Dim, but still distinct

UGC 11105

A spiral galaxy, with two prominent arms that are tightly wound around the brighter core. The arms disperse into a wide halo of stars and dust at their ends, giving the galaxy an oval shape. It is flanked by a number of bright stars in the foreground, each with a little cross over it due to light diffraction, and some distant background galaxies as well. Credit: ESA/Hubble & NASA, R. J. Foley (UC Santa Cruz)

This image of the spiral galaxy UGC 11105 is not as bright and vivid as some other Hubble Pictures of the Week. This softly luminous galaxy — lying in the constellation Hercules, about 110 million light-years from Earth — seems outshone by the sparkling foreground stars that surround it. The type II supernova which took place in this galaxy in 2019, while no longer visible in this image, definitely outshone the galaxy at the time! To be more precise, UGC 11105 has an apparent magnitude of around 13.6 in the optical light regime (this image was created using data that covers the heart of the optical regime, in addition to ultraviolet data). Astronomers have different ways of quantifying how bright celestial objects are, and apparent magnitude is one of them.

Firstly, the ‘apparent’ part of this quantity refers to the fact that apparent magnitude only describes how bright objects appear to be from Earth, which is not the same thing as measuring how bright they actually are. For example, in reality the variable star Betelgeuse is about 21 000 times brighter than our Sun, but because the Sun is much, much closer to Earth, Betelgeuse appears to be vastly less bright than it. The ‘magnitude’ part is a little harder to describe, because the magnitude scale does not have a unit associated with it, unlike, for example, mass, which we measure in kilograms, or length, which we measure in metres. Magnitude values only have meaning relative to other magnitude values. Furthermore, the scale is not linear, but is a type of mathematical scale known as ‘reverse logarithmic’, which also means that lower-magnitude objects are brighter than higher-magnitude objects.

As an example, UGC 11105 has an apparent magnitude of around 13.6 in the optical, whereas the Sun has an apparent magnitude of about -26.8. Accounting for the reverse logarithmic scale, this means that the Sun appears to be about 14 thousand trillion times brighter than UGC 11105 from our perspective here on Earth, even though UGC 11105 is an entire galaxy! The faintest stars that humans can see with the naked eye come in at about sixth magnitude, with most galaxies being much dimmer than this. Hubble, however, has been known to detect objects with apparent magnitudes up to the extraordinary value of 31, so UGC 11105 does not really present much of a challenge.

Source: ESA/Hubble/potw

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Gemini South Captures Twisted Dusty Disk of NGC 4753, Showcasing the Aftermath of Past Merger

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The Twisted Dusty Disk of NGC 4753 

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Multiple Viewing Orientations of NGC 4753

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Videos

 

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Cosmoview Episode 74: Gemini South Captures Twisted Dusty Disk of NGC 4753, Showcasing the Aftermath of Past Merger

 

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Cosmoview Episodio 74: Telescopio Gemini Sur en Chile captura imagen de peculiar galaxia enredada en su propia red de brazos polvorientos

 

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Pan on NGC 4753 

 

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Zooming into NGC 4753

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Tangled dust lanes winding throughout the galactic halo of NGC 4753 suggest a turbulent merger with a dwarf galaxy over 1 billion years ago

The lenticular galaxy NGC 4753, captured by the Gemini South telescope, one half of the International Gemini Observatory operated by NSF’s NOIRLab, is a truly remarkable object. Its prominent and complex network of dust lanes that twist around its galactic nucleus define its ‘peculiar’ classification and are the likely result of a galactic merger with a nearby dwarf galaxy about 1.3 billion years ago.

An astounding number of galaxies populate the observable Universe, with recent estimates placing that number anywhere from 100 billion to 2 trillion. And, akin to snowflakes, no two are exactly alike. But depending on their visual appearance and physical features they can be divided into four broad classes: elliptical, lenticular, irregular and spiral, with many subclasses in between. However, galaxies are dynamic objects that evolve over time as they interact with their surrounding environment, meaning that an individual galaxy may fall under multiple classifications throughout its lifetime.

Such is thought to be the case with NGC 4753, which astronomers hypothesize began as a normal lenticular galaxy but morphed into the more specific peculiar class after a merger with a nearby dwarf galaxy over a billion years ago.

Discovered by astronomer William Herschel in 1784, NGC 4753 displays some truly fascinating features. In this image captured by the Gemini South telescope, one half of the International Gemini Observatory operated by NSF’s NOIRLab, the galaxy’s intricate dust lanes are a sight to behold. NGC 4753 is located about 60 million light-years away in the constellation Virgo. It is a member of the NGC 4753 Group of galaxies within the Virgo II Cloud — a series of at least 100 galaxy clusters and individual galaxies stretching off the southern edge of the Virgo Supercluster.

NGC 4753’s distinct dust lanes, appearing to twist and turn around the galaxy’s nucleus, have long intrigued astronomers, and are the irregular features that give it its ‘peculiar’ classification. Seen nearly edge-on from Earth, this galaxy can appear rather mystifying. But in 1992 a team of astronomers led by Tom Steiman-Cameron, now a senior research scientist at Indiana University, published a detailed study of NGC 4753 in which they found that its complicated shape is likely the result of a merger with a small companion galaxy.

“Galaxies that gobble up another galaxy often look like train wrecks,” said Steiman-Cameron, ”and this is a train-wreck galaxy.”

Galaxy mergers occur when two (or more) galaxies collide, causing their material to mix and significantly altering the shape and behavior of each galaxy involved. In the case of NGC 4753, it is thought that the once standard lenticular galaxy merged with a nearby gas-rich dwarf galaxy about 1.3 billion years ago. The gas of the dwarf galaxy, coupled with bursts of star formation triggered by this galactic collision, injected the system with vast amounts of dust. The galaxy’s inward spiral due to gravity then caused the accumulated dust to smear out into a disk shape. And this is where the story gets interesting.

