Wednesday, October 22, 2025

Astronomers Spot Magnetically-Guided Streamer Funneling Star-Building Material into Newborn System in Perseus

Credit: NSF/AUI/NSF NRAO/P.Vosteen

Scientific Paper



New ALMA observations reveal spiral-shaped gas streamer guided by magnetic fields in a star-forming nursery

A team of astronomers led by Paulo Cortes, a scientist with the U.S. National Science Foundation National Radio Astronomy Observatory and the Joint ALMA Observatory, have made a groundbreaking discovery about how young star systems grow. Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA), their team observed— for the first time ever— a narrow, spiral-shaped streamer of gas guided by magnetic fields, channeling matter from the surrounding cloud of a star-forming region in Perseus, directly onto a newborn binary star system.

Stars are born from clouds of gas and dust, but recent observations show star birth is far more dynamic than previously thought. The team’s data captured both the dust and molecules swirling around the newborn binary star system, known as SVS13A, revealing that magnetic fields don’t just thread through these stellar nurseries— they actively steer the flow of material, providing a preferred route for gas to travel onto the disk where new stars and planets form.

Imagine a garden hose, but instead of water it’s smoothly delivering star-building material through a winding path carved by invisible forces. That’s the picture emerging from the ALMA observations: a channel of gas, dubbed a “sub-Alfvénic streamer,” regulated by spiral magnetic field lines. “This new data gives us a new window into star formation,” shares Cortes, “This streamer shows how magnetic fields can regulate star formation by shaping the infall of material, like a dedicated highway for the cars to move along.”

The ALMA images and data reveal two spiral arms of dust encircling the stars, with a streamer of gas that closely follows the same path. This remarkable alignment suggests gas in the streamer moves slowly compared to what was previously believed, supporting the idea of a magnetized channel rather than a turbulently collapsing cloud. The fact that such a streamer exists and connects the cloud to the disk— feeding material in a controlled way— means that gravity and magnetism both play crucial roles in building stars and shaping the planets that may eventually form around them.

This pioneering result, accepted for publication in Astrophysical Journal Letters, marks the first time astronomers have directly mapped both the streamer and its guided magnetic field in a single observation.




About NRAO

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

About ALMA

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.


Distant galaxy A1689-zD1 found to have unusually low dust-to-gas ratio

False-color JWST/NIRCam RGB image cutout (blue: F150W; green: F277W; red: F444W), overlaid with [C ii]-158µm emission contours showing 3, 5, 7, 10σ (white solid lines). A scalebar is shown in the image plane. Credit: arXiv (2025). DOI: 10.48550/arxiv.2510.07936


Using the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/sub-millimeter Array (ALMA), an international team of astronomers has carried out comprehensive multiwavelength observations of a distant massive galaxy known as A1689-zD1.

The new observations, detailed in a paper published October 9 on the pre-print server arXiv, yield important insights into the properties of the galaxy, especially regarding dust production in this system.

A1689-zD1 is a bright highly-lensed massive galaxy at a redshift of approximately 7.13. It has a diameter of about 3,000 light years and its stellar mass is estimated to be some 2.6 billion solar masses.

Previous observations of A1689-zD1 have found that it has a metallicity close to the solar value and that it contains a substantial amount of dust—with an estimated mass of 15 million solar masses. Due to this, A1689-zD1 is an excellent place to study the existence of interstellar dust at early cosmic epochs.

That is why a group of astronomers led by Kasper E. Heintz of the University of Copenhagen, Denmark, decided to explore the dust content with JWST and ALMA.

"We revisited this galaxy to gauge the baryonic matter components in the ISM [interstellar medium], with particular focus on constraining the build up of cosmic dust," the researchers explained.

Hintz's team performed the rest-frame ultraviolet to far-infrared modeling of the spectral energy distribution (SED) of A1689-zD1 to determine its stellar mass, dust mass, visual attenuation, and star-formation rate. The ALMA observations were also used to constrain the total dynamical mass of the source, and infer the gas mass using common gas tracers but bounded by the overall dynamics of the system.

The study found that although A1689-zD1 has a substantial dust mass, its dust-to-gas (DTG) and dust-to-metal (DTM) mass ratios are remarkably low—at a level of 0.00051 and 0.061, respectively. The astronomers note that this is due to the high metallicity of A1689-zD1 and its substantial gas mass, which was calculated to be 28 billion solar masses.

Therefore, the DTG and DTM mass ratios for A1689-zD1 are an order of magnitude lower than that found in the Milky Way and the Large Magellanic Cloud (LMC) or the Small Magellanic Cloud (SMC). These ratios also suggest that the bulk neutral atomic hydrogen (HI) gas in the line-of-sight to A1689-zD1 is relatively dust-poor compared to its chemical enrichment.

The authors of the paper conclude that the obtained results point to a potential change in the relative dust abundance or composition of early galaxies.

"We find that this deviation in the DTG and DTM mass ratios appears to be ubiquitous in other metal-rich galaxies at similar redshifts, z ≳ 6. This suggests that the processes that form and destroy dust at later times, or the dust emissivity itself, are drastically different for galaxies in the early universe," the scientists conclude.

by Tomasz Nowakowski, Phys.org
edited by Sadie Harley, reviewed by Robert Egan




Written for you by our author Tomasz Nowakowski, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.



More information: Kasper E. Heintz et al, Inefficient dust production in a massive, metal-rich galaxy at z=7.13 uncovered by JWST and ALMA, arXiv (2025). DOI: 10.48550/arxiv.2510.07936

Journal information: arXiv



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Tuesday, October 21, 2025

Discovery of a Brown Dwarf Orbiting a Red Dwarf through the Synergy of Ground- and Space-Based Observatories

Figure 1: Infrared image of the brown dwarf companion J1446B (marked by the arrow). The host star (J1446) is masked in white during image processing. The white bar at the lower right corresponds to an angular distance equivalent to 10 astronomical units (roughly the distance between Saturn and the Sun). (Credit: Taichi Uyama (Astrobiology Center/CSUN) / W. M. Keck Observatory)


By combining the power of ground-based and space-based telescopes, astronomers have discovered a new brown dwarf—a type of object that lies between a star and a planet—orbiting a small star about 55 light-years from Earth. In addition, infrared observations revealed variations in its brightness, suggesting that clouds and storms may be forming and moving within the brown dwarf’s atmosphere.

In our Milky Way Galaxy, the most common type of stars is small, cool stars known as M dwarfs, or red dwarfs. They make up more than half of the all stars in our Galaxy. Because M dwarfs are intrinsically faint, it has been difficult to determine how many of them have planets or brown dwarfs as companions. Brown dwarfs are too light to shine like normal stars, yet heavier than planets—objects, so they bridge the gap between the two. Understanding how frequently such companions exist, and what masses they have, is essential for learning how stars and planets form and evolve.

