Tuesday, October 31, 2023

MSH 15-52: X-ray Telescopes Reveal the "Bones" of a Ghostly Cosmic Hand

MSH 15-52
Credit X-ray: NASA/CXC/Stanford Univ./R. Romani et al. (Chandra); NASA/MSFC (IXPE);
Infrared: NASA/JPL-Caltech/DECaPS; Image Processing: NASA/CXC/SAO/J. Schmidt






Rotating neutron stars with strong magnetic fields, or pulsars, serve as laboratories for extreme physics, offering high-energy conditions that cannot be replicated on Earth. Young pulsars can create jets of matter and antimatter moving away from the poles of the pulsar, along with an intense wind, forming a “pulsar wind nebula”.

In 2001, NASA’s Chandra X-ray Observatory first observed the pulsar PSR B1509-58 and revealed that its pulsar wind nebula (referred to as MSH 15-52) resembles a human hand. The pulsar is located at the base of the “palm” of the nebula. Now Chandra’s data of MSH 15-52 have been combined with data from NASA’s newest X-ray telescope, the Imaging X-ray Polarimetry Explorer (IXPE) to unveil the magnetic field “bones” of this remarkable structure, as reported in our press release. IXPE stared at MSH 15-52 for 17 days, the longest it has looked at any single object since it launched in December 2021.

In a new composite image, Chandra data are seen in orange (low-energy X-rays), green, and blue (higher-energy X-rays), while the diffuse purple represents the IXPE observations. The pulsar is in the bright region at the base of the palm and the fingers are reaching toward low energy X-ray clouds in the surrounding remains of the supernova that formed the pulsar. The image also includes infrared data from the second data release of the Dark Energy Camera Plane Survey (DECaPS2) in red and blue.

The IXPE data provides the first map of the magnetic field in the ‘hand’. It reveals information about the electric field orientation of X-rays determined by the magnetic field of the X-ray source. This is called “X-ray polarization”.


SN1006, Labeled (Credit: X-ray: NASA/CXC/Stanford Univ./R. Romani et al. (Chandra); NASA/MSFC (IXPE);
Infared: NASA/JPL-Caltech/DECaPS; Image Processing: NASA/CXC/SAO/J. Schmidt)

First medical X-ray by Wilhelm Röntgen of his wife Anna Bertha Ludwig's hand.
Credit: Wilhelm Röntgen, via Wikipedia

An additional X-ray image shows the magnetic field map in MSH 15-52. In this image, short straight lines represent IXPE polarization measurements, mapping the direction of the local magnetic field. Orange “bars” mark the most precise measurements, followed by cyan and blue bars with less precise measurements. The complex field lines follow the `wrist', 'palm' and 'fingers' of the hand, and probably help define the extended finger-like structures.

The amount of polarization — indicated by bar length — is remarkably high, reaching the maximum level expected from theoretical work. To achieve that strength, the magnetic field must be very straight and uniform, meaning there is little turbulence in those regions of the pulsar wind nebula.

One particularly interesting feature of MSH 15-52 is a bright X-ray jet directed from the pulsar to the “wrist” at the bottom of the image. The new IXPE data reveal that the polarization at the start of the jet is low, likely because this is a turbulent region with complex, tangled magnetic fields associated with the generation of high-energy particles. By the end of the jet the magnetic field lines appear to straighten and become much more uniform, causing the polarization to become much larger.

A paper describing these results by Roger Romani of Stanford University and collaborators was published in The Astrophysical Journal on October 23, 2023, and is available at https://arxiv.org/abs/2309.16067 IXPE is a collaboration between NASA and the Italian Space Agency with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. Ball Aerospace, headquartered in Broomfield, Colorado, manages spacecraft operations together with the University of Colorado's Laboratory for Atmospheric and Space Physics in Boulder.

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








Visual Description:

This release features a composite image of a pulsar wind nebula, which strongly resembles a ghostly purple hand with sparkling fingertips.

A pulsar is a highly magnetized collapsed star that rotates and creates jets of matter flowing away from its poles. These jets, along with intense winds of particles, form pulsar wind nebulae. Here, the pulsar wind nebula known as MSH 15-52 resembles a hazy purple cloud set against a black, starry backdrop.

Both NASA's Chandra X-ray Observatory and the Imaging X-ray Polarimetry Explorer (IXPE) have observed MSH 15-52. Their observations revealed that the shape of this pulsar wind nebula strongly resembles a human hand, including five fingers, a palm and wrist. The bright white spot near the base of the palm is the pulsar itself.

The three longest fingertips of the hand-shape point toward our upper right, or 1:00 on a clock face. There, a small, mottled, orange and yellow cloud appears to sparkle or glow like embers. This orange cloud is part of the remains of the supernova explosion that created the pulsar. The backdrop of stars was captured in infrared light.




Fast Facts for (MSH 15-52):

Scale: Image is about 20 arcmin (93 light-years) across.
Category: Supernovas & Supernova Remnants, Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 15h 13m 55.52s | Dec -59° 08´ 08.8"
Constellation: Circinus
Observation Dates: 10 pointings between 14 Aug 2000 and 19 June 2008
Observation Time: 93 hours 50 minutes (3 days 21 hours 50 minutes)
Obs. ID: 754, 3833, 3834, 4384, 5534, 5535, 5562, 6116, 6117, 9138
Instrument: ACIS
References: Romani, R. et al., ApJ, 2023; arXiv:2309.16067
Color Code: X-ray: orange, green, blue (Chandra), purple (IXPE); Infrared: red, blue
Distance Estimate: About 16,000 light-years


Monday, October 30, 2023

Ultracompact: The Black Hole at the center of our Milky Way


This image shows the motion of the flares on the sky from a combined fit of the astrometric flare data, taking into account constraints from the polarimetry data. The colours indicate the progression of the flare orbit over time. The background image is a simulated image of the black hole at the center of our Milky Way with the circle indicating the shadow size of the black hole. © MPE


Every now and then, luminous gas is seen swirling around Sagittarius A*, the black hole at the center of the Milky Way. Now, astronomers at the Max Planck Institute for Extraterrestrial Physics (MPE) have succeeded in measuring the black hole mass from this motion – and it perfectly matches the measurement honoured with the Nobel Prize in Physics in 2020, which has been refined ever since. The conclusion: the 4.3 million solar masses are contained within an orbit smaller than that of Venus around the Sun. A truly astounding mass concentration!