Steiman-Cameron and his team found that a phenomenon known as differential precession is responsible for NGC 4753’s entangled dust lanes. Precession occurs when a rotating object's axis of rotation changes orientation, like a spinning top that wobbles as it loses momentum. And differential means that the rate of precession varies depending on the radius. In the case of a dusty accretion disk orbiting a galactic nucleus, the rate of precession is faster toward the center and slower near the edges. This varying, wobble-like motion results from the angle at which NGC 4753 and its former dwarf companion collided and is the cause of the strongly twisted dust lanes we see wrapped around the galaxy’s luminous nucleus today.

“For a long time nobody knew what to make of this peculiar galaxy,” said Steiman-Cameron. “But by starting with the idea of accreted material smeared out into a disk, and then analyzing the three-dimensional geometry, the mystery was solved. It’s now incredibly exciting to see this highly-detailed image by Gemini South 30 years later.”

Though NGC 4753 appears to be exceptionally unique, this may be a misconception. According to Steiman-Cameron, if one were to view the twisted dusty disk from directly above it likely would look no different than a standard spiral galaxy. It’s due only to our fortuitous, nearly edge-on view that we are able to see the full scope of its tangled dust lanes, meaning these peculiar features may not be as rare in the Universe as they seem.

 

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

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More information

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 (operated in cooperation with the Department of Energy’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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Links

• Explore NGC 4753 in more detail
• Photos of the Gemini South telescope
• Videos of the Gemini South telescope

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Contacts

Josie Fenske
Jr. Public Information Officer
NSF’s NOIRLab
Email: josie.fenske@noirlab.edu

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Lightest black hole or heaviest neutron star?

An artist’s impression of the system assuming that the massive companion star is a black hole. The brightest background star is its orbital companion, the radio pulsar PSR J0514-4002E. The two stars are separated by 8 million kilometers and circle each other every 7 days. MPIfR; Daniëlle Futselaar (artsource.nl)

MeerKAT uncovers a mysterious object at the boundary between black holes and neutron stars

An international team of astronomers, led by researchers from the Max Planck Institute for Radio Astronomy, have used the MeerKAT radio telescope to discover an intriguing object of an unknown nature in the globular cluster NGC 1851. The massive object is heavier than the heaviest neutron stars known and yet simultaneously lighter than the lightest black holes known and is in orbit around a rapidly spinning millisecond pulsar. This could be the first discovery of the much-coveted radio pulsar - black hole binary; a stellar pairing that would allow new tests of Einstein’s general relativity. The research was published today in the journal Science.

Neutron stars, the ultra-dense remains of a supernova explosion, can only be so heavy. Once they’ve acquired too much mass, perhaps by consuming another star or maybe by colliding with another of their kind, they will collapse. What exactly they become once they collapse is the cause of much speculation, with various wild and wonderful flavours of exotic stars being proposed. The prevailing opinion, however, is that neutron stars collapse to become black holes, objects so gravitationally attractive that even light cannot escape them. Theory, backed by observation, tells us that the lightest black holes that can be created by collapsing stars are about 5 times more massive than the Sun. This is considerably larger than the 2.2 times the mass of the sun required for neutron star collapse, giving rise to what is known as the black hole mass gap. The nature of compact objects in this mass gap is unknown and detailed study has thus far proved challenging due to only fleeting glimpses of such objects being caught in observations of gravitational-wave merger events in the distant universe.

The team used the sensitive MeerKAT radio telescope, located in the Karoo semi-desert in South Africa
Credit: SARAO

Discovery in the mass gap

The discovery of an object in this mass-gap in our own galaxy by a team of astronomers from the international Transients and Pulsars with MeerKAT (TRAPUM) collaboration may help finally understand these objects. Their work, published this week in the journal Science, reports on a massive pair of compact stars in the globular cluster NGC 1851 in the southern constellation Columba (the dove). By using the sensitive MeerKAT radio telescope in South Africa, in combination with powerful instrumentation built by engineers at the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, they were able to detect faint pulses from one of the stars, identifying it as a radio pulsar, a type of neutron star that spins rapidly and shines beams of radio light into the Universe like a cosmic lighthouse.

This pulsar, designated PSR J0514-4002E, spins more than 170 times a second, with every rotation producing a rhythmic pulse, like the ticking of a clock. By observing small changes in this ticking over time, using a technique called pulsar timing, they were able to make extremely precise measurements of its orbital motion. “Think of it like being able to drop an almost perfect stopwatch into orbit around a star almost 40,000 light years away and then being able to time those orbits with microsecond precision,” says Ewan Barr, who led the study together with MPIfR colleague and PhD candidate Arunima Dutta.

An invisible partner

“By regularly timing the pulsar and carefully analyzing our observations, we were able to precisely pinpoint the pulsar’s location. But when we looked at Hubble images of NGC 1851, we saw nothing at that position,” explains Prajwal Voraganti Padmanabh, a postdoctoral researcher at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hannover. “Hence, the object in orbit with the pulsar is not a normal star, but an extremely dense remnant of a collapsed star.” Furthermore, the observed change with time of the closest point of approach between the two stars (the periastron) showed that the companion has a mass that was simultaneously bigger than that of any known neutron star and yet smaller than that of any known black hole, placing it squarely in the black-hole mass gap.

“Whatever this object is, it is exciting news”, says Paulo Freire, of the MPIfR. “If it is a black hole, it will be the first pulsar - black hole system known, which has been a Holy Grail of pulsar astronomy for decades! If it is a neutron star, this will have fundamental implications for our understanding of the unknown state of matter at these incredible densities.”