An international research team led by the Astrobiology Center, California State University Northridge, and Johns Hopkins University has now discovered a brown dwarf companion orbiting a nearby M dwarf LSPM J1446+4633 (hereafter J1446), located about 55 light-years from Earth (Figure 1). The companion, J1446B, has a mass of about 60 times that of Jupiter and orbits its host star at a distance 4.3 times the Earth–Sun separation, completing one orbit in about 20 years. In addition, near-infrared observations revealed brightness variations of about 30%, indicating possible cloud activity or atmospheric circulation on the brown dwarf.

"Studying the weather on these distant objects not only helps us to understand how their atmosphere form, but also informs our larger search for life planets beyond the solar system" says Taichi Uyama, researcher with the Astrobiology Center of Japan and lead author of the study.

The key to this discovery was the combination of three complementary observation techniques: (1) precise radial velocity measurements using InfraRed Doppler (IRD) on the Subaru Telescope, (2) direct imaging with the W. M. Keck Observatory, and (3) astrometric measurements of the host star’s motion with the Gaia spacecraft.

By analyzing all three datasets together, the team accurately determined the mass and orbit of the companion (Figure 2). In particular, the Subaru Telescope’s six years of data from its strategic program (IRD-SSP) were crucial. Radial velocity data alone cannot break the degeneracy between mass and orbital inclination, but adding direct imaging and Gaia astrometry resolves this ambiguity.

Figure 2: Orbit modeling of J1446B. (Left) The projected orbit inferred from W. M. Keck Observatory’s direct imaging (blue dot at upper right) and the acceleration in the host star’s motion measured by Gaia (red arrow). Axes show right ascension and declination in arcseconds. The black curve represents the most probable orbit, while the colored curves indicate other possible orbits; color corresponds to the estimated mass of J1446B (color scale shown on right). (Right) Radial velocity variations of the host star measured by IRD (red points), along with simulated orbital solutions color-coded by companion mass. The lower panel shows residuals from the fit. (Credit: Qier An (UCSB) / Uyama et al. (2025))


Previous studies have demonstrated the power of combining Hipparcos and Gaia astrometry (Note 1) with direct imaging to detect and characterize companions (Note 2). However, Hipparcos was unable to measure the positions of faint red dwarfs like J1446. This study is the first to apply Gaia-only data to such a system, successfully constraining the orbit and dynamical mass of a brown dwarf companion.

This discovery provides a critical benchmark for testing brown dwarf formation scenarios and atmospheric models. Future observations may even allow researchers to map the weather patterns of this intriguing object. This result highlights the power of combining ground-based and space-based telescopes to uncover hidden worlds beyond our Solar System.

These results appeared as Uyama et al. "Direct Imaging Explorations for Companions from the Subaru/IRD Strategic Program II; Discovery of a Brown-dwarf Companion around a nearby Mid-M-dwarf LSPM J1446+4633" in the Astronomical Journal on October 20, 2025.

This research was supported by JSPS KAKENHI (Grant Numbers: 24K07108, 24K07086). The development and operation of IRD were supported by JSPS KAKENHI (Grant Numbers: 18H05442, 15H02063, and 22000005).

These results appeared as Uyama et al. "Direct Imaging Explorations for Companions from the Subaru/IRD Strategic Program II; Discovery of a Brown-dwarf Companion around a nearby Mid-M-dwarf LSPM J1446+4633" in the Astronomical Journal on October 20, 2025.

This research was supported by JSPS KAKENHI (Grant Numbers: 24K07108, 24K07086). The development and operation of IRD were supported by JSPS KAKENHI (Grant Numbers: 18H05442, 15H02063, and 22000005).




(Note 1) The Gaia spacecraft, launched in 2013, is an astrometric mission designed to create a detailed 3D map of stars in the Milky Way. Its extremely precise positional measurements enable the detection of companions and planets through the astrometric method, which relies on subtle stellar motions. Hipparcos, launched in 1989, was Gaia’s predecessor and provided the first space-based astrometric catalog.

(Note 2) For details on the research methods, please refer to the Science Results on January 2023.



Relevant Links
  • W. M. Keck Observatory October 20, 2025 Press Release Astrobiology Center October 21, 2025 Press Release


About the Subaru Telescope

The Subaru Telescope is a large optical-infrared telescope operated by the National Astronomical Observatory of Japan, National Institutes of Natural Sciences with the support of the MEXT Project to Promote Large Scientific Frontiers. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical, and natural significance in Hawai`i.


Monday, October 20, 2025

Focusing on NGC 3370

A spiral galaxy occupies most of the image. It is a slightly tilted disc of stars, yellow-white in the centre and blue in the outskirts, showing light from different stars in the galaxy. Its spiral arms c.url outwards from the centre, speckled with blue star clusters. Dark reddish threads of dust swirl around the galaxy’s centre. Th,bre backdrop is two medium-sized and many small, distant galaxies on a black background. Credit: ESA/Hubble & NASA, A. Riess, K. Nol

Today’s ESA/Hubble Picture of the Week features a galaxy that Hubble has captured multiple times over more than 20 years. The galaxy is called NGC 3370, and it is a spiral galaxy located nearly 90 million light-years away in the constellation Leo (The Lion).

What is it about this galaxy that makes it a popular target for researchers? NGC 3370 is home to two kinds of objects that astronomers prize for their usefulness in determining distances to faraway galaxies: Cepheid variable stars and Type Ia supernovae.

Cepheid variable stars change in both size and temperature as they pulsate. As a result, the luminosity of these stars varies over a period of days to months. It does so in a way that reveals something important: the more luminous a Cepheid variable star is, the more slowly it pulsates. By measuring how long a Cepheid variable’s brightness takes to complete one cycle, astronomers can determine how bright the star actually is. Paired with how bright the star appears from Earth, this information gives the distance to the star and its home galaxy.

Type Ia supernovae provide a way to measure distances in a single explosive burst rather than through regular brightness variations. Type Ia supernovae happen when the dead core of a star ignites in a sudden flare of nuclear fusion. These explosions peak at very similar luminosities, and much like for a Cepheid variable star, knowing the intrinsic brightness of a supernova explosion allows for its distance to be measured. Observations of Cepheid variable stars and Type Ia supernovae are both critical for precisely measuring how fast our Universe is expanding.

A previous Hubble image of NGC 3370 was released in 2003. The image released today zooms in on the galaxy, presenting a richly detailed view that incorporates wavelengths of light that were not included in the previous version. NGC 3370 is a member of the NGC 3370 group of galaxies along with other Hubble targets NGC 3447 and NGC 3455.

