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Highlights Archives - AAS Nova Research highlights from the journals of the American Astronomical Society Tue, 20 Oct 2026 15:55:32 +0000 en-US hourly 1 Highlights Archives - AAS Nova 32 32 Featured Image: Examining Galactic Filaments Tue, 20 Oct 2026 16:00:06 +0000 The center of our galaxy is known to host hundreds of radio-emitting filaments, but the energy source for these features remains a mystery. New simulations attempt to shed light on what powers galactic non-thermal filaments. The post Featured Image: Examining Galactic Filaments appeared first on AAS Nova. ]]> This image of the galactic center from the MeerKAT radio array shows wispy vertical lines known as galactic non-thermal filaments. These structures, which are tens of parsecs long and less than a tenth of a parsec wide, are found throughout a complex region called the central molecular zone. The filaments’ radio emission appears to come from charged particles spiraling around magnetic field lines, but it’s not yet known where the speeding particles that power this emission come from. Recently, Mohan Richter-Addo (University of Wisconsin–Madison) and collaborators used magnetohydrodynamics simulations to explore two potential sources: 1) the electron–positron winds of a pulsar or 2) a proton-rich mix of particles accelerated by interstellar shocks. The team found few discernible differences between simulated filaments illuminated by these two sources, but this work provided new avenues for future exploration. One facet that emerged from the team’s investigation is that filaments should grow longer as they age, with the maximum length set by the underlying magnetic field. This suggests that magnetohydrodynamic turbulence might play a role in shaping the filaments. To learn more about this exploration of galactic non-thermal filaments, be sure to check out the article linked below. Citation “The Effects of Cosmic-Ray Protons on Galactic Nonthermal Filaments,” Mohan Richter-Addo et al 2026 ApJ 1009 164. doi:10.3847/1538-4357/aea0c7 The post Featured Image: Examining Galactic Filaments appeared first on AAS Nova. ]]> "The Effects of Cosmic-Ray Protons on Galactic Nonthermal Filaments," Mohan Richter-Addo et al 2026 ApJ 1009 164. doi:10.3847/1538-4357/aea0c7 Not All Black Holes Who Wander Are Lost /2026/10/19/not-all-black-holes-who-wander-are-lost/?utm_source=rss&utm_medium=rss&utm_campaign=not-all-black-holes-who-wander-are-lost Mon, 19 Oct 2026 16:00:37 +0000 /?p=16390 Astrobites reports on a new diagnostic tool used to understand how the neighborhood a black hole grows up in may affect the rest of its life. The post Not All Black Holes Who Wander Are Lost appeared first on AAS Nova. ]]> 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. Title: Tracing Black Hole and Galaxy Growth Across Environments Since Cosmic Noon Authors: Emma Jane Weller et al. First Author’s Institution: Yale University Status: Published in ApJ They say you can’t choose your hometown, but it still ends up shaping who you become. Turns out the same is true for black holes. The galaxy a black hole grows up in will have a major impact on how it will live out the rest of its life. Similarly, the black hole can leave a lasting impression on its galaxy! Astronomers have long known that a galaxy’s stellar mass (the combined mass of all its stars) tracks pretty tightly with the mass of the black hole sitting at its centre: bigger galaxy, bigger black hole. This is one pillar of the idea that galaxies and their central black holes coevolve; that is, their life stories are tangled up with one another from early on. But ever since JWST started spotting suspiciously large black holes in the early universe, astronomers have been debating whether this relationship holds steady across cosmic time, or whether the rules were different when the universe and everything in it was younger. Not Everyone Stays in the Town Centre Most previous studies of the relationship between black holes and their galaxies have focused only on the central black hole: the biggest, most famous resident of a galaxy, sitting right downtown at its centre. That’s a reasonable place to start, since the central black hole is usually the most massive one around and tends to dominate the story. But this article’s authors wanted to know what happens to everyone else in town, too! That includes satellite black holes, which are the central black holes of smaller “satellite” galaxies that orbit a bigger “primary” galaxy, a bit like a small town around a big city. It also includes a stranger, more recently discovered population: wandering black holes. These are the black hole equivalent of someone whose hometown got swallowed up by an expanding metropolis, and who never quite settled into their new surroundings. Here’s how it happens: when a small satellite galaxy merges with a larger one, the satellite gets torn apart by tidal forces and its gas and stars are stripped away. However, its central black hole is often left behind, drifting through the new, much bigger galaxy on a wide orbit. The process that would normally drag a black hole down to the centre of a galaxy, called dynamical friction, is painfully slow, so wanderers can spend billions of years roaming the outskirts. Two Cities, Two Sets of Rules To study how these different black hole “life paths” shape, and are shaped by, their host galaxies, the authors turned to two cosmological simulations, ASTRID and TNG300, which handle black hole physics quite differently. In TNG300, black holes are assumed to start fairly massive and are snapped straight to the centre of their host galaxy at every timestep. This makes mergers happen quickly and often, but it also means there’s no such thing as a wandering black hole in TNG300. ASTRID, on the other hand, seeds smaller black holes and lets them move more realistically through their galaxy using a subgrid dynamical friction model. This is what allows wandering black holes, with their slow, aimless orbits, to exist and be studied in the first place. Figure 1 reveals a lot at once. First, ASTRID (the simulation that allows wandering black holes and tidally stripped satellites) has whole new neighbourhoods on the map that simply don’t exist in TNG300. Those populations clearly aren’t following the same tidy, linear coevolution that central black holes enjoy with their galaxies. Second, the most massive black holes tend to be the most yellow, meaning mergers did the heavy lifting for their growth. This is especially pronounced in TNG300, where roughly 80–90% of the growth of the most massive black holes comes from mergers. Meanwhile, the wanderers and stripped satellites sit at the deep-purple end: these black holes have barely merged with anyone at all. Figure 1: How black hole mass relates to host galaxy stellar mass, shown at two snapshots in cosmic history, 8 and 5 billion years ago, for both simulations (ASTRID: top row; TNG300: bottom row). Colour shows what fraction of each black hole’s growth since the last snapshot came from mergers, from purple (grown almost entirely by slowly swallowing gas) to yellow (grown mostly by swallowing other black holes). [Weller et al. 2026] Four Kinds of Black Hole Life Stories Pulling all of this together, the authors sketch out a kind of “neighborhood map” of black hole fates, sorted by where a black hole ends up on the mass-relation plot and how it got there (see Figure 2). Figure 2: The distinct black hole populations revealed by the black hole mass–stellar mass relation, and the evolutionary path that lands each population in its corner of the map. [Weller et al. 2026] Normal centrals are the homebodies. They sit at the centre of primary or satellite galaxies and grow up steadily alongside their hometown, climbing the mass relation together through a healthy mix of accretion and the occasional merger. Their galaxies keep forming stars the whole time in a functional, unremarkable, thoroughly nice place to live. High-mass centrals are the ones who “made it.” These are central black holes in big primary galaxies, and their growth comes overwhelmingly from mergers with other black holes. Once they get big enough, they start throwing their weight around: their jets blast gas out of the galaxy, shutting down both star formation and their own further growth. Stripped satellites are the annexed suburbs. They start out on the normal mass relation, but a merger with a bigger galaxy tears away their gas and stars, shrinking their stellar mass while their black hole is left comparatively overweight for its new, smaller home. With their gas reserves gone, star formation grinds to a halt, and their black