At the center of our Milky Way there is a black hole with a mass of 4.3 million solar masses – several teams have established this beyond any reasonable doubt over the past four decades. In 2020, this finding was even honoured by the Nobel Prize in Physics for MPE director Reinhard Genzel. Since then, the research has focused on using the galactic centre as a laboratory to test the theory of general relativity in the very strong gravitational field close to this black hole – and to pin down its properties with high precision.

The team at MPE has now used GRAVITY, the near-infrared interferometer at ESO’s Very Large Telescope Interferometer (VLTI) to closely monitor the emission from the region around the black hole and probe for extremely bright states: flares. Such flares occur once or twice per day, and the emission becomes bright enough that it is possible to trace the motion of surrounding gas. The team analysed flares observed during 2018, 2021 and 2022, for which GRAVITY simultaneously delivered position and polarisation measurements.

This combined data set allowed the team to determine the mass of the black hole with high accuracy to be 4.297 million solar masses, a strong and independent constraint to previous measurements. The new data also show that the mass has to be enclosed inside the flares’ radius of around nine gravitational radii, which is smaller than the orbital radius of the planet Venus around the Sun.

“The mass we derived now from the flares at just a few gravitational radii is compatible with the value measured from the orbits of stars at several thousand gravitational radii,” emphasizes Diogo Ribeiro, who was responsible for the theoretical modelling at MPE. “This strengthens the case for a single black hole at the center of the Milky Way.”

Studying the motion of this orbiting gas can also shed light on the formation history of the structures at the Galactic Center. The orientation of the flare orbits is close to that of a stellar disk observed at 100,000 gravitational radii, suggesting a physical connection. “It is great to see the repeated, similar behaviour of the flares,” points out Antonia Drescher, who analysed the polarimetric measurements. “All of them show a clockwise looped motion on the sky; all have a similar radius and a similar orbital period. This is really beautiful to see.”

Strong winds from the stars farther out probably fuel the accretion flow of gas, which carries the initial angular momentum down to scales close to the event horizon. “The amount of information from the polarization was extremely fruitful and we learn a lot about the physics in the Galactic Center region from the joint data set,” adds Ribeiro. The dynamics of the flares may even carry information on the spin of the black hole – an open question today.




Contacts:

Diogo Currito Ribeiro
tel:+49 89 30000-3852
tel:+49 89 30000-0

dribeiro@mpe.mpg.de

Antonia Drescher
phd student
tel:+49 89 30000-3853
tel:+49 89 30000-

drescher@mpe.mpg.de

Stefan Gillessen
scientist
tel:+49 89 30000-3839
tel:017699664139
tel:+49 89 30000-3390

ste@mpe.mpg.de



Original publication:

GRAVITY Collaboration
Polarimetry and astrometry of NIR flares as event horizon scale, dynamical probes for the mass of Sgr A*
A&A 677, L10 (2023)

Source | DOI




More Information


GRAVITY instrument confirms black hole status of the Milky Way centre





Sunday, October 29, 2023

IXPE Untangles Theories Surrounding Historic Supernova Remnant


This new image of supernova remnant SN 1006 combines data from NASA’s Imaging X-ray Polarimetry Explorer and NASA’s Chandra X-ray Observatory. The red, green, and blue elements reflect low, medium, and high energy X-rays, respectively, as detected by Chandra. The IXPE data, which measure the polarization of the X-ray light, is show in purple in the upper left corner, with the addition of lines representing the outward movement of the remnant’s magnetic field. X-ray: NASA/CXC/SAO (Chandra); NASA/MSFC/Nanjing Univ./P. Zhou et al. (IXPE); IR: NASA/JPL/CalTech/Spitzer; Image Processing: NASA/CXC/SAO/J.Schmidt

NASA’s IXPE (Imaging X-ray Polarimetry Explorer) telescope has captured the first polarized X-ray imagery of the supernova remnant SN 1006. The new results expand scientists’ understanding of the relationship between magnetic fields and the flow of high-energy particles from exploding stars.

“Magnetic fields are extremely difficult to measure, but IXPE provides an efficient way for us to probe them,” said Dr. Ping Zhou, an astrophysicist at Nanjing University in Jiangsu, China, and lead author of a new paper on the findings, published in The Astrophysical Journal. “Now we can see that SN 1006’s magnetic fields are turbulent, but also present an organized direction.”

Situated some 6,500 light-years from Earth in the Lupus constellation, SN 1006 is all that remains after a titanic explosion, which occurred either when two white dwarfs merged or when a white dwarf pulled too much mass from a companion star. Initially spotted in spring of 1006 CE by observers across China, Japan, Europe, and the Arab world, its light was visible to the naked eye for at least three years. Modern astronomers still consider it the brightest stellar event in recorded history.

Since modern observation began, researchers have identified the remnant’s strange double structure, markedly different from other, rounded supernova remnants. It also has bright “limbs” or edges identifiable in the X-ray and gamma-ray bands.

“Close-proximity, X-ray-bright supernova remnants such as SN 1006 are ideally suited to IXPE measurements, given IXPE’s combination of X-ray polarization sensitivity with the capability to resolve the emission regions spatially,” said Douglas Swartz, a Universities Space Research Association researcher at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “This integrated capability is essential to localizing cosmic-ray acceleration sites.”

Previous X-ray observations of SN 1006 offered the first evidence that supernova remnants can radically accelerate electrons, and helped identify rapidly expanding nebulae around exploded stars as a birthplace for highly energetic cosmic rays, which can travel at nearly the speed of the light.

Scientists surmised that SN 1006’s unique structure is tied to the orientation of its magnetic field, and theorized that supernova blast waves in the northeast and southwest move in the direction aligned with the magnetic field, and more efficiently accelerate high-energy particles.

IXPE’s new findings helped validate and clarify those theories, said Dr. Yi-Jung Yang, a high-energy astrophysicist at the University of Hong Kong and coauthor of the paper.

“The polarization properties obtained from our spectral-polarimetric analysis align remarkably well with outcomes from other methods and X-ray observatories, underscoring IXPE’s reliability and strong capabilities”, Yang said.