Links



Sunday, October 19, 2025

NuSTAR Coordinations with IXPE

An image of NuSTAR data from the Crab in color overlaid on Chandra data in white, showing the ring-shaped X-ray nebula surrounding the central neutron star. The Crab is used as a calibration target for X-ray observatories and was observed jointly with NuSTAR and IXPE last month. Image credit: NASA.
Download Image

NuSTAR is performing a series of observations this month coordinated with NASA’s Imaging X-ray Polarimetry Explorer (IXPE). Most targets observed by IXPE are also now observed by NuSTAR, either as part of joint observing proposals submitted to peer reviewed General Observer (GO) programs, or in response to requests from the community to provide short exposures to aid in scientific analysis of IXPE observations. NuSTAR’s broad range of timing and energy sensitivity can deliver precise constraints on the X-ray continuum shape and variability, complementary to the X-ray polarimetry measurements by IXPE. The observations this month have included symbiotic X-ray binaries and pulsars as well as target-of-opportunity observations of transient X-ray flares requiring quick scheduling responses of the NuSTAR and IXPE teams. A simultaneous observation of the Crab nebula was also performed last month, which is used as a calibration target for X-ray missions. Combined analysis of the NuSTAR and IXPE data will improve the detailed calibration of each mission. Multi-mission cross calibration has become an important aspect of investigations of astrophysical X-ray sources with the number of coordinated observations with NuSTAR and other X-ray observatories continuing to rise. This increase in the usefulness of joint observations was reflected in the doubling of the number of proposals requesting coordinated NuSTAR observations submitted to the IXPE GO cycle-3 program last month. The total NuSTAR observing time requested by the astrophysics community was more than five times that available for the joint program, which has become highly competitive. The selection of proposals for observations in IXPE cycle-3 is expected to be released before the end of the year, with observations beginning February 1st, 2026.

Authors: Karl Forster (NuSTAR Operations Lead, California Institute of Technology)



Saturday, October 18, 2025

Investigation of the First Radio-Bright Off-Nuclear Tidal Disruption Event

Illustration of a tidal disruption event.
Credit:
DESY, Science Communication Lab

Catastrophic encounters between stars and massive black holes usually take place in the nuclei of galaxies, but not always. Researchers recently reported on the brightest-ever radio emission from an off-nuclear tidal disruption event caused by a wandering or recoiling black hole.

Signature of a Roaming Black Hole

Tidal disruption events occur when a star ventures too close to a massive black hole. The tidal forces of the black hole stretch the star until it’s partially or entirely disrupted, sometimes causing jets or outflows to spray from the shredded star. One thing that often distinguishes a tidal disruption event from the sea of other possible transients is the location, close to the nucleus of a galaxy.

But not all tidal disruption events happen in the center of a galaxy. In rare cases, a massive black hole roaming elsewhere in a galaxy may encounter a star, sending out a tell-tale signal in an unexpected location.

One such event is AT 2024tvd, which was discovered at optical wavelengths by the Zwicky Transient Facility. Though the initial identification placed it at the center of its host galaxy, follow-up observations suggested that it was in fact 2,600 light years from the center. What can radio observations tell us about this rare off-center event?

Radio observations of AT 2024tvd on two dates after its optical discovery. The tidal disruption event was not detected at 88 days post-discovery (left) and outshone the center of its host galaxy on 160 days post-discovery (right). Credit: Sfaradi et al. 2025

Radio Reconnaissance

Less than three months after AT 2024tvd was discovered, Itai Sfaradi (University of California, Berkeley) and collaborators launched a months-long radio-wavelength observing campaign using the Very Large Array, the Atacama Large Millimeter/submillimeter Array, the Arcminute Microkelvin Imager Large Array, the Allen Telescope Array, and the Submillimeter Array. Radio observations are critical for investigating jets and outflows from tidal disruption events. The observations, which spanned centimeter and millimeter wavelengths, revealed two emission peaks from the tidal disruption event. The first peak occurred roughly 131 days after the event was discovered, and the second followed at day 194.

About 40% of the tidal disruption events that have been identified at optical wavelengths show this kind of delayed brightening at radio wavelengths, but AT 2024tvd stands out as having the fastest radio evolution ever seen. Even among fairly fast-evolving flares, AT 2024tvd is unusual, having a brighter second peak than peer events.

Demonstration of the fast evolution of AT 2024tvd’s radio emission (red and orange stars) compared to other radio-bright tidal disruption events (other symbols). Credit: Sfaradi et al. 2025

Prompt or Delayed, Outflow or Jet?

To understand the origin of the fast-evolving, extremely bright radio emission from AT 2024tvd, Sfaradi’s team modeled the emission that would arise from outflows and jets. For both wide-angle outflows and narrow jets, the team considered both prompt — arising simultaneously with the event’s optical detection — and delayed sources.

The team’s modeling highlighted several possible scenarios. In the first, both bright radio peaks arose from a single outflow that was launched about 84 days after the star met its doom. The double-peaked behavior is due to the outflow interacting with a complex distribution of material surrounding the black hole. It’s also possible for the two peaks to arise from separate outflows or jets, one launched around 84 days and the other around either 170 or 190 days, depending on whether the second source is a mildly relativistic outflow or a relativistic jet.

Sfaradi and collaborators posited that AT 2024tvd’s unusual radio behavior could be due to its off-nuclear location, but they acknowledged that this event might simply occupy a region of tidal disruption event parameter space that had yet to be explored. Sensitive interferometric or polarimetric observations may reveal more about how AT 2024tvd interacts with its environment, helping to illuminate the nature of this rare event.

By Kerry Hensley

Citation

“The First Radio-Bright Off-Nuclear TDE 2024tvd Reveals the Fastest-Evolving Double-Peaked Radio Emission,” Itai Sfaradi et al 2025 ApJL 992 L18. doi:10.3847/2041-8213/ae0a26



Friday, October 17, 2025

Webb sheds more light on composition of planetary debris around nearby white dwarf

The JWST/MIRI spectrum of GD 362. The three colored curves show the spectra in MIRI/MRS channels 1, 2, and 3.
Credit: arXiv (2025). DOI: 10.48550/arxiv.2510.07595



Using the James Webb Space Telescope (JWST), astronomers have performed infrared observations of a planetary debris disk around a nearby white dwarf known as GD 362. Results of the new observations, presented October 8 on the arXiv preprint server, yield important insights into the chemical composition of this disk.

White dwarfs (WDs) are stellar cores left behind after a star has exhausted its nuclear fuel. Due to their high gravity, they are known to have atmospheres of either pure hydrogen or pure helium.

However, there exists a small fraction of WDs that shows traces of heavier elements, and they are believed to be accreting planetary material. Studies of this material around WDs, which often forms dust disks, is essential to improving our knowledge of how planets form and evolve.

