Features RSS

collage of multiple illustrations and images

There’s been a lot of astronomy in the news lately! Many recent news stories have featured research published in the AAS journals, so today we’re taking a look at four research articles that have recently gotten attention from the media.

New Horizons Navigates by the Stars

Starting closest to home, the first article describes a technological demonstration that took place on the edge of our solar system. In the nearly 20 years since its launch, the New Horizons spacecraft has ventured from Cape Canaveral to its current berth in the Kuiper Belt, roughly 61 au (5.7 billion miles or 9.1 billion kilometers) from Earth. In that time, New Horizons became the first spacecraft to venture close to Pluto and its moons as well as a second Kuiper Belt object called Arrokoth.

images of Proxima Centauri and Wolf 359 from New Horizons and from Earth

The difference in the position of Proxima Centauri (top row) and Wolf 359 (bottom row) as seen from New Horizons (left column) and Earth (right column) is evident by eye. [Adapted from Lauer et al. 2025]

New Horizons has also traveled a large enough distance for nearby stars to shift their positions relative to the background of more distant stars, enabling a measurement of the spacecraft’s position in space. Tod Lauer (NSF National Optical Infrared Astronomy Research Laboratory) and collaborators demonstrated this ability using New Horizons Long Range Reconnaissance Imager (LORRI) observations from April 2020, when the spacecraft was 47 au from the Sun. The stars used for the parallax measurements were Proxima Centauri and Wolf 359, two of the nearest stars to Earth. The team measured the stars’ positions relative to the positions of background stars and compared the results to observations made from Earth.

From the apparent shift in position of the two stars, the team determined the location of the spacecraft in space as well as the error in their measurement. They were able to ascertain the position of the spacecraft to within 0.44 au of its true position.

Though this measurement is far less accurate than localization with the Deep Space Network, it’s still an important step toward understanding the future prospects for autonomous spacecraft navigation via the stars. Looking ahead to future interstellar navigation systems, the team showed that measurements of a few nearby stars (Proxima Centauri and Barnard’s Star are the best bets for journeys within tens of thousands of astronomical units of the Sun) are more useful than measurements of a larger number of more distant stars. Basing measurements on a larger number of images to cut down on random scatter in the position of the star would also improve the results, as would simply using newer instruments. Ultimately, other types of navigation systems, such as those based on measurements of pulsars, are more likely to reach the precision necessary for autonomous spacecraft navigation. However, this method remains interesting, given that the straightforward nature of the imaging and analysis is already well within the capabilities of modern spacecraft systems.

First Detection of Semiheavy Water Ice Around a Low-Mass Protostar

Next up is a discovery from 457 light-years away in the Taurus molecular cloud. With a mass of 0.3–0.5 solar mass, a disk spanning 75–125 au, and a surrounding envelope of 0.9 solar mass, the isolated low-mass protostar L1527 is likely to grow into a star of similar mass to the Sun. That makes it an excellent target for investigating how planetary systems like our own acquire critical molecules like water.

Katerina Slavicinska (Leiden Observatory) and coauthors used JWST to search L1527 for semiheavy water (HDO) — a water molecule in which one of the hydrogen atoms is replaced with a deuterium atom. HDO has been detected in many locations throughout our solar system, including in Earth’s oceans, and water in our solar system tends to contain a high abundance of HDO molecules. A high deuterium abundance can be linked to formation in a cold environment, suggesting that our solar system’s water may have formed in the icy clouds out of which the Sun and the planets were born.

JWST spectrum of L1527

JWST spectrum of L1527. [Slavicinska et al. 2025]

Thanks to JWST’s high resolution and sensitivity, Slavicinska’s team was able to detect HDO ice in L1527, where previous, lower-resolution observations had only hinted at the presence of the molecule. They also measured emission from H2O ice, yielding a ratio of the abundances of the two types of water. The ice HDO/H2O ratio of L1527 is consistent with the gas HDO/H2O ratios of other isolated low-mass protostars and 4–7 times higher than the gas HDO/H2O ratios of clustered low-mass protostars.

plot of the ratio of semiheavy water to water for various solar system objects and protostars

HDO/H2O ratios for various solar system objects and protostars. Click to enlarge. [Slavicinska et al. 2025]

This difference may be due to differences in the star-forming environments of clustered protostars, or it may signal that the water in these protostars underwent gas-phase processing at some point. If environmental factors are the cause, that would suggest that L1527 should have a higher HDO/H2O ratio than objects in our solar system, since the Sun likely formed in a cluster environment.

This study demonstrates JWST’s ability to investigate the chemistry of young stars and probe the chemical evolution of protostars and planetary systems. Slavicinska and coauthors identified two important next steps to advance our understanding of the chemistry of star- and planet-forming environments: 1) measuring gas-phase and ice-phase HDO/H2O ratios in the same object to understand how gas-phase chemistry alters water around protostars and 2) measuring the HDO/H2O ratios of larger samples of isolated and clustered protostars in order to understand the impact of environmental factors.