“For the first time, we can map the magnetic field structures of supernova remnants at higher energies with enhanced detail and accuracy – enabling us to better understand the processes driving the acceleration of these particles.” Dr. Yi-Jung Yang (High-energy astrophysicist at the University of Hong Kong)

Researchers say the results demonstrate a connection between the magnetic fields and the remnant’s high-energy particle outflow. The magnetic fields in SN 1006’s shell are somewhat disorganized, per IXPE’s findings, yet still have a preferred orientation. As the shock wave from the original explosion passes through the surrounding gas, the magnetic fields become aligned with the shock wave’s motion. Charged particles are trapped by the magnetic fields around the original point of the blast, where they quickly receive bursts of acceleration. Those speeding high-energy particles, in turn, transfer energy to keep the magnetic fields strong and turbulent.

IXPE has observed three supernova remnants – Cassiopeia A, Tycho, and now SN 1006 – since launching in December 2021, helping scientists develop a more comprehensive understanding of the origin and processes of the magnetic fields surrounding these phenomena.

Scientists were surprised to find that SN 1006 is more polarized than the other two supernova remnants, but that all three show magnetic fields oriented such that they point outward from the center of the explosion. As researchers continue to explore IXPE data, they are re-orienting their understanding of how particles get accelerated in extreme objects like these.

IXPE is a collaboration between NASA and the Italian Space Agency with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. Ball Aerospace, headquartered in Broomfield, Colorado, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.

By Beth Ridgeway

Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe

Elizabeth Landau
NASA Headquarters

elizabeth.r.landau@nasa.gov
202-358-0845

Jonathan Deal
NASA’s Marshall Space Flight Center

jonathan.e.deal@nasa.gov
256-544-0034

Source: NASA/IXPE


Saturday, October 28, 2023

A dynamic duo … or trio?

Two spiral galaxies. Each glows brightly in the centre, where a bar stretches from side to side. The upper one is more round and its arms form two thin rings. The lower galaxy is flatter and its arms make one outer ring; a dusty knot atop its upper arm marks out a third object. Gravity is pulling gas and dust together where the galaxies come close. A number of small galaxies surround them on a black background. Credit: ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/NOIRLab/NSF/AURA. Acknowledgement: L. Shatz

This striking image captures the interacting galaxy pair known as Arp-Madore 2339-661, so named because they belong to the Arp-Madore catalogue of peculiar galaxies. However, this particular peculiarity might be even odder than first meets the eye, as there are in fact three galaxies interacting here, not just two.

The two clearly defined galaxies are NGC 7733 (smaller, lower right) and NGC 7734 (larger, upper left). The third galaxy is currently referred to as NGC 7733N, and can actually be spotted in this picture if you look carefully at the upper arm of NGC 7733, where there is a visually notable knot-like structure, glowing with a different colour to the arm and obscured by dark dust. This could easily pass as part of NGC 7733, but analysis of the velocities (speed, but also considering direction) involved in the galaxy shows that this knot has a considerable additional redshift, meaning that it is very likely its own entity and not part of NGC 7733. This is actually one of the many challenges that observational astronomers face: working out whether an astronomical object really is just one, or one lying in front of another as seen from Earth’s perspective!

All three galaxies lie quite close to each other, roughly 500 million light-years from Earth in the constellation Tucana, and, as this image shows, they are interacting gravitationally with one another. In fact, some science literature refers to them as a ‘merging group’, meaning that they are on a course to ultimately become a single entity.

Links



Friday, October 27, 2023

Gemini South Captures Cosmic ‘Cotton Candy’

PR Image noirlab2329a
Gemini South Reveals Tangled Spiral Arms of the Peculiar Galaxy NGC 7727



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Chaotic jumble of merging spiral galaxies hints at possible fate of Milky Way and Andromeda galaxies

Gemini South, one half of the International Gemini Observatory operated by NSF’s NOIRLab, captures the billion-year-old aftermath of a spiral galaxy collision. At the heart of this chaotic interaction, entwined and caught in the midst of the chaos, is a pair of supermassive black holes — the closest such pair ever recorded from Earth.

The swirling arms of a spiral galaxy are among the most recognized features in the cosmos: long sweeping bands spun off from a central core, each brimming with dust, gas, and dazzling pockets of newly formed stars. Yet this opulent figure can warp into a much more bizarre and amorphous shape during a merger with another galaxy. The same sweeping arms are suddenly perturbed into disarray, and two supermassive black holes at their respective centers become entangled in a tidal dance. This is the case of NGC 7727, a peculiar galaxy located in the constellation of Aquarius about 90 million light-years from the Milky Way.ever recorded from Earth.

Astronomers have captured an evocative image of this merger’s aftermath using the Gemini Multi-Object Spectrograph (GMOS) mounted on the Gemini South telescope in Chile, part of the International Gemini Observatory operated by NSF’s NOIRLab. The image reveals vast swirling bands of interstellar dust and gas resembling freshly-spun cotton candy as they wrap around the merging cores of the progenitor galaxies. From the aftermath has emerged a scattered mix of active starburst regions and sedentary dust lanes encircling the system.ever recorded from Earth.

What is most noteworthy about NGC 7727 is undoubtedly its twin galactic nuclei, each of which houses a supermassive black hole, as confirmed by astronomers using the European Southern Observatory’s Very Large Telescope (VLT). Astronomers now surmise the galaxy originated as a pair of spiral galaxies that became embroiled in a celestial dance about one billion years ago. Stars and nebulae spilled out and were pulled back together at the mercy of the black holes’ gravitational tug-of-war until the irregular tangled knots we see here were created.

The two supermassive black holes, one measuring 154 million solar masses and the other 6.3 million solar masses, are approximately 1600 light-years apart [1]. It is estimated that the two will eventually merge into one in about 250 million years to form an even more massive black hole while dispersing violent ripples of gravitational waves across spacetime.

Because the galaxy is still reeling from the impact, most of the tendrils we see are ablaze with bright young stars and active stellar nurseries. In fact, about 23 objects found in this system are considered candidates for young globular clusters. These collections of stars often form in areas where star formation is higher than usual and are especially common in interacting galaxies as we see here.

Once the dust has settled, NGC 7727 is predicted to eventually become an elliptical galaxy composed of older stars and very little star formation. Similar to Messier 87, an elliptical galaxy with a supermassive black hole at its heart, this may be the fate of the Milky Way and the Andromeda Galaxy when they fuse together in billions of years’ time.



More information

[1] The supermassive black hole at the center of the Milky Way contains a relatively modest 4.3 million solar masses. The most massive black hole observed to date contains approximately 66 billion solar masses.


NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), 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 Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). 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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Contacts

Josie Fenske
NSF’s NOIRLab Communications
Email:
josie.fenske@noirlab.edu

Thursday, October 26, 2023

NASA's Webb Makes First Detection of Heavy Element from Star Merger

Kilonova and Host Galaxy
Credits: Image: NASA, ESA, CSA, STScI, Andrew Levan (IMAPP, Warw)

Kilonova Emission Spectrum
Credits: Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI)





A team of scientists has used multiple space and ground-based telescopes, including NASA’s James Webb Space Telescope, NASA’s Fermi Gamma-ray Space Telescope, and NASA’s Neil Gehrels Swift Observatory, to observe an exceptionally bright gamma-ray burst, GRB 230307A, and identify the neutron star merger that generated an explosion that created the burst. Webb also helped scientists detect the chemical element tellurium in the explosion’s aftermath.

Other elements near tellurium on the periodic table – like iodine, which is needed for much of life on Earth – are also likely to be present among the kilonova’s ejected material. A kilonova is an explosion produced by a neutron star merging with either a black hole or with another neutron star.

“Just over 150 years since Dmitri Mendeleev wrote down the periodic table of elements, we are now finally in the position to start filling in those last blanks of understanding where everything was made, thanks to Webb,” said Andrew Levan of Radboud University in the Netherlands and the University of Warwick in the UK, lead author of the study.

While neutron star mergers have long been theorized as being the ideal “pressure cookers” to create some of the rarer elements substantially heavier than iron, astronomers have previously encountered a few obstacles in obtaining solid evidence.

Kilonovas are extremely rare, making it difficult to observe these events. Short gamma-ray bursts (GRBs), traditionally thought to be those that last less than two seconds, can be byproducts of these infrequent merger episodes. (In contrast, long gamma-ray bursts may last several minutes and are usually associated with the explosive death of a massive star.)

The case of GRB 230307A is particularly remarkable. First detected by Fermi in March, it is the second brightest GRB observed in over 50 years of observations, about 1,000 times brighter than a typical gamma-ray burst that Fermi observes. It also lasted for 200 seconds, placing it firmly in the category of long duration gamma-ray bursts, despite its different origin.

“This burst is way into the long category. It’s not near the border. But it seems to be coming from a merging neutron star,” added Eric Burns, a co-author of the paper and member of the Fermi team at Louisiana State University.

The collaboration of many telescopes on the ground and in space allowed scientists to piece together a wealth of information about this event as soon as the burst was first detected. It is an example of how satellites and telescopes work together to witness changes in the universe as they unfold.

After the first detection, an intensive series of observations from the ground and from space, including with Swift, swung into action to pinpoint the source on the sky and track how its brightness changed. These observations in the gamma-ray, X-ray, optical, infrared, and radio showed that the optical/infrared counterpart was faint, evolved quickly, and became very red – the hallmarks of a kilonova.

“This type of explosion is very rapid, with the material in the explosion also expanding swiftly,” said Om Sharan Salafia, a co-author of the study at the INAF - Brera Astronomical Observatory in Italy. “As the whole cloud expands, the material cools off quickly and the peak of its light becomes visible in infrared, and becomes redder on timescales of days to weeks.”

At later times it would have been impossible to study this kilonova from the ground, but these were the perfect conditions for Webb’s NIRCam (Near-Infrared Camera) and NIRSpec (Near-Infrared Spectrograph) instruments to observe this tumultuous environment. The spectrum has broad lines that show the material is ejected at high speeds, but one feature is clear: light emitted by tellurium, an element rarer than platinum on Earth.

The highly sensitive infrared capabilities of Webb helped scientists identify the home address of the two neutron stars that created the kilonova: a spiral galaxy about 120,000 light-years away from the site of the merger.

Prior to their venture, they were once two normal massive stars that formed a binary system in their home spiral galaxy. Since the duo was gravitationally bound, both stars were launched together on two separate occasions: when one among the pair exploded as a supernova and became a neutron star, and when the other star followed suit.

In this case, the neutron stars remained as a binary system despite two explosive jolts and were kicked out of their home galaxy. The pair traveled approximately the equivalent of the Milky Way galaxy’s diameter before merging several hundred million years later.

Scientists expect to find even more kilonovas in the future due to the increasing opportunities to have space and ground-based telescopes work in complementary ways to study changes in the universe. For example, while Webb can peer deeper into space than ever before, the remarkable field of view of NASA’s upcoming Nancy Grace Roman Space Telescope will enable astronomers to scout where and how frequently these explosions occur.

“Webb provides a phenomenal boost and may find even heavier elements,” said Ben Gompertz, a co-author of the study at the University of Birmingham in the UK. “As we get more frequent observations, the models will improve and the spectrum may evolve more in time. Webb has certainly opened the door to do a lot more, and its abilities will be completely transformative for our understanding of the universe.”

These findings have been published in the journal Nature.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing 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.



About This Release

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Abigail Major
Space Telescope Science Institute, Baltimore, Maryland

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Space Telescope Science Institute, Baltimore, Maryland

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Wednesday, October 25, 2023

NASA’s Webb Discovers New Feature in Jupiter’s Atmosphere

Jupiter (NIRCam Image)
Credits: Image: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI)

Jupiter Jet Pullouts (NIRCam Image)
Credits: Image: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI)

Jupiter’s Atmosphere (Illustration)
Credits: Image: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley). Illustration: Andi James (STScI)




NASA’s James Webb Space Telescope has discovered a new, never-before-seen feature in Jupiter’s atmosphere. The high-speed jet stream, which spans more than 3,000 miles (4,800 kilometers) wide, sits over Jupiter’s equator above the main cloud decks. The discovery of this jet is giving insights into how the layers of Jupiter’s famously turbulent atmosphere interact with each other, and how Webb is uniquely capable of tracking those features.

“This is something that totally surprised us,” said Ricardo Hueso of the University of the Basque Country in Bilbao, Spain, lead author on the paper describing the findings. “What we have always seen as blurred hazes in Jupiter’s atmosphere now appear as crisp features that we can track along with the planet’s fast rotation.”

The research team analyzed data from Webb’s NIRCam (Near-Infrared Camera) captured in July 2022. The Early Release Science program – jointly led by Imke de Pater from the University of California, Berkeley and Thierry Fouchet from the Observatory of Paris – was designed to take images of Jupiter 10 hours apart, or one Jupiter day, in four different filters, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere.

“Even though various ground-based telescopes, spacecraft like NASA’s Juno and Cassini, and NASA’s Hubble Space Telescope have observed the Jovian system’s changing weather patterns, Webb has already provided new findings on Jupiter’s rings, satellites, and its atmosphere,” de Pater noted.