holes, starved of fuel, barely grow either. Wanderers are the ones who moved to the big city and never quite settled in. They start out on the normal relation inside a satellite galaxy, but when that galaxy merges into something much bigger, they’re left drifting through unfamiliar, low-density territory. With little gas around to feed on and almost no chance of merging with anyone else, their growth basically stalls. This four-way map is a genuinely useful new way to read the black hole–galaxy relation: a black hole’s exact position on the plot isn’t just a number, it’s a fossil record of everywhere it’s ever “lived.” There’s plenty more in the article we haven’t covered here, including how quenching plays out over time, how these results stack up against the local universe, and a closer look at how star formation rates and black hole accretion rates track each other across all four populations. If any of this piqued your interest, the full article is well worth a read. Original astrobite edited by Ryan White and Chloe Klare. About the author, Jayde Willingham: I am a first-year PhD student at Swinburne University of Technology studying the early universe and how the first galaxies came to be. My work combines observations and theoretical modelling to explore how galaxies form, evolve, and shape the universe we see today. When I’m not at my desk or doing SciComm, I’m probably reading a good book with a hot beverage under a cozy blanket. The post Not All Black Holes Who Wander Are Lost appeared first on AAS Nova. ]]> Not available Astronomers Get a Better Look at a Rare White Dwarf–Brown Dwarf Pair /2026/10/16/astronomers-get-a-better-look-at-a-rare-white-dwarf-brown-dwarf-pair/?utm_source=rss&utm_medium=rss&utm_campaign=astronomers-get-a-better-look-at-a-rare-white-dwarf-brown-dwarf-pair Fri, 16 Oct 2026 16:00:41 +0000 /?p=16398 The white dwarf–brown dwarf pair J0404+1112 — one of only about a dozen known systems like it — offers researchers a chance to study a substellar atmosphere blasted with intense radiation. The post Astronomers Get a Better Look at a Rare White Dwarf–Brown Dwarf Pair appeared first on AAS Nova. ]]> Researchers have followed up on the discovery of a rare binary system containing a white dwarf and a brown dwarf. This unusual pairing offers valuable insights into the physics of atmospheres subjected to strong radiation. Odd Couple In 2025, researchers searching through observations from the Transiting Exoplanet Survey Satellite (TESS) spotted an eclipsing binary system in which a brown dwarf orbits the white dwarf J0404+1112 every 2.93 hours. Only about a dozen white dwarf–brown dwarf binaries have been confirmed so far, and each newfound system offers clues to how substellar or planetary companions survive a star’s transition from main-sequence star to swollen red giant to blazing white dwarf. Because the two objects orbit one another so closely, this remarkable system also offers researchers an opportunity to study the dynamics and chemistry of an atmosphere blasted with high-energy radiation, with important implications for close-in brown dwarfs and giant planets. Insights from New Observations Eclipse photometry of J0404+1112 from TESS, SPECULOOS, the Gran Telescopio Canarias, and the United Kingdom Infra-Red Telescope. [de Wit et al. 2026]Based on early data from TESS and SPECULOOS, Julien de Wit (Massachusetts Institute of Technology) and collaborators posited that the J0404+1112 system contained an unusually puffy low-mass white dwarf and a 25-Jupiter-mass brown dwarf. However, the initial data couldn’t fully constrain the white dwarf’s properties, leaving degeneracies between its temperature, radius, and other factors. Now, the team has obtained new photometry from the Gran Telescopio Canarias and the United Kingdom Infra-Red Telescope, plus spectroscopy from the Gran Telescopio Canarias, to get a better sense of the system. These observations allowed them to break the degeneracies in the white dwarf’s properties, showing it to be an 0.60-solar-mass white dwarf that has been cooling for more than 10 million years to a present-day temperature of 28,000K. The brown dwarf also appears to be more massive than initially thought, weighing in at roughly 40 Jupiter masses. This diagram shows the relative sizes of the brown dwarf and the white dwarf. [AAS Nova/Kerry Hensley] Like Night and Day Because the system’s orbit is almost exactly edge on from our point of view, the white dwarf is completely eclipsed as the much larger brown dwarf passes in front of it. This allows the contributions from the two components to be separated, and for the emission from the brown dwarf’s nightside to be measured. The authors constrained the brown dwarf’s nightside temperature to roughly 1750K. Its dayside temperatures are likely to be significantly higher — potentially around 3750K at the point where the white dwarf is directly overhead — but more data are needed to constrain the dayside temperature of this world. Day–night temperature difference (left) and irradiation flux (right) of the brown dwarf in this system compared to other white dwarf–brown dwarf systems and hot and ultra-hot Jupiters. Click to enlarge. [de Wit et al. 2026]The estimated day–night temperature difference for this brown dwarf places it in the realm of hot and ultra-hot Jupiters. However, it’s subjected to more ultraviolet radiation than a typical hot or ultra-hot Jupiter orbiting a main-sequence star. This makes J0404+1112 a valuable system for disentangling the interconnected effects of temperature, radiation environment, atmospheric composition, and other factors on hot or ultra-hot Jupiters and other strongly irradiated brown dwarfs. We can certainly expect to learn more about this rare system as new data are collected! Citation “J0404+1112: A 3 hr Eclipsing White Dwarf–Brown Dwarf Probing Multiple Atmospheric Regimes,” J. de Wit et al 2026 ApJL 1009 L40. doi:10.3847/2041-8213/ae9a97 The post Astronomers Get a Better Look at a Rare White Dwarf–Brown Dwarf Pair appeared first on AAS Nova. ]]> "J0404+1112: A 3 hr Eclipsing White Dwarf–Brown Dwarf Probing Multiple Atmospheric Regimes," J. de Wit et al 2026 ApJL 1009 L40. doi:10.3847/2041-8213/ae9a97 Catching the Culprit Behind Globular Clusters’ Disappearing Binaries /2026/10/14/catching-the-culprit-behind-globular-clusters-disappearing-binaries/?utm_source=rss&utm_medium=rss&utm_campaign=catching-the-culprit-behind-globular-clusters-disappearing-binaries Wed, 14 Oct 2026 16:00:08 +0000 /?p=16368 Globular clusters have far fewer binary stars than the solar neighborhood. New research identifies black hole burning as the culprit. The post Catching the Culprit Behind Globular Clusters’ Disappearing Binaries appeared first on AAS Nova. ]]> Roughly one-third of stars in the Milky Way are in binary or multiple systems, but only ~1–10% of stars in globular clusters have a companion. Did globular clusters start with fewer binaries than the solar neighborhood, or have they since been wiped out? Survival of the Tightest Map of the semi-major axis–primary mass parameter space for binary systems. Solid lines show the boundary between hard (below the line) and soft (above the line) binaries for a variety of models. Models A–K span a variety of cluster masses and virial radii (a proxy for cluster density). [O’Connor et al. 2026]Globular clusters (GCs) are dense, ancient, gravitationally bound groups of stars. A team led by Christopher O’Connor at Northwestern University explored whether the lack of binary systems could be the result of some process unique to GCs. First, the team developed an analytical formalism to understand how binaries in a GC evolve depending on the binary stars’ masses, distance from each other, and interactions with other stars in the cluster. It turns out that the fate of a binary system depends on whether it is dynamically “hard” or “soft.” Hard binaries are generally tightly bound, and they tend to get “harder” from stellar flybys, which are common in a crowded cluster environment. Soft binaries are the opposite — they have much shorter lifetimes since encounters with other stars tend to loosen them. The team found that, assuming GCs have the same initial distribution of binaries as the solar neighborhood, the dissolution of soft binaries is sufficient to explain the present-day scarcity of binaries in GCs. Burning Away the Binaries What actually tears the soft binaries apart? The answer is a process called “black hole burning.” As some of the most massive objects in a globular cluster, black holes in binary systems can transfer energy when they interact with passing stars. This influx of energy can excite soft binaries to the point of