Notice anything unusual about these galaxies? Each of the scenes above is crafted from observations from the Hubble Arp Galaxy Survey, which turned the talents of the Hubble Space Telescope toward 216 targets in the Arp and Arp–Madore catalogs. These catalogs contain galaxies that are visibly out of equilibrium, either caught in the middle of an interaction with another galaxy, sporting strange structures, or illuminated by brilliant starbursts. Julianne Dalcanton (Flatiron Institute; University of Washington), Meredith Durbin (University of Washington; University of California, Berkeley), and Benjamin Williams (University of Washington) designed the survey to create an archive of previously unobserved sources in these catalogs of peculiar galaxies. In addition to providing a new high-resolution view of these sources, the team hopes that the survey will serve as a launchpad for new investigations and complementary observations from facilities like JWST and the Atacama Large Millimeter/submillimeter Array. To learn more about the Hubble Arp Galaxy Survey and see more of the new images, be sure to check out the full article linked below.

Citation

“The Hubble Arp Galaxy Survey,” Julianne J. Dalcanton et al 2026 ApJS 283 25. doi:10.3847/1538-4365/adfc67

The post Featured Image: Disequilibrium on Display appeared first on AAS Nova.

The seemingly warped and stretched galaxies in the image above show the work of gravitational lensing, in which the powerful gravitational pull of galaxies or galaxy clusters bends the light from background objects. Xiaosheng Huang (University of San Francisco and Lawrence Berkeley National Laboratory) and coauthors have used a neural network to amass a sample of 3,500 gravitational lensing candidates in data from the Dark Energy Spectroscopic Instrument (DESI) Legacy Surveys. Now, the team has used the Hubble Space Telescope to confirm some of the most promising candidates. Four of the newly confirmed systems are presented in the image above, with the DESI data shown in color and the higher-resolution Hubble data in black and white. Huang and collaborators also demonstrated the ability of their forward-modeling pipeline, GIGA-Lens, to constrain lens properties rapidly, even for large images like those from Hubble. Ultimately, Huang and coauthors hope to identify lensing systems that can be used to search for low-mass dark matter halos and test our theories of cosmology, as well as those that can be monitored for signs of lensed supernovae — providing a way to measure the expansion rate of the universe. To learn more about this sample of gravitational lenses and what the team plans to do next, be sure to check out the full research article linked below.

Citation

“DESI Strong Lens Foundry. I. HST Observations and Modeling with GIGA-Lens,” Xiaosheng Huang et al 2026 ApJ 998 69. doi:10.3847/1538-4357/ae22d2

The post Featured Image: A Treasure Trove of Strong Lenses appeared first on AAS Nova.

In 1999–2000, the Hubble Space Telescope captured what was then the most detailed image ever taken of the Crab Nebula. In the quarter-century since the release of that image, the nebula — the remnant of a star observed to explode as a supernova in July 1054 — has been slowly unfurling and changing as the ejected stellar material expands into space. Now, as reported in a research article by William Blair (Johns Hopkins University) and collaborators, astronomers have turned Hubble’s inquisitive eye toward the Crab Nebula once again. One of the new images is shown above (click for the full view!). By comparing the new and old Hubble images, Blair’s team uncovered dramatic changes in the nebula’s intricate filamentary structure. These changes are due to the nebula’s three-dimensional expansion as well as evolution in the density of its knots and filaments. To learn more about the new Hubble portrait of the Crab Nebula, be sure to check out the full article linked below.

Citation

“The Crab Nebula Revisited Using HST/WFC3,” William P. Blair et al 2026 ApJ 997 81. doi:10.3847/1538-4357/ae2adc

The post Featured Image: Hubble Revisits the Crab Nebula appeared first on AAS Nova.

The disks of gas and dust that collect around young stars — protoplanetary disks — hold the secrets to how planets form. When a protoplanetary disk is tilted edge-on from our perspective, the disk’s dense, dusty midplane blocks the light from the star at the center, revealing structures like winds and jets wafting off of the disk. Pictured above and to the right is the spectacular edge-on protoplanetary disk IRAS23077+6707, which is also known as Dracula’s Chivito. (Delightfully, the name combines references to the backgrounds of two of the astronomers who identified the object as a protoplanetary disk: one hailing from Transylvania and another from Uruguay, where a sandwich called a chivito is the national dish.) Though the distance to this disk is not known, estimates place it around 1,000 light-years away, which would make the disk about 4,200 au across — larger than any other known protoplanetary disk. Recently, a team led by Kristina Monsch (Center for Astrophysics ∣ Harvard & Smithsonian) published their Hubble Space Telescope observations of Dracula’s Chivito. These observations show in great detail the structure within the disk, including large-scale asymmetries, wispy tendrils, and potential signs of dust grains settling toward the midplane. To learn more about this exceptional protoplanetary disk, be sure to check out the full research article linked below.