A Massive Planet Approaches Its Doom

TOI-2109b is an ultra-hot Jupiter exoplanet that orbits its host star every 16 hours, giving it the shortest period of any known hot Jupiter. Orbiting its host star so closely, TOI-2109b is susceptible to powerful tidal forces that can lead to an exchange of angular momentum between the planet and its home star, potentially causing the planet to spiral inward and be engulfed by its star.

orbital periods, temperatures, and radii of ultra-short-period hot Jupiters

Comparison of the orbital period, temperature, and radius of TOI-2109b to other ultra-short-period Jupiters. [Alvarado-Montes et al. 2025]

Jaime Alvarado-Montes (Macquarie University) and collaborators investigated how and when TOI-2109b’s doom might come about. Critical to the discussion is the uncertain age of TOI-2109, which likely lies in the range of 1.09–2.65 billion years. If the star’s age is on the lower end of the range, TOI-2109b’s orbit would decay slowly (~4 milliseconds per year); if the star’s age is on the higher end of the range, the planet’s orbit would decay quickly (~1,100 milliseconds per year). The decay rate depends on the star’s age because planets lose their kinetic energy due to friction inside their host stars, and the efficiency of this process depends upon the interior structure of the star, which changes with age.

Alvarado-Montes and coauthors used data from the Transiting Exoplanet Survey Satellite (TESS), the CHaracterising ExOPlanet Satellite (CHEOPS), and multiple ground-based telescopes to constrain the rate of change of TOI-2109b’s orbital period. Taking into account changes in transit timing due to an outer planet candidate in the system, deviations from spherical symmetry, and other factors, the authors find a likely orbital decay rate of just 2.6 milliseconds per year. This is consistent with the rate predicted for a “young” host star, and it’s expected to shift TOI-2109b’s mid-transit time by a few seconds over a three-year period. This change is potentially detectable with high-cadence observations, helping to understand not just the fate of TOI-2109b, but of ultra-short-period planets as a whole.

Discovery of a Mysterious Long-Period Transient

Finally, Fengqiu Adam Dong (National Radio Astronomy Observatory; Green Bank Observatory) and coauthors recently described their discovery of an unusual long-period transient radio signal. Long-period radio transients exhibit signals that repeat with periods ranging from 10 seconds to multiple hours. While the exact origin of these signals remains unknown, researchers suspect that magnetic white dwarfs and neutron stars are the cause, with the two sources perhaps representing different classes under the long-period radio transient umbrella.

The signal was detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope, which was searching for bursts of radio emission from pulsars within our galaxy. The newly discovered radio signal, which comes from a source named CHIME J1634+44, has a primary period of 841 seconds and a secondary period of 4,206 seconds, making it decidedly un-pulsar-like. Dong’s team performed follow-up observations of CHIME J1634+44 with the Very Large Array, the Neil Gehrels Swift Observatory, and the Green Bank Telescope. The Very Large Array and the Green Bank Telescope each detected two bursts from the source, bringing the total number of bursts reported in this study to 89.

images of CHIME J1634+44

Continuum images of CHIME J1634+44 from the Very Large Array. The two panels show the autocorrelation function of the left-hand (left) and right-hand (right) circularly polarized components of the signal. CHIME J1634+44 is only detected in one of these two images, which suggests a 100% circularly polarized signal. [Dong et al. 2025]

CHIME J1634+44 is unusual in a number of ways. Its emission is almost entirely circularly polarized, meaning that the plane in which the electric and magnetic waves of the radio signal oscillates rotates in a circle as the signal travels through space. The time between pulses is also decreasing, slowly but steadily. If the pulsation period coincides with an object’s spin period, this means that the object is spinning faster as time goes on; this could occur if the source of the bursts is accreting material from a companion. If instead the pulsation period is linked to the orbital period of an object in a binary system, emission of gravitational waves could be causing the orbit to shrink.

What kind of object could produce this signal? Dong and coauthors considered binary systems containing either a white dwarf or a neutron star. Neither scenario perfectly fits the available evidence, but the team concluded that a binary system containing a neutron star is the likeliest source of the long-period, highly polarized, steadily accelerating pulses of CHIME J1634+44. The strongest evidence in favor of this scenario is that neutron stars are known to exhibit strongly polarized pulses of similar luminosity to those from CHIME J1634+44. Dong’s team expects that CHIME J1634+44 will remain an important test of theories of long-period radio transients — and as new information emerges about its identity, CHIME J1634+44 might just find its way into the news again!

Citation

“A Demonstration of Interstellar Navigation Using New Horizons,” Tod R. Lauer et al 2025 AJ 170 22. doi:10.3847/1538-3881/addabe

“HDO Ice Detected Toward an Isolated Low-Mass Protostar with JWST,” Katerina Slavicinska et al 2025 ApJL 986 L19. doi:10.3847/2041-8213/addb45

“Orbital Decay of the Ultra-Hot Jupiter TOI-2109b: Tidal Constraints and Transit-Timing Analysis,” Jaime A. Alvarado-Montes et al 2025 ApJ 988 66. doi:10.3847/1538-4357/ade057

“CHIME/Fast Radio Burst Discovery of an Unusual Circularly Polarized Long-Period Radio Transient with an Accelerating Spin Period,” Fengqiu Adam Dong et al 2025 ApJL 988 L29. doi:10.3847/2041-8213/adeaab

Through detailed simulations of gas and dust, a recent study revealed that the behavior of dust within protoplanetary disks is a bit more complex than previously assumed.

Dust Traps in Protoplanetary Disks

As a planet forms within a protoplanetary disk — dust and gas orbiting a new star — tidal interactions between the budding body and the dusty material surrounding it can create pressure bumps where dust builds up. These dust traps appear as rings in observations of protoplanetary disks.

Dust traps are thought to play a critical role in the disk’s evolution and the early stages of planet formation. Dust traps may prevent solid material from migrating inward, starving the inner disk and impeding planet growth interior to the trap. These reservoirs may also serve as a chemical barrier, keeping volatile materials like water from moving to the inner regions of a disk.