While Jupiter is different from Earth in many ways – Jupiter is a gas giant, Earth is a rocky, temperate world – both planets have layered atmospheres. Infrared, visible, radio, and ultraviolet-light wavelengths observed by these other missions detect the lower, deeper layers of the planet’s atmosphere – where gigantic storms and ammonia ice clouds reside.

On the other hand, Webb’s look farther into the near-infrared than before is sensitive to the higher-altitude layers of the atmosphere, around 15-30 miles (25-50 kilometers) above Jupiter’s cloud tops. In near-infrared imaging, high-altitude hazes typically appear blurry, with enhanced brightness over the equatorial region. With Webb, finer details are resolved within the bright, hazy band.

The newly discovered jet stream travels at about 320 miles per hour (515 kilometers per hour), twice the sustained winds of a Category 5 hurricane here on Earth. It is located around 25 miles (40 kilometers) above the clouds, in Jupiter’s lower stratosphere.

By comparing the winds observed by Webb at high altitudes, to the winds observed at deeper layers from Hubble, the team could measure how fast the winds change with altitude and generate wind shears.

While Webb’s exquisite resolution and wavelength coverage allowed for the detection of small cloud features used to track the jet, the complementary observations from Hubble taken one day after the Webb observations were also crucial to determine the base state of Jupiter’s equatorial atmosphere and observe the development of convective storms in Jupiter’s equator not connected to the jet.

“We knew the different wavelengths of Webb and Hubble would reveal the three-dimensional structure of storm clouds, but we were also able to use the timing of the data to see how rapidly storms develop,” added team member Michael Wong of the University of California, Berkeley, who led the associated Hubble observations.

The researchers are looking forward to additional observations of Jupiter with Webb to determine if the jet’s speed and altitude change over time.
“Jupiter has a complicated but repeatable pattern of winds and temperatures in its equatorial stratosphere, high above the winds in the clouds and hazes measured at these wavelengths,” explained team member Leigh Fletcher of the University of Leicester in the United Kingdom. “If the strength of this new jet is connected to this oscillating stratospheric pattern, we might expect the jet to vary considerably over the next 2 to 4 years – it’ll be really exciting to test this theory in the years to come.”
“It’s amazing to me that, after years of tracking Jupiter’s clouds and winds from numerous observatories, we still have more to learn about Jupiter, and features like this jet can remain hidden from view until these new NIRCam images were taken in 2022,” continued Fletcher.

The researchers’ results were recently published in Nature Astronomy.

The James Webb Space Telescope is the world's premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing 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.



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Tuesday, October 24, 2023

CfA-led Mission to Explore the Sun Selected by NASA for Next Step


NASA recently selected ECCCO, a CfA-SwRI collaboration, for Phase A mission development. This image shows a coronal mass ejection (CME) forming in the corona, highlighting how ECCCO's new, wide-field extreme-ultraviolet view of the corona will help better connect the sources of outflows from the solar corona, such as CMEs and the solar wind, to their origins near the Sun. Credit: Courtesy of Dan Seaton/SwRI/NOAA



ECCCO, a proposed mission from the CfA and SwRI to study the Sun's middle corona, has been selected by NASA for more development.


Cambridge, MA -- NASA has selected a new heliophysics mission focused on investigating the Sun's middle corona — an enigmatic region of the Sun's atmosphere driving solar activity — for a "Phase A" mission definition study.

The mission, called the EUV CME and Coronal Connectivity Observatory (ECCCO), is being led by the Smithsonian Astrophysical Observatory (SAO), part of the Center for Astrophysics | Harvard & Smithsonian (CfA).

According to NASA, "the purpose of Phase A is to develop a proposed mission/system architecture that is credible and responsive to program expectations, requirements, and constraints on the project, including resources."

"ECCCO will answer fundamental questions about the origins of the mass and energy flow that link the Sun to the outer corona and overall heliosphere, the 'bubble' of space encompassing the solar system 'inflated' by the solar wind," said Smithsonian Astrophysical Observatory astrophysicist Dr. Kathy Reeves, ECCCO principal investigator from the CfA. "We'll have unique data that have the potential to reveal the deep connection between the Sun and its larger environment in the heliosphere."

SAO will be responsible for ECCCO's design, development, acquisition, assembly, testing, pre-flight calibration, and delivery of the science payload (one imager and two spectrometers). It will also lead and direct the science planning of the investigation, oversee development of the operations plan, support payload operations, and be responsible for archiving of the flight data. Finally, SAO will manage and administer the contract with NASA and coordinate formal reporting to NASA.

The mission focuses on imaging and spectroscopy of the middle corona in extreme ultraviolet (EUV) wavelengths, tracking events like coronal mass ejections (CMEs) from their origins until they leave the Sun. CMEs are huge bursts of charged particles from the corona threaded with intense magnetic fields ejected from the Sun over the course of several hours. CMEs reaching Earth can generate geomagnetic storms and cause anomalies in and disruptions to modern conveniences such as electronic grids and GPS systems.

The Southwest Research Institute (SwRI) is a partner with the CfA on ECCCO and will manage the project as well as its science and mission operations centers. Ball Aerospace will build the spacecraft.

"We've explored the Sun itself extensively over the last few decades," said Dan Seaton, the deputy principal investigator for ECCCO from SwRI. “Yet the middle corona remains a great mystery, and ECCCO will finally help reveal its secrets."

ECCCO's innovative high-sensitivity instruments, when trained on the middle corona, will return wide-field data that are critical to understanding eruptive events and solar wind streams. The ECCCO-I imager sees the full multi-thermal corona from the surface of the Sun out to three solar radii away from the star. The twin ECCCO-S spectrographs are designed to provide unprecedented temperature and density diagnostics from the solar disk to the middle corona.

"We are thrilled that ECCCO is moving to this next important step," said CfA Director Lisa Kewley. "The Sun is our nearest star and affects the entire Solar System including Earth, and ECCCO will help us learn so much more about its behavior."

The ECCCO mission builds on the CfA's extensive history and expertise of designing and building instruments for many different questions in science, including heliophysics. For example, the CfA has played major roles with such missions as the Parker Solar Probe, the Solar Dynamics Observatory, the Hi-C telescope, the Hinode solar observatory, and many others.

NASA's Explorers Program, to which ECCCO belongs, provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined and efficient management approaches.




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The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.



