Wednesday, June 26, 2024

First-of-Its-Kind Detection Made in Striking New Webb Image

Serpens (NIRCam)
Credits: Image: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)


Serpens North – Aligned Outflows Crop (NIRCam)
Credits: Image: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)

Serpens Center Crop (NIRCam)
Credits: Image: NASA, ESA, CSA, STScI, Klaus Pontoppidan (NASA-JPL), Joel Green (STScI)




For the first time, a phenomenon astronomers have long hoped to directly image has been captured by NASA’s James Webb Space Telescope’s Near-Infrared Camera (NIRCam). In this stunning image of the Serpens Nebula, the discovery lies in the northern area (seen at the upper left) of this young, nearby star-forming region.

Astronomers found an intriguing group of protostellar outflows, formed when jets of gas spewing from newborn stars collide with nearby gas and dust at high speeds. Typically these objects have varied orientations within one region. Here, however, they are slanted in the same direction, to the same degree, like sleet pouring down during a storm.

The discovery of these aligned objects, made possible due to Webb’s exquisite spatial resolution and sensitivity in near-infrared wavelengths, is providing information into the fundamentals of how stars are born.

“Astronomers have long assumed that as clouds collapse to form stars, the stars will tend to spin in the same direction,” said principal investigator Klaus Pontoppidan, of NASA’s Jet Propulsion Laboratory in Pasadena, California. “However, this has not been seen so directly before. These aligned, elongated structures are a historical record of the fundamental way that stars are born.”

So just how does the alignment of the stellar jets relate to the rotation of the star? As an interstellar gas cloud crashes in on itself to form a star, it spins more rapidly. The only way for the gas to continue moving inward is for some of the spin (known as angular momentum) to be removed. A disk of material forms around the young star to transport material down, like a whirlpool around a drain. The swirling magnetic fields in the inner disk launch some of the material into twin jets that shoot outward in opposite directions, perpendicular to the disk of material.

In the Webb image, these jets are signified by bright clumpy streaks that appear red, which are shockwaves from the jet hitting surrounding gas and dust. Here, the red color represents the presence of molecular hydrogen and carbon monoxide.

“This area of the Serpens Nebula – Serpens North – only comes into clear view with Webb,” said lead author Joel Green of the Space Telescope Science Institute in Baltimore. “We’re now able to catch these extremely young stars and their outflows, some of which previously appeared as just blobs or were completely invisible in optical wavelengths because of the thick dust surrounding them.”

Astronomers say there are a few forces that potentially can shift the direction of the outflows during this period of a young star’s life. One way is when binary stars spin around each other and wobble in orientation, twisting the direction of the outflows over time.

Stars of the Serpens

The Serpens Nebula, located 1,300 light-years from Earth, is only one or two million years old, which is very young in cosmic terms. It’s also home to a particularly dense cluster of newly forming stars (~100,000 years old), seen at the center of this image. Some of these stars will eventually grow to the mass of our Sun.

“Webb is a young stellar object-finding machine,” Green said. “In this field, we pick up sign posts of every single young star, down to the lowest mass stars.” “It’s a very complete picture we’re seeing now,” added Pontoppidan. 

So, throughout the region in this image, filaments and wisps of different hues represent reflected starlight from still-forming protostars within the cloud. In some areas, there is dust in front of that reflection, which appears here with an orange, diffuse shade.

This region has been home to other coincidental discoveries, including the flapping “Bat Shadow,” which earned its name when 2020 data from NASA’s Hubble Space Telescope revealed a star’s planet-forming disk to flap, or shift. This feature is visible at the center of the Webb image.

Future Studies

The new image, and serendipitous discovery of the aligned objects, is actually just the first step in this scientific program. The team will now use Webb’s NIRSpec (Near-Infrared Spectrograph) to investigate the chemical make-up of the cloud.

The astronomers are interested in determining how volatile chemicals survive star and planet formation. Volatiles are compounds that sublimate, or transition from a solid directly to a gas, at a relatively low temperature – including water and carbon monoxide. They’ll then compare their findings to amounts found in protoplanetary disks of similar-type stars.

“At the most basic form, we are all made of matter that came from these volatiles. The majority of water here on Earth originated when the Sun was an infant protostar billions of years ago,” Pontoppidan said. “Looking at the abundance of these critical compounds in protostars just before their protoplanetary disks have formed could help us understand how unique the circumstances were when our own solar system formed.”

These observations were taken as part of General Observer program 1611. The team’s initial results have been accepted for publication in the Astrophysical Journal.

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 CSA (Canadian Space Agency).




About This Release

Credits:

Media Contact:

Hannah Braun
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents


Tuesday, June 25, 2024

Astronomers see a massive black hole awaken in real time

PR Image eso2409a
Artist’s impression: the galaxy SDSS1335+0728 lighting up

PR Image eso2409b
Artist’s impression: the black hole at the centre of the galaxy SDSS1335+0728 awakens



Videos

Zooming into the galaxy SDSS1335+0728 and its newly awakened black hole
PR Video eso2409a
Zooming into the galaxy SDSS1335+0728 and its newly awakened black hole

Artist’s animation of the black hole at the centre of SDSS1335+0728 awakening in real time
PR Video eso2409b
Artist’s animation of the black hole at the centre of SDSS1335+0728 awakening in real time



In late 2019 the previously unremarkable galaxy SDSS1335+0728 suddenly started shining brighter than ever before. To understand why, astronomers have used data from several space and ground-based observatories, including the European Southern Observatory’s Very Large Telescope (ESO’s VLT), to track how the galaxy’s brightness has varied. In a study out today, they conclude that they are witnessing changes never seen before in a galaxy — likely the result of the sudden awakening of the massive black hole at its core.

Imagine you’ve been observing a distant galaxy for years, and it always seemed calm and inactive,” says Paula Sánchez Sáez, an astronomer at ESO in Germany and lead author of the study accepted for publication in Astronomy & Astrophysics. “Suddenly, its [core] starts showing dramatic changes in brightness, unlike any typical events we've seen before.” This is what happened to SDSS1335+0728, which is now classified as having an ‘active galactic nucleus’ (AGN) — a bright compact region powered by a massive black hole — after it brightened dramatically in December 2019 [1].