While a perfect dust trap completely isolates material from the rest of the disk, recent observations and 2D simulations have shown that dust traps may be a bit more permeable — leaking smaller sized grains, mixing material, and changing the disk’s appearance. However, these results only account for two dimensions of the complex three-dimensional environment in which dust traps reside. Thus, 3D hydrodynamical simulations are necessary to provide more realistic details of dust dynamics within planet-hosting protoplanetary disks. 

Dusty Simulations

Dust-gas density ratios for 3d models at 1500 orbits

Z-axis averaged dust–gas density ratios (top) and dust–gas surface density ratios for the 3D simulations after 1,500 orbits. For the simulations with higher diffusion and lower planet mass, there is clear leaking of dust beyond the dust trap ring (edges marked with dotted red lines). Click to enlarge. [Huang et al 2025]

In a recent study, Pinghui Huang (Chinese Academy of Sciences; University of Victoria) and collaborators performed multiple 2D and 3D numerical simulations of gas and dust within a protoplanetary disk with a forming planet. The simulations varied the mass of the planet and the level of turbulent diffusion — how well material and energy flow and mix within the gas. These variations allowed the authors to explore how dust traps behave within different types of systems. 

The simulations showed that the embedded planet will perturb the gas and dust, producing density shocks that create gaps and, subsequently, pressure bumps where dust traps coalesce. From their analysis, the authors found that dust traps become leakier at higher levels of diffusion and when the embedded planet is lower in mass. Essentially, if the gas flows and mixes more efficiently, the perturbations of the planet are erased more quickly, and if the planet is sufficiently small, its ability to disrupt the disk is much weaker. Dust remains coupled to the gas, flowing through these weak traps without becoming stuck. Additionally, the 3D simulations show higher amounts of leakage compared to the 2D simulations, which the authors attributed to the asymmetric and complex vertical geometry of the disk.

Trapping over time.

Flux-trapping ratio (left) and mass-trapping ratio (right) as a function of time for the 2D (top) and 3D (bottom) simulations. The higher-mass planet in Model A causes more flux and mass-trapping than the lower-mass planets and more turbulent systems. Additionally, the 3D simulations show significantly lower flux and mass-trapping than the 2D simulations. Click to enlarge. [Huang et al 2025]

Implications and Comparison to Observations

What then are the consequences of leaky dust traps? In planet formation theory, dust traps determine the mass at which a planet creates a sufficient pressure bump that isolates small pebbles and dust exterior to its orbit. For perfect dust traps, this isolation of material from the planet and inner disk creates a clear chemical distinction between the inner and outer disk. However, as shown by the 3D simulations, dust traps are imperfect, allowing small particles to filter through; the authors suggest this may mean that the growing planet slows but does not stop the migration of solid materials in a disk.

Recent observations of protoplanetary disks reveal the presence of larger volatiles within the inner disk. Specifically, the disk PDS 70 shows water emission in its inner disk despite having two confirmed giant planets orbiting in the outer disk. Without leaky dust traps, volatiles like water would be trapped in the pressure bumps created by these planets. However, as the authors have shown, the complex reality of dust dynamics within protoplanetary disks allows heavier elements to leak through, enriching the inner disk. Further observations and detailed 3D simulations will allow astronomers to understand the extent of leaky dust traps and reveal the realistic conditions driving early planet formation.

Citation

“Leaky Dust Traps in Planet-Embedded Protoplanetary Disks,” Pinghui Huang et al 2025 ApJ 988 94. doi:10.3847/1538-4357/addd1f

Betelgeuse and its companion star

Astronomers may have directly imaged a companion star to the famous red supergiant Betelgeuse at last. Though the tentative detection only loosely constrains the star’s physical properties, it appears to be a 1.6-solar-mass pre-main-sequence star. The discoverers suggest the name Siwarha, Arabic for “Her Bracelet,” given that the star circles Betelgeuse, “Hand of the Giant.”

Betelgeuse in the Spotlight

constellation Orion

A photograph of the constellation Orion. Betelgeuse is the bright yellow star located left of center. [E. Slawik/NOIRLab/NSF/AURA/M. Zamani; CC BY 4.0]

Situated at the shoulder of the constellation Orion, the red supergiant Betelgeuse is one of the most recognizable stars in the night sky. It’s also the subject of countless scientific studies and amateur observations that stretch back for centuries.

Betelgeuse is a variable star. On top of its well-constrained 400-day pulsation period, the star has exhibited two behaviors that have drawn interest in recent years: a deep, prolonged dimming episode in 2019–2022 that is thought to be due to an immense ejection of mass from the star’s surface, and a 6-year variation in the star’s photometry, astrometry, and radial velocity.

Multiple studies have attributed the 6-year variability to one or more companion stars. In general, these studies predict that the companion star circles Betelgeuse on a tight, 6-year, nearly edge-on orbit. As reported in a new article published in the Astrophysical Journal Letters, observations have likely proved these predictions correct.

Speckle Detection

Steve Howell (NASA Ames Research Center) and collaborators searched for Betelgeuse’s predicted companion star using the 8.1-meter Gemini North telescope. The team used the ‘Alopeke instrument in speckle imaging mode, which involves taking thousands of milliseconds-long snapshots to avoid smearing due to atmospheric fluctuations.

Betelgeuse and its companion star in observations

Observations of Betelgeuse from 2020 (left) and 2024 (right). An arrow points to the companion. Note that the image processing introduces a 180º ambiguity in the location of the companion, which is resolved by analyzing phase information. [Howell et al. 2025]

The team imaged Betelgeuse in 2020 and 2024. The 2020 observations coincided with when the companion star was predicted to lie behind Betelgeuse from our vantage point, and no companion appears in these images. The 2024 observations were taken just a few days after the companion’s predicted greatest angular separation from the star — and show evidence for a star just beside Betelgeuse.