Citation

“Hubble Reveals Complex Multiscale Structure in the Edge-On Protoplanetary Disk IRAS23077+6707,” Kristina Monsch et al 2026 ApJ 996 45. doi:10.3847/1538-4357/ae247f

The post Featured Image: Hubble Samples a Dusty Cosmic Sandwich appeared first on AAS Nova.

Editor’s Note: For the remainder of 2025, we’ll be looking at a few selections that we haven’t yet discussed on AAS Nova from among the most-downloaded articles published in AAS journals this year. The usual posting schedule will resume January 2nd.

The Bullseye: HST, Keck/KCWI, and Dragonfly Characterization of a Giant Nine-ringed Galaxy

Published February 2025

Main takeaway:

Using a combination of the Hubble Space Telescope, the Dragonfly Telephoto Array, and the Keck Cosmic Web Imager, Imad Pasha (Yale University) and collaborators discovered and performed deep follow-up observations of a giant collisional ring galaxy aptly nicknamed the “Bullseye” galaxy (LEDA 1313424). The team identified a staggering nine rings in the Bullseye with a likely tenth that has since faded — the most rings found in any collisional ring galaxy to date. The rings are a result of a small blue dwarf galaxy shooting through the Bullseye’s core about 50 million years ago, sending ripples through the galaxy.

Why it’s interesting:

Galaxy mergers and interactions are commonplace in the universe, but it is very rare for a dwarf galaxy to strike right through a large galaxy’s core. When this does happen, the collision sends shock waves through the impaled galaxy, sweeping gas and dust outward and forming rings where star formation can occur (hence the name, collisional ring galaxy). These galaxies are valuable sites to explore galactic structure and evolution as well as provide a unique case to study galaxy mergers and interactions. Previously discovered collisional ring galaxies have at most two or three rings, so when Pasha and collaborators found the stunning nine in the Bullseye, it was clear they caught something significant.

Catching the Bullseye at a lucky time in its evolution:

Why does the Bullseye have so many rings? Theoretical studies of these head-on collisions predict that many rings will form and travel outward after the initial crash; however, the rings tend to dissolve after only a few hundred million years. Catching this collision only 50 million years after it happened means we are witnessing the earlier stages of the Bullseye’s evolution. This lucky discovery not only confirms theoretical predictions for collisional ring galaxies, it also may be a clue to how another unique galaxy type, giant low-surface brightness galaxies, originate. Given the wispy ring material found at very large radii from the Bullseye, the authors suggested that collisional ring galaxies may evolve into giant low-surface brightness galaxies as they expand outward and fade. Further investigation and a larger sample of collisional ring galaxies are necessary to confirm this hypothesis, but the Bullseye provides interesting and critical observational evidence of these predictions for the first time.

Citation

Imad Pasha et al 2025 ApJL 980 L3. doi:10.3847/2041-8213/ad9f5c

The post Selections from 2025: The Nine-Ringed Bullseye Galaxy appeared first on AAS Nova.

Editor’s Note: For the remainder of 2025, we’ll be looking at a few selections that we haven’t yet discussed on AAS Nova from among the most-downloaded articles published in AAS journals this year. The usual posting schedule will resume January 2nd.

Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS

Published August 2025

Main takeaway:

David Jewitt (University of California, Los Angeles) and collaborators used the Hubble Space Telescope to observe the interstellar object 3I/ATLAS just a few weeks after it was discovered. These observations allowed the team to constrain the object’s mass-loss rate and the size of its nucleus, placing its radius between 0.22 and 2.8 kilometers.

Why it’s interesting:

3I/ATLAS is just the third known object to visit our solar system from another planetary system. With such a small sample size, every interstellar object discovered is a source of fascination. Are these objects more like comets or asteroids? How many of them roam the space between the stars? What, exactly, launches them into interstellar space? Using all available tools, including powerful observatories like Hubble, researchers can extract as much information as possible when interstellar objects make their brief journeys through our solar system, and get us closer to answering these key questions.

How these observations were planned, and what happened afterward:

After interstellar objects 1I/ʻOumuamua and 2I/Borisov zipped through the solar system in 2017 and 2019, respectively, researchers knew it was only a matter of time before the next interstellar interloper paid a visit. In preparation for the next arrival, Jewitt’s team proposed a target-of-opportunity observation with Hubble. This allowed them to disrupt the telescope’s planned observing schedule once 3I/ATLAS was discovered, getting an early high-resolution look that could guide further observations. Since then, researchers have published more than 30 articles in the AAS journals alone about 3I/ATLAS. In these articles, researchers have sought to understand where 3I/ATLAS came from, investigated its polarization properties, collected JWST data of the object, found it in pre-discovery data, and much more, crafting a comprehensive view of a rare visitor to our neighborhood.

Citation

David Jewitt et al 2025 ApJL 990 L2. doi:10.3847/2041-8213/adf8d8

The post Selections from 2025: Hubble Observes 3I/ATLAS appeared first on AAS Nova.

Multiple research teams have turned to the famous red supergiant Betelgeuse in search of a possible companion star hiding in its glare. A carefully designed spectroscopic search has placed new constraints on the identity of Betelgeuse’s stellar buddy.