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Monday, October 23, 2023

Astronomers detect most distant fast radio burst to date

PR Image eso2317a
Artist’s impression of a record-breaking fast radio burst



An international team has spotted a remote blast of cosmic radio waves lasting less than a millisecond. This 'fast radio burst' (FRB) is the most distant ever detected. Its source was pinned down by the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in a galaxy so far away that its light took eight billion years to reach us. The FRB is also one of the most energetic ever observed; in a tiny fraction of a second it released the equivalent of our Sun’s total emission over 30 years.

The discovery of the burst, named FRB 20220610A, was made in June last year by the ASKAP radio telescope in Australia [1] and it smashed the team’s previous distance record by 50 percent.

“Using ASKAP’s array of dishes, we were able to determine precisely where the burst came from,” says Stuart Ryder, an astronomer from Macquarie University in Australia and the co-lead author of the study published today in Science. “Then we used [ESO’s VLT] in Chile to search for the source galaxy, [2] finding it to be older and further away than any other FRB source found to date and likely within a small group of merging galaxies.”

The discovery confirms that FRBs can be used to measure the 'missing' matter between galaxies, providing a new way to 'weigh' the Universe.

Current methods of estimating the mass of the Universe are giving conflicting answers and challenging the standard model of cosmology. “If we count up the amount of normal matter in the Universe — the atoms that we are all made of — we find that more than half of what should be there today is missing,” says Ryan Shannon, a professor at the Swinburne University of Technology in Australia, who also co-led the study. “We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and diffuse that it's impossible to see using normal techniques.”

“Fast radio bursts sense this ionised material. Even in space that is nearly perfectly empty they can 'see' all the electrons, and that allows us to measure how much stuff is between the galaxies,” Shannon says.

Finding distant FRBs is key to accurately measuring the Universe’s missing matter, as shown by the late Australian astronomer Jean-Pierre ('J-P') Macquart in 2020. “J-P showed that the further away a fast radio burst is, the more diffuse gas it reveals between the galaxies. This is now known as the Macquart relation. Some recent fast radio bursts appeared to break this relationship. Our measurements confirm the Macquart relation holds out to beyond half the known Universe,” says Ryder.

“While we still don’t know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe,” says Shannon.

The result represents the limit of what is achievable with telescopes today, although astronomers will soon have the tools to detect even older and more distant bursts, pin down their source galaxies and measure the Universe’s missing matter. The international Square Kilometre Array Observatory is currently building two radio telescopes in South Africa and Australia that will be capable of finding thousands of FRBs, including very distant ones that cannot be detected with current facilities. ESO’s Extremely Large Telescope, a 39-metre telescope under construction in the Chilean Atacama Desert, will be one of the few telescopes able to study the source galaxies of bursts even further away than FRB 20220610A.

Source: ESO/News



Notes

[1] The ASKAP telescope is owned and operated by CSIRO, Australia’s national science agency, on Wajarri Yamaji Country in Western Australia.

[2] The team used data obtained with the FOcal Reducer and low dispersion Spectrograph 2 (
FORS2), the X-shooter and the High Acuity Wide-field K-band Imager (HAWK-I) instruments on ESO’s VLT. Data from the Keck Observatory in Hawai'i, US, was also used in the study.




More information

This research was presented in a paper titled “A luminous fast radio burst that probes the Universe at redshift 1” (doi: 10.1126/science.adf2678) to appear in Science.

The team is composed of S. D. Ryder (School of Mathematical and Physical Sciences, Macquarie University, Australia [SMPS]; Astrophysics and Space Technologies Research Centre, Macquarie University, Sydney, Australia [ASTRC]), K. W. Bannister (Australia Telescope National Facility, Commonwealth Science and Industrial Research Organisation, Space and Astronomy, Australia [CSIRO]), S. Bhandari (The Netherlands Institute for Radio Astronomy, the Netherlands; Joint Institute for Very Long Baseline Interferometry in Europe, the Netherlands), A. T. Deller (Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Australia [CAS]), R. D. Ekers (CSIRO; International Centre for Radio Astronomy Research, Curtin Institute of Radio Astronomy, Curtin University, Australia [ICRAR]), M. Glowacki (ICRAR), A. C. Gordon (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, USA [CIERA]), K. Gourdji (CAS), C. W. James (ICRAR), C. D. Kilpatrick (CIERA; Department of Physics and Astronomy, Northwestern University, USA), W. Lu (Department of Astronomy, University of California, Berkeley, USA; Theoretical Astrophysics Center, University of California, Berkeley, USA), L. Marnoch (SMPS; ASTRC; CSIRO; Australian Research Council Centre of Excellence for All-Sky Astrophysics in 3 Dimensions, Australia), V. A. Moss (CSIRO), J. X. Prochaska (Department of Astronomy and Astrophysics, University of California, Santa Cruz, USA [Santa Cruz]; Kavli Institute for the Physics and Mathematics of the Universe, Japan), H. Qiu (SKA Observatory, Jodrell Bank, UK), E. M. Sadler (Sydney Institute for Astronomy, School of Physics, University of Sydney, Australia; CSIRO), S. Simha (Santa Cruz), M. W. Sammons (ICRAR), D. R. Scott (ICRAR), N. Tejos (Instituto de Física, Pontificia Universidad Católica De Valparaíso, Chile) and R. M. Shannon (CAS).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.



Links



Contacts

Stuart Ryder
Adjunct Fellow, School of Mathematical and Physical Sciences, Macquarie University
Sydney, Australia
Tel: +61 419 970834
Email:
Stuart.Ryder@mq.edu.au

Ryan Shannon
Associate Professor, Swinburne University
Hawthorn, Australia
Tel: +61 3 9214 5205
Email:
rshannon@swin.edu.au

Bárbara Ferreira
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Cell: +49 151 241 664 00
Email:
press@eso.org


Sunday, October 22, 2023

Extreme Weight Loss: Star Sheds Unexpected Amounts of Mass Just Before Going Supernova


Artist's conception of pre-explosion mass loss by the progenitor star of SN 2023ixf. In the year prior to going supernova the red supergiant star now known as SN 2023ixf shed an unexpected amount of mass equivalent to the mass of the Sun. This artist's conception illustrates what the final stages of mass loss might have looked like before the star exploded. Credit: Melissa Weiss/CfA.