More to Learn

Howell and coauthors performed additional analyses to rule out interference from hot pixels, cosmic rays, or atmospheric diffraction. They also considered that the star could lie in the background or foreground, but they found both possibilities unlikely. After further calculations, the team estimated that the companion is six magnitudes fainter than Betelgeuse and separated by just 52 milliarcseconds at an angle of 115º. These quantities agree well with predictions for the companion’s position.

location of Betelgeuse in 2020 and 2024

The on-sky proper motion of Betelgeuse from 2020 to 20204. The companion is shown as the small black circle. This shows that if the companion star were actually a background star, it would have been plainly visible in the 2020 observations. [Howell et al. 2025]

Given the tentative detection — at the level of 1.5σ — it’s difficult to pin down the properties of the companion star. The team placed the star’s mass between 1.4 and 2.0 solar masses, with the likeliest value being 1.6 solar masses. If the companion has the same age as Betelgeuse, this star would be on the cusp of joining the main sequence. However, it may never reach that stage of life; Betelgeuse’s demise in a core-collapse supernova is imminent, in the astronomical sense, and the companion may spiral in to merge with Betelgeuse even before then. (It currently orbits at just 4 au — closer than the distance between the Sun and Jupiter.)

The team closed with a call to the community to turn their instruments toward Betelgeuse on 26 November 2027, when the companion will once again be at its greatest angular separation. Our exploration of this long-sought-after star has just begun!

Citation

“Probable Direct Imaging Discovery of the Stellar Companion to Betelgeuse,” Steve B. Howell et al 2025 ApJL 988 L47. doi:10.3847/2041-8213/adeaaf

Milky Way center

New research shows that a past collision between the Milky Way’s central black hole and a smaller black hole could explain the dynamics of the S-stars, a group of stars that orbit precariously close to our galaxy’s supermassive black hole.

Journey to the Center of the Milky Way

The center of the Milky Way harbors a supermassive black hole (Sagittarius A* or Sgr A*) with a mass of 4 million Suns. The nearest neighbors of this behemoth are a compact disk of massive young stars and a collection of stars called the S-stars, which inhabit the innermost 48 light-days of our galaxy.

While the stars in the disk are orderly, arranged on orbits with moderate eccentricities and low inclinations, the S-stars orbit Sgr A* every which way, careening around the black hole with a wide range of eccentricities and inclinations. So far, the cause of this unusual distribution of stars is unknown.

When Black Holes Collide

Past research has struggled to explain the S-stars’ orbits. A successful theory of S-star origins must account for the stars’ eccentric orbits (e = 0.61, on average) and high orbital inclinations (i = 79º, on average), and it must produce these characteristics within the 15-million-year lifetime of the stars.

diagram showing the proposed formation pathway for the Milky Way's S-stars

Schematic showing the proposed formation pathway for the Milky Way’s S-star population. Click to enlarge. [Akiba et al. 2025]

In a recent research article, a team led by Tatsuya Akiba (University of Colorado Boulder) offered a new hypothesis to explain these traits: Sgr A* absorbed a smaller black hole in the not-so-distant past, and the aftermath of the merger created the distribution of stars seen today.

The premise is not far-fetched: at the ripe old age of nearly 14 billion years, the Milky Way has likely gulped down neighboring dwarf galaxies and globular clusters multiple times. When a black hole embedded within one of these meals of stars and gas merges with the Milky Way’s central black hole, the collision causes Sgr A* to recoil — potentially rearranging the stars in its vicinity in the process.

Radical Reorganization

Akiba and collaborators used N-body simulations to explore the outcomes of such a collision. In their simulations, Sgr A* is situated within an axisymmetric disk of stars or gas. A smaller black hole falls toward Sgr A*, spirals inward, and merges with the larger black hole. The asymmetric emission of gravitational waves causes Sgr A* to recoil, warping the surrounding collection of stars and gas into an eccentric disk. For the eccentricity of the disk to match what is seen in the disk of stars surrounding Sgr A* today, the incoming black hole must have a mass of roughly 200,000 solar masses.

simulation results

Simulation snapshots taken at the simulation onset (left column) and after 2 million years (right column). Orbits with inclination greater than 30 degrees are shown in magenta. Note the difference in scale between the rows. [Akiba et al. 2025]

After the merger, the stars orbiting farther out torqued the inclinations and eccentricities of the innermost stars up to high values through what’s called the eccentric Kozai–Lidov mechanism. After 2 million years of simulation time, this interaction produced a stellar distribution similar to what is seen today: a disk of moderate eccentricity surrounding “S-stars” with eccentric and highly inclined orbits.

While the properties of the modeled S-stars don’t exactly match the properties of the real deal — the simulated stars have, on average, lower inclinations and eccentricities — the authors noted that this work represents a first foray into their hypothesis. Modeling that explores a broader range of parameter space is needed to fully understand the origins of the stars at the center of the Milky Way.

Citation

“On the Formation of S Stars from a Recent Massive Black Hole Merger in the Galactic Center,” Tatsuya Akiba et al 2025 ApJL 987 L27. doi:10.3847/2041-8213/addc5d

Lagoon and Trifid Nebulae

Editor’s Note: Shortly after the publication of this article, we became aware that the disk described in this work was previously discovered by Wei-Hao Wang, as reported in the Astronomer’s Telegram in July 2024.

On 23 June 2025, the public got its first look at images from the NSF–DOE Vera C. Rubin Observatory — and the discoveries are already starting to roll in.

