized X-ray astronomy, but this is just a taste of what’s to come. This combination of sky area and depth is transformational. We are already sampling a cosmological volume of the hot Universe much larger than has been possible before. Over the next few years, we’ll be able to probe even further, out to where the first giant cosmic structures and supermassive black holes were forming.”

The Shapley supercluster of galaxies is one of the most massive concentrations of galaxies in the local universe at a distance of about 650 million light-years (z~0.05). Each of the dozen extended structures is itself a cluster of galaxies, consisting of 100s to 1000s of individual galaxies, each denoting an intersection of filaments making up the large-scale structure in the Universe. This image spans 16 degrees across the sky (about 30 times the size of the full moon), which translates into about 180 million light-years across at the distance of the Shapley supercluster. The images on the left show a zoom of the the most massive clusters in the Shapley supercluster.  Credit: Esra Bulbul, Jeremy Sanders (MPE)

Further information:

On 11 June 2020, the eROSITA telescope completed its first survey of the entire X-ray sky. Launched on 13 July 2019 on-board the SRG spacecraft and now orbiting the second Lagrange point of the Earth-Sun-system, the telescope is in continuous scanning mode. During the first all-sky survey, each point in the sky was exposed to the eROSITA telescope for an average duration of 150-200 seconds. The regions close to the ecliptic poles, where the great circles traced by the telescope on the sky intersect, were revisited many times, accumulating exposures of up to a few hours. SRG will continue scanning the sky for three and half years more, with eROSITA performing seven more all-sky surveys in the process.

eROSITA is the primary instrument aboard SRG, a joint Russian-German science mission supported by the Russian Space Agency (Roskosmos), in the interests of the Russian Academy of Sciences represented by its Space Research Institute (IKI), and the Deutsches Zentrum für Luft- und Raumfahrt (DLR). The SRG spacecraft was built by Lavochkin Association (NPOL) and its subcontractors, and is operated by NPOL with support from the Max-Planck Institute for Extraterrestrial Physics (MPE).

The development and construction of the eROSITA X-ray instrument was led by the Max Planck Institute for Extraterrestrial Physics (MPE), with contributions from the Dr. Karl Remeis Observatory Bamberg, the University of Hamburg Observatory, the Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute for Astronomy and Astrophysics of the University of Tübingen, with the support of DLR and the Max Planck Society. The Argelander Institute for Astronomy of the University of Bonn and the Ludwig-Maximilians-Universität Munich also participated in the science preparation for eROSITA.

The eROSITA data shown here were processed using the eSASS software system developed by the German eROSITA consortium.

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Contacts

Dr. Andrea Merloni
Senior Scientist
+49 (0)89 30000-3893
+49 (0)89 30000-3569

Dr. Peter Predehl
Senior Scientist
+49 (0)89 30000-3505
+4915112113639
+49 (0)89 30000-3569

Prof. Dr. Kirpal Nandra
director
+49 (0)89 30000-3401

+49 (0)89 30000-3569

Source:  Max Planck Institute for Extraterrestrial Physics

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