A possible evolutionary history for the NGC 1851E system is captured in this figure. On the left of the figure it is shown how the millisecond pulsar (MSP), PSR J0514-4002E, was spun up via the capture of matter from a stellar companion in a low-mass x-ray binary (LMXB). What remains after the low-mass x-ray binary stage, is a rapidly spinning pulsar and a white dwarf that orbit each other - a typical configuration seen throughout the Galaxy. On the right the formation of the massive companion object is shown. Here two neutron stars in orbit (NS + NS) can be seen. The loss of energy by gravitational wave emission causes this orbit to shrink with time, eventually resulting in an explosive neutron star merger. The outcome of the merger is an isolated low-mass black hole (BH) or possibly a supermassive neutron star. At some later time the black hole and the pulsar - white dwarf binary meet, resulting in an exchange encounter in which the lightest of the three stars (in this case the white dwarf) is kicked out of orbit. The result is a stable pulsar - black hole system. Credit: Thomas Tauris (Aalborg University / MPIfR)

The most exotic binary pulsar discovered yet

The team proposes that the formation of the massive object, and its subsequent pairing with the fast-spinning radio pulsar in a tight orbit, is the result of a rather exotic formation history only possible due to its particular local environment. The system is found in the globular cluster NGC 1851, a dense collection of old stars that are much more tightly packed than the stars in the rest of the Galaxy. Here, it is so crowded that the stars can interact with each other, disrupting orbits and in the most extreme cases colliding. It is one such collision between two neutron stars that is proposed to have created the massive object that now orbits the radio pulsar. However, before the present binary was created, the radio pulsar must have first acquired material from a donor star in a so-called low-mass X-ray binary. Such a “recycling” process is needed to spin up the pulsar to its current rotation rate. The team believes that this donor star was then replaced by the current massive object in a so-called exchange encounter. “This is the most exotic binary pulsar discovered yet,” says Thomas Tauris from Aalborg University, Denmark. “Its long and complex formation history pushes at the limits of our imagination.”

While the team cannot conclusively say whether they have discovered the most massive neutron star known, the lightest black hole known or even some new exotic star variant, what is certain is that they have uncovered a unique laboratory for probing the properties of matter under the most extreme conditions in the Universe.

“We're not done with this system yet,“ says Arunima Dutta. She concludes, “uncovering the true nature of the companion will a turning point in our understanding of neutron stars, black holes, and whatever else might be lurking in the black hole mass gap”.

Source: Max Planck Institute for Gravitational Physics/News

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Media contact:

Dr. Benjamin Knispel
Press Officer AEI Hannover
+49 511 762-19104
benjamin.knispel@aei.mpg.de

Dr. Prajwal Voraganti Padmanabh
Junior Scientist/Postdoc
+49 511 762-17024
prajwal.voraganti.padmanabh@aei.mpg.de

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Publication

E. Barr et al.
A pulsar in a binary with a compact object in the mass gap between neutron stars and black holes
Science Vol 383, Issue 6680, pp. 275-279 (2024)
Source | DOI

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Further information

Homepage of the “Pulsars” research group

This group's main research aspects are computing-intense searches for and studies of pulsars – rapidly spinning neutron stars – through gamma rays and radio waves in previously inaccessible parameter spaces using efficient data analysis and powerful computing resources.

More

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Fundamental Physics in Radio Astronomy at MPIfR

TRAPUM homepage
Information about the Transients and Pulsars with MeerKAT Project

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NASA's Hubble Finds Water Vapor in Small Exoplanet's Atmosphere

Exoplanet GJ 9827d (Artist's Concept)
Credits: Artwork: NASA, ESA, Leah Hustak (STScI), Ralf Crawford (STScI)

Release Images

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Astronomers using NASA's Hubble Space Telescope observed the smallest exoplanet where water vapor has been detected in the atmosphere. At only approximately twice Earth's diameter, the planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy.

"This would be the first time that we can directly show through an atmospheric detection, that these planets with water-rich atmospheres can actually exist around other stars," said team member Björn Benneke of the Trottier Institute for Research on Exoplanets at Université de Montréal. "This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets."

"Water on a planet this small is a landmark discovery," added co-principal investigator Laura Kreidberg of Max Planck Institute for Astronomy in Heidelberg, Germany. "It pushes closer than ever to characterizing truly Earth-like worlds."

However, it remains too early to tell whether Hubble spectroscopically measured a small amount of water vapor in a puffy hydrogen-rich atmosphere, or if the planet's atmosphere is mostly made of water, left behind after a primeval hydrogen/helium atmosphere evaporated under stellar radiation.

"Our observing program , led by principal investigator Ian Crossfield of Kansas University in Lawrence, Kansas , was designed specifically with the goal to not only detect the molecules in the planet's atmosphere, but to actually look specifically for water vapor. Either result would be exciting, whether water vapor is dominant or just a tiny species in a hydrogen-dominant atmosphere," said the science paper's lead author, Pierre-Alexis Roy of the Trottier Institute for Research on Exoplanets at Université de Montréal.

"Until now, we had not been able to directly detect the atmosphere of such a small planet. And we're slowly getting in this regime now," added Benneke. "At some point, as we study smaller planets, there must be a transition where there's no more hydrogen on these small worlds, and they have atmospheres more like Venus (which is dominated by carbon dioxide)."

Because the planet is as hot as Venus, at 800 degrees Fahrenheit, it definitely would be an inhospitable, steamy world if the atmosphere were predominantly water vapor.

At present the team is left with two possibilities. One scenario is that the planet is still clinging to a hydrogen-rich atmosphere laced with water, making it a mini-Neptune. Alternatively, it could be a warmer version of Jupiter's moon Europa, which has twice as much water as Earth beneath its crust. "The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapor on top of some smaller rocky body," said Benneke.

If the planet has a residual water-rich atmosphere, then it must have formed farther away from its host star, where the temperature is cold and water is available in the form of ice, than its present location. In this scenario, the planet would have then migrated closer to the star and received more radiation. The hydrogen was heated and escaped, or is still in the process of escaping the planet's weak gravity. The alternative theory is that the planet formed close to the hot star, with a trace of water in its atmosphere.

The Hubble program observed the planet during 11 transits—events in which the planet crossed in front of its star—that were spaced out over three years. During transits, starlight is filtered through the planet's atmosphere and has the spectral fingerprint of water molecules. If there are clouds on the planet, they are low enough in the atmosphere so that they don't completely hide Hubble's view of the atmosphere, and Hubble is able to probe water vapor above the clouds.

"Observing water is a gateway to finding other things," said Thomas Greene, astrophysicist at NASA's Ames Research Center in California's Silicon Valley. "This Hubble discovery opens the door to future study of these types of planets by the James Webb Space Telescope . JWST can see much more with additional infrared observations, including carbon-bearing molecules like carbon monoxide, carbon dioxide, and methane. Once we get a total inventory of a planet's elements, we can compare those to the star it orbits and understand how it was formed."