GD 362, also known as WD 1729+371, is a white dwarf located some 182.9 light years away. It has a radius of about 8,790 kilometers, a mass of approximately 0.57 solar masses, and its effective temperature is estimated to be 9,825 K.

Previous observations of GD 362 show that it is one of the most heavily polluted white dwarfs, and showcases an exceptionally strong infrared excess. It turned out that it possesses a helium-dominated atmosphere with a high metal abundance, and also an anomalously large mass of hydrogen. Moreover, a dust disk was identified, located within 140 to 1,400 stellar radii of GD 362.

Recently, a team of astronomers led by William T. Reach of the Space Science Institute in Boulder, Colorado, employed JWST's Near Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) to take a closer look at the disk around GD 362, hoping to shed more light on its chemical composition.

The spectral resolution and sensitivity of the two instruments allowed Reach's team to measure the composition of solid planetary material around GD 362. The mid-infrared spectrum was found to be dominated by an exceptionally strong 9–11 µm silicate feature, three times brighter than its underlying continuum, which extends to at least 2 µm, and requires hot debris (with a temperature of about 950 K) close to the white dwarf.

The results indicate that the disk around GD 362 contains a mix of amorphous and crystalline olivines and pyroxenes plus amorphous carbon. It was found that the elemental abundances of carbon, oxygen, magnesium, aluminum and iron are within a factor of two, relative to silicon.

It was noted that no evidence for water in the spectrum, nor were other hydrogen-bearing species found. This suggests the dust in the disk is drier and lower in hydrogen than in chondritic meteorites.

"Overall, the results indicate that GD 362 is surrounded by a disk with solids having elemental abundances approximately matching those seen in the atmosphere of the white dwarf, supporting the connection between disk and atmosphere arising from accretion of planetary material," the authors of the paper conclude.

by Tomasz Nowakowski, Phys.org
Stephanie Baum, reviewed by Robert Egan




Written for you by our author Tomasz Nowakowski, edited by Stephanie Baum, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.



More information: William T. Reach et al, Composition of planetary debris around the white dwarf GD 362, arXiv (2025). DOI: 10.48550/arxiv.2510.07595

Journal information: arXiv


Thursday, October 16, 2025

First-ever Detection of “Heavy Water” in a Planet-forming Disk

This artist’s impression shows the evolution of heavy water molecules (H2O, HDO, and D2O) as they have been observed in giant molecular clouds, a planet forming-disk, and comets—before they eventually may have made their way to Earth.Credit: NSF/AUI/NSF NRAO/P. Vosteen/B. Saxton.
Hi-Res File



New ALMA data traces water found in comets, and planet formation, back to the dawn of the cosmos

The discovery of ancient water in a planet-forming disk reveals that some of the water found in comets—and maybe even Earth—is older than the disk’s star itself, offering breakthrough insights into the history of water in our Solar System.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have made a first-ever detection of doubly deuterated water (D₂O, or “heavy water”) in a planet-forming disk around V883 Ori, a young star. This means that the water in this disk, and by extension the water in comets that form here, predates the birth of the star itself, having journeyed through space from ancient molecular clouds long before this solar system formed.

“Our detection indisputably demonstrates that the water seen in this planet-forming disk must be older than the central star and formed at the earliest stages of star and planet formation,” shares Margot Leemker, lead author on this paper, and a postdoc with the Department of Physics, University of Milan. “This presents a major breakthrough in understanding the journey of water through planet formation, and how this water made its way to our Solar System, and possibly Earth, through similar processes.”

Does this mean that the water in your morning cup of coffee could be older than the Sun? The chemical fingerprinting of D₂O shows that these water molecules have survived the violent processes of star and planet formation, travelling billions of kilometers through space and time before, ending up in planetary systems like our own. Instead of being destroyed and reformed in the disk, the bulk of this water is inherited from the earliest, coldest stages of star formation, a cosmic hand-me-down that may also be present on Earth today.

“Until now, we weren’t sure if most of the water in comets and planets formed fresh in young disks like V883 Ori, or if it’s ‘pristine,’ originating from ancient interstellar clouds,” shares John Tobin, a scientist with the U.S. National Science Foundation National Radio Astronomy Observatory, and second author on this new paper. The detection of heavy water, using sensitive isotopologue ratios (D₂O/H₂O), proves the water’s ancient heritage and provides a missing link between clouds, disks, comets, and ultimately planets. This finding is the first direct evidence of water’s interstellar journey from clouds to the materials that form planetary systems—unchanged and intact.

Water is fundamental to life and habitability. Knowing where planetary water comes from helps us understand the ingredients for life in our Solar System and in others. This discovery suggests that many young planets, and maybe even worlds beyond our own, could inherit water billions of years older than themselves, reminding us how deeply interconnected our existence is with the universe’s ancient past.




About NRAO

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

About ALMA

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.


Wednesday, October 15, 2025

Black holes don’t suck, they get fed!

Circinus Galaxy
Credit: ALMA(ESO/NAOJ/NRAO)/ESO/W. Goesaert et al.

Today’s Picture of the Week gives us a closer look at how black holes in the centre of galaxies feast. As some of you already know, the common belief that black holes simply suck in anything that comes near them, is wrong. Material can only fall into a black hole when it’s slowed down somehow — so what's pumping the brakes?

To answer this question, a team of astronomers led by Wout Goesaert, now a PhD candidate at Leiden University, the Netherlands, mapped how molecular gas is distributed in the Circinus galaxy, about 13 million light-years away. The galaxy is shown in the top left corner in visible light. The two insets are images taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. Gas is streaming towards the black hole through two spiral arms that are embedded in the disc, seen in the innermost regions of the top-right picture. These arms feed the doughnut-shaped cloud around the black hole seen at the bottom.

The gravitational influence of the spiral arms perturbs the motion of the molecular gas, which falls right into the monster's mouth, the same way a satellite would fall onto Earth if its orbit was disturbed. The feeding process is very inefficient though: the team found that about 90% of the material does not end up in the black hole but is rather spat back out, like a massive toddler refusing to eat.

Links

Source: ESO/potw


Tuesday, October 14, 2025

IC Stars

IC 348 is a star-forming region in our Milky Way galaxy.
X-ray: NASA/CXC/SAO; Infrared: NASA/ESA/CSA/STScI; Image Processing: NASA/CXC/SAO/J. Major
Text credit: Megan Watzke


Data from NASA’s Chandra X-ray Observatory and NASA’s James Webb Space Telescope combine to reveal an otherworldly view of the star-forming region IC 348. In this image released on July 23, 2025, X-rays from Chandra are red, green, and blue, while infrared data from Webb are pink, orange, and purple.

The wispy structures that dominate the image are interstellar material that reflect the light from the cluster’s stars; this is known as a reflection nebula. The point-like sources in Chandra’s X-ray data are young stars in the cluster developing there.