Artist's conception of SN 2023ixf. One of the nearest Type II supernovae in a decade and among the brightest to date, SN 2023ixf is a young supernova, discovered earlier this year by amateur astronomer Kōichi Itagaki of Yamagata, Japan. This artist’s conception shows the bright explosion of SN 2023ixf, which occurred after an unexpected amount of mass loss unlike anything astronomers have seen before. Credit: Melissa Weiss/CfA


Composite KeplerCam griz image of SN 2023ixf. Captured using the 1.2m telescope at CfA's Fred Lawrence Whipple Observatory on June 27, 2023, just over a month after SN 2023ixf's progenitor star exploded, the image in this composite combines together green, red, near-infrared and infrared light to highlight both SN 2023ixf and the Pinwheel Galaxy. SN 2023ixf is located in one of the spiral arms of the galaxy, as expected for the explosions of massive stars. Credit: S. Gomez/STScI


Unlabeled composite KeplerCam griz image of SN 2023ixf. Captured using the 1.2m telescope at CfA's Fred Lawrence Whipple Observatory on June 27, 2023, just over a month after SN 2023ixf's progenitor star exploded, the image in this composite combines together green, red, near-infrared and infrared light to highlight both SN 2023ixf and the Pinwheel Galaxy. SN 2023ixf is located in one of the spiral arms of the galaxy, as expected for the explosions of massive stars. Credit: S. Gomez/STScI



Evidence of extreme pre-explosion mass loss in a recently discovered supernova indicates there may be more going on in the last year of a star's life than previously thought.

Cambridge, Mass. — A newly discovered nearby supernova whose star ejected up to a full solar mass of material in the year prior to its explosion is challenging the standard theory of stellar evolution. The new observations are giving astronomers insight into what happens in the final year prior to a star’s death and explosion.

SN 2023ixf is a new Type II supernova discovered in May 2023 by amateur astronomer Kōichi Itagaki of Yamagata, Japan shortly after its progenitor, or origin star, exploded. Located about 20 million light-years away in the Pinwheel Galaxy, SN 2023ixf's proximity to Earth, the supernova's extreme brightness, and its young age make it a treasure trove of observable data for scientists studying the death of massive stars in supernova explosions.

Type II or core-collapse supernovae occur when red supergiant stars at least eight times, and up to about 25 times the mass of the Sun, collapse under their own weight and explode. While SN 2023ixf fit the Type II description, followup multi-wavelength observations led by astronomers at the Center for Astrophysics | Harvard & Smithsonian (CfA), and using a wide range of CfA's telescopes, have revealed new and unexpected behavior.

Within hours of going supernova, core-collapse supernovae produce a flash of light that occurs when the shock wave from the explosion reaches the outer edge of the star. SN 2023ixf, however, produced a light curve that didn’t seem to fit this expected behavior. To better understand SN 2023ixf's shock breakout, a team of scientists led by CfA postdoctoral fellow Daichi Hiramatsu analyzed data from the 1.5m Tillinghast Telescope, 1.2m telescope, and MMT at the Fred Lawrence Whipple Observatory, a CfA facility located in Arizona, as well as data from the Global Supernova Project— a key project of the Las Cumbres Observatory, NASA's Neil Gehrels Swift Observatory, and many others. This multi-wavelength study, which was published this week in The Astrophysical Journal Letters, revealed that, in sharp contradiction to expectations and stellar evolution theory, SN 2023ixf's shock breakout was delayed by several days.

"The delayed shock breakout is direct evidence for the presence of dense material from recent mass loss," said Hiramatsu, adding that such extreme mass loss is atypical of Type II supernovae. "Our new observations revealed a significant and unexpected amount of mass loss— close to the mass of the Sun— in the final year prior to explosion.

SN 2023ixf challenges astronomers’ understanding of the evolution of massive stars and the supernovae they become. Although scientists know that core-collapse supernovae are primary origin points for the cosmic formation and evolution of atoms, neutron stars, and black holes, very little is known about the years leading up to stellar explosions. The new observations point to potential instability in the final years of a star's life, resulting in extreme mass loss. This could be related to the final stages of nuclear burn-off of high-mass elements, like silicon, in the star's core.

In conjunction with multi-wavelength observations led by Hiramatsu, Edo Berger, professor of astronomy at Harvard and CfA, and Hiramatsu's advisor, conducted millimeter-wave observations of the supernova using CfA's Submillimeter Array (SMA) on the summit of Maunakea, Hawai'i. These data, which are published in The Astrophysical Journal Letters, directly tracked the collision between the supernova debris and the dense material lost before the explosion. "SN 2023ixf exploded exactly at the right time," said Berger. "Only a few days earlier we commenced a new ambitious three-year program to study supernova explosions with the SMA, and this nearby exciting supernova was our first target."

"The only way to understand how massive stars behave in the final years of their lives up to the point of explosion is to discover supernovae when they are very young, and preferably nearby, and then to study them across multiple wavelengths," said Berger. "Using both optical and millimeter telescopes we effectively turned SN 2023ixf into a time machine to reconstruct what its progenitor star was doing up to the moment of its death."

The supernova discovery itself, and the immediate followup, have significant meaning to astronomers around the world, including those doing science in their own backyards. Itagaki discovered the supernova on May 19, 2023, from his private observatory in Okayama, Japan. Combined data from Itagaki and other amateur astronomers determined the time of the explosion to an accuracy of within two hours, giving professional astronomers at CfA and other observatories a head start in their investigations. CfA astronomers have continued to collaborate with Itagaki on on-going optical observations.

"The partnership between amateur and professional astronomers has a long-standing tradition of success in the supernova field," said Hiramatsu. "In the case of SN 2023ixf, I received an urgent email from Kōichi Itagaki as soon as he discovered SN 2023ixf. Without this relationship, and Itagaki's work and dedication, we would have missed the opportunity to gain critical understanding of the evolution of massive stars and their supernova explosions."





About the Center for Astrophysics | Harvard & Smithsonian

The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.



Media Contact:

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Center for Astrophysics | Harvard & Smithsonian

amy.oliver@cfa.harvard.edu


Saturday, October 21, 2023

Three’s a Crowd for Stars Around Supermassive Black Hole Binaries

Simulation of the light from a supermassive black hole binary.