Some phenomena, like supernova explosions or tidal disruption events — when a star gets too close to a black hole and is torn apart — can make galaxies suddenly light up. But these brightness variations typically last only a few dozen or, at most, a few hundreds of days. SDSS1335+0728 is still growing brighter today, more than four years after it was first seen to ‘switch on’. Moreover, the variations detected in the galaxy, which is located 300 million light-years away in the constellation Virgo, are unlike any seen before, pointing astronomers towards a different explanation.

The team tried to understand these brightness variations using a combination of archival data and new observations from several facilities, including the X-shooter instrument on ESO’s VLT in Chile’s Atacama Desert [2]. Comparing the data taken before and after December 2019, they found that SDSS1335+0728 is now radiating much more light at ultraviolet, optical, and infrared wavelengths. The galaxy also started emitting X-rays in February 2024. “This behaviour is unprecedented,” says Sánchez Sáez, who is also affiliated with the Millennium Institute of Astrophysics (MAS) in Chile.

The most tangible option to explain this phenomenon is that we are seeing how the [core] of the galaxy is beginning to show (...) activity,” says co-author Lorena Hernández García, from MAS and the University of Valparaíso in Chile. “If so, this would be the first time that we see the activation of a massive black hole in real time.

Massive black holes — with masses over one hundred thousand times that of our Sun — exist at the centre of most galaxies, including the Milky Way. “These giant monsters usually are sleeping and not directly visible,” explains co-author Claudio Ricci, from the Diego Portales University, also in Chile. “In the case of SDSS1335+0728, we were able to observe the awakening of the massive black hole, [which] suddenly started to feast on gas available in its surroundings, becoming very bright.

[This] process (...) has never been observed before,” Hernández García says. Previous studies reported inactive galaxies becoming active after several years, but this is the first time the process itself — the awakening of the black hole — has been observed in real time. Ricci, who is also affiliated with the Kavli Institute for Astronomy and Astrophysics at Peking University, China, adds: “This is something that could happen also to our own Sgr A*, the massive black hole (...) located at the centre of our galaxy," but it is unclear how likely this is to happen.

Follow-up observations are still needed to rule out alternative explanations. Another possibility is that we are seeing an unusually slow tidal disruption event, or even a new phenomenon. If it is in fact a tidal disruption event, this would be the longest and faintest such event ever observed. “Regardless of the nature of the variations, [this galaxy] provides valuable information on how black holes grow and evolve,” Sánchez Sáez says. “We expect that instruments like [MUSE on the VLT or those on the upcoming Extremely Large Telescope (ELT)] will be key in understanding [why the galaxy is brightening].”

Source: ESO/News



Notes

[1] The SDSS1335+0728 galaxy’s unusual brightness variations were detected by the Zwicky Transient Facility (ZTF) telescope in the US. Following that, the Chilean-led Automatic Learning for the Rapid Classification of Events (ALeRCE) broker classified SDSS1335+0728 as an active galactic nucleus.

[2] The team collected archival data from NASA’s Wide-field Infrared Survey Explorer (WISE) and Galaxy Evolution Explorer (GALEX), the Two Micron All Sky Survey (2MASS), the Sloan Digital Sky Survey (SDSS), and the eROSITA instrument on IKI and DLR’s Spektr-RG space observatory. Besides ESO’s VLT, the follow-up observations were conducted with the Southern Astrophysical Research Telescope (SOAR), the W. M. Keck Observatory, and NASA’s Neil Gehrels Swift Observatory and Chandra X-ray Observatory.




More information

This research was presented in a paper entitled “SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole” published in Astronomy & Astrophysics (https://aanda.org/10.1051/0004-6361/202347957).

The team is composed of P. Sánchez-Sáez (European Southern Observatory, Garching, Germany [ESO] and Millenium Institute of Astrophysics, Chile [MAS]), L. Hernández-García (MAS and Instituto de Física y Astronomía, Universidad de Valparaíso, Chile [IFA-UV]), S. Bernal (IFA-UV and Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes, Chile [TITANS]), A. Bayo (ESO), G. Calistro Rivera (ESO and German Space Agency [DLR]), F. E. Bauer (Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Chile; Centro de Astroingeniería, Pontificia Universidad Católica de Chile, Chile; MAS; and Space Science Institute, USA), C. Ricci (Instituto de Estudios Astrofísicos, Universidad Diego Portales, Chile [UDP] and Kavli Institute for Astronomy and Astrophysics, China), A. Merloni (Max-Planck-Institut für Extraterrestrische Physik, Germany [MPE]), M. J. Graham (California Institute of Technology, USA), R. Cartier (Gemini Observatory, NSF National Optical-Infrared Astronomy Research Laboratory, Chile, and UDP), P. Arévalo (IFA-UV and TITANS), R.J. Assel (UDP), A. Concas (ESO and INAF - Osservatorio Astrofisico di Arcetri, Italy), D. Homan (Leibniz-Institut für Astrophysik Potsdam, Germany [AIP]), M. Krumpe (AIP), P. Lira (Departamento de Astronomía, Universidad de Chile, Chile [UChile], and TITANS), A. Malyali (MPE), M. L. Martínez-Aldama (Astronomy Department, Universidad de Concepción, Chile), A. M. Muñoz Arancibia (MAS and Center for Mathematical Modeling, University of Chile, Chile [CMM-UChile]), A. Rau (MPE), G. Bruni (INAF - Institute for Space Astrophysics and Planetology, Italy), F. Förster (Data and Artificial Intelligence Initiative, University of Chile, Chile; MAS; CMM-UChile; and UChile), M. Pavez-Herrera (MAS), D. Tubín-Arenas (AIP), and M. Brightman (Cahill Center for Astrophysics, California Institute of Technology, USA).

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, Czechia, 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

Paula Sánchez Sáez
European Southern Observatory (ESO)
Garching bei München, Germany
Tel: +49 89 3200 6580
Email:
Paula.SanchezSaez@eso.org

Lorena Hernández García
Millennium Institute of Astrophysics (MAS)
Santiago, Chile
Email:
lorena.hernandez@uv.cl

Claudio Ricci
Diego Portales University
Santiago, Chile
Email:
claudio.ricci@mail.udp.cl

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


Monday, June 24, 2024

Massive black holes in low-mass galaxies: what happened to the X-ray Corona?