Monday, October 13, 2025

A well-studied spiral

A spiral galaxy featuring a bright, glowing core that is crossed by a horizontal bar of yellowish light. Spiral arms emerge from each end of this bar and wrap around it, creating a disc that is stretched out to the right. Some areas, mostly along the arms, glow pink where stars are forming in nebulae. Webs of dark reddish dust also follow the arms. A star in our galaxy shines prominently, off to the right. Credit: ESA/Hubble & NASA, R. Chandar, J. Lee and the PHANGS-HST team

The celestial object that is displayed in this NASA/ESA Hubble Space Telescope Picture of the Week is NGC 7496, a galaxy located over 24 million light-years away in the constellation Grus (The Crane). NGC 7496 is a dusty spiral galaxy with a bar of stars stretching across its centre. Adding to its intrigue is an active galactic nucleus: a supermassive black hole that feasts on gas at the very heart of the galaxy. Astronomers have observed NGC 7496 at wavelengths from radio to ultraviolet in order to study the galaxy’s active galactic nucleus, dust clouds, and star formation. Hubble first observed this galaxy as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) programme. This programme has enlisted the abilities of several powerful astronomical observatories, including the Atacama Large Millimetre/submillimetre Array (ALMA), the Very Large Telescope, and the NASA/ESA/CSA James Webb Space Telescope, in addition to Hubble. NGC 7496 was the first galaxy in the PHANGS sample that Webb observed.

Each of these observatories offers a different perspective on this well-studied galaxy. With its unique ultraviolet capabilities and fine resolution, Hubble’s view reveals young star clusters bursting with high-energy radiation. Hubble’s observations of NGC 7496 help to reveal the ages and masses of these young stars, as well as the extent to which their starlight is blocked by dust.

A previous Hubble image of NGC 7496 was released in 2022. Today’s image incorporates new data that highlight the galaxy’s star clusters, which are surrounded by glowing red clouds of hydrogen gas. Astronomers collected these data in order to study nebulae like those that massive stars leave behind when they explode as supernovae and those from which newborn stars are made.



Sunday, October 12, 2025

Artist's illustration of a white dwarf accreting mass from a binary companion and erupting in a nova.
Credit:
NASA's Goddard Space Flight Center/S. Wiessinger
 
Two light curves of M31N 2017-01e outbursts from 2024 (top) and 2019 (bottom) showing how the light evolves over time. Click to enlarge. Credit: Chamoli et al 2025  

Flashing on and fading quickly, recurrent novae are captivating astronomical phenomena. A recent study identifies one system that challenges our current understanding.

Rapid Recurrent Novae

When a white dwarf — the white-hot remnant of a dead star — has a close binary companion, the white dwarf can pull material from the companion star onto its boiling surface. Ignited in a bright flash, the accreted material is blown out from the white dwarf in a nova explosion that gradually expands and fades over time. Some novae, known as recurrent novae, repeat on observable timescales, creating a “new” star in the sky on periods ranging from one to one hundred years.

Our nearest galactic neighbor, Andromeda, hosts the most rapid recurrent novae observed to date, including the shortest-period known recurrent nova, M31N 2008-12a. M31N 2008-12a has erupted once a year for millions of years and will eventually meet its fate in a supernova explosion.

Discovered in 2017, the second-shortest-period nova M31N 2017-01e has an outburst about every 2.5 years. This nova has sparked intrigue among researchers due to its low-amplitude outbursts and rapid evolution compared to other recurrent novae. While M31N 2017-01e exhibits some emission features typical for recurrent novae, recent studies have suggested that the system’s companion star may be a moderately young, blue B-type star. Most novae occur in systems where the white dwarf’s companion is a late-type main-sequence, subgiant, or giant star, making M31N 2017-01e an unusual case requiring further investigation.

Optical image showing the location of sources near the location of M31N 2017-01e. The yellow circle corresponds to a radius of 5 arcseconds and is centered on the nova. Labeled S0, the source coincides with the location of the nova with sub-arcsecond resolution. Credit: Modified from Chamoli et al 2025

Dialing In on M31N 2017-01e

Aiming to constrain the nature and companion star of the nova, Shatakshi Chamoli (Indian Institute of Astrophysics and Pondicherry University) and collaborators performed a multiwavelength analysis using ultraviolet and optical observations of M31N 2017-01e.

In monitoring the nova during and in between outbursts, the authors identified a source at the reported location of M31N 2017-01e that exhibited variability and color consistent with previous observations of the system. Through a detailed photometric analysis, the authors found that the color and emission properties of the source are consistent with a hot, early-type star as was previously suggested. Though all the observational signs point toward a B-type companion, there’s one glaring obstacle to that scenario: such a massive star would typically be unable to transfer the amount of mass necessary to fuel the nova’s frequent eruptions without the accretion becoming unstable.

Be a Companion

What else, then, could the companion be? The authors considered another stellar companion known as a Be star — a rapidly rotating, early-type star that occasionally hosts a disk of loose stellar material. With a blue color and spectral features similar to B-type stars, a Be star could match the observational properties of the nova’s companion while solving the problem of its accretion. Outbursts of M31N 2017-01e likely arise due to the white dwarf lying very near or within the Be star’s circumstellar disk, siphoning material and adequately fueling the system’s recurring eruptions. To confirm this hypothesis, researchers will need to perform follow-up infrared observations to search for the tell-tale signs of a dusty disk around the companion star.

This system is rare and challenges the assumed properties of recurrent novae. From this study, it is clear that nova progenitors are potentially quite diverse and require further multiwavelength observational programs to identify more systems like M31N 2017-01e.

By Lexi Gault

Citation

“Challenging Classical Paradigms: Recurrent Nova M31N 2017-01e, a BeWD System in M31?,” Shatakshi Chamoli et al 2025 ApJ 991 174. doi:10.3847/1538-4357/adf843



Saturday, October 11, 2025

Event Horizon Telescope images reveal new dark matter detection method

Simulated images of the supermassive black hole M87*. Left panel shows radiation from astrophysical plasma and right panel illustrates potential emission from dark matter annihilation. Credit: Yifan Chen.




According to a new Physical Review Letters study, black holes could help solve the dark matter mystery. The shadowy regions in black hole images captured by the Event Horizon Telescope can act as ultra-sensitive detectors for the invisible material that makes up most of the universe's matter.

Dark matter makes up roughly 85% of the universe's matter, but scientists still don't know what it actually is. While researchers have proposed countless ways to detect it, this study introduces black hole imaging as a fresh detection method—one that comes with some distinct benefits.

The Event Horizon Telescope's stunning images of supermassive black holes have revealed more than just the geometry of spacetime; they've opened an unexpected window into the search for dark matter.