dissolution, the study shows. Black hole burning can also prevent core collapse in GCs. Left to itself, a cluster’s core gradually loses energy to its outskirts, causing the core to grow hotter and denser with stars. This leads to more dynamical interactions between stars that can then get flung from the core or enter new tight binaries. Black hole burning pumps energy back into the core and prevents this from happening. Putting the Theory to the Test The total number of black holes in a cluster (top) and the binary fraction (bottom) as a function of time for three different cluster models. In the densest cluster (blue), binary dissolution starts early on, mainly driven by stellar collisions. For the other two models, binary dissolution mainly occurs after the number of black holes reaches its peak and black hole burning commences. [Adapted from O’Connor et al. 2026]To validate their analytical results, the team performed N-body simulations of GC dynamics with the Cluster Monte Carlo code. They found that, in moderate-to-low-density clusters, the decline of binary systems is powered mainly by black hole burning. In more compact clusters, however, stellar collisions also play an important role in the dissolution of binary systems, and at earlier times than the onset of black hole burning. In general, the final binary fractions of the simulated clusters agree with those predicted by the team’s analytical formalism. This further supports the theory that there is a universal initial binary distribution between galactic GCs and our solar neighborhood. Constraining this distribution is pivotal for refining dynamical models of GCs. In short, GCs and the solar neighborhood likely started with the same amount of binary systems, and interstellar dynamics handled the rest. Citation “A Common Origin for Binary Fractions in the Field and in Dense Clusters,” Christopher E. O’Connor et al 2026 ApJ 1009 L80. doi:10.3847/1538-4357/aea078 The post Catching the Culprit Behind Globular Clusters’ Disappearing Binaries appeared first on AAS Nova. ]]> “A Common Origin for Binary Fractions in the Field and in Dense Clusters,” Christopher E. O’Connor et al 2026 ApJ 1009 L80. doi:10.3847/1538-4357/aea078 Drawing Back the Curtain on Solar Spicules /2026/10/13/drawing-back-the-curtain-on-solar-spicules/?utm_source=rss&utm_medium=rss&utm_campaign=drawing-back-the-curtain-on-solar-spicules Tue, 13 Oct 2026 16:00:19 +0000 /?p=16363 Why do spicules — tiny spikes of plasma on the Sun — appear to rotate, split, and merge? New simulations reveal the possible cause of these motions. The post Drawing Back the Curtain on Solar Spicules appeared first on AAS Nova. ]]> The Sun’s surface is peppered with spikes of plasma called spicules that appear to shift and twist over time. Recent simulations suggest a new explanation for the motion of solar spicules. Solar spicules as seen by the Hinode mission. [Adapted from Dey et al. 2026] Jets in Motion Solar spicules are tiny jets of solar plasma that last just a few minutes. When viewed along the solar limb, spicules resemble blades of grass blowing in the wind. Observations show these structures moving in a variety of ways: twisting, shifting side to side, splitting, and joining together. Though spicules were first identified more than a century ago, where these motions come from is still up for debate. In a recent research article, Sahel Dey (University of Newcastle; Indian Institute of Astrophysics; Indian Institute of Science) and collaborators performed 3D magnetohydrodynamics simulations to investigate the source of solar spicules’ motion. The team’s simulations encompassed a volume of 6,000 × 9,000 × 37,000 kilometers that stretched from beneath the visible surface of the Sun up to the lower region of the Sun’s outer atmosphere, or corona. In this region, they applied a uniform vertical magnetic field, mimicking the conditions within a coronal hole, where the Sun’s magnetic field streams outward into the solar system A) A three-dimensional view of simulated solar spicules, showing curtain-like structures. B) Intensity of synthetic emission from the spicules in panel A, integrated along the line of sight. The cyan circle indicates the same region in both panels. [Adapted from Dey et al. 2026]Convection low in the simulation region generates slow magnetohydrodynamic waves, which create pockets of hot, upward-moving plasma and launch the spicules. When looking at the 3D structure of the spicules, Dey and collaborators found that they are not individual jets as they appear to be in photographs of the Sun. Instead, the sea of spicules creates an interconnected structure similar to a folded curtain. Simulating Spicules The jet-like appearance arises when this arrangement is viewed from the side; the team created synthetic images of their simulated spicules that show individual jet-like features. These “jets” have properties similar to those of real spicules, lasting just 5–10 minutes, journeying upward at 20–70 kilometers per second, and reaching heights of 6,000–16,000 kilometers. These simulations clearly demonstrate that what appear to be individual jets can arise from curtain-like plasma structures. Dey and collaborators showed that this network of spicules evolves over time, buoyed upward from below by a series of shocks, pulled down gradually by gravity, and buffeted by adjacent plasma. Three-dimensional view of spicules (purple–yellow regions) and coronal swirling conduits (represented by spiraling black lines). [Adapted from Dey et al. 2026]The team showed that when spicules seem to rotate, merge, or split, these are largely apparent motions. For example, when two spicules appear to merge, this could be caused by different sections of a plasma curtain aligning along the line of sight. Some of the spicule rotation is due to what the authors term coronal swirling conduits: columns of rotating plasma interspersed within the network of spicules. These swirling plasma columns can transfer some of their motion to the spicules, especially when the spicules are falling back toward the solar surface. This work demonstrates that a curtain-like configuration provides a viable explanation for the observed variety of spicule motions. Going forward, it will be critical to test this possibility further, as correctly interpreting the underlying structures of solar spicules is key to understanding how mass and energy are transferred to the solar corona. Citation “Solar Spicule Rotation Driven by Plasma Curtain–Vortex Interactions,” Sahel Dey et al 2026 ApJ 1008 132. doi:10.3847/1538-4357/ae8999 The post Drawing Back the Curtain on Solar Spicules appeared first on AAS Nova. ]]> "Solar Spicule Rotation Driven by Plasma Curtain–Vortex Interactions," Sahel Dey et al 2026 ApJ 1008 132. doi:10.3847/1538-4357/ae8999 The Invisible Architecture Between the Stars /2026/10/12/the-invisible-architecture-between-the-stars/?utm_source=rss&utm_medium=rss&utm_campaign=the-invisible-architecture-between-the-stars Mon, 12 Oct 2026 16:00:58 +0000 /?p=16341 Astrobites reports on why interstellar magnetic fields can appear ordered or tangled, depending on which gas clouds you measure and how. The post The Invisible Architecture Between the Stars appeared first on AAS Nova. ]]> 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. Title: Phase-Dependent Magnetic Coherence in the Turbulent Interstellar Medium Authors: Iryna S. Butsky et al. First Author’s Institution: Stanford University Status: Accepted to ApJ The space between stars isn’t empty, because it’s threaded with magnetic fields that shape how gas moves and steer cosmic rays as they race across the galaxy. As a result, understanding how the magnetic field is structured within different components of the interstellar medium, specifically clouds of different temperatures, is a key part of understanding how the interstellar medium we see today takes shape. Because magnetic fields are invisible, astronomers need tracers to reveal their structure. One such tracer is the emission from dust grains. Dust grains are not spherical, and a dust grain’s long axis tends to align at a right angle to the magnetic field, causing dust grains to emit light that vibrates in a particular direction. This is called polarized emission. If the magnetic field in a region is very ordered, the grains all align the same way, and a large fraction of their emitted light vibrates in the same direction, giving a high polarization fraction. This fraction is therefore used as a proxy for whether the field can maintain a consistent direction on large scales (an ordered/regular magnetic field). Comparing the polarization fraction with other tracers of gas lets astronomers infer the field’s structure in the interstellar medium. Previous observations found that the polarization fraction correlates with the fraction of cold gas, but not with the total amount of gas along the line of sight. This suggests that the field is preferentially ordered within cold clouds rather than warm clouds. Curiously, this seemed to contradict other studies that found the field to be more ordered in the warm clouds. Such disagreements are where simulations become useful: because the true magnetic field is known in a simulation, astronomers c