Two examples of X-ray-detected MBH candidates. On the top we show the eROSITA eRASS-4 X-ray images centered at the input optical coordinates, while on the bottom the optical image with overlayed X-ray contours. For the vast majority of MBH candidates, X-ray counterparts such those shown here were not found. © Legacy Surveys/D. Lang (Perimeter Institute); R. Arcodia.

Illustration of accretion disk corona.
Nahks Tr'Ehnl and Niel Brandt, Penn State University



Identifying massive black holes in low-mass galaxies is crucial for understanding black hole formation and growth over cosmic time but challenging due to their low accretion luminosities. Astronomers at MPE, led by Riccardo Arcodia, used the eROSITA X-ray telescope's all-sky survey to study massive black hole candidates selected based on variability in other wavelength ranges. Surprisingly, despite being flagged as accreting MBHs, the X-rays were weak and didn't match predictions from more massive AGN scaling relations. This discrepancy suggests either the absence of a canonical X-ray corona or the presence of unusual accretion modes and spectral energy distributions in these dwarf galaxy MBHs.

The centre of the Milky Way harbours a supermassive black hole – as do basically all galaxies of similar size and bigger than our Milky Way. But what about small galaxies? There is a hot debate in the astronomy community on whether all, or only some, low-mass galaxies are populated by “massive black holes”, anything between a few thousands to a few million solar masses. If these could be found and analysed, we could also learn something about the galaxies in the early Universe and how black holes grow over cosmic times, as the local dwarf galaxies closely resemble these first galaxies. So far, about 500 massive black holes have been found in the nearby Universe, as they need to be active and luminous enough to discern emission from their immediate vicinity from the host galaxy’s overall emission.

A team of astronomers has now used the all-sky survey with the eROSITA X-ray telescope to study massive black hole candidates selected by their variability in other wavelength ranges. “The variability at optical or infrared wavelengths indicates that there is some activity in the galactic nucleus. So, if there is a massive black hole accreting material, it should emit X-rays,” explains Riccardo Arcodia, who led the study at the Max Planck Institute for Extraterrestrial Physics (MPE) and is now working at the MIT Kavli Institute for Astrophysics and Space Research.

The only selection criterion for the sample was a cut on stellar mass to single out low-mass galaxies, leading to about 200 sources/MBHs. The team then looked for X-ray emission at the positions of these galaxies in the eROSITA all-sky survey and found only 17 sources, four of which had never been seen in X-rays before.

“The predicted X-ray luminosity of most of these candidates should be well above the detection limit of the eROSITA all-sky survey,” points out Andrea Merloni, eROSITA’s principal investigator. “Moreover, our stacking analysis of the non-detected sources shows that their emission is consistent with predictions for the X-ray emission of the galaxy alone.” While a possible X-ray weakness of massive black holes in dwarf galaxies was reported before for a few cases, this is the first confirmation on a large sample of homogeneous X-ray observations.

This means that the massive black holes in dwarf galaxies most likely behave differently than their supermassive counterparts. High-energy X-rays are typically produced in a region of hot plasma in the immediate vicinity of the black hole called the corona. In low-mass galaxies, the gravitational pull towards the centre is less strong and their interstellar medium is clumpier than in more massive ones, which might lead to differences in the magnetic field or the interplay between the accretion disk and the black hole corona. “This could be the reason why a classical corona was not found in these low-mass black holes”, says first author Riccardo Arcodia. “A different accretion mode in low-mass galaxies would also imply that selection techniques at different wavebands do not offer the same agreement seen at higher masses”, he adds. Future multi-wavelength studies on large samples are needed to test whether this is the case, or whether the X-ray emission alone is unusually low.

“This work serves as a pilot study for future synergies between eROSITA and VRO/LSST, which will perform a 10-year optical survey of the southern sky,” explains Mara Salvato, eROSITA Spokesperson and chair of the eROSITA followup working group. “We expect to find hundreds of LSST’s massive black hole candidates in eROSITA data, and hopefully learn a lot more about what is going on with the less-massive black holes at the centers of dwarf galaxies.”




Contact:

Riccardo Arcodia
Postdoc
tel:+49 (0)89 30000-3643

arcodia@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

Dr. Andrea Merloni
tel:+49 89 30000-3893

am@mpe.mpg.de

Max Planck Institute for Extraterrestrial Physics, Garching



Original Publication

R. Arcodia, A.Merloni, J.Comparat et al
O Corona, where art thou? eROSITA’s view of UV-optical-IR variability-selected massive black holes in low-mass galaxies.
A&A, 681, A97 (2024)

Source | DOI



Further Information


eROSITA witnesses the awakening of massive black holes
April 29, 2021
Using the SRG/eROSITA all-sky survey data, scientists at the MPE have found two previously quiescent galaxies that now show quasi-periodic eruptions.

more



The X-ray sky opens to the world
January 31, 2024
First eROSITA sky-survey data release makes public the largest ever catalogue of high-energy cosmic sources


more





Sunday, June 23, 2024

Seeing Triple

SN H0pe

What at first appears to be a glowing strand of molten iron in the image above is something far wilder: a distant galaxy whose light has been stretched into galactic taffy by the immense gravity of an intervening galaxy cluster. This phenomenon, known as strong gravitational lensing, multiplies and magnifies images of faraway sources, allowing astronomers to use massive objects like galaxy clusters as natural telescopes. Look closely at the zoomed-in version of the image: three points of light stand out against the glow of the lensed galaxy. These three dots are multiple images of a single supernova cataloged as SN H0pe. Researchers plan to use this rare multiply imaged supernova to calculate the Hubble constant, which quantifies the universe’s expansion rate. Using observations from JWST, a team led by Justin Pierel (Space Telescope Science Institute) calculated the time delay of the light from the images, finding arrival times offset by 49 and 117 days. The value of the Hubble constant derived from these observations will be reported in a future publication. In the meantime, be sure to check out the details of these initial calculations in the article linked below.