Phys.org spoke to co-authors Jing Shu from Peking University and Yifan Chen from the Niels Bohr Institute. "I have always been fascinated by instruments like the Event Horizon Telescope (EHT), which allow us to probe the extreme environments around supermassive black holes and challenge the boundaries of known physical laws," Shu said.

Chen added, "I've been fascinated by the idea of using black holes as detectors for new particles. Their extreme gravity makes them natural concentrators of matter, creating a unique meeting point for particle physics, gravity, and astrophysical observation."

The research team focused on a striking feature of black hole images: the shadow region that appears dark in EHT observations of M87* and Sagittarius A*.

A cosmic darkroom

The Event Horizon Telescope is a global network of radio observatories working in concert to achieve Earth-sized resolution through Very Long Baseline Interferometry. Working at a frequency of 230 GHz, the telescope captures synchrotron radiation—light produced when electrons spiral along the intense magnetic field lines near supermassive black holes.

To understand what they're seeing, astrophysicists run complex computer simulations.

The magnetically arrested disk (MAD) model has consistently delivered the best agreement with EHT observations. The MAD model depicts strong magnetic fields penetrating the accretion disk, where they both regulate the flow of infalling matter and power jets that erupt perpendicular to the disk.

Crucially, the MAD model explains why black hole shadows appear dark: most electrons reside in the accretion disk, while the jet regions above and below are relatively particle-poor, creating a sharp contrast in the images.

"Ordinary astrophysical plasma is often expelled by powerful jets, leaving the shadow region especially faint," Chen explained. "Dark matter, however, could continuously inject new particles that radiate in this region."

Because dark matter is expected to concentrate densely near the black hole's center, even faint annihilation signals could stand out against this low astrophysical background, making the shadow an ideal testing ground.

Modeling dark matter

The gravitational pull of supermassive black holes causes dark matter to concentrate dramatically in their vicinity, forming what physicists call a "dark matter spike." These regions achieve densities orders of magnitude higher than anywhere else in the galaxy.

Since dark matter annihilation rates depend on density squared, these enhanced densities could produce detectable signals—if the annihilation occurs at all.

The research team developed a sophisticated framework that builds directly on the MAD model by adding dark matter physics to the astrophysical baseline.

The team applied general relativistic magnetohydrodynamic (GRMHD) simulations along with detailed particle propagation modeling. With this framework, they could model how electrons and positrons from hypothetical dark matter annihilation would behave in the magnetic field structures extracted from the MAD model.

Unlike previous studies that relied on simplified spherical models, this approach uses the realistic, asymmetric magnetic field configurations extracted from the MAD simulations—the same fields that shape the astrophysical emission we observe.

"What we see in black hole images is not the black hole itself, but light emitted by ordinary electrons in the surrounding accretion disk, whose behavior we can model using well-known physics," Shu said.

"If dark matter particles were annihilating near the black hole, they would produce extra electrons and positrons whose radiation looks slightly different from the normal emission."

The critical distinction emerges in spatial distribution. In the MAD model, electrons concentrate in the accretion disk with sparse populations in the jet regions—creating the dark shadow.

But electrons and positrons from dark matter annihilation would be distributed more uniformly throughout both disk and jet regions, because dark matter annihilation continuously supplies particles even where astrophysical processes produce few electrons.

The team examined two annihilation channels—bottom quark-antiquark pairs and electron-positron pairs—across dark matter masses ranging from sub-GeV to approximately 10 TeV.

For each scenario, they calculated the resulting synchrotron radiation and generated synthetic black hole images that combined both astrophysical emission (from MAD) and potential dark matter signals.

Morphology as a probe

The researchers' approach to exploiting the morphology of the black hole images rather than just the total brightness makes the work stand out.

They required that dark matter annihilation signals remain below astrophysical emission at every point in the image, particularly within the inner shadow region.

"By comparing these predictions with real EHT images at the 'darkroom,' we can search for subtle signals that may reveal dark matter," Shu said.

This morphological approach proves significantly more powerful than previous constraints based on total intensity alone. The analysis excludes substantial regions of previously unexplored parameter space, setting limits on annihilation cross sections down to approximately 10-27 cm³/s for current EHT observations.

"Our exclusions based on current EHT observations already probe large regions of previously unexplored parameter space, surpassing other searches that assume similar density profiles," Chen said.

The constraints remain robust against astrophysical uncertainties, including variations in black hole spin and plasma temperature parameters—factors that typically introduce significant uncertainties in indirect dark matter searches.

Future prospects The true power of this approach will be realized with anticipated EHT upgrades. Future improvements promise to increase dynamic range by nearly 100 times and achieve angular resolution equivalent to approximately one gravitational radius, enabling them to probe deeper into the darkest regions of the shadow.

"The key upgrade is improving the telescope's dynamic range, which is its ability to reveal very faint details right next to extremely bright features," Chen explained.

"A common example is the 'high dynamic range' (HDR) mode on many smartphones, which uses advanced processing to bring out details in both dark shadows and bright highlights in the same image."

These enhancements could enable detection of dark matter with annihilation cross sections near the thermal relic value, a theoretically well-motivated target, for masses up to approximately 10 TeV.

Looking ahead, the researchers envision several directions for expanding this research.

"The black hole shadow is not just a static image; it is a dynamic, multi-layered laboratory," Shu said. "Beyond the intensity maps, polarization data from the EHT also open new windows, because polarization encodes how magnetic fields and plasma shape the radiation."

Multi-frequency observations will also prove crucial, according to Shu. Different radiation mechanisms scale differently with frequency, allowing researchers to determine the source of radiation—essentially using multiple colors to distinguish dark matter signals from astrophysical backgrounds.

by Tejasri Gururaj, Phys.org




More information: Yifan Chen et al, Illuminating Black Hole Shadows with Dark Matter Annihilation, Physical Review Letters (2025). DOI: 10.1103/yxqg-363n.

Journal information: Physical Review Letters



Written for you by our author Tejasri Gururaj, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journali.sm alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.


Friday, October 10, 2025

Astronomers 'image' a mysterious dark object in the distant Universe

Overlay of the infrared emission (black and white) with the radio emission (colour). The dark, low-mass object is located at the gap in the bright part of the arc on the right-hand side. © Credit: Keck/EVN/GBT/VLBA

The zoom in shows the pinch in the luminous radio arc, where the extra mass from the dark object is gravitationally ‘imaged’ using the sophisticated modelling algorithms of the team. The dark object is indicated by the white blob at the pinch point of the arc, but no light from it has so far been detected at optical, infrared or radio wavelengths. © Credit: Keck/EVN/GBT/VLBA



An international team of astronomers has found a low mass dark object in the distant Universe, not by directly observing any emitted light, but by detecting its tiny gravitational distortion of the light from another distant galaxy. This mysterious object has a mass of about one million times that of our Sun, and its discovery seems consistent with the current best theory about how galaxies like our own Milky Way formed.