Trifid and Lagoon

Trifid Nebula closeup

A closeup of the Trifid Nebula from one of the Rubin Observatory first-look images. [Adapted from NSF–DOE Vera C. Rubin Observatory; CC BY 4.0]

One of the first-look images from Rubin features two photogenic star-forming regions in the Milky Way: the Trifid Nebula (Messier 20) and the Lagoon Nebula (Messier 8). The image, which was constructed from 678 exposures totaling 7.2 hours of observations, demonstrates Rubin’s ability to quickly cover large swaths of sky.

The Trifid and Lagoon nebulae are both HII regions, making them ideal places to search for circumstellar and protoplanetary disks, as well as proplyds — protoplanetary disks that are in the process of being evaporated by the intense radiation from nearby massive stars. The glowing gas of an HII region provides the background illumination needed to pick out the silhouettes of dark and dusty disks.

disk candidate

The Trifid Nebula disk candidate identified in this work. [Adapted from Zamani & Rector 2025]

Disk Detected

Published today in the Research Notes of the AAS, Mahdi Zamani (Zamani Scientific Visualizations & Imaging) and Travis Rector (University of Alaska Anchorage) reported the results of their search for proplyds in the Rubin image of the Trifid and Lagoon nebulae. The team detected one candidate circumstellar or protoplanetary disk on the edge of the Trifid Nebula, surrounded by tenuous, filamentary clouds of gas and dust.

The Rubin data don’t show evidence for ionized gas surrounding the disk, so it’s not yet clear if the object should be classified as a proplyd. The disk has a projected distance of 7.5 light-years from HD 164492A, the O-type star whose intense radiation is responsible for energizing the surrounding nebula, and may also be capable of ionizing the disk studied here.

Disk Detected

infrared image of the stars and protostars in the orion nebula

The Orion molecular cloud complex is among the most active star-forming regions in the Milky Way, home to hundreds of protostars and thousands of pre-main-sequence stars. [ESO/H. Drass et al.; CC BY 4.0]

This disk candidate is remarkable for both its size and location. With an estimated diameter of 4,000 au, it’s larger than most known circumstellar disks. Finding a disk outside the nearby Orion Nebula is also comparatively rare, since searches in more distant star-forming regions require finer resolution than the nearby Orion Nebula. (Orion is about 1,300 light-years away, and the Trifid Nebula is about 4,000 light-years away.)

Researchers have searched the Trifid Nebula previously for signs of protoplanetary disks, but while those searches found evidence for disks around hot stars near the center of the cluster, this particular disk candidate went undetected. Previous searches likely didn’t cover a large enough area of the nebula, or perhaps lacked the resolution needed to differentiate between the dusty disk and the nearby filamentary gas clouds. With Rubin’s broad field of view and precise resolution, the observatory was well-positioned to spot this disk candidate.

Citation

“The Potential Discovery of a Circumstellar Disk in M20 from Rubin First Look,” Mahdi Zamani and T. A. Rector 2025 Res. Notes AAS 9 172. doi:10.3847/2515-5172/ade982

Infinity Galaxy

Researchers have discovered a rare ring-galaxy duo that appears to harbor a supermassive black hole formed through direct collapse — a process similar to what may have jump-started the growth of the first supermassive black holes in the universe.

Searching for Oddballs

To find something remarkable, sometimes you have to go looking for it. As described in an article published today in the Astrophysical Journal Letters, a research team led by Pieter van Dokkum (Yale University; Dragonfly Focused Research Organization) recently struck gold in their search for unusual objects.

Van Dokkum and coauthors searched for interesting objects in publicly available images from COSMOS-Web, a JWST program dedicated to understanding how galaxies have evolved over the course of cosmic history. Having already published their discovery of a complete Einstein ring in the COSMOS-Web field, the team is now revealing a second finding: a galaxy featuring two bright, compact nuclei, two starry rings, and an unexpected inhabitant right in the center.

four views of the Infinity Galaxy

Four views of the Infinity Galaxy from Hubble and JWST. [van Dokkum et al. 2025]

Gathering Data

To learn more about this strange object, named the Infinity Galaxy for its resemblance to the infinity symbol, the team gathered data from the Hubble Space Telescope, the Keck I telescope, the Chandra X-ray Observatory, and the Very Large Array. The resulting multiwavelength portrait allowed the team to weigh the two nuclei, showing them to be massive — containing 80 billion and 180 billion solar masses of stars — and extremely compact. The new data also revealed that the cloud of gas between the nuclei contains a 1-million-solar-mass black hole.

The nuclei, the rings, and the gas between them appear to be the result of two disk galaxies that shot through one another, forming a pair of collisional ring galaxies. To achieve the infinity-symbol shape, the galaxies must have met one another face on, forming two parallel nucleus–ring systems that we see from an angle of about 40º. As the galaxies collided, some of their gas would have been torn away, left tangled together in the void between the two nuclei.

To the Infinity Galaxy and Beyond

radio and X-ray observations of the Infinity Galaxy

Radio (left) and X-ray (right) observations of the Infinity Galaxy, demonstrating that the black hole candidate is a strong radio and X-ray source. Click to enlarge. [Adapted from van Dokkum et al. 2025]

That explains the nuclei, the rings, and the gas between them — but where did the black hole come from? It’s possible that the black hole’s position between the two nuclei is simply a coincidence, either due to a chance alignment with an unrelated galaxy that hosts the black hole, or because the black hole happened to end up there after being ejected from one of the galaxies involved in the collision, or even from another galaxy that merged with the Infinity Galaxy.