Citation

“JWST Photometric Time-Delay and Magnification Measurements for the Triply Imaged Type Ia “SN H0pe” at z = 1.78,” J. D. R. Pierel et al 2024 ApJ 967 50. doi:10.3847/1538-4357/ad3c43



Saturday, June 22, 2024

Investigating the Origins of the Crab Nebula With NASA's Webb

Crab Nebula
Credits: Image: NASA, ESA, CSA, STScI, Tea Temim (Princeton University)




A team of scientists used NASA’s James Webb Space Telescope to parse the composition of the Crab Nebula, a supernova remnant located 6,500 light-years away in the constellation Taurus. With the telescope’s MIRI (Mid-Infared Instrument) and NIRCam (Near-Infrared Camera), the team gathered data that is helping to clarify the Crab Nebula’s history.

The Crab Nebula is the result of a core-collapse supernova from the death of a massive star. The supernova explosion itself was seen on Earth in 1054 CE and was bright enough to view during the daytime. The much fainter remnant observed today is an expanding shell of gas and dust, and outflowing wind powered by a pulsar, a rapidly spinning and highly magnetized neutron star.

The Crab Nebula is also highly unusual. Its atypical composition and very low explosion energy previously have been explained by an electron-capture supernova — a rare type of explosion that arises from a star with a less-evolved core made of oxygen, neon, and magnesium, rather than a more typical iron core.

“Now the Webb data widen the possible interpretations,” said Tea Temim, lead author of the study at Princeton University in New Jersey. “The composition of the gas no longer requires an electron-capture explosion, but could also be explained by a weak iron core-collapse supernova.”

Studying the Present to Understand the Past

Past research efforts have calculated the total kinetic energy of the explosion based on the quantity and velocities of the present-day ejecta. Astronomers deduced that the nature of the explosion was one of relatively low energy (less than one-tenth that of a normal supernova), and the progenitor star’s mass was in the range of eight to 10 solar masses — teetering on the thin line between stars that experience a violent supernova death and those that do not.

However, inconsistencies exist between the electron-capture supernova theory and observations of the Crab, particularly the observed rapid motion of the pulsar. In recent years, astronomers have also improved their understanding of iron core-collapse supernovae and now think that this type can also produce low-energy explosions, providing that the stellar mass is adequately low.

Webb Measurements Reconcile Historic Results

To lower the level of uncertainty surrounding the Crab’s progenitor star and nature of the explosion, the team led by Temim used Webb’s spectroscopic capabilities to hone in on two areas located within the Crab’s inner filaments.

Theories predict that because of the different chemical composition of the core in an electron-capture supernova, the nickel to iron (Ni/Fe) abundance ratio should be much higher than the ratio measured in our Sun (which contains these elements from previous generations of stars). Studies in the late 1980s and early 1990s measured the Ni/Fe ratio within the Crab using optical and near-infrared data and noted a high Ni/Fe abundance ratio that seemed to favor the electron-capture supernova scenario.

The Webb telescope, with its sensitive infrared capabilities, is now advancing Crab Nebula research. The team used MIRI’s spectroscopic abilities to measure the nickel and iron emission lines, resulting in a more reliable estimate of the Ni/Fe abundance ratio. They found that the ratio was still elevated compared to the Sun, but only modestly and much lower in comparison to prior estimates.

The revised values are consistent with electron-capture, but do not rule out an iron core-collapse explosion from a similarly low-mass star. (Higher-energy explosions from higher-mass stars are expected to produce ratios closer to solar abundances.) Further observational and theoretical work will be needed to distinguish between these two possibilities.

“At present, the spectral data from Webb covers two small regions of the Crab, so it’s important to study much more of the remnant and identify any spatial variations,” said Martin Laming of the Naval Research Laboratory in Washington and a co-author of the paper. “It would be interesting to see if we could identify emission lines from other elements, like cobalt or germanium.”

Mapping the Crab’s Current State

Besides pulling spectral data from two small regions of the Crab Nebula’s interior to measure the abundance ratio, the telescope also observed the remnant’s broader environment to understand details of the synchrotron emission and the dust distribution.

The images and data collected by MIRI enabled the team to isolate the dust emission within the Crab and map it in high resolution for the first time. By mapping the warm dust emission with Webb, and even combining it with the Herschel Space Observatory’s data on cooler dust grains, the team created a well-rounded picture of the dust distribution: The outermost filaments contain relatively warmer dust, while cooler grains are prevalent near the center.

“Where dust is seen in the Crab is interesting because it differs from other supernova remnants, like Cassiopeia A and Supernova 1987A," said Nathan Smith of the Steward Observatory at the University of Arizona and a co-author of the paper. “In those objects, the dust is in the very center. In the Crab, the dust is found in the dense filaments of the outer shell. The Crab Nebula lives up to a tradition in astronomy: The nearest, brightest, and best-studied objects tend to be bizarre.”

These findings have been accepted for publication in The Astrophysical Journal Letters.

The observations were taken as part of General Observer program 1714.

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 CSA (Canadian Space Agency).




About This Release

Credits:

Media Contact:

Abigail Major
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science: Tea Temim (Princeton University)

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.


Friday, June 21, 2024

Black hole’s business-as-usual in the earliest universe highlights galaxy evolution problem

Artist's conception of an early quasar. The black hole in the center is surrounded by a bright accretion disk. Farther outside is the "dust torus", an irregular, larger and markedly thicker disk that can obscure an outside observer's view of the accretion disk. The dust torus predominantly emits mid-infrared light, and its properties can be read off the overall shape ("continuum") of the spectrum. The accretion disk's magnetic fields produce a focused high-energy jet of particles that emitted from the immediate neighbourhood of the black hole, beaming away at right angles to the disk. Above and below the disk are irregular gas clouds. Since their shapes are not known, they are shown here in stylized form, as spheres. The gas clouds that are close to the center orbit the black hole at high speeds. This produces broad emission lines in the quasar's spectrum, and that region of gas is called the "broad-line region". The gas clouds farther away, shown here as somewhat larger sphere, move less quickly, producing narrower emission lines; they form what is called the "narrow-line region".© T. Müller / MPIA



Using the space telescope JWST, astronomers have examined one of the most distant known black holes in the universe. Their observations provide a glimpse of the growth of black holes in the early universe, less than a billion years after the Big Bang. Surprisingly, the early black hole in question seems to be “feeding” in much the same manner as its more recent kin. Astronomers have been struggling for a while now to explain how the earliest black holes gained their considerable masses. The new results all but rule out unusually efficient feeding mechanisms at early times as a possible solution. The results have been published in the journal Nature Astronomy.