“Hunting for dark objects that don't seem to emit any light is clearly challenging,” said Dr. Devon Powell at the Max Planck Institute for Astrophysics (MPA) and lead author of the study published in Nature Astronomy. “Since we can’t see them directly, we instead use very distant galaxies as a backlight to look for their gravitational imprints.”

Dark matter is an enigmatic form of matter not expected to emit light, yet it is essential to understanding how the rich tapestry of stars and galaxies we see in the night sky evolved. As a fundamental building block of the universe, a key question for astronomers is whether dark matter is smooth or clumpy, as this could reveal what it is made of. As dark matter cannot be seen, its properties can only be determined by observing the gravitational lensing effect, whereby the light from a more distant object is distorted and deflected by the gravity of the dark object.

The team used a network of telescopes from around the world, including the Green Bank Telescope (GBT), the Very Long Baseline Array (VLBA) and the European Very Long Baseline Interferometric Network (EVN). The data from this international network were correlated at the Joint Institute for VLBI ERIC (JIVE) in the Netherlands, forming an Earth-sized super-telescope that could capture the subtle signals of gravitational lensing by the dark object. They discovered that the object has a mass a million times greater than that of our Sun and is located in a distant region of space, approximately 10 billion light years from Earth, when the universe was only 6.5 billion years old.

This is the lowest mass object to be found using this technique, by a factor of about 100. To achieve this level of sensitivity, the team had to create a high-fidelity image of the sky using radio telescopes located around the world. Professor John McKean from the University of Groningen (RuG), the University of Pretoria (UP) and the South African Radio Astronomy Observatory (SARAO), who led the data collection and is the lead author of a companion paper, said: “From the first high-resolution image, we immediately saw a pinch in the gravitational arc, which is the tell-tale sign that we were onto something. Only another small clump of mass between us and the distant radio galaxy could cause this.”

To analyse the massive dataset, the team had to develop new modelling algorithms that could only be run on supercomputers. “The data are so large and complex that we had to develop new numerical approaches to model them. This was not straightforward as it had never been done before,” said Dr Simona Vegetti at MPA. “We expect every galaxy, including our own Milky Way, to be filled with dark matter clumps, but finding them and convincing the community that they exist requires a great deal of number crunching,” she continued. The team applied a special technique called gravitational imaging, which allowed them to ‘see’ the invisible dark matter clump by mapping its gravitational lensing effect against the radio-luminous arc.

“Given the sensitivity of our data, we were expecting to find at least one dark object, so our discovery is consistent with the so-called ‘cold dark matter theory’ on which much of our understanding of how galaxies form is based,” said Powell. “Having found one, the question now is whether we can find more and whether their number will still agree with the models.”

The team are now analysing the data further to better understand what the mysterious dark object could be, but they are also looking into other parts of the sky to see if they can find more examples of such low-mass dark objects using the same technique. If they continue to find such mysterious objects in other parts of the universe, and if they really turn out to be completely devoid of stars, then some theories of dark matter may be ruled out.




Additional Information:

Gravitational lensing: This is an astrophysical tool used by astronomers to measure the mass properties of structure in the Universe. It is a consequence of Einstein’s Theory of General Relativity, where mass in the Universe curves space. If the mass of the foreground lensing object (typically a galaxy or cluster of galaxies) is sufficiently dense, then the light from distant objects is distorted and multiple images are even seen. In the case of this system, called B1938+666, the foreground infrared luminous galaxy (seen at the centre of the ring), results in a beautiful Einstein ring of the distant galaxy. However, the distant galaxy is also bright at radio wavelengths, showing the beautiful multiple images and gravitational arcs (seen in red).

Very Long Baseline Interferometry: The radio observations were taken using a combination of radio telescopes that are combined to form a so-called Very Long Baseline Interferometer. This observational method allows astronomers to improve the imaging sharpness of the data and reveal very small fluctuations in the brightness that otherwise could not be seen. For example, the resolving power of the VLBI data is a factor 13 better than the infrared imaging from the W. M. Keck Telescope adaptive optics system (also shown in the figures in black and white). The telescopes used in the observations were the Green Bank Telescope and the Very Long Baseline Array of the National Radio Astronomy Observatory in the United States, and the telescopes of the European Very Long Baseline Interferometric Network.

Gravitational imaging: This is a novel method astronomers use to ‘see’ mass in the Universe even though it does not emit any light. This method uses the extended gravitational arcs to look for small aberrations that can only be caused by an additional, invisible component of mass. By combining this method and the exquisite high angular resolu,hrtion imaging from the VLBI data, the team were able to detect the presence of the lowest mass dark object currently measured.



Thursday, October 09, 2025

Cosmic Tug-of-War: Gravity Reshapes Magnetic Fields in Star Clusters

This image from NASA’s Spitzer Space Telescope shows a star formation region in molecular cloud NGC 6334, also known as the Cat's Paw Nebula. The colors correspond with emission at 3.6 microns (blue), 4.5 microns (green), and 8 microns (red). This cloud is actively forming massive stars, and is located in the constellation Scorpius, between 4,200 to 5,500 light-years from Earth. ALMA data overlaid on the image shows details of four specific areas that were observed (NGC 6334I, NGC 6334I(N), NGC 6334IV and NGC 6334V), revealing invisible forces of magnetism and gravity as they wrestle and shape the formation of stars deep within the giant molecular cloud. The color scale in the ALMA images represents the intensity of the dust emission at 1.3mm and the drapery lines represent the orientation of the magnetic field. Credit: Credit for composite image: background, NASA/JPL-Caltech; overlay: ESO/NAOJ/NSF NRAO; image created by NSF/AUI/NSF NRAO/M. Weiss.




A record-breaking ALMA survey delivers the first statistical evidence that collapsing gas clouds realign their magnetic fields, tipping the cosmic balance in favor of gravity

Astronomers have captured the clearest picture yet of how massive stars are born, revealing a dramatic interplay between gravity and magnetic fields in some of our galaxy’s most dynamic star forming regions. A team led by Dr. Qizhou Zhang from the Center for Astrophysics | Harvard & Smithsonian used the Atacama Large Millimeter/submillimeter Array (ALMA) to conduct the largest and most detailed survey to date of magnetic fields in 17 regions where clusters of massive stars are forming. These observations, reaching down to just a few thousand astronomical units (about 10 times the distance from the Sun to Pluto) offer the first statistical insight into how the invisible forces of magnetism and gravity wrestle and shape the formation of stars deep within giant molecular clouds.

Star formation requires gas in space to be squeezed to densities more than ten trillion times greater than what’s typically found in interstellar clouds. But this epic collapse isn’t driven by gravity alone—magnetic fields and turbulence both push back, resisting the pull. For decades, astronomers have debated which force dominates as gas clouds shrink and stars ignite.