Credit: NASA's Goddard Space Flight Center/Scott Noble; simulation data, d'Ascoli et al. 2018

Title: Uncovering Hidden Massive Black Hole Companions with Tidal Disruption Events
Authors: Brenna Mockler et al.
First Author’s Institution: The Observatories of the Carnegie Institution for Science & Department of Physics and Astronomy at the University of California, Los Angeles
Status: Accepted to ApJ

Two Is Company

Today, astronomers believe that nearly every galaxy hosts a supermassive black hole at its center. In addition, galaxies are thought to grow through mergers, in a process known as hierarchical growth. Essentially, smaller galaxies smash together to form a larger galaxy, and this process repeats many times as the universe evolves. When two galaxies hosting supermassive black holes merge, the black holes should sink to the center of the new galaxy rather rapidly, where they could start orbiting each other as a supermassive black hole binary. These binaries are therefore a natural consequence of this picture of hierarchical galaxy evolution and should be a relatively common occurrence in the universe.

However, finding supermassive black hole binaries has been rather difficult with current instrumentation and technology. A supermassive black hole makes itself known when it accretes gas from its surroundings, becoming a luminous active galactic nucleus. As two accreting black holes get closer and closer together, our telescopes become incapable of resolving them as two individual active galactic nuclei. There are other ways to infer that a binary exists when the black holes are close together, but these methods can be tricky — either the signals could also be produced by some other astrophysical phenomenon, or they take decades to confirm. The next generation of gravitational wave detectors, like the Laser Interferometer Space Antenna, will surely help, but we’d still like to be able to look for supermassive black hole binaries in the next decade or more before these detectors are built!

Introducing the Star of the Show

One of the best ways to observe something we can’t see is by looking for its interactions with things we can see. Today’s authors study the interplay of a supermassive black hole binary with stars in the centers of galaxies, highlighting this as a potential way to uncover these binaries. To start, let’s consider just a single supermassive black hole and throw a star at it. Most of the time, this star will orbit the black hole, just like our planets orbit the Sun. However, in some cases, when the orbit is eccentric enough, the star can get just a bit too close to the supermassive black hole, leading to the star’s demise. This measure of “too close” is set by the distance at which the star’s self-gravity can no longer hold itself together against the tidal forces of the black hole, and the star gets ripped to shreds. We call this phenomenon a tidal disruption event, and these events release a huge amount of energy from a previously quiet black hole.

Okay, but how do we get stars onto these elliptical orbits so that they’re disrupted? And how often does this happen? Many research articles have investigated these questions (check out some of the many Astrobites written on tidal disruption events), both from a theoretical and observational perspective. It turns out that one way to get stars onto these highly elliptical orbits is to scatter them off of other stars (through a process called two-body relaxation). This process is relatively rare; both theory and observations agree that the rate for tidal disruption events around single black holes is somewhere around one every 104–105 years (per galaxy).

But what happens when we deposit these stars around a supermassive black hole binary? The authors of today’s article investigate this very question. In particular, they investigate the interaction of stars around the smaller of the two black holes (see Figure 1 for a schematic of this set up).


Figure 1: Cartoon schematic of the setup considered in today’s article. We have two supermassive black holes with masses m1 and m2, with m1 < m2. The authors investigate stellar orbits around the smaller black hole (m1). Credit: Mockler et al. 2023

And Now Three’s a Crowd

To explore the effects of a binary supermassive black holes on the rate of tidal disruption events, the authors perform dynamical simulations of the three-body problem we just set up above. They focus in particular on the effects of the eccentric Kozai–Lidov (EKL) mechanism, which is a dynamical effect in a three-body system that allows the eccentricity and inclination of the outer binary (i.e., the star and the lower-mass black hole) to oscillate. EKL oscillations can lead to extreme eccentricities, which is a great way to make tidal disruption events happen! To explore the effects of EKL on the system, the authors test different combinations of binary masses and stellar density profiles. There’s a large range of possible parameters in this problem, so they limit their tests to those in which the timescale for the EKL mechanism is the shortest dynamical timescale (which leads to EKL being the dominant mechanism driving the system’s evolution).

The simulations revealed that there should be a burst of tidal disruption events lasting 1–100 million years, depending on the exact simulation parameters. During this time period, the tidal disruption event rates greatly exceed that expected from two-body relaxation, which is what sets the rates of these events in single supermassive black hole systems. However, if the stars near the black hole are not replenished after this period, either from star formation near the galactic nucleus or some dynamical effects, then the rates of EKL-driven tidal disruption events drop to less than those of two-body relaxation. This is highlighted in Figure 2, which shows the EKL-driven tidal disruption event rate as a function of time in these dynamical simulations. So, our best hope for catching tidal disruption events around the smaller black hole in a binary pair is relatively quickly after it enters the binary.


Figure 2: Rate of tidal disruption events occurring around the smaller supermassive black hole as a function of time in the simulations. The shaded blue regions represent different masses of the smaller supermassive black hole, each of which is 10 times less massive than the larger supermassive black hole. The shaded grey region shows the observed rate of optically selected tidal disruption events, and the grey hashed region denotes the rate of tidal disruption events in “post-starburst” (PSB) galaxies (galaxies seen about a few millions of years after a recent burst of star formation, which is often driven by a merger). Finally, the dashed and dotted lines show the rates of tidal disruption events from two-body relaxation (i.e., ordinary tidal disruption events around a single supermassive black hole). The simulations show a burst of tidal disruption events relative to the two-body relaxation rate for the first 1–100 million years. Adapted from Mockler et al. 2023

Finding Supermassive Black Hole Binaries with Tidal Disruption Events

To end, the authors leave us with a potential way to search for supermassive black hole binaries using these tidal disruption events. This method relies upon the fact that the two black holes in the binary will dominate two different observable properties. On one hand, the gravitational potential of the galactic nucleus where these two black holes reside will be dominated by the larger of the two black holes, meaning that host galaxy properties that scale with the galaxy’s central black hole mass will be set by this larger black hole. On the other hand, the light curve from a given tidal disruption event is set by the mass of the black hole that the star is accreting onto, which in this case is the smaller black hole. This means that if we see a tidal disruption event that seems to be coming from a small black hole, but it’s actually happening in a galaxy that’s far too big to host such a black hole, then there’s strong evidence that this could be a supermassive black hole binary system! And so, while three may be a crowd, this unlucky star will actually shed some light on its black hole companions as it leaves the party.

Original astrobite edited by Mark Dodici.




About the author, Megan Masterson:

I’m a 3rd-year PhD student at MIT studying transient accretion events around supermassive black holes, including tidal disruption events and changing-look active galactic nuclei. I primarily use X-ray observations to observe the inner accretion flow of these transients, but I am also interested in multi-wavelength follow-up to get the full picture of these fascinating systems. In my free time, I enjoy hiking and watching soccer.



Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.