The first billion years of cosmic history pose a challenge: The earliest known black holes in the centers of galaxies have surprisingly large masses. How did they get so massive, so quickly? The new observations described here provide strong evidence against some proposed explanations, notably against an “ultra-effective feeding mode” for the earliest black holes.

The limits of supermassive black hole growth

Stars and galaxies have changed enormously over the past 13.8 billion years, the lifetime of the Universe. Galaxies have grown larger and acquired more mass, either by consuming surrounding gas or (occasionally) by merging with each other. For a long time, astronomers assumed that the supermassive black holes in the centers of galaxies would have grown gradually along with the galaxies themselves.

But black hole growth cannot be arbitrarily fast. Matter falling onto a black hole forms a swirling, hot, bright "accretion disk." When this happens around a supermassive black hole, the result is an active galactic nucleus. The brightest such objects, known as quasars, are among the brightest astronomical objects in the whole cosmos. But that brightness limits how much matter can fall onto the black hole: Light exerts a pressure, which can keep additional matter from falling in.

How did black holes get so massive, so fast?

That is why astronomers were surprised when, over the past twenty years, observations of distant quasars revealed very young black holes that had nevertheless reached masses as high as 10 billion solar masses. Light takes time to travel from a distant object to us, so looking at far-away objects means looking into the distant past. We see the most distant known quasars as they were in an era known as “cosmic dawn,” less than one billion years after the Big Bang, when the first stars and galaxies formed.

Explaining those early, massive black holes is a considerable challenge for current models of galaxy evolution. Could it be that early black holes were much more efficient at accreting gas than their modern counterparts? Or could the presence of dust affect quasar mass estimates in a way that made researchers overestimate early black hole masses? There are numerous proposed explanations at this time, but none that is widely accepted.

A closer look at early black-hole growth

Deciding which – if any – of the explanations are correct requires a more complete picture of quasars than had been available before. With the advent of the space telescope JWST, specifically the telescope’s mid-infrared instrument MIRI, astronomers' ability to study distant quasars took a gigantic leap. For measuring distant quasar spectra, MIRI is 4000 more times more sensitive than any previous instrument.

Instruments like MIRI are built by international consortia, with scientists, engineers and technicians working closely together. Naturally, a consortium is very interested in testing whether their instrument performs as well as planned. In return for building the instrument, consortia typically are given a certain amount of observation time. In 2019, years before JWST launched, the MIRI European Consortium decided to use some of this time to observe what was then the most distant known quasar, an object that goes by the designation J1120+0641.

Observing one of the earliest black holes

Analysing the observations fell to Dr. Sarah Bosman, a post-doctoral researcher at the Max Planck Institute for Astronomy (MPIA) and member of the MIRI European consortium. MPIA’s contributions to the MIRI instrument include building a number of key internal parts. Bosman was asked to join the MIRI collaboration specifically to bring in expertise on how to best use the instrument to study the early Universe, in particular the first supermassive black holes.

The observations were carried out in January 2023, during JWST’s first cycle of observations, and lasted for about two and a half hours. They constitute the first mid-infrared study of a quasar in the period of cosmic dawn, a mere 770 million years after the Big Bang (redshift z=7). The information stems not from an image, but from a spectrum: the rainbow-like decomposition of the object's light into components at different wavelengths.

Tracing dust and fast-moving gas

The overall shape of the mid-infrared spectrum ("continuum") encodes the properties of a large torus of dust that surrounds the accretion disk in typical quasars. This torus helps to guide matter onto the accretion disk, "feeding" the black hole. The bad news for those whose preferred solution to the massive early black holes lies in alternative quick modes of growth: The torus, and by extension the feeding mechanism in this very early quasar, appear to be the same as for its more modern counterparts. The only difference is one that no model of quick early quasar growth predicted: a somewhat higher dust temperature around a hundred Kelvin warmer than the 1300 K found for the hottest dust in less distant quasars.

The shorter-wavelength part of the spectrum, dominated by the emissions from the accretion disk itself, shows that for us as distant observers, the quasar's light is not dimmed by more-than-usual dust. Arguments that maybe we are merely overestimating early black hole masses because of additional dust are not the solution either.

Early quasars “shockingly normal”

The quasar's broad-line region, where clumps of gas orbit the black hole at speeds near the speed of light – which permit deductions about the black hole mass, and the density and ionization of the surrounding matter – look normal as well. By almost all the properties that can be deduced from the spectrum, J1120+0641 is no different from quasars at later times.

“Overall, the new observations only add to the mystery: Early quasars were shockingly normal. No matter in which wavelengths we observe them, quasars are nearly identical at all epochs of the Universe,” says Bosman. Not only the supermassive black holes themselves, but also their feeding mechanisms were apparently already completely "mature" when the Universe was a mere 5% of its current age. By ruling out a number of alternative solutions, the results strongly support the idea that supermassive black holes started out with considerable masses from the get-go, in astronomy lingo: that they are "primordial" or "seeded large." Supermassive black holes did not form from the remnants of early stars, then grew massive very fast. They must have formed early with initial masses of at least a hundred thousand solar masses, presumably via the collapse of massive early clouds of gas.

Background information

The results described here have been published as S. Bosman et al., "JWST rest-frame infrared spectroscopy reveals a mature quasar at cosmic dawn" in the journal Nature Astronomy.

The MPIA scientists involved are Sarah Bosman (also University of Heidelberg), Fabian Walter, Leindert Boogaard, Manuel Gudel and Thomas Henning, in collaboration with the MIRI Guaranteed Time Observations (MIRI GTO) team.