New ALMA observations by Zhang’s team have provided crucial answers. By measuring how the directions of magnetic fields change at different distances from young protostars, the researchers found that as gas becomes denser, gravity begins to win this cosmic tug-of-war. Magnetic fields, which start out mainly resisting gravity, are gradually pulled into alignment with infalling gas, showing a clear sign that gravity takes over as the leading force shaping the collapsing cloud.

This study marks the first time astronomers have statistically traced how magnetic fields behave as gravity pulls a star-forming cloud inward at precise measurements, in thousands of astronomical units, across a large sample of massive cluster-forming regions. The findings revealed a surprising pattern: the magnetic field orientations do not just occur randomly. Instead, they show two preferences: sometimes lining up with the direction of gravity, or sometimes perpendicular—evidence for a complex and evolving relationship between these two cosmic forces.

“With ALMA’s extraordinary sensitivity and resolution, we can now probe these cosmic birthplaces in unprecedented detail,” said Zhang. “We see that gravity actually reorients the magnetic field as clouds collapse, offering new clues about how massive stars—and the clusters they inhabit—emerge from the interstellar medium.”

Understanding how stars form is fundamental to almost every field of astronomy, shaping everything from the origins of our own Sun to the evolution of galaxies. This work not only settles long-standing debates about the relative importance of magnetic fields and gravity in massive star formation, but also gives scientists powerful new tools to test and refine theories about the life cycles of stars, planets, and cosmic clouds.

As the largest ALMA polarimetric study of its kind, this project sets a new standard for understanding both the visible and invisible components of our galaxy. The results reveal that while magnetic fields shape star-forming clouds, gravity ultimately takes the lead in birthing the most massive stars—an insight made possible by ALMA’s cutting-edge technology.

Link



About NRAO

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

About ALMA

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.


Finding Avatar’s Pandora: Exomoons with Astrometry

Illustration of a giant planet with a large moon orbiting a distant star.
Credit:
NASA/ESA/L. Hustak


Authors: Kevin Wagner et al.
First Author’s Institution: University of Arizona
Status: Published in ApJL

Six of the eight planets in our solar system host at least one moon; the innermost planets Mercury and Venus are the exceptions. The origins of these moons are widely studied and hotly debated. Earth’s very own moon seems to have formed in the aftermath of a collision between the young Earth and another protoplanet. Mars seems to have captured two asteroids as its moons, Phobos and Deimos, a process thought to have produced many of the irregular satellites orbiting the gas giants as well. Using our solar system as a model, the presence of moons seems like a natural outcome of planet formation.

Why then don’t we observe exomoons, moons orbiting any of the ~6,000 known exoplanets? Well, the largest moon in our solar system, Ganymede, is 2.5% as massive as Earth and has 40% of the radius, making it marginally larger than Mercury but still less massive. You might have heard how difficult it is to find Earth-like exoplanets, and finding exomoons is even harder. A few exomoon candidates have been announced via microlensing and transits, but the authors of today’s article investigate whether a different technique, astrometry, could help find moons.

Astrometry involves precisely tracking the positions of objects like stars or planets on the sky. In a simple star–planet system, the star and planet trace out ellipses around their shared center of mass. With a moon present, there is an additional deviation, as the planet wobbles to and fro due to the gravitational tug of the moon. The authors of today’s article check whether moons can be detected by tracking such wobbles exhibited by directly imaged planets.

To start, the authors consider whether any known planets are promising targets for astrometric moon searches. There just so happens to be a giant planet candidate in Alpha Centauri, and if there were a massive moon orbiting this large planet around this nearby star, it would be as good as it gets. The authors simulate orbits of this system (a Saturn-like planet in a 1.8 au orbit around a Sun-like star at a distance of 4.2 light-years) with a 30-Earth-mass moon injected. They simulate observing such a system with a space-based 6.5-meter telescope (similar to the planned Habitable Worlds Observatory) with realistic noise over a 3-year observing campaign. The simulated and modeled orbits are shown in Figure 1. After the authors subtract the best-fit planet orbit, they are left with what is shown in Figure 2, where a clear periodic perturbation from the moon as it orbits is visible.

Figure 1: Left: The zoomed-out orbit of the hypothetical Alpha Centauri star–planet–moon system. The blue curve shows the Keplerian orbital fit. Right: The zoomed-in orbit. The red points are the simulated observations, showing deviations caused by the moon. Credit: Wagner et al. 2025

Figure 2: Left: Deviations in position of the planet’s orbit over time. The red points show the simulated observations, and the black curve shows the data smoothed. Right: Zoom-in showing the moon’s effect on the planet’s motion. Adapted from Wagner et al. 2025


The authors then repeat this procedure with more realistically sized moons and a more optimistic observing campaign (5-year baseline, 1-hour observing cadence, precision of 0.1 milliarcsecond) looking at the Alpha Centauri giant planet candidate. They use the difference in the chi-squared (χ2) test statistic to determine whether the presence of a moon is statistically preferred. Figure 3 shows the moon-induced deviations for two different moon masses and the resulting χ2 difference. Using their χ2 difference threshold of ~5, the lowest-mass detectable moon is ~0.2 Earth mass. This is much more massive than the Moon, which is around 1% of Earth’s mass. The authors additionally vary the moon’s orbital period and find that periods of 4–30 days are detectable.

Figure 3: Left: Moon-induced planet position deviations over the first 90 observing days. Middle: Deviations from the entire 5-year observing baseline folded around the best-fit moon orbital period. Right: χ2 difference as a function of period, showing a peak in the signal at the moon’s orbital period. Adapted from Wagner et al. 2025


The authors continue to consider more specific observing scenarios: a 39-meter ground-based telescope (similar to the planned European Extremely Large Telescope) and a 3-meter space telescope built specifically to find moons. They find that the ground-based telescope observing once per day could detect an Earth-mass moon around a Saturn-like planet over a 5-year observing campaign. The dedicated space telescope observing once per hour could make the same detection observing over 5 years. While detecting moons astrometrically is neither easy nor fast, it may be feasible to start finding moons around planets orbiting nearby stars in the coming decades.

All of this is great news for fans of the hit movie (and still the highest-grossing movie of all time) Avatar, which features a habitable exomoon in the Alpha Centauri system. Searching for moons will help us understand their properties and formation, probe whether our solar system is unique, and even look for life on rocky moons orbiting gas giants in the habitable zones of their stars.

Original astrobite edited by Ryan White.




About the author, Kylee Carden:

I am a PhD student at Johns Hopkins University, where I am an observer of planets outside the solar system. I’m interested in dynamics, disks, demographics, the Roman Space Telescope. I am a huge fan of my cat Piccadilly, cycling, and visiting underappreciated tourist sites.



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