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Highlights Archives - AAS Nova Research highlights from the journals of the American Astronomical Society Wed, 07 Oct 2026 19:59:04 +0000 en-US hourly 1 Highlights Archives - AAS Nova 32 32 Tilting WASP-12b Doesn’t Solve the Mystery of Its Inspiral Wed, 07 Oct 2026 19:59:04 +0000 The hot Jupiter WASP-12b is on a collision course with its host star, and it's heading that way faster than expected. New research examines a possible explanation for the planet's speedy inspiraling. The post Tilting WASP-12b Doesn’t Solve the Mystery of Its Inspiral appeared first on AAS Nova. ]]> In 3 million years or less, WASP-12b will tumble into its host star. It’s not surprising that the planet will meet its end this way, but it is surprising that it will happen so soon. New work tests a potential explanation for the planet’s rapid orbital decay. Diagnosing a Doomed Planet Roughly twice as wide as Jupiter and almost 50% more massive, exoplanet WASP-12b zips around its Sun-like stellar host every 1.09 days at a distance of just 0.023 au (3.4 million kilometers or 2.1 million miles). If placed in our solar system, WASP-12b would easily dethrone Mercury as the nearest planet to the Sun. Observations show that WASP-12b’s already tiny orbit is shrinking, with each orbital period growing shorter at a rate of 29 milliseconds per year (Earth-year, that is). While we would expect the planet to slowly spiral inward due to tidal interactions with its star, it’s moving several orders of magnitude faster than predicted. The planet’s motion has so far defied all attempts to explain it, and now, a new research article by Caleb Lammers (Princeton University) and collaborators appears to topple yet another hypothesis for WASP-12b’s unexpectedly fast orbital decay. A Tidy Tidal Explanation? Previous work has proposed that WASP-12b’s rapidly shrinking orbit is due to obliquity tides, which could come into play if the planet had a nonzero obliquity, or axial tilt. Tidal dissipation generally works to keep close-in giant planets like WASP-12b from having a significant axial tilt. However, if you throw a second planet into the system, the companion can exert a torque that could force WASP-12b to remain tilted. This outside forcing, the hypothesis suggests, changes the orbital, spin, and tilt evolution of WASP-12b and ultimately pushes it toward its star far faster than expected without the tilt or the companion. Constraints on the mass and orbital distance of the companion planet in the obliquity-tide scenario. The color shows the radial velocity signal associated with each combination of parameters. The green line shows the maximum radial velocity allowed by observations. Click to enlarge. [Lammers et al. 2026]Lammers and coauthors examined this hypothesis by tracking how the angular momentum of a system containing both WASP-12b and a companion planet would evolve over time. As WASP-12b spirals inward, it loses angular momentum. For the planet’s lost angular momentum to be absorbed by the star and the companion planet — while maintaining a stable orbital configuration for both planets — the companion must orbit at least 0.06 au from the star and have a mass of at least 65 Earth masses. The Mystery Persists This companion mass and orbital distance are both larger than predicted by previous work, which had suggested that a 10–20-Earth-mass planet at 0.04 au would be sufficient to drive WASP-12b’s inward journey. Lammers and coauthors analyzed WASP-12’s radial velocity data for evidence of such a planet tugging on the star, but found none; only under extremely particular conditions could such a planet exist and not be detected in current data. Radial velocity constraints on the properties of a hypothetical second planet in the WASP-12 system, obtained via injection-recovery tests. [Lammers et al. 2026]Taking their calculations further, the team found it unlikely that this mechanism is at work in planetary systems in general, not just in the WASP-12 system. This leaves the mystery of WASP-12b’s rapid orbital decay wide open, and with only 3 million years to ponder it before the planet’s demise. Citation “The Mysterious Inspiral of WASP-12 b: Why Obliquity Tides Cannot Drive Orbital Decay,” Caleb Lammers et al 2026 ApJL 1009 L43. doi:10.3847/2041-8213/aea405 The post Tilting WASP-12b Doesn’t Solve the Mystery of Its Inspiral appeared first on AAS Nova. ]]> "The Mysterious Inspiral of WASP-12 b: Why Obliquity Tides Cannot Drive Orbital Decay," Caleb Lammers et al 2026 ApJL 1009 L43. doi:10.3847/2041-8213/aea405 Featured Image: Echoes of Giant Pulses /2026/10/06/featured-image-echoes-of-giant-pulses/?utm_source=rss&utm_medium=rss&utm_campaign=featured-image-echoes-of-giant-pulses Tue, 06 Oct 2026 16:00:10 +0000 /?p=16294 A new catalog of giant pulses from the Crab Nebula pulsar reveals a feature predicted to exist but not seen until now. The post Featured Image: Echoes of Giant Pulses appeared first on AAS Nova. ]]> What at first might appear to be abstract pixel art or a fuzzy photograph of skyglow from a distant city is actually a representation of radio emission from the pulsar at the center of the Crab Nebula. When a pulsar’s radio emission passes through a region of ionized gas — like the complex filaments of the Crab Nebula — the plasma deflects the radio signal from its intended course. This detour can create “echoes”: copies of the pulsar signal that arrive later than the original pulse. Thierry Serafin Nadeau (University of Toronto) and collaborators studied these echoes from the Crab pulsar by compiling an archive of giant pulses detected over 2.5 years by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). Giant pulses, which are brighter and narrower than typical pulses, offer a powerful way to probe plasma echoes. The image above shows sweeping parabola-shaped echoes during two particularly active periods. The color shows the frequencies at which power was received: mainly at low (blue), high (red), or all (yellow-white) frequencies. This dataset revealed for the first time a feature predicted to exist but never seen: echoes from plasma structures that never pass directly in front of the pulsar from our point of view. To learn more about the echoes of the Crab pulsar, be sure to check out the research article linked below. Citation “Echoes in Different Tempo: Long-Term Monitoring of Crab Echoes with CHIME,” Thierry Serafin Nadeau et al 2026 ApJ 1006 82. doi:10.3847/1538-4357/ae7336 The post Featured Image: Echoes of Giant Pulses appeared first on AAS Nova. ]]> "Echoes in Different Tempo: Long-Term Monitoring of Crab Echoes with CHIME," Thierry Serafin Nadeau et al 2026 ApJ 1006 82. doi:10.3847/1538-4357/ae7336 SPHEREx: The Niftiest Space Telescope You May Not Have Heard Of /2026/10/05/spherex-the-niftiest-space-telescope-you-may-not-have-heard-of/?utm_source=rss&utm_medium=rss&utm_campaign=spherex-the-niftiest-space-telescope-you-may-not-have-heard-of Mon, 05 Oct 2026 16:00:25 +0000 /?p=16275 Astrobites reports on NASA’s SPHEREx mission, which is collecting an infrared spectrum for every point in the sky — potentially revolutionizing our understanding of cosmic inflation, galaxy formation, and interstellar ices. The post SPHEREx: The Niftiest Space Telescope You May Not Have Heard Of appeared first on AAS Nova. ]]> 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. Title: The SPHEREx Satellite Mission Authors: James J. Bock et al. First Author’s Institution: California Institute of Technology; Jet Propulsion Laboratory Status: Published in ApJ You know JWST. You’ve likely heard about the recently launched Nancy Grace Roman Space Telescope. But did you know that NASA launched a third space telescope focused on infrared astronomy just last year? That telescope, called SPHEREx (short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, but we’ll forgive the tortured acronym), is currently carrying out its ambitious mission to record an infrared spectrum for every point in the sky. Let’s break down SPHEREx’s three main science goals and then discuss how SPHEREx will accomplish its mission. Goal #1: Stress-Testing