You can access the original paper via press@nature.com or https://press.nature.com




Contact:

Dr. Sarah Bosman
tel:+49 6221 528-375

bosman@mpia.de
Max Planck Institute for Astronomy, Heidelberg

Dr. Markus Pössel
Head of press relations and outreach
tel:+49 6221 528-261

pr@mpia.de
Max Planck Institute for Astronomy, Heidelberg


Thursday, June 20, 2024

It’s Twins! Astronomers Discover Parallel Disks and Jets Erupting From a Pair of Young Stars

At left, a mid-infrared image of the rho Ophiuchi molecular cloud complex by NASA’s Spitzer Space Telescope, the focus pointing to star system WL20. At right, WL20 expands to reveal an artist’s impression of this new discovery. Astronomers couldn't believe their luck when observations across multiple radio and infrared wavelengths from ALMA and JWST revealed twin disks and jets erupting from a pair of young binary stars in WL20. Credit: U.S. NSF/ NSF NRAO/B. Saxton.; NASA/JPL-Caltech/Harvard-Smithsonian CfA. Hi-Res File

These brightly colored shapes represent astronomical data collected by NRAO's ALMA and NASA's JWST telescopes. At left, a composite image overlaps ALMA and JWST data revealing the discs and parallel jets emitting from the pair of binary stars in WL20. At right, the breakdown of the separate ALMA data, and JWST data representing various chemical compositions, is shown. Credit: U.S. NSF/ NSF NRAO/ ALMA(ESO/NAOJ/NRAO)/ NASA/ JPL-Caltech/ JWST/ B. Saxton. Hi-Res File



Telescopes from the U.S. National Science Foundation’s National Radio Astronomy Observatory and NASA’s Jet Propulsion Laboratory discover dynamic duo

Most of the Universe is invisible to the human eye. The building blocks of stars are only revealed in wavelengths that are outside of the visible spectrum. Astronomers recently used two very different, and very powerful, telescopes to discover twin disks—and twin parallel jets—erupting from young stars in a multiple star system. This discovery was unexpected, and unprecedented, given the age, size, and chemical makeup of the stars, disks, and jets. Their location in a known, well-studied part of the Universe adds to the thrill.

Observations from the U.S. National Science Foundation’s (NSF) National Radio Astronomy Observatory’s (NRAO) Atacama Large Millimeter/submillimeter Array (ALMA) and NASA’s James Webb Space Telescope’s (JWST) Mid-Infrared Instrument (MIRI) were combined for this research.

ALMA and JWST’s MIRI observe very different parts of the electromagnetic spectrum. Using them together allowed astronomers to discover these twins, hidden in radio and infrared wavelengths in star system WL20, located in the nearby rho Ophiuchi molecular cloud complex, over 400 light years away from the Earth’s Solar System.

“What we discovered was absolutely wild,” shares astronomer Mary Barsony, “We’ve known about star system WL20 for a long time. But what caught our attention is that one of the stars in the system appeared much younger than the rest. Using MIRI and ALMA together, we actually saw that this ONE star was TWO stars right next to each other. Each of these stars was surrounded by a disk, and each disc was emitting jets parallel to the other.”

ALMA spotted the discs, while MIRI found the jets. Co-author Valentin J.M. Le Gouellec of NASA-ARC retrieved and reduced ALMA archival data to reveal the discs’ composition, while Lukasz Tychoniec of Leiden Observatory provided high-resolution images, revealing the discs massive size, approximately 100 times the distance between the Earth and the Sun. Another co-author, Martijn L. van Gelder, provided resources to process the data collected by MIRI, revealing the chemical makeup of the jets.

Adds Barsony, “So if it weren’t for MIRI, we wouldn’t even know that these jets existed, which is amazing.” ALMA’s high resolution observations of the disks surrounding the two newly observed stars revealed the disks’ structure, as Barsony explains,“Someone looking at this ALMA data not knowing there were twin jets would think, oh, it’s a large edge on disk with a central hole, instead of two edge on disks and two jets. That’s pretty remarkable.”

Another remarkable thing about this discovery is that it may never have had the opportunity to happen. Explains JPL scientist Michael Ressler, “A lot of the research about binary protostars focuses on a few nearby star forming regions. I had been awarded some observing time of my own with JWST, and I chose to split it into a few small projects. For one project, I decided to study binaries in the Perseus star forming region. However, I had been studying WL20, which is in the rho Ophiuchus region in nearly the opposite part of the sky, for nearly 30 years, and I thought, ‘why not sneak it in? I’m never going to get another chance, even if it doesn’t quite fit with the others.’ We had a very fortunate accident with what we found, and the results are stunning.”

By combining multi-wavelength data from ALMA and JWST, these new findings shed light on the complex processes involved in the formation of multiple star systems. Astronomers plan to utilize ALMA’s future upgraded capabilities, like the Wideband Sensitivity Upgrade, to continue unraveling the mysteries surrounding the birth of stars and planetary systems.




About ALMA & NRAO

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The NRAO is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About JWST

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 CSA (Canadian Space Agency).



Wednesday, June 19, 2024

A transformation in progress

Clouds of gas and dust with many stars. The clouds form a flat blue background towards the bottom, and become more thick and smoky towards the top. They are lit on one side by stars in the nebula. A thick arc of gas and dust reaches around from the top, where it is brightly lit by many stars in and around it, to the bottom where it is dark and obscuring. Other large stars lie between the clouds and the viewer. Credit: ESA/Hubble & NASA, J. Tan (Chalmers University & University of Virginia), R. Fedriani (Institute for Astrophysics of Andalusia)

A visually striking collection of interstellar gas and dust is the focus of this week's Hubble Picture of the Week. Named RCW 7, the nebula is located just over 5300 light-years from Earth in the constellation Puppis.

Nebulae are areas of space that are rich in the raw material needed to form new stars. Under the influence of gravity, parts of these molecular clouds collapse until they coalesce into protostars, surrounded by spinning discs of leftover gas and dust. In the case of RCW 7, the protostars forming here are particularly massive, giving off strongly ionising radiation and fierce stellar winds that have transformed it into what is known as a H II region.