GJ 9827d was discovered by NASA's Kepler Space Telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, lies 97 light-years from Earth in the constellation Pisces.

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

Source: HubbleSite/News

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About This Release

Credits:

Release: NASA, ESA, STScI

Media Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Science Contact:

Pierre-Alexis Roy
Trottier Institute for Research on Exoplanets at Université de Montréal

Björn Benneke
Trottier Institute for Research on Exoplanets at Université de Montréal

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents

• Science Paper: The science paper by Pierre-Alexis Roy et al., PDF (1.21 MB)
• NASA's Hubble Portal
• ESA/Hubble's Release
• Trottier's Release
• MPIA's Release
• NASA Goddard's Video (on YouTube)
  
  

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Are Binary Black Hole Spins and Mass Ratios Correlated?

An artist's rendition of two black holes approaching a collision.
Credit: LIGO/Caltech/MIT/R. Hurt (IPAC)

When researchers scour the detections of merging black holes made by gravitational wave observatories, they use models and statistics to make careful inferences about the population of black holes in our universe. In a recent article, researchers explored whether an emerging trend in gravitational wave data is real or an artifact of previous analysis methods.

llustration of the first black hole merger detected by LIGO.
Credit: Aurore Simmonet (Sonoma State University)

A New Window on the Universe

The detection of gravitational waves from merging black holes in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) gave scientists a new way to investigate black holes. By analyzing the spacetime ripples from colliding black holes, researchers hope to understand how the black holes formed (through the collapse of massive stars or the successive mergers of existing black holes?) and how they came to exist in binary systems (by first belonging to a stellar binary system or by forming solo and linking up with another black hole later?).

One potential result that has emerged from several analyses of gravitational wave signals is that the effective spins and the ratios of the masses of merging black hole binaries appear to be anticorrelated. But as with all results that are extracted delicately, statistically from complex data sets, it’s important to ask if this is a real feature of the data, with real implications for how black hole binary systems are assembled, or if it’s a result of our models or statistical analyses.

Top: The black hole spins are aligned with the system’s orbital angular momentum (positive effective spin). Bottom: The black hole spins are misaligned with the system’s orbital angular momentum (negative effective spin). Credit: Kerry Hensley

Statistical Investigation

Christian Adamcewicz (Monash University and OzGrav) and collaborators approached this question by applying a new statistical treatment to detections of black hole mergers. This new treatment features a new model for effective spin and allows for a subpopulation of black hole binaries with zero effective spin, which hasn’t yet been ruled out and might have an impact that hasn’t been accounted for.

The team applied their population model to the third catalog of gravitational wave signals from the LIGO and Virgo detectors and used Bayesian statistical methods to extract the properties of the overarching population of black holes. They found that the previously reported anticorrelation between effective spin and mass ratio is likely real, ruling out the possibility of there being no correlation at 99.7% probability.

More Work, a Paradox, and Astrophysical Possibilities

Adamcewicz and collaborators acknowledge that this work doesn’t provide a final verdict on this question (as they put it, “a modeler’s job is never done”), and that other statistical effects need to be rooted out. One lingering possibility is that this result is due to the amalgamation paradox, which arises when trends present in different factors disappear or flip when the factors are considered together.

If the observed anticorrelation holds up to further statistical scrutiny, a number of astrophysical phenomena could be responsible for this effect. Extensive mass transfer between black hole progenitor stars, stars evolving within a common envelope and accreting matter at a high rate, or even black hole binary systems assembled within the accretion disks of active galactic nuclei should all be investigated with future black hole population models.

By Kerry Hensley

Citation

“Evidence for a Correlation Between Binary Black Hole Mass Ratio and Black Hole Spins,” Christian Adamcewicz et al 2023 ApJ 958 13. doi:10.3847/1538-4357/acf763

Source: American Astronomical Society/AAS-Nova

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Webb shines light on early interstellar grain growth

Illustration of the growth of interstellar dust grains, evolving from the ice mantle-free interstellar medium (left), acquiring first ice mantles in the cloud (centre), and increasing in size in the densest cloud phase (right). © Dartois et al. 2024

In a groundbreaking study, the James Webb Space Telescope (JWST) observed the early stages of the growth of dust grains in the dense Chamaeleon I cloud. These cold dust grains have accumulated molecular solids on their surface early in the process leading to star formation, challenging previous assumptions on where and when grain growth occurs. The findings indicate that the growth of these „icy grains” begins even before the protostellar phase. This not only sheds light on the intricacies of grain evolution before the birth of stars and planets but also poses challenges for chemical abundance determination due to the deformation of observed profiles.

When diffuse interstellar grains grow it has a profound impact on how they interact with light, causing them to start scattering light in a significant and wavelength-selective manner. The wide range of wavelengths analysed by JWST makes it an essential tool to detect these changes imprinted upon the spectra and enabling astronomers to size grains in the micron to few microns range.

“It is challenging to interpret these distorted infrared ice feature profiles observed by Webb in such dense cloud regions, requiring an intricate combination of laboratory experiments and mathematical modelling. However, the payoff is unparalleled insights into the grain size distribution” said astronomer Emmanuel Dartois of the Molecular Science Institute of Orsay, in Orsay, France, the member of the international Ice Age team who led the newly published Webb study.

This scattering, altering spectroscopic profiles of ice bands observed in the infrared range, turns them into specific tracers of grain size changes. A detailed analysis of these profiles, conducted by observing the extinction of light from stars behind the dense Chamaeleon cloud, confirms that icy grains reach sizes on the order of microns. “Thanks to the outstanding sensitivity of JWST, we can finally unveil detailed information on dust grains in interstellar clouds where stars and planets form,” says Paola Caselli, co-author and head of the Center for Astrochemical Studies at MPE. “Previously, grain growth has only been roughly inferred, but with these new data and the synergy between experimentalists and theoreticians, we can put stringent limits on the size of dust grains, the building blocks of planets. These dust grains do not just contain material which will coagulate into pebbles and rocks, but also volatiles such as water and organic molecules, the building blocks of prebiotic molecules, possibly representing the first steps toward life.”