Cosmic Inflation According to our best current models of cosmology, the very early universe experienced a rapid burst of accelerating expansion called cosmic inflation. During inflation, small regions of the universe that by chance had slightly higher energy density than their neighbors (due to quantum fluctuations) expanded to huge scales. Because these regions were very gravitationally attractive, once inflation ended, they became the seeds where matter accumulated and eventually formed galaxies. This means that the distribution of galaxies that we see today is a reflection of the properties of inflation (i.e., what the quantum fluctuations were like and how inflation supersized them). SPHEREx will assemble the largest atlas of galaxies ever, recording the three-dimensional positions of hundreds of millions of galaxies across the entire sky. To do this, SPHEREx must figure out how far away these galaxies are from Earth, using their redshifts. SPHEREx’s low-resolution infrared spectroscopy allows for moderately precise measurements of these redshifts. By performing statistical analyses of how galaxies are separated from each other, SPHEREx will test different theories of inflation, like whether inflation was driven by multiple fields. Goal #2: Frozen Assets Astronomers are racing to find evidence for life (or at least habitability) in the atmospheres of exoplanets through transmission spectroscopy. However, we don’t know for sure how molecules that could be used in biological processes (called biogenic molecules, these include water, carbon dioxide, carbon monoxide, and methanol) even end up on planets. We think that a large fraction of these molecules are frozen onto dust grains throughout the interstellar medium. When a new star forms in the interstellar medium, this ice and dust would become part of the star’s protoplanetary disk. The ice species can help create planetesimals (which may grow into planets) or can later deliver biogenic molecules to planetary surfaces. Earth’s oceans likely came (at least in part) from collisions with icy asteroids. As Figure 1 shows, SPHEREx will measure the abundance of ice species in different environments that track the history of solar system formation, from dense clouds in the interstellar medium that may soon form stars to regions around newborn stars and evolving protoplanetary disks. In this way, SPHEREx will track how biogenic molecules from the interstellar medium can end up on planets. Figure 1: Examples of the sources SPHEREx will look at to search for biogenic ice species. In the top left, what the spectra of these sources will look like if those species are present: each type of ice leaves a distinct fingerprint in an infrared spectrum. [Bock et al. 2026] Goal #3: Your Noise Is SPHEREx’s Signal SPHEREx will measure an infrared spectrum for every point in the sky — even those that don’t contain galaxies or stars that we can resolve. These points are instead dominated by diffuse extragalactic background light. This light comes from many different sources, including stars, dust, and quasars, from the early universe to the present day, all added together incoherently. For most telescopes, the extragalactic background light is just a frustrating source of noise. For SPHEREx, it’s a treasure trove. We can compare the properties of the extragalactic background light that SPHEREx measures (its spectrum and how it fluctuates across the sky) to theoretical predictions and see if we seem to be missing anything. SPHEREx’s very broad infrared spectra — capturing redshifted light from the very early universe — and total sky coverage are crucial for this purpose. For instance, the SPHEREx team will try to isolate emission from the first stars and galaxies, which ionized most of the gas in the universe in the epoch of reionization. By understanding this and other contributions to the extragalactic background light, we can test hypotheses about how galaxies form and evolve. Making It Happen Beyond inflation, ices, and extragalactic background light, SPHEREx’s all-sky infrared spectra will be invaluable for countless other science cases, like studying asteroids, characterizing the atmospheres of stars that host exoplanets, and even understanding the upper atmosphere of Earth, through which SPHEREx orbits. But how can SPHEREx even make a spectrum for every point in the sky? An image of some part of the sky is fundamentally two-dimensional, and measuring how the brightness of every point changes with wavelength adds a third dimension. Astronomers have come up with many ways to solve this problem. Integral field spectroscopy approaches typically involve splitting an image into small regions or strips, then using a dispersive element like a prism or grating to make a spectrum of each region, and finally putting these spectra side by side on a camera. Figure 2 shows an example of this strategy, as well as what the final three-dimensional “datacube” looks like after processing. Figure 2: A demonstration of the principle of integral field spectroscopy. [ESO; CC BY 4.0]This approach is fairly complicated, relying on fancy optics, a prism or grating, and oftentimes optical fibers. From Figure 2, note that you could also make the final “datacube” product if you simply took many images with narrow filters that let through different wavelengths of light. This takes to an extreme the approach astronomers use for spectral energy distribution fitting. Of course, this would require an exorbitant number of filters. Here, the SPHEREx team had a stroke of genius: instead of having many different filters, what if you had a filter where the transmitted wavelength changes linearly across the filter? Each row would let through a different wavelength. To get a full spectrum for all points in an image, you could take many exposures, moving the telescope slightly between each exposure so points in the image fall on different rows each time. This is the SPHEREx survey strategy, with a few complications. First, before any filter, SPHEREx splits incoming light into two beams, with short-wave infrared light (SWIR, with 0.75 μm < λ < 2.42 μm) going in one direction and mid-wave infrared light (MWIR, 2.42 μm < λ < 5.00 μm) going in another. SPHEREx makes images with these two beams on different sets of detectors, so it can measure the brightness of an object at one SWIR wavelength and one MWIR wavelength simultaneously. The SPHEREx field of view covers 10.5° by 3.5°, with the SWIR and MWIR images each spread across three detectors. Every detector has a different linearly variable filter. To get a complete infrared spectrum of a given point in the sky, SPHEREx moves that point to 17 different positions on each detector. This requires 51 different telescope (17 × 3 detectors) pointings in all and yields 102 spectral values (51 × 2 for the SWIR and MWIR beams). Figure 3 shows the 17 bands on each of the six SPHEREx detectors, each corresponding to a different wavelength value. Figure 3: The wavelength of light that each part of each SPHEREx detector is sensitive to. A point in the sky is imaged on one short-wave infrared detector (top row) and one mid-wave infrared detector (bottom row) simultaneously. SPHEREx measures each point in the sky at 102 different wavelengths by placing the point at 17 different positions on each of the detectors. [Adapted from Bock et al. 2026]While it would take decades to collect spectra for every point on the sky with conventional methods for integral field spectroscopy, the SPHEREx team devised a nifty solution that will collect this dataset in a few years. Soon, SPHEREx will start answering questions about cosmic inflation, interstellar ices, and extragalactic background light, while its rich dataset will be relevant for decades to come. So tell all your friends about SPHEREx (even if you can’t remember what the acronym stands for)! Original astrobite edited by Veronika Dornan. About the author, Chris Layden: Chris is a PhD candidate in astrophysics at the Massachusetts Institute of Technology. His primary research interest is developing instrumentation that enables high-speed astronomical observations. With such instruments, he studies the most rapidly varying phenomena in the sky, including millisecond pulsars, accreting black holes, and solar system objects whizzing past background stars. Outside of astronomy, Chris enjoys reading classic novels, playing ultimate frisbee, and hanging out with his wife and dog. The post SPHEREx: The Niftiest Space Telescope You May Not Have Heard Of appeared first on AAS Nova. ]]> Not available Supernova, Kilonova, or Both? Another Look at SN 2025ulz /2026/10/02/supernova-kilonova-or-both-another-look-at-sn-2025ulz/?utm_source=rss&utm_medium=rss&utm_campaign=supernova-kilonova-or-both-another-look-at-sn-2025ulz Fri, 02 Oct 2026 16:00:18 +0000 /?p=16268 Last year, gravitational wave detectors triggered on what may have been a collision involving a sub-solar-mass neutron star. New research investigates a potential link between this event and a supernova. The post Supernova, Kilonova, or Both? Another Look at SN 2025ulz appeared first on AAS Nova. ]]> A tentative gravitational wave signal sent astronomers searching for a possible electromagnetic counterpart. New radio observations weigh in on whether the candidate counterpart is a standard supernova or a sign of something rarer. A Potential Neutron Star Merger These images from the Hubble Space Telescope show the fading light of the kilonova associated with the gravitational wave event GW170817. [NASA and ESA Acknowledgment: A. Levan (U. Warwick), N. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI)]In 2025, the LIGO-Virgo-KAGRA collaboration announced an interesting gravitational wave candidate, S250818k. Despite a 71% chance that the gravitational wave signal wasn’t astrophysical in origin, S250818k raised eyebrows as a potential kilonova: a compact-object collision involving at least one neutron star. S250818k offered a rare opportunity to associate the light from a kilonova with a gravitational wave detection, a feat achieved only once so far, in 2017. The intrigue surrounding S250818k was heightened even further by the possibility that the collision involved at least one sub-solar-mass neutron star. Such a lightweight neutron star would fall below the lower mass limit set by stellar evolution models, requiring a different formation pathway. S250818k’s kilonova potential rose and fell once researchers spotted an electromagnetic transient in its source region. Early optical observations revealed a kilonova-like color and rapid fading, while later observations showed brightening similar to a supernova interacting with circumstellar gas. This led the event to be classified as supernova SN 2025ulz — and therefore unlikely to be the source of the gravitational wave signal. Illustration of a kilonova that occurs in the wake of a supernova. First, a massive star collapses. Then, neutron stars form in the aftermath. Finally, the neutron stars collide, producing a kilonova whose signal might be hidden by the supernova. [Caltech/K. Miller and R. Hurt (IPAC)] A Kilonova in a Supernova? Unlikely, but not impossible. Tanner O’Dwyer (Johns Hopkins University) and collaborators investigated the supernova for signs that it wasn’t a typical collapsing star. The team was motivated by theories suggesting that the collapse of a rapidly rotating massive star could produce both a kilonova and a supernova — potentially uniting gravitational wave signal S250818k and supernova SN 2025ulz. In theory, the demise of a fast-spinning massive progenitor could produce one or more sub-solar-mass neutron stars. This could happen if 1) the collapsing stellar core splits into two neutron stars, or 2) in a twist on the star-formation process, neutron stars coalesce out of neutron-rich material in the disk surrounding the dying star. In either scenario, the neutron stars could merge shortly after the star’s collapse, generating kilonova emission that might be obscured by the expanding supernova. Looking Deeply in the Radio Very Large Array detection of a radio counterpart to SN 20215ulz. The circle shows the optical position of the supernova, and the “x” shows the optical position of the host galaxy. [Adapted from O’Dwyer et al. 2026]Radio observations offer a way to distinguish between a typical supernova, which would have relatively slow-moving ejecta, and a collapsing rapidly rotating progenitor, which could produce a relativistic jet. Searching for a radio counterpart to the supernova in observations from the Very Large Array, the upgraded Giant Metrewave Radio Telescope, and MeerKAT, O’Dwyer and coauthors found a faint but significant radio source in stacked observations made 51–96 days after the gravitational wave trigger. The team found that standard supernova ejecta and relativistic jet models can both plausibly fit the data. In the supernova scenario, the estimated expansion speed and progenitor mass-loss rate place the event well within the bounds of known stripped-envelope supernovae. Though the data were also compatible with an off-axis relativistic jet, the authors were unable to resolve degeneracies in the event’s properties, including the jet energy and the interstellar medium density. Ultimately, the authors suggested that a supernova fits the data more naturally. While this radio investigation didn’t unambiguously link S250818k and SN 2025ulz via an exotic kilonova-plus-supernova mechanism, it’s clear that radio observations have an important role to play in examining future gravitational wave signals. Citation “Identification of a Radio Counterpart to SN 2025ulz in the S250818k Localization Area,” Tanner O’Dwyer et al 2026 ApJL 1009 L44. doi:10.3847/2041-8213/aea4a5 The post Supernova, Kilonova, or Both? Another Look at SN 2025ulz appeared first on AAS Nova. ]]> "Identification of a Radio Counterpart to SN 2025ulz in the S250818k Localization Area," Tanner O’Dwyer et al 2026 ApJL 1009 L44. doi:10.3847/2041-8213/aea4a5 The Solar System Has a New Life Expectancy, and It’s a Billion Times Shorter /2026/09/30/the-solar-system-has-a-new-life-expectancy-and-its-a-billion-times-shorter/?utm_source=rss&utm_medium=rss&utm_campaign=the-solar-system-has-a-new-life-expectancy-and-its-a-billion-times-shorter Wed, 30 Sep 2026 16:00:03 +0000 /?p=16260 New simulations suggest the outer solar system could disassemble within about one billion years after the Sun becomes a white dwarf. The post The Solar System Has a New Life Expectancy, and It’s a Billion Times Shorter appeared first on AAS Nova. ]]> Isaac Newton suspected that the gravitational dance between the Sun and Jupiter would eventually destabilize the solar system, but modern computational research has shown that its long-term stability is, statistically, pretty secure. However, new simulations with more realistic solar mass-loss conditions make a strong case for the disassembly of the outer solar system — and on timescales much shorter than previously thought. Kick It Up a Notch Final outer planet orbital configurations for two simulations — one stable and one unstable. t=0 at the onset of white dwarf formation. Click to enlarge. [Adapted from Batygin et al. 2026]Several studies have investigated what will happen to the orbits of planets in our solar system as the Sun sheds its mass during its transition to a white dwarf. These studies have found that while the semimajor axes of the planets will expand by approximately a factor of 2, their orbits remain stable on timescales longer than the age of the universe (approximately 1018 years). This expanded orbital architecture will make the solar system more prone to jostles from stellar flybys, but even accounting for this, the giant planets’ orbits wouldn’t disassemble for another 30–100 billion years. However, all of these studies modeled solar mass loss as a smooth function, so the dismantling of the solar system was left up to external forcings. In reality, stars on the red giant branch undergo mass ejections that are random in time and direction, corresponding to velocity “kicks” that can alter the dynamics of the planets. A team led by Konstantin Batygin at the California Institute of Technology conducted numerical experiments to analyze the orbital dynamics of the outer solar system under different solar mass-loss conditions. First, they tested the classic case of smooth mass loss and validated previous findings that, despite planetary orbits doubling in size, the dynamics are pretty tame. This holds true even when mass is ejected anisotropically: if the timing is smooth, the asymmetries cancel out. Outer Solar System, Your Days Are Numbered Next, they simulated stochastic kicks and found that the behavior of the outer planets was largely tied to the ejection mass of each kick. For very small ejection masses (≤ 10-7 M☉), dynamics mimic the smooth mass-loss case. For intermediate values (10-7 to 10-6 M☉), there’s a roughly 20% chance Jupiter–Saturn and Uranus–Neptune enter mean-motion resonances: an orbital configuration where planets’ periods are a ratio of small integers. These resonant configurations don’t protect the giant planets, however: resonant simulations disassemble slightly more often than nonresonant simulations. For larger ejection masses (≥ 10-5 M☉), the outer solar system disassembles on the timescale of billions of years. Instability onset time — or how long after white dwarf formation the outer solar system disassembles — as a function of ejection mass. The larger the ejection mass, the greater the chance of instability. Click to enlarge. [Batygin et al. 2026]Which ejection masses are the most accurate for our Sun? Well, unfortunately for our beloved outer planets, ejection models and observed kick amplitudes suggest a future ejection mass of 10-4 M☉. With kicks like these, not only is there a considerable chance of orbit destabilization, but it could happen before the white dwarf even forms. About 40% of simulations lead to disruption or violent scattering while the Sun is in its red giant phase, and roughly 90% break down within 3 billion years. This new discovery reduces the life expectancy of the solar system from one billion billion years to a meager one billion years after white dwarf formation. Citation “Terminal Instability of the Solar System Triggered by Stochastic Solar Mass Loss,” Konstantin Batygin et al 2026 ApJL 1009 L22. doi:10.3847/2041-8213/aea290 The