H II regions are filled with hydrogen ions — where H I refers to a normal hydrogen atom, H II is hydrogen that has lost its electron. The ultraviolet radiation from the massive protostars excites the hydrogen, causing it to emit light and giving this nebula its soft pinkish glow. Here Hubble is studying a particular massive protostellar binary named IRAS 07299-1651, still in its glowing cocoon of gas in the curling clouds towards the top of the nebula. To expose this star and its siblings, this image was captured using the Wide Field Camera 3 in near-infrared light. The massive protostars here are brightest in ultraviolet light, but they emit plenty of infrared light which can pass through much of the gas and dust around them and be seen by Hubble. Many of the other, larger-looking stars in this image are not part of the nebula, but sit between it and our Solar System.

The creation of an H II region marks the beginning of the end for a molecular cloud. Over only a few million years, the radiation and winds from the massive stars gradually disperse the gas — even more so as the most massive stars come to the end of their lives in supernova explosions. Only a fraction of the gas will be incorporated into new stars in this nebula, with the rest being spread throughout the galaxy to eventually form new molecular clouds.

Links


Tuesday, June 18, 2024

NASA's Hubble Finds Surprises Around a Star That Erupted 40 Years Ago

Nova in Binary Star System HM Sagittae (Artist's Concept)
Credits: Artwork: NASA, ESA, Leah Hustak (STScI)

Symbiotic Star Mira HM Sge
Credits: Science: NASA, ESA, Ravi Sankrit (STScI), Steven Goldman (STScI)
Image Processing: Joseph DePasquale (STScI)





Astronomers have used new data from NASA's Hubble Space Telescope and the retired SOFIA (Stratospheric Observatory for Infrared Astronomy) as well as archival data from other missions to revisit one of the strangest binary star systems in our galaxy – 40 years after it burst onto the scene as a bright and long-lived nova. A nova is a star that suddenly increases its brightness tremendously and then fades away to its former obscurity, usually in a few months or years.

Between April and September 1975, the binary system HM Sagittae (HM Sge) grew 250 times brighter. Even more unusual, it did not rapidly fade away as novae commonly do, but has maintained its luminosity for decades. Recently, observations show that the system has gotten hotter, but paradoxically faded a little.

HM Sge is a particular kind of symbiotic star where a white dwarf and a bloated, dust-producing giant companion star are in an eccentric orbit around each other, and the white dwarf ingests gas flowing from the giant star. That gas forms a blazing hot disk around the white dwarf, which can unpredictably undergo a spontaneous thermonuclear explosion as the infall of hydrogen from the giant grows denser on the surface until it reaches a tipping point. These fireworks between companion stars fascinate astronomers by yielding insights into the physics and dynamics of stellar evolution in binary systems.

"In 1975 HM Sge went from being a nondescript star to something all astronomers in the field were looking at, and at some point that flurry of activity slowed down," said Ravi Sankrit of the Space Telescope Science Institute (STScI) in Baltimore. In 2021, Steven Goldman of STScI, Sankrit and collaborators used instruments on Hubble and SOFIA to see what had changed with HM Sge in the last 30 years at wavelengths of light from the infrared to the ultraviolet (UV).

The 2021 ultraviolet data from Hubble showed a strong emission line of highly ionized magnesium that was not present in earlier published spectra from 1990. Its presence shows that the estimated temperature of the white dwarf and accretion disk increased from less than 400,000 degrees Fahrenheit in 1989 to greater than 450,000 degrees Fahrenheit now. The highly ionized magnesium line is one of many seen in the UV spectrum, which analyzed together will reveal the energetics of the system, and how it has changed in the last three decades.

"When I first saw the new data," Sankrit said, "I went – 'wow this is what Hubble UV spectroscopy can do!' – I mean it's spectacular, really spectacular."

With data from NASA's flying telescope SOFIA, which retired in 2022, the team was able to detect the water, gas, and dust flowing in and around the system. Infrared spectral data shows that the giant star, which produces copious amounts of dust, returned to its normal behavior within only a couple years of the explosion, but also that it has dimmed in recent years, which is another puzzle to be explained.

With SOFIA astronomers were able to see water moving at around 18 miles per second, which they suspect is the speed of the sizzling accretion disk around the white dwarf. The bridge of gas connecting the giant star to the white dwarf must presently span about 2 billion miles.

The team has also been working with the AAVSO (American Association of Variable Star Observers), to collaborate with amateur astronomers from around the world who help keep telescopic eyes on HM Sge; their continued monitoring reveals changes that haven't been seen since its outburst 40 years ago.

"Symbiotic stars like HM Sge are rare in our galaxy, and witnessing a nova-like explosion is even rarer. This unique event is a treasure for astrophysicists spanning decades," said Goldman.

The initial results from the team's research were published in The The Astrophysical Journal , and Sankrit is presenting research focused on the UV spectroscopy at the 244th meeting of the American Astronomical Societyin Madison, Wisconsin.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble 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 and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.




About This Release

Credits:

Media Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Science Contact:

Ravi Sankrit
Space Telescope Science Institute, Baltimore, Maryland

Steven Goldman
Space Telescope Science Institute, Baltimore, Maryland

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

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Monday, June 17, 2024

ALMA Observations Reveal New Insights into Planet Formation in Binary Star Systems

DF Tau - FO Tau
Credit: S. Dagnello, NSF/AUI/NRAO


At the 244th meeting of the American Astronomical Society (AAS), researchers unveiled groundbreaking findings from a pioneering high-angular resolution program that sheds new light on the process of planet formation in circumstellar disks around young stars in binary systems. Leveraging the unparalleled capabilities of the Atacama Large Millimeter/submillimeter Array (ALMA) and near-infrared, component-resolved spectroscopy at the Keck II 10-meter telescope, the study offers a transformative understanding of the conditions that nurture or inhibit planet formation.

Primordial disks of gas and dust around young stars have long been recognized as the sites of planet formation. However, the conditions that ensure disk lifetimes adequate for planet formation, and the triggers that lead to their early disk dissipation, have remained elusive. Circumstellar disks in pre-main sequence binary systems provide a unique and ideal laboratory to explore these questions. By analyzing disk properties—such as size, substructure, and inclination—in relation to stellar characteristics like rotation speed and magnetic field strength, researchers are beginning to decode the complex interplay that governs these stellar environments. Binary and multiple star systems are extremely common, underscoring the significance of their study.