We dedicate this article to the memory of Professor Harold Linnartz, our dear friend and colleague, who will be sadly missed by the whole Ice Age team.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/Press Releases

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Contact:

Paola Caselli
director
+49 89 30000-3400
+49 89 30000-3399
caselli@mpe.mpg.de

Hannelore Hämmerle
press officer
+49 89 30000-3980
+49 89 30000-3569
hanneh@mpe.mpg.de

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Original publication

E. Dartois, J. A. Noble, P. Caselli et al.
Spectroscopic sizing of interstellar icy grains with JWST
Nature Astronomy, 9 Jan 2024

DOI

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More Information

L'art de mesurer la taille des grains interstellaires : ce que révèle JWST
CNRS Press Release
(in French)

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Tilted Orbits

This illustration shows a brown dwarf with no orbital tilt (above), versus one with a high orbital tilt (below). Astronomers think that brown dwarfs with no, or low, tilts likely formed like planets, while those with high tilts formed like stars. Credit: Caltech/S. Giacalone

Steven Giacalone
Credit: Caltech/S. Giacalone

How the orbital inclinations of brown dwarfs reveal clues about their formation

Within the family of celestial orbs in the universe, brown dwarfs are somewhat like misfits. They are less massive and cooler than stars but are 10 to 80 times more massive than Jupiter. Brown dwarfs are sometimes called "failed stars," because they lack the mass to ignite nuclear fusion and shine with starlight.

One mystery that surrounds these oddballs is how they formed: Some theories propose that they form like stars do, out of collapsing clouds of material, while others suggest they form like planets, taking shape within rotating dusty disks that circle young stars. It is also possible, scientists propose, that brown dwarfs may form both like stars and planets.

Steven Giacalone, a National Science Foundation (NSF) Postdoctoral Scholar Fellowship Trainee in Astronomy at Caltech, and his colleagues are addressing the mystery by studying the orbital tilts of brown dwarfs that circle very closely around companion stars. Brown dwarfs, as well as some other exoplanets, can have orbits that are tilted to varying degrees relative to the rotational direction of their host stars. If a brown dwarf has an orbital tilt, then it is out of whack with its partner star: the brown dwarf will loop above and below a plane that aligns with the star's equator. This is unlike the planets in our own solar system that orbit in a plane that aligns with the Sun's rotational direction.

Using the Keck Planet Finder (KPF), a new planet-hunting instrument at the W. M. Keck Observatory in Hawaiʻi, Giacalone and his colleagues wanted to assess whether a brown dwarf named GPX-1b has an orbital tilt. They say that a tilt would indicate that the object probably formed like a star and not like a planet.

"For a brown dwarf to have made its way into a tilted close-in orbit, it would have had to have been knocked around by a larger planetary body or captured by the star as the brown dwarf passed by," explains Giacalone, who works in the group of Andrew Howard, a professor of astronomy at Caltech and the principal investigator of KPF. "That would mean it started out like a star."

On the other hand, if the brown dwarf has an orbit aligned with the equatorial plane of its central star, then "it most likely migrated inward similar to planets via interactions with the disk in which it formed," Giacalone says.

The results revealed GPX-1b is not tilted in its orbit, but that it circles in a plane that aligns with the host star's equator.

"This is only one data point, and preliminary, but it suggests that the brown dwarf migrated close to its companion star in a similar manner to planets," says Giacalone, who presented the results at the 243rd meeting of the American Astronomical Society (AAS) in New Orleans on January 10, 2024. "Theory has predicted that brown dwarfs should be able to form like planets, but observational evidence is only just beginning to be gathered to support that idea."

The result contrasts with what is known about brown dwarfs with wide separations from their companion stars. "The wide-separation brown dwarfs are known to have high orbital tilts and do not form in a disk, but rather, like stars," Giacalone says. "The short-separation ones like GPX-1b, on the other hand, probably do form in the disk if they have low orbital tilts, meaning they form like planets. In other words, we think brown dwarfs can form either like stars or planets."

KPF, a high-precision spectrograph, was able to determine the orbital inclination of the object by watching it pass in front of, or transit, its star. The brown dwarf was discovered by NASA's TESS (Transiting Exoplanet Survey Satellite) mission and the Galactic Plane eXoplanet Survey (GPX) in 2021. It is one of a small number of brown dwarfs known to pass in front of, or transit, its host star.

The researchers hope to use KPF to study the orbital inclinations of more brown dwarfs in the future. "We have demonstrated the power of KPF for studying these systems," Giacalone says. "Because close-in brown dwarfs are so rare, they are mostly found around relatively faint and distant stars. That means we need large telescopes like Keck and advanced instruments like KPF to study them accurately."

Written by Whitney Clavin

Contact:

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

Source: Caltech/News

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Luminous in Lepus

IC 438

A large spiral galaxy seen close-up. The left side of the image shows the galaxy's core and its tightly-curled inner spiral arms. On the right side, one of the arms reaches down from above, curving across the dark background. There is a bright star inside the arc of the arm, and a couple more next to the galaxy. Credit: ESA/Hubble & NASA, R. J. Foley (UC Santa Cruz)

This image shows the spiral galaxy IC 438, which lies about 130 million light-years from Earth in the constellation Lepus (the Hare). Lepus lies just south of the celestial equator (the ring around the middle of Earth that falls at right angles to its rotation axis). Appropriately, Lepus is flanked by the constellations Canis Major (the Greater Dog) and Orion (the Hunter), whilst Canis Minor (the Lesser Dog) lies very nearby, meaning that in artistic representations of the constellations, Lepus is often shown as being pursued by Orion and his two hunting dogs.

Lepus is one of the 88 constellations that are officially recognised by the International Astronomical Union (IAU). It is worth clarifying that, whilst the actual constellations themselves only comprise a handful of stars, the area of sky covered by those stars is often referred to using the name of the constellation. For example, when we say that IC 438 is in Lepus, we do not mean that the galaxy is part of the constellation — perhaps obviously, as it is not a single star, but an entire galaxy! Rather, we mean that it falls in the region of sky covered by the Lepus constellation stars.