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AAS Nova Research highlights from the journals of the American Astronomical Society Mon, 19 Oct 2026 15:59:55 +0000 en-US hourly 1 wp-content/uploads/2017/10/cropped-favicon-1-32x32.png AAS Nova 32 32 Tree-Ring Structure of Galactic Bar Resonance in N-Body Simulations Mon, 19 Oct 2026 16:00:48 +0000 ?p=16352 Rimpei Chiba et al 2026 ApJ 1006 132 Even in a noisy environment with fluctuations in pattern speed and encounters with the Sagittarius dwarf galaxy, a tree-ring structure arises in phase space measurements of the Milky Way’s galactic bar. The post Tree-Ring Structure of Galactic Bar Resonance in N-Body Simulations appeared first on AAS Nova. ]]> Rimpei Chiba et al 2026 ApJ 1006 132 Even in a noisy environment with fluctuations in pattern speed and encounters with the Sagittarius dwarf galaxy, a tree-ring structure arises in phase space measurements of the Milky Way’s galactic bar. The post Tree-Ring Structure of Galactic Bar Resonance in N-Body Simulations appeared first on AAS Nova. ]]> Not available Not All Black Holes Who Wander Are Lost 2026/10/19/not-all-black-holes-who-wander-are-lost/?utm_source=rss&utm_medium=rss&utm_campaign=not-all-black-holes-who-wander-are-lost Mon, 19 Oct 2026 16:00:37 +0000 ?p=16390 Astrobites reports on a new diagnostic tool used to understand how the neighborhood a black hole grows up in may affect the rest of its life. The post Not All Black Holes Who Wander Are Lost appeared first on AAS Nova. ]]> 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. Title: Tracing Black Hole and Galaxy Growth Across Environments Since Cosmic Noon Authors: Emma Jane Weller et al. First Author’s Institution: Yale University Status: Published in ApJ They say you can’t choose your hometown, but it still ends up shaping who you become. Turns out the same is true for black holes. The galaxy a black hole grows up in will have a major impact on how it will live out the rest of its life. Similarly, the black hole can leave a lasting impression on its galaxy! Astronomers have long known that a galaxy’s stellar mass (the combined mass of all its stars) tracks pretty tightly with the mass of the black hole sitting at its centre: bigger galaxy, bigger black hole. This is one pillar of the idea that galaxies and their central black holes coevolve; that is, their life stories are tangled up with one another from early on. But ever since JWST started spotting suspiciously large black holes in the early universe, astronomers have been debating whether this relationship holds steady across cosmic time, or whether the rules were different when the universe and everything in it was younger. Not Everyone Stays in the Town Centre Most previous studies of the relationship between black holes and their galaxies have focused only on the central black hole: the biggest, most famous resident of a galaxy, sitting right downtown at its centre. That’s a reasonable place to start, since the central black hole is usually the most massive one around and tends to dominate the story. But this article’s authors wanted to know what happens to everyone else in town, too! That includes satellite black holes, which are the central black holes of smaller “satellite” galaxies that orbit a bigger “primary” galaxy, a bit like a small town around a big city. It also includes a stranger, more recently discovered population: wandering black holes. These are the black hole equivalent of someone whose hometown got swallowed up by an expanding metropolis, and who never quite settled into their new surroundings. Here’s how it happens: when a small satellite galaxy merges with a larger one, the satellite gets torn apart by tidal forces and its gas and stars are stripped away. However, its central black hole is often left behind, drifting through the new, much bigger galaxy on a wide orbit. The process that would normally drag a black hole down to the centre of a galaxy, called dynamical friction, is painfully slow, so wanderers can spend billions of years roaming the outskirts. Two Cities, Two Sets of Rules To study how these different black hole “life paths” shape, and are shaped by, their host galaxies, the authors turned to two cosmological simulations, ASTRID and TNG300, which handle black hole physics quite differently. In TNG300, black holes are assumed to start fairly massive and are snapped straight to the centre of their host galaxy at every timestep. This makes mergers happen quickly and often, but it also means there’s no such thing as a wandering black hole in TNG300. ASTRID, on the other hand, seeds smaller black holes and lets them move more realistically through their galaxy using a subgrid dynamical friction model. This is what allows wandering black holes, with their slow, aimless orbits, to exist and be studied in the first place. Figure 1 reveals a lot at once. First, ASTRID (the simulation that allows wandering black holes and tidally stripped satellites) has whole new neighbourhoods on the map that simply don’t exist in TNG300. Those populations clearly aren’t following the same tidy, linear coevolution that central black holes enjoy with their galaxies. Second, the most massive black holes tend to be the most yellow, meaning mergers did the heavy lifting for their growth. This is especially pronounced in TNG300, where roughly 80–90% of the growth of the most massive black holes comes from mergers. Meanwhile, the wanderers and stripped satellites sit at the deep-purple end: these black holes have barely merged with anyone at all. Figure 1: How black hole mass relates to host galaxy stellar mass, shown at two snapshots in cosmic history, 8 and 5 billion years ago, for both simulations (ASTRID: top row; TNG300: bottom row). Colour shows what fraction of each black hole’s growth since the last snapshot came from mergers, from purple (grown almost entirely by slowly swallowing gas) to yellow (grown mostly by swallowing other black holes). [Weller et al. 2026] Four Kinds of Black Hole Life Stories Pulling all of this together, the authors sketch out a kind of “neighborhood map” of black hole fates, sorted by where a black hole ends up on the mass-relation plot and how it got there (see Figure 2). Figure 2: The distinct black hole populations revealed by the black hole mass–stellar mass relation, and the evolutionary path that lands each population in its corner of the map. [Weller et al. 2026] Normal centrals are the homebodies. They sit at the centre of primary or satellite galaxies and grow up steadily alongside their hometown, climbing the mass relation together through a healthy mix of accretion and the occasional merger. Their galaxies keep forming stars the whole time in a functional, unremarkable, thoroughly nice place to live. High-mass centrals are the ones who “made it.” These are central black holes in big primary galaxies, and their growth comes overwhelmingly from mergers with other black holes. Once they get big enough, they start throwing their weight around: their jets blast gas out of the galaxy, shutting down both star formation and their own further growth. Stripped satellites are the annexed suburbs. They start out on the normal mass relation, but a merger with a bigger galaxy tears away their gas and stars, shrinking their stellar mass while their black hole is left comparatively overweight for its new, smaller home. With their gas reserves gone, star formation grinds to a halt, and their black holes, starved of fuel, barely grow either. Wanderers are the ones who moved to the big city and never quite settled in. They start out on the normal relation inside a satellite galaxy, but