Betelgeuse and Its Buddy

Betelgeuse, a nearby red supergiant, is a variable star with a 400-day primary pulsation period and a 2,100-day secondary variation period. Recent studies have speculated that this secondary period is due to the presence of an 0.5–2.0-solar-mass companion star (often nicknamed “Betelbuddy”), and researchers using a speckle imaging technique likely spotted this companion earlier this year.

As is often the case when there’s an intriguing astronomical possibility, multiple research teams have sought out Betelgeuse’s purported stellar companion in different ways. One avenue recently described in a published paper was spectroscopic, searching for signs of ultraviolet emission lines from a growing young star.

Spectroscopic Search

In just 10 million years, Betelgeuse has sped through its main-sequence lifetime and taken on a new starring role as a red supergiant. In contrast, a 0.5–2.0-solar-mass companion star would not have even reached the main sequence in the same span of time. How is it possible to spot a tiny young stellar object next to a much brighter supergiant?

A team led by Jared Goldberg (Flatiron Institute) found a possible way forward in the far-ultraviolet, where young stellar objects and red supergiants both display prominent emission lines. Though Betelgeuse would greatly outshine its stellar buddy, the companion’s orbital motion should shift its emission lines relative to those of Betelgeuse, bringing them into view. To guide their search, the team consulted spectra of known young stellar objects, finding a dozen ultraviolet spectral lines that either rival the strength of those from Betelgeuse or aren’t present in Betelgeuse’s spectrum at all.

The search is on: Goldberg and collaborators observed Betelgeuse with the Hubble Space Telescope in November 2024, timed to when the companion star’s emission lines would be shifted relative to Betelgeuse. The observations split Betelgeuse’s disk into quadrants, only one or two of which should contain the companion, helping the team tease out the signal from the smaller star, if present. Ultimately, though, no statistically significant signals were found.

When Finding Nothing Tells You Something

A lack of a significant detection doesn’t mean that the companion isn’t there, but it does place constraints on its identity. The data confidently rule out a companion star twice as massive as the Sun, marginally permit a star in the 1.1–1.5-solar-mass range, and favor a star lower than 1.1 solar masses.

Researchers assigned a likely mass of about 1.5 solar masses to the probable companion star imaged earlier this year. Though this is at the limit of what’s permitted by the ultraviolet observations, Goldberg and coauthors note that the companion star’s ultraviolet output could be suppressed due to tidal coupling with Betelgeuse or other processes. If the star’s ultraviolet emission is lower than expected, a 1.5-solar-mass companion remains consistent with Hubble’s non-detection of the star.

This is a fantastic example of how multiple lines of inquiry can converge on similar solutions. With the companion star expected to swing around to a favorable observing position again in 2027, this is certainly not the last chapter in the tale of Betelgeuse and Betelbuddy.

Citation

“Betelgeuse, Betelgeuse, Betelgeuse, Betel-buddy? Constraints on the Dynamical Companion to α Orionis from HST,” Jared A. Goldberg et al 2025 ApJ 994 101. doi:10.3847/1538-4357/ae0c0c

The post Hubble on the Hunt: A Spectroscopic Search for Betelbuddy appeared first on AAS Nova.

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

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.

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.

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

The post Citizen Science Born in the Pandemic: The Hubble Image Similarity Project appeared first on AAS Nova.

The bright spot visible within its fuzzy host galaxy in the image above is the optical and infrared light from a superlative gamma-ray burst. Discovered in October 2022, GRB 221009A was the brightest gamma-ray burst ever observed by humans, and likely a once-in-ten-millennia event, earning it the nickname “the Brightest of All Time” or BOAT gamma-ray burst. This image shows the afterglow of this burst nearly a year after it exploded onto the scene. In a recent article, Huei Sears (Rutgers University) and collaborators analyzed Hubble and JWST observations made 185–345 days after the discovery of the burst. These observations captured the burst’s fading light and showed a distinct shift in the rate at which the light dimmed at around 50 days. This shift is evidence of powerful jets from the source of the burst. Sears’s team also discovered a blue component to the afterglow emission. This blue component may be due to the burst’s afterglow echoing off of dust in the host galaxy — if confirmed, this will mark the first time this feature has been detected. To learn more about what astronomers have discovered in the years since GRB 221009A was first spotted, be sure to check out the full research article linked below!

Citation

“Late-Time HST and JWST Observations of GRB 221009A: Evidence for a Break in the Light Curve at 50 Days,” Huei Sears et al 2025 ApJ 984 196. doi:10.3847/1538-4357/adc306

The post Featured Image: Hubble and JWST Check Up on the BOAT Gamma-Ray Burst appeared first on AAS Nova.

A newly-released Hubble image shows Messier 88, a black hole-powered spiral galaxy that is gradually plunging toward the crowded heart of the Virgo Cluster.

The post Hubble Captures Active Spiral Galaxy: Messier 88 appeared first on Sci.News: Breaking Science News.