The IAU’s 88 official constellations are by no means the only constellations ever described by humanity. Humans have been studying and naming the stars for a very long time, and different cultures of course have their own constellations. The IAU constellations are Eurocentric, with many taken from Ptolemy’s list of constellations. Collectively, the 88 constellations divide the night sky into 88 regions which completely cover it, so that the approximate location of any celestial object can be described using one of the 88.

The impetus behind Hubble examining this galaxy was a type Iax supernova that took place in 2017, a kind of supernova that arises from a binary system of two stars. While this data was obtained over three years after the supernova occurred, and so it’s not visible in this image, there’s still a lot to learn from studying the aftermath of supernovae like this one.

Source: ESA/Hubble/potw

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Observers measure how Andromeda’s central black hole is fed

The long way needed to feed the black hole of Andromeda: from 6500 light years down to its door. The image shows the majestic of this galaxy with its many spiral arms filled with millions of stars. In the centre of the galaxy there is a supermassive black hole (small square in the image). A zoom up in this inset is bellow. It depicts long, narrow features circularising towards the centre. These are filaments of dust and gas which is being pulled into to the black hole. A further zoom of the zone (right image) shows the filaments targeting with precision the black hole location. Credit: Spitzer Space Telescope

A team of scientists led by the Observatory of Munich University and the Instituto de Astrofísica de Canarias have obtained direct visualization of the process of feeding the supermassive black hole at the centre of the Andromeda galaxy. The study reveals the existence of long filamentary structures of gas and dust which move in a spiral starting at a distance from the black hole and ending up at the black hole itself. The results, which have been published in the Astrophysical Journal, were obtained using images from the Hubble and Spitzer space telescopes.

The Andromeda Galaxy, which is visible to the naked eye, is one of the nearest galaxies to the Milky Way. In its centre it houses a very massive black hole, which has a mass more than 100 million times that of the Sun. Even so, this black hole, as well as the one at the centre of our own galaxy called Sagittarius A* are among the least active known of the supermassive black holes at galaxy centres: they emit very little radiation.

The activity of a black hole depends on how it is being “fed”, that is to say on how the material which falls into it gets closer as it falls. It is hard to track this in the Milky Way because of our position very close to the plane of the Galaxy, where dust obscuration is very high, and the field is crowded with stars, but the situation with Andromeda is different, and we can observe the black hole with much less impediment.

Now, by combining observations from the Hubble Space Telescope and the Spitzer Space Telescoope, a team of scientists, led by the group of Computational Astrophysics from the Munich University Observatory (USM) and the Instituto de Astrofísica de Canarias (IAC) has been able to study in detail how the black hole of the Andromeda galaxy is carefully fed.

“Black holes are greedy feeders, but nevertheless sensitive” explains Christian Alig, a researcher at the USM who is the first author of the article. “When they are fed slowly and bit by bit they don’t show signs of feeding, but if the feeding is forced and excessive they react violently and aggressively.”

Filaments of material and spiral trajectories

Thanks to the two powerful space telescope the team has discovered that the black hole at the centre of Andromeda feeds by way of long filaments of dust and gas, starting some way from the centre of the galaxy. “The filaments approach the black hole little by little, and in a spiral, similarly to the way the water goes down the hole in the sink” explains Almudena Prieto, a researcher at the IAC who is a co-author of the paper.

Using powerful computers it has been possible to simulate the transport and whereabouts of this material through time and space. The image shows snapshots of the path versus time (indicated in the upper panels in units of millions of years) increasing from left to right. The network of paths, or filaments (streaks of colour in each image) appears to get more complicated as they approach the centre of the galaxy. However the motion is ordered and progressive, with the filaments rotating slowly in a spiral towards the black hole. The journey lasts for over 100 million years.

While the Hubble can see the darkening produced by the dust of the filaments in visible light, the Spitzer telescope can pick out the same filaments in the infrared. Using joint observations with the both telescopes has revealed a complete view of the accretion process of the material around the black hole. Because the Andromeda galaxy is so near, the Spitzer observations of its centre are the most detailed observations of the centre of a galaxy made with this telescope until now, and have a level of precision comparable to that achieved by the Hubble Space Telescope.

This study is part of the PARSEC project, whose aim is to investigate over a wide range of wavelengths, the nuclei of the nearest galaxies, and the accretion processes of their central black holes. Led by the IAC the project has almost 50 members in institutions in a large number of countries.

Article: C. Alig, A. Prieto et al. “The Accretion Mode in Sub-Eddington Supermassive Black Holes: Getting into the Central Parsecs of Andromeda”. 2023 ApJ 953 109. DOI: 10.3847/1538-4357/ace2c3

Contact at the IAC:
Almudena Prieto, almudena.prieto@iac.es

Source: Spitzer Space Telescope/News

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M87* One Year Later: Proof of a persistent black hole shadow

The Event Horizon Telescope (EHT) Collaboration has released new images of M87* from observations taken in April 2018, one year after the first observations in April 2017. The new observations in 2018, which feature the first participation of the Greenland Telescope, reveal a familiar, bright ring of emission of the same size as we found in 2017. This bright ring surrounds a dark central shadow, and the brightest part of the ring in 2018 has shifted by about 30º relative from 2017 to now lie in the 5 o’clock position. Credit: EHT Collaboration. Download image (220KB)

The Event Horizon Telescope (EHT) Collaboration has released new images of M87*, the supermassive black hole at the center of the galaxy Messier 87, using data from observations taken in April 2018. With the participation of the newly commissioned Greenland Telescope and a dramatically improved recording rate across the array, the 2018 observations give us a view of the source independent from the first observations in 2017. A recent paper published in the journal Astronomy & Astrophysics presents new images from the 2018 data that reveal a familiar ring the same size as the one observed in 2017. This bright ring surrounds a deep central depression, “the shadow of the black hole,” as predicted by general relativity. Excitingly, the brightness peak of the ring has shifted by about 30º compared to the images from 2017, which is consistent with our theoretical understanding of variability from turbulent material around black holes.