when that galaxy merges into something much bigger, they’re left drifting through unfamiliar, low-density territory. With little gas around to feed on and almost no chance of merging with anyone else, their growth basically stalls. This four-way map is a genuinely useful new way to read the black hole–galaxy relation: a black hole’s exact position on the plot isn’t just a number, it’s a fossil record of everywhere it’s ever “lived.” There’s plenty more in the article we haven’t covered here, including how quenching plays out over time, how these results stack up against the local universe, and a closer look at how star formation rates and black hole accretion rates track each other across all four populations. If any of this piqued your interest, the full article is well worth a read. Original astrobite edited by Ryan White and Chloe Klare. About the author, Jayde Willingham: I am a first-year PhD student at Swinburne University of Technology studying the early universe and how the first galaxies came to be. My work combines observations and theoretical modelling to explore how galaxies form, evolve, and shape the universe we see today. When I’m not at my desk or doing SciComm, I’m probably reading a good book with a hot beverage under a cozy blanket. The post Not All Black Holes Who Wander Are Lost appeared first on AAS Nova. ]]> Not available Astronomers Get a Better Look at a Rare White Dwarf–Brown Dwarf Pair 2026/10/16/astronomers-get-a-better-look-at-a-rare-white-dwarf-brown-dwarf-pair/?utm_source=rss&utm_medium=rss&utm_campaign=astronomers-get-a-better-look-at-a-rare-white-dwarf-brown-dwarf-pair Fri, 16 Oct 2026 16:00:41 +0000 ?p=16398 The white dwarf–brown dwarf pair J0404+1112 — one of only about a dozen known systems like it — offers researchers a chance to study a substellar atmosphere blasted with intense radiation. The post Astronomers Get a Better Look at a Rare White Dwarf–Brown Dwarf Pair appeared first on AAS Nova. ]]> Researchers have followed up on the discovery of a rare binary system containing a white dwarf and a brown dwarf. This unusual pairing offers valuable insights into the physics of atmospheres subjected to strong radiation. Odd Couple In 2025, researchers searching through observations from the Transiting Exoplanet Survey Satellite (TESS) spotted an eclipsing binary system in which a brown dwarf orbits the white dwarf J0404+1112 every 2.93 hours. Only about a dozen white dwarf–brown dwarf binaries have been confirmed so far, and each newfound system offers clues to how substellar or planetary companions survive a star’s transition from main-sequence star to swollen red giant to blazing white dwarf. Because the two objects orbit one another so closely, this remarkable system also offers researchers an opportunity to study the dynamics and chemistry of an atmosphere blasted with high-energy radiation, with important implications for close-in brown dwarfs and giant planets. Insights from New Observations Eclipse photometry of J0404+1112 from TESS, SPECULOOS, the Gran Telescopio Canarias, and the United Kingdom Infra-Red Telescope. [de Wit et al. 2026]Based on early data from TESS and SPECULOOS, Julien de Wit (Massachusetts Institute of Technology) and collaborators posited that the J0404+1112 system contained an unusually puffy low-mass white dwarf and a 25-Jupiter-mass brown dwarf. However, the initial data couldn’t fully constrain the white dwarf’s properties, leaving degeneracies between its temperature, radius, and other factors. Now, the team has obtained new photometry from the Gran Telescopio Canarias and the United Kingdom Infra-Red Telescope, plus spectroscopy from the Gran Telescopio Canarias, to get a better sense of the system. These observations allowed them to break the degeneracies in the white dwarf’s properties, showing it to be an 0.60-solar-mass white dwarf that has been cooling for more than 10 million years to a present-day temperature of 28,000K. The brown dwarf also appears to be more massive than initially thought, weighing in at roughly 40 Jupiter masses. This diagram shows the relative sizes of the brown dwarf and the white dwarf. [AAS Nova/Kerry Hensley] Like Night and Day Because the system’s orbit is almost exactly edge on from our point of view, the white dwarf is completely eclipsed as the much larger brown dwarf passes in front of it. This allows the contributions from the two components to be separated, and for the emission from the brown dwarf’s nightside to be measured. The authors constrained the brown dwarf’s nightside temperature to roughly 1750K. Its dayside temperatures are likely to be significantly higher — potentially around 3750K at the point where the white dwarf is directly overhead — but more data are needed to constrain the dayside temperature of this world. Day–night temperature difference (left) and irradiation flux (right) of the brown dwarf in this system compared to other white dwarf–brown dwarf systems and hot and ultra-hot Jupiters. Click to enlarge. [de Wit et al. 2026]The estimated day–night temperature difference for this brown dwarf places it in the realm of hot and ultra-hot Jupiters. However, it’s subjected to more ultraviolet radiation than a typical hot or ultra-hot Jupiter orbiting a main-sequence star. This makes J0404+1112 a valuable system for disentangling the interconnected effects of temperature, radiation environment, atmospheric composition, and other factors on hot or ultra-hot Jupiters and other strongly irradiated brown dwarfs. We can certainly expect to learn more about this rare system as new data are collected! Citation “J0404+1112: A 3 hr Eclipsing White Dwarf–Brown Dwarf Probing Multiple Atmospheric Regimes,” J. de Wit et al 2026 ApJL 1009 L40. doi:10.3847/2041-8213/ae9a97 The post Astronomers Get a Better Look at a Rare White Dwarf–Brown Dwarf Pair appeared first on AAS Nova. ]]> "J0404+1112: A 3 hr Eclipsing White Dwarf–Brown Dwarf Probing Multiple Atmospheric Regimes," J. de Wit et al 2026 ApJL 1009 L40. doi:10.3847/2041-8213/ae9a97 A Point-Spread Function for the Extreme Ultraviolet High-Resolution Imager on Board Solar Orbiter Fri, 16 Oct 2026 16:00:30 +0000 ?p=16313 Stefan J. Hofmeister et al 2026 ApJS 286 3 Researchers have assessed the diffusion and scattering within an ultraviolet instrument on board Solar Orbiter, which takes detailed observations of our home star from as close as about 60 au. The post A Point-Spread Function for the Extreme Ultraviolet High-Resolution Imager on Board Solar Orbiter appeared first on AAS Nova. ]]> Stefan J. Hofmeister et al 2026 ApJS 286 3 Researchers have assessed the diffusion and scattering within an ultraviolet instrument on board Solar Orbiter, which takes detailed observations of our home star from as close as about 60 au. The post A Point-Spread Function for the Extreme Ultraviolet High-Resolution Imager on Board Solar Orbiter appeared first on AAS Nova. ]]> Not available Inferring Globular Cluster Initial Mass Function from Stellar Streams Thu, 15 Oct 2026 16:00:06 +0000 ?p=16311 Claire S. Ye and Raymond G. Carlberg 2026 ApJL 1007 L25 Pairing cold dark matter simulations with observations of stellar streams and globular clusters, researchers have extracted a declining power-law-like globular cluster initial mass function. The post Inferring Globular Cluster Initial Mass Function from Stellar Streams appeared first on AAS Nova. ]]> Claire S. Ye and Raymond G. Carlberg 2026 ApJL 1007 L25 Pairing cold dark matter simulations with observations of stellar streams and globular clusters, researchers have extracted a declining power-law-like globular cluster initial mass function. The post Inferring Globular Cluster Initial Mass Function from Stellar Streams appeared first on AAS Nova. ]]> Not available Electromagnetic Flares from Compact-Object Mergers in Active Galactic Nucleus Disks: Signatures and Predictions Wed, 14 Oct 2026 16:00:10 +0000 ?p=16309 Hiromichi Tagawa et al 2026 ApJ 1006 121 Emission arising from the merger of stellar-mass black holes in an active galactic nucleus disk should be identifiable through monitoring of order 1,000 active galactic nuclei of sufficient luminosity for a year. The post Electromagnetic Flares from Compact-Object Mergers in Active Galactic Nucleus Disks: Signatures and Predictions appeared first on AAS Nova. ]]> Hiromichi Tagawa et al 2026 ApJ 1006 121 Emission arising from the merger of stellar-mass black holes in an active galactic nucleus disk should be identifiable through monitoring of order 1,000 active galactic nuclei of sufficient luminosity for a year. The post Electromagnetic Flares from Compact-Object Mergers in Active Galactic Nucleus Disks: Signatures and Predictions appeared