The authors favor a different explanation, in which the location of the black hole is no coincidence. In this scenario, the colliding galaxies crushed a gas cloud between them so forcefully that the condensed gas collapsed directly into a black hole. The authors estimated that the collision happened 50 million years ago and created a 300,000-solar-mass black hole that subsequently grew to its current mass of 1 million solar masses. Direct collapse has been proposed to be a source of the seeds of supermassive black holes in the early universe, though there are some differences between the proposed process in the early universe and what may be happening in the Infinity Galaxy.

Van Dokkum and collaborators concluded their article by saying that future observations could clarify whether the black hole is truly associated with the Infinity Galaxy — and as reported in a press release today, preliminary analysis of follow-up observations with JWST show just that. With the black hole now definitively placed within the Infinity Galaxy, the evidence for direct collapse is strengthened, though more work is needed to probe this possibility.

Citation

“The ∞ Galaxy: A Candidate Direct-Collapse Supermassive Black Hole Between Two Massive, Ringed Nuclei,” Pieter van Dokkum et al 2025 ApJL 988 L6. doi:10.3847/2041-8213/addcfe

Falling into a supermassive black hole will leave a star mangled and destroyed but not without a fiery end. A recent study explores an intriguing case, uncovering new possibilities for stars lost to black hole bites.

Tidal Disruption Events

Invisible in light but strong in gravitational influence, some supermassive black holes reveal themselves when a star comes close enough to be ripped apart by the black hole’s tidal forces. This violent encounter produces a flare of radiation known as a tidal disruption event, allowing astronomers to explore the otherwise hidden properties of supermassive black holes and their influence on the material around them. 

Tidal disruption events vary depending on the properties of the host galaxy, the supermassive black hole, and the star itself. These events often appear as X-ray flares, but over the past decade, researchers have discovered a new class of optical-ultraviolet tidal disruption events. Emitting primarily in ultraviolet and optical wavelengths, these flares are significantly less energetic than predicted, leaving researchers wondering — what drives these disruptions?

Optical and ultraviolet light curves for the two observed flares of AT 2022dbl. The flares have very similar light curves across wavelengths. Click to enlarge. [Makrygianni et al 2025]

Origins of AT 2022dbl

New detections of optical-ultraviolet tidal disruption events can provide insights into their origins, and one such discovery is particularly intriguing. AT 2022dbl first flared in 2022 and emitted a second, nearly identical flare 700 days later in 2024 — behavior uncommon among this class of tidal disruption events — raising many questions about AT 2022dbl’s origins. Did this supermassive black hole perhaps capture two unrelated stars? Is this actually the same flare seen twice due to gravitational lensing? Could a single star have survived the first flare only to be disrupted again?

Lydia Makrygianni (Lancaster University) and collaborators performed follow-up imaging and spectroscopy of AT 2022dbl to probe how the two flares compare to each other and to other observations of optical-ultraviolet tidal disruption events. With these observations and detailed analysis, the team determined that gravitational lensing, the tidal disruption of two separate stars, and even the possibility of a hidden binary companion to the supermassive black hole slurping up some stellar crumbs each cannot account for the two flares of AT 2022dbl.

Ultimately, the authors concluded that the two flares of AT 2022dbl are related to the same star, leaving two possibilities. First, loose debris from the initial flare bound to a tidal tail around the black hole could have ignited the second flare; however, the authors found that there would not be enough loose material bound to the black hole to produce the bright second flare. Rather, the second and likeliest explanation is two repeated disruptions of the same star.

Disrupting Expectations

Light curves of AT 2022dbl flares compared to other optical-ultraviolet tidal disruption events. Both flares show similar peak luminosities and decline rates to other events. Click to enlarge. [Makrygianni et al 2025]

Assuming that the two tidal disruption events are from the same star, this implies that the first flare was a partial disruption, removing only some material without destroying the star entirely. The second flare could be a complete disruption or another partial disruption, but observations of a third flare in 2026 would be necessary to confirm this. 

Other optical-ultraviolet tidal disruption events appear similar to the flares of AT 2022dbl, and these have generally been assumed to be complete disruptions. With the discovery and classification of AT 2022dbl, the similar optical-ultraviolet tidal disruption events could also be partial disruptions, with their second flares on longer timescales yet to be observed. Future observations of optical-ultraviolet tidal disruption events are required to further understand the mechanisms driving them, and this study opens up new possibilities to consider. 

Citation

“The Double Tidal Disruption Event AT 2022dbl Implies that at Least Some ‘Standard’ Optical Tidal Disruption Events Are Partial Disruptions,” Lydia Makrygianni et al 2025 ApJL 987 L20. doi:10.3847/2041-8213/ade155

solar wind

Spacecraft scattered throughout the solar system keep tabs on the solar wind, but the measurements are dotted with data gaps. How can scientists prevent these gaps from biasing their studies of the solar wind?

Sampling the Solar Wind

intracluster medium

Left: the distribution of hot gas between the galaxies in the cluster Abell 2029. Right: the visible light from the galaxies in the cluster. [X-ray: NASA/CXC/UCI/A.Lewis et al. Optical: Pal.Obs. DSS]

The solar wind is a tenuous, fast-moving, turbulent plasma that constantly streams out from the Sun. Studying the solar wind is important for understanding how potentially damaging space weather events like coronal mass ejections travel through the solar system. Solar wind studies also have far-reaching implications, since solar-wind-like plasmas exist throughout the universe, such as in the sparse medium between galaxies in a cluster.