“A fundamental requirement of science is to be able to reproduce results,” says Dr. Keiichi Asada, an associate research fellow at Academia Sinica Institute for Astronomy and Astrophysics in Taiwan. “Confirmation of the ring in a completely new data set is a huge milestone for our collaboration and a strong indication that we are looking at a black hole shadow and the material orbiting around it.”

In 2017, the EHT took the first image of a black hole. This object, M87*, is the beating heart of the giant elliptical galaxy Messier 87 and lives 55 million light years away from Earth. The image of the black hole revealed a bright circular ring, brighter in the southern part of the ring. Further analysis of the data also revealed the structure of M87* in polarized light, giving us greater insight into the geometry of the magnetic field and the nature of the plasma around the black hole.

The new era of black hole direct imaging, spearheaded by the extensive analysis of the 2017 observations of M87* opened a new window that lets us investigate black hole astrophysics and allows us to test the theory of general relativity at a fundamental level. Our theoretical models tell us that the state of the material around M87* should be uncorrelated between 2017 and 2018. Thus, multiple observations of M87* will help us place independent constraints on the plasma and magnetic field structure around the black hole and help us disentangle the complicated astrophysics from the effects of general relativity.

To help accomplish new and exciting science, the EHT is under continuous development. The Greenland Telescope joined the EHT for the first time in 2018, just five months after its construction was completed far above the Arctic Circle. This new telescope significantly improved the image fidelity of the EHT array, improving the coverage, particularly in the North-South direction. The Large Millimeter Telescope also participated for the first time with its full 50 m surface, greatly improving the sensitivity. The EHT array was also upgraded to observe in four frequency bands around 230 GHz, compared to only two bands in 2017.

Repeated observations with an improved array are essential to demonstrate the robustness of our findings and strengthen our confidence in our results. In addition to the groundbreaking science, the EHT also serves as a technology testbed for cutting-edge development in high-frequency radio interferometry.

“Advancing scientific endeavors requires continuous enhancement in data quality and analysis techniques,” says Rohan Dahale, a PhD candidate at the Instituto de Astrofísica de Andalucía (IAA-CSIC) in Spain. “The inclusion of the Greenland Telescope in our array filled critical gaps in our earth-sized telescope. The 2021, 2022, and the forthcoming 2024 observations witness improvements to the array, fueling our enthusiasm to push the frontiers of black hole astrophysics.”

The analysis of the 2018 data features eight independent imaging and modeling techniques, including methods used in the previous 2017 analysis of M87* and new ones developed from the collaboration’s experience analyzing Sgr A*.

The image of M87* taken in 2018 is remarkably similar to what we saw in 2017. We see a bright ring of the same size, with a dark central region and one side of the ring brighter than the other. The mass and distance of M87* will not appreciably increase throughout a human lifetime, so general relativity predicts that the ring diameter should stay the same from year to year. The stability of the measured diameter in the images from 2017 to 2018 robustly supports the conclusion that M87* is well described by general relativity. “One of the remarkable properties of a black hole is that its radius is strongly dependent on only one quantity: its mass,” says Dr. Nitika Yadlapalli Yurk, a former graduate student at the California Institute of Technology (Caltech), now a postdoctoral fellow at the Jet Propulsion Laboratory in California. “Since M87* is not accreting material (which would increase its mass) at a rapid rate, general relativity tells us that its radius will remain fairly unchanged over human history. It’s pretty exciting to see that our data confirm this prediction.”

While the size of the black hole shadow did not change between 2017 and 2018, the location of the brightest region around the ring did change significantly. The bright region rotated about 30º counterclockwise to settle in the bottom right part of the ring at about the 5 o’clock position. Historical observations of M87* with a less sensitive array and fewer telescopes also indicated that the shadow structure changes yearly (Wielgus 2020, ApJ, 901, 67) but with less precision. While the 2018 EHT array still cannot observe the jet emerging from M87*, the black hole spin axis predicted from the location of the brightest region around the ring is more consistent with the jet axis seen at other wavelengths.

“The biggest change, that the brightness peak shifted around the ring, is actually something we predicted when we published the first results in 2019,” says Dr. Britt Jeter, a postdoctoral fellow at Academia Sinica Institute for Astronomy and Astrophysics in Taiwan. “While general relativity says the ring size should stay pretty fixed, the emission from the turbulent, messy accretion disk around the black hole will cause the brightest part of the ring to wobble around a common center. The amount of wobble we see over time is something we can use to test our theories for the magnetic field and plasma environment around the black hole.”

While all the EHT papers published so far have featured an analysis of our first observations in 2017, this result represents the first efforts to explore the many additional years of data we’ve collected. In addition to 2017 and 2018, the EHT conducted successful observations in 2021 and 2022 and is scheduled to observe in the first half of 2024. Each year, the EHT array has improved in some way, either through the addition of new telescopes, better hardware, or additional observing frequencies. Within the collaboration, we are working very hard to analyze all this data and are excited to show you more results in the future.

Source: National Astronomical Observatory of Japan (NAOJ)/News/Science

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Detailed Article(s)

M87* One Year Later: Proof of a persistent black hole shadow
Event Horizon Telescope Japan

M87* One Year Later: Proof of a persistent black hole shadow
Event Horizon Telescope

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Release Information

Researcher(s) Involved in this Release

Shoko Koyama (Assistant Professor @ Graduate School of Science and Technology / College of Creative Studies, Niigata University, Visiting Scholar @ Institute of Astronomy and Astrophysics, ACADEMIA SINICA)

Masanori Nakamura (Professor @ Department of General Science and Education, Hachinohe National College of Technology, Visiting Scholar @ Institute of Astronomy and Astrophysics, ACADEMIA SINICA)

Yutaro Kofuji (Doctoral Student @ Department of Astronomy, School of Science, The University of Tokyo)
Mareki Honma (Professor / Director @ Mizusawa VLBI Observatory, National Astronomical Observatory of Japan)

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Coordinated Release Organization(s)