This innovative research combines millimeter imaging of circumstellar disks with ALMA and high-resolution spectroscopy of young stars using Keck with the NIRSPEC spectrometer. By focusing on binaries with relatively well-determined orbits, the team can control for orbital parameters and highlight critical relationships between the properties of circumstellar disks and their host stars.

The study’s detailed examination of the DF Tau binary, quasi-twin stars with an average separation of 14 astronomical units (where 1 au equals the Earth-Sun distance) in an elongated orbit, reveals cool dust in two circumstellar disks detected by ALMA. One disk is magnetically locked to its central star and is actively accreting material onto the star, while the inner region of the other disk appears to have eroded and decoupled from its rapidly rotating central star, suggesting a potential link between stellar rotation, magnetic disk locking, and early disk dissipation. Misalignments between DF Tau’s orbit, circumstellar disks, and stellar inclinations may impact the disk evolution.

In contrast, another young star twin, FO Tau, a 22 au binary in a more circular orbit, displays ALMA-detected disks well-aligned with the binary orbit. Both components exhibit modest rotation speeds and appear to be magnetically locked to their disks. These observations reveal similar behavior in both disks and stars, providing fresh insights into the dynamics of disk longevity and dissipation.

High-angular resolution observations from ALMA have shown intricate disk sub-structures, including spiral patterns, gaps, and ring formations around single stars and wide binary companions. Although disk substructures are as yet unresolved in DF Tau and FO Tau, the ability to determine bulk disk properties in close binary systems marks a significant advance in our understanding of planet formation environments.

Supported in part by NSF awards AST-1313399 and AST-2109179, this research reveals unique progress in the field of astronomy. The insights gained not only enhance our comprehension of circumstellar disk dynamics but also pave the way for future discoveries in the mechanisms of planet formation.

This work was also supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency’s scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.




About ALMA & NRAO

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

NRAO is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.




For Press & Media Inquiries Contact:

Corrina Jaramillo Feldman
Public Information Officer – New Mexico
VLA, VLBA, ngVLA

cfeldman@nrao.edu
505-366-7267


Sunday, June 16, 2024

Stars on the Run

Zeta Ophiuchi, the bright star at the center of this image, is a potential runaway star thought to have been ejected from its home cluster by a supernova. Credit: NASA/JPL-Caltech/UCLA

OB stars are typically born in clusters, like the Trapezium Cluster at the heart of the Orion Nebula, shown here.
Credit:
ESO/IDA/Danish 1.5 m/R.Gendler, J.-E. Ovaldsen, and A. Hornstrup; CC BY 4.0

A substantial number of O and B stars say goodbye to their birth clusters and spend their lives zooming through space alone. New research uses the most recent Gaia data to investigate the properties of these runaway stars.

Massive Stars Far from Home

The majority of the most massive stars in our galaxy — those with spectral types O and B, also called OB stars — live and die within their natal star clusters, never traveling far from where they were born during their brief, luminous lives. But roughly 20–30% of OB stars lead significantly more adventurous lives. So-called runaway stars careen through space on a solo adventure or with a single companion, traveling light-years from their birthplaces.

Stars can be ejected from their birth clusters by dynamical interactions or supernova explosions. Dynamical ejection happens when stars in a crowded cluster pass too close to one another, slingshotting one or more stars into space. A star that explodes as a supernova can expel its close binary companion from the cluster. In rare cases, the exploding star and its companion can escape the cluster together. It’s not yet known which process creates more runaway stars or how the two populations of runaways differ.

Vectors showing the motion across the sky of the stars in the authors’ sample. Eclipsing binaries (EB) and double-lined spectroscopic binaries (SB2) were ejected dynamically. High-mass X-ray binaries (HMXB) have experienced a supernova. Credit: Phillips et al. 2024

A Search for Runaway Stars

Diving into this question, a team led by Grant Phillips (University of Michigan) investigated more than 300 potential runaways in a nearby dwarf galaxy, the Small Magellanic Cloud. The stars in their sample were chosen for being at least 90 light-years from other OB stars (with the exception of stars in binary systems, which may have escaped their home cluster together).

The binary systems in the sample immediately gave away how they were launched into space: binary systems that don’t contain a neutron star or a black hole can’t have experienced a supernova — those binaries must have been kicked out of their clusters through dynamical interactions. Binary systems that do contain a neutron star or a black hole must have experienced a supernova. As for solo runaway stars, the team’s earlier research suggested that typical OB stars tend to be expelled through dynamical interactions, while stars with emission lines in their spectra due to rapid rotation — OBe stars — tend to be ejected by supernovae.

Mass and velocity distributions for stars ejected dynamically (left) and via supernovae (right).
Credit: Phillips et al. 2024


Population Comparison

Using the third release of Gaia spacecraft data, Phillips’s team calculated the velocities of the stars in their sample. They found that the velocities of the single OBe stars overlapped well with those of the post-supernova binary systems, although the OBe stars’ velocities extended to higher values. While this could be an effect of small-number statistics, it could also be due to some stars reaching high velocities through a two-step process: first, dynamical ejection as a member of a binary system; then, an extra velocity kick when the binary companion goes supernova.

The velocities of typical OB stars are similar to the velocities of binary systems ejected dynamically, supporting the hypothesis that these stars are also ejected this way. Intriguingly, the velocity distribution for typical OB stars may have two peaks. The authors speculate that the peaks could point to two groups of dynamical interactions: stars ejected by just a single other star versus stars ejected by a binary system.

Underpinning these findings is the rich, precise dataset from Gaia, which allowed the team to identify systematic offsets from their previous work based on earlier data releases from the spacecraft. Hopefully, future data releases can give even more clues to the origins of these runaway stars!

Citation

“Runaway OB Stars in the Small Magellanic Cloud. III. Updated Kinematics and Insights into Dynamical versus Supernova Ejections,” Grant D. Phillips et al 2024 ApJ 966 243. doi:10.3847/1538-4357/ad3909