Luckily, there are many spacecraft that sample the solar wind from various locations within our solar system. Unluckily, many of these spacecraft do not continuously monitor the solar wind. For example, when a spacecraft orbiting a planet dips into the planet’s atmosphere, this detour creates an hours-long gap in solar wind monitoring.

The Impact of Data Gaps

How do these data gaps affect studies of the solar wind? In a recent research article, Daniel Wrench and Tulasi Parashar (Victoria University of Wellington) approached this question in terms of how gaps affect the structure function: a mathematical description of how the solar wind fluctuates over different length or time scales.

Wrench and Parashar introduced random artificial gaps into data from the Parker Solar Probe, which monitors the solar wind continuously, and compared the structure functions calculated from the continuous and interrupted data sets. They used the difference between the true structure function — calculated from the continuous data set — and the structure functions from the artificially gapped data sets to develop a correction factor.

bar plot of correction method performance

Performance of the correction factor method (black) compared to the uncorrected, gapped data (red) or gaps filled using linear interpolation (blue). MAPE is the mean absolute percentage error. [Wrench & Parashar 2025]

The team then tested their correction factor using data from the Wind spacecraft, which continuously monitors the solar wind from the L1 Lagrange point. The team calculated the structure function from 1) the continuous data set, 2) the artificially gapped data, 3) the gapped data with linear interpolation used to fill the gaps, and 4) the gapped data with the correction factor applied. This test showed that the correction factor performs better than other commonly used gap-handling methods, such as linear interpolation, which can systematically underestimate the structure function. Using the correction factor, the error in the structure function remained below 50% even when 95% of the data were missing.

plot of structure function from Voyager 1 data

Structure function calculated from uncorrected Voyager 1 data (red), linearly interpolated data (blue), and corrected data (black). Both the linear interpolation method and the correction factor method remove the artifact around a lag of 3×104 seconds, but the correction factor method does not suppress the signal like the linear interpolation method does. [Adapted from Wrench & Parashar 2025]

Correcting Voyager 1

Finally, the authors applied their validated method to data from Voyager 1. Data from the two Voyager spacecraft are extremely scientifically valuable — no other spacecraft have ventured as far from the Sun and can measure the solar wind at such large distances. The data are also extremely sparse; one segment used in this work was missing 85% of the data. This means that an effective method of correcting these data has potentially huge scientific significance.

Wrench and Parashar applied their correction factor to the Voyager 1 data, showing that this method handily removes artifacts while avoiding the underestimation introduced by linear interpolation. While the authors saved the interpretation of the newly corrected Voyager 1 data for future research, this study makes it clear that even large data gaps needn’t hinder studies of the solar wind.

Citation

“Debiasing Structure Function Estimates from Sparse Time Series of the Solar Wind: A Data-Driven Approach,” Daniel Wrench and Tulasi N. Parashar 2025 ApJ 987 28. doi:10.3847/1538-4357/addc6a

Illustration of Jupiter and a Jupiter-like exoplanet

Of the nearly 6,000 currently known exoplanets, few closely resemble any of the planets in our solar system. New research suggests that JWST is capable of directly imaging exoplanets with temperatures and orbital distances similar to Jupiter and Saturn, placing truly familiar exoplanets within our observational grasp.

Increasingly Cold Discoveries

Epsilon Indi Ab

A JWST image of the exoplanet Epsilon Indi Ab, one of the coldest exoplanets to be directly imaged. The planet’s temperature is estimated to be just 275K (35℉/2℃). [NASA, ESA, CSA, STScI, Elisabeth Matthews (MPIA)]

JWST has already proven itself to be a powerful tool to directly image exoplanet systems. The telescope has imaged increasingly cold planets, but the gas giants in our solar system are substantially colder than the coldest planet imaged by JWST so far. This raises the question of whether JWST is capable of directly imaging Jupiter and Saturn if they orbited another star.

Answering this question requires a deep dive into the abilities of JWST’s instruments. The current go-to method for directly imaging planets with JWST is coronagraphy with its Near-Infrared Camera (NIRCam). In this observing mode, the instrument blocks the light from the star, allowing the fainter thermal glow of the planet to shine through.

But as Rachel Bowens-Rubin (University of Michigan and Eureka Scientific) and collaborators note in a recent research article, this may not be the best way to detect cold giant planets. Models suggest that these planets have cloudy atmospheres, which means that they wouldn’t be bright at NIRCam’s preferred near-infrared wavelengths, and would instead be detected more easily in the mid-infrared, where JWST’s Mid-Infrared Instrument (MIRI) reigns.

Combining Data and Models

To examine the capabilities of both of these instruments, Bowens-Rubin’s team analyzed JWST observations from the Cool Kids on the Block program, which targets cold, low-mass giant planets around nearby low-mass stars with NIRCam coronagraphy and MIRI imaging. The team used observations of nearby M-dwarf stars Wolf 359 and EV Lac to construct constrast curves: the level of planet–star flux contrast that is detectable by each instrument as a function of distance from each star. These curves depend on the flux of the star and the planet as well as the limitations of the instrument — the detector noise and background noise.

plot of coldest planets detectable by MIRI and NIRCam

Temperatures of coldest detectable planets as a function of separation from the host star for Wolf 350 and EV Lac. Results are shown for MIRI F2100W imaging and NIRCam F444W coronagraphy. Click to enlarge. [Bowens-Rubin et al. 2025]

Bowens-Rubin and coauthors converted the contrast curves into information about the coldest planet each instrument can detect. To do this, the team modeled the atmospheres of planets with temperatures down to 50K and generated thermal emission spectra, which allowed them to relate the temperature of their modeled planets to the level of contrast.