Niigata University
Osaka Metropolitan University
Kogakuin University
National Astronomical Observatory of Japan
The Institute of Statistical Mathematics
The Graduate University for Advanced Studies, SOKENDAI
Tokyo Institute of Technology
School of Science, The University of Tokyo
Institute for Cosmic Ray Research The University of Tokyo
Tohoku University
Hachinohe National College of Technology
Institute of Astronomy and Astrophysics, ACADEMIA SINICA
EHT collaboration

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Paper(s)

Event Horizon Telescope Collaboration et al. “The persistent shadow of the supermassive black hole of M87.I.Observations, calibration, imaging, and analysis”, in Astronomy & Astrophysics, DOI: 10.1051/0004-6361/202347932

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Related Link(s)

M87* One Year Later: Proof of a persistent black hole shadow (The Graduate University for Advanced Studies, SOKENDAI)
M87* One Year Later: Proof of a persistent black hole shadow (School of Science, The University of Tokyo)

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Four Pulsars Discovered in New Survey

The supernova remnant 30 Doradus B encloses a pulsar at its center.
X-ray: NASA/CXC/Penn State Univ./L. Townsley et al.;
Optical: NASA/STScI/HST; Infrared: NASA/JPL/CalTech/SST;
Image Processing: NASA/CXC/SAO/J. Schmidt, N. Wolk, K. Arcand

A pilot survey using the world’s largest radio dish has led to the discovery of four pulsars, two of which are ultra-precise millisecond pulsars. This survey highlights the wealth of pulsars that await discovery at intermediate galactic latitudes.

An artist’s impression of a pair of pulsars.
Credit: Michael Kramer (Jodrell Bank Observatory, University of Manchester)

Small Stars with a Big Impact

When massive stars explode as supernovae, they can leave behind their extremely dense, collapsed cores in the form of neutron stars. Neutron stars spin rapidly and have strong magnetic fields, leading many of them to produce beams of radio emission along their poles. When these beams sweep across our field of view, we see brief, regular pulses of emission and call the objects pulsars.

Several thousand pulsars have been discovered in our galaxy, but there’s a need to find even more: pulsars provide a path to studying stellar evolution, the interiors of neutron stars, and even gravitational waves. Millisecond pulsars — those with the shortest rotation periods, around 10 milliseconds or less — are especially precious, as their pulses are exceptionally regular. By monitoring the arrival times of the pulses from many millisecond pulsars at once, researchers have found evidence for the gravitational wave background, which is thought to be the combined signals of millions of distant supermassive black hole binaries.

Pulse profiles of the four newly discovered pulsars.

Click to enlarge. Credit: Zhi et al. 2024

A Small FAST Survey

Where and how do we find pulsars? The word pulsar is short for pulsating radio source, and most pulsars are identified in surveys by their characteristic pulses of radio emission. Like most stars, pulsars are concentrated in the thin disk of our galaxy, but interstellar clouds of gas and dust in this region can scatter pulsar signals. Searching the area just above the galactic plane makes for easier pulsar discovery, and current evidence suggests that millisecond pulsars may be more common in these higher-latitude regions.

Using the Five-hundred Aperture Spherical Telescope (FAST) — the world’s largest radio dish — Qijun Zhi (Guizhou Normal University) and collaborators searched for pulsars in a small area of the sky about 5 degrees above the galactic midplane. The survey discovered four new pulsars and recovered all seven of the known pulsars in the search area. Of the four newly discovered pulsars, two are of the coveted millisecond variety, with rotation periods of 3.9 and 4.6 milliseconds. One of these two millisecond pulsars especially warrants further study, since it is bright enough to possibly be included in pulsar timing arrays in the future.

llustration of how galactic latitude is measured.
Credit: AAS Nova/Kerry Hensley

More Pulsars to Come

The pilot survey described in this study complements the efforts of other pulsar surveys. FAST is currently at work on the Commensal Radio Astronomy FAST Survey and the Galactic Plane Pulsar Survey, both of which aim to find pulsars at galactic latitudes below 10 degrees. These surveys have led to the discovery of roughly 800 pulsars so far, about 200 of which are millisecond pulsars.

Zhi and collaborators expect that many more pulsars await discovery at intermediate galactic latitudes, 5 to 15 degrees above the midplane of the Milky Way. Considering the success of their limited pilot study, the team expects that roughly 900 millisecond pulsars could be found in that region.

Citation

“Discovery of Four Pulsars in a Pilot Survey at Intermediate Galactic Latitudes with FAST,” Q. J. Zhi et al 2024 ApJ 960 79. doi:10.3847/1538-4357/ad0eca

By Kerry Hensley

Source: American Astronomical Society/AAS-Nova

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Gone but not forgotten

UGC 5189A

A galaxy that is flat and misshapen. Above and on its right it is covered by plumes of shining gas and dust, while its centre and left side are more dim and patchy. A trail of dark, dim dust stretches from below the galaxy up and off to the left, where there are three more bright patches. The background around the galaxy is quite dark, with only a few small background galaxies and one star visible. Credit: ESA/Hubble & NASA, A. Filippenko

This image features a relatively small galaxy known as UGC 5189A, which is located about 150 million light-years away in the constellation Leo. This galaxy was observed by Hubble to study a supernova explosion in 2010 known as SN 2010jl. This particular supernova was notable for having been an exceptionally luminous supernova event. In fact, over a period of three years, SN 2010jl released at least 2.5 billion times more visible energy alone than our Sun emitted over the same timeframe across all wavelengths.

Even after supernovae have faded to non-observable levels, it can still be of interest to study the environments where they occurred. This can provide astronomers with valuable information: supernovae can take place for a variety of reasons, and understanding the environments in which they took place can help improve our understanding of the conditions necessary for them to be triggered. Furthermore, follow-up studies after supernovae can improve our understanding of the immediate aftermath of such events, from their potent effects on the gas and dust around them, to the stellar remnants they leave behind.

To this end, UGC 5189A has been observed many times by Hubble since 2010. This image is from data collected in three of the latest Hubble studies of UGC 5189A, which also examined several other relatively nearby galaxies that recently hosted supernovae — ‘relatively nearby’, in this context, meaning roughly 100 million light years away.

Source: ESA/Hubble/potw

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