NIRCam vs. MIRI

This analysis showed that MIRI is the best choice for directly imaging cold planets around nearby stars (within 65 light-years). MIRI should be able to detect giant planets with temperatures down to 94K around Wolf 359 and 114K around EV Lac — about the temperature of Saturn and slightly colder than Jupiter, respectively. For Wolf 359, sub-100K planets are detectable at orbital distances of at least 4.8 au, meaning these planets could also have similar orbital separations to Jupiter and Saturn.

plot coldest planets detectable by NIRCam and MIRI as a function of distance from Earth

Temperatures of planets detectable to a signal-to-noise ratio of 3 as a function of distance from Earth. Detection limits for MIRI and NIRCam are shown as red and blue lines, respectively. Click to enlarge. [Bowens-Rubin et al. 2025]

NIRCam coronagraphy can match MIRI’s performance only for the unlikely case of cloud-free giant planets; for cloudy planets around nearby stars, MIRI can spot planets 90–130K colder than NIRCam can. NIRCam has the advantage for more distant stars — beyond about 200 light-years — but only planets significantly warmer than Jupiter and Saturn are detectable at these distances.

As impressive as these results are already, Bowens-Rubin and coauthors noted that future work, such as developing strategies to mitigate MIRI’s “brighter-fatter effect” that limits sensitivity at small angular separations from the host star, could enhance the search for exo-Saturns and exo-Jupiters even further.

Citation

“NIRCam Yells at Cloud: JWST MIRI Imaging Can Directly Detect Exoplanets of the Same Temperature, Mass, Age, and Orbital Separation as Saturn and Jupiter,” Rachel Bowens-Rubin et al 2025 ApJL 986 L26. doi:10.3847/2041-8213/addbde

images from the Hubble Image Similarity Project

Motivated by a desire to support community members financially during the coronavirus pandemic, researchers employed 30 local citizen scientists in the Hubble Image Similarity Project. This project quantified the similarities between astronomical images, providing a way to test the results of image-search algorithms.

Seeking Similarities

Eagle Nebula

The Eagle Nebula, pictured here in an image from Kitt Peak National Observatory, is a star-forming region in the Milky Way. [T.A.Rector (NRAO/AUI/NSF and NOIRLab/NSF/AURA) and B.A.Wolpa (NOIRLab/NSF/AURA); CC BY 4.0]

Say you have an image of a star-forming region, featuring eye-catching gas clouds, dense and dusty knots, and newborn stars. How would you go about finding other images that resemble yours?

You might start your search with an astronomical image database, using filters for object type or instrument to sift through thousands and thousands of options. But even filtering out everything but star-forming regions might yield vastly different results, given the widely varying shapes, colors, and sizes of these regions.

Or maybe you’ll feed your image into a neural network that has been trained to spot similar images. The results may seem promising, but how can you tell whether the algorithm has found the images that are the most similar? Would another algorithm do better?

The Hubble Image Similarity Project

Astronomical image collections rarely contain information about similarities between images in their metadata, and while neural networks appear to excel at gathering similar images, the results of these models are generally unverified. The Hubble Image Similarity Project, led by Richard White (Space Telescope Science Institute) and Josh Peek (Space Telescope Science Institute and Johns Hopkins University), addressed these issues with a team of citizen scientists who generated similarity information for astronomical images, providing a quantitative means to test the results of neural networks.

example of how the Hubble Image Similarity Project selects image cutouts for study

An example of individual test images (green squares) extracted from a Hubble Legacy Archive image (red square). Low-contrast areas have been excluded, leaving the galaxy’s spiral arms for analysis. Click to enlarge. [White & Peek 2025]

White and Peek began by amassing a sample of images from the Hubble Legacy Archive. This sample included many different object types, such as galaxies, planetary nebulae, star-forming regions, and star clusters. After trimming and binning the images, converting them to 8-bit grayscale, filtering out low-contrast images, and eliminating satellite trails, image artifacts, and repeated observations of the same patch of sky, 2,098 images of 666 objects remained.

Citizen Scientists, Assemble

White and Peek recruited 30 members of the community within walking distance of the Space Telescope Science Institute to identify similar astronomical images, and the reviewers were paid for their work. In the three phases of the project, reviewers considered test images one at a time and 1) selected all similar images from a set of 15 comparison images, 2) selected the most similar image from a narrowed-down set of 6 comparison images, and finally 3) selected the most similar image from a set of 3 comparison images.

similar images from the Hubble Image Similarity Project and a visualization of the data

Examples of similar images according to the image similarity matrix. In the lower-right corner is a visualization of the similarity data. The semicircle of data points in the bottom half of this visualization represents galaxies, while star clusters occupy the small arc near the top and nebulae sit in the island in the center of the plot. Click to enlarge. [Adapted from White & Peek 2025]

The citizen science team ultimately compared 5.4 million pairs of images, and White and Peek used these comparisons to produce an image similarity matrix. The matrix describes the metaphorical “distance” between the images, with the most similar images being the smallest distance apart.

Similar images resemble one another in terms of structure, texture, and other factors that White and Peek say are “difficult even to describe in words” — for example, the diffuse glow of a galaxy interrupted by a bright star with diffraction spikes, or a nebula speckled with stars and dense dusty clumps. The similarity data from this study are available online and can be used to test the performance of image-search algorithms. In future work, the authors plan to carry out a similar project using images of the Martian landscape.

Citation

“The Hubble Image Similarity Project,” Richard L. White and J. E. G. Peek 2025 AJ 169 306. doi:10.3847/1538-3881/adcb43

1 … 7 8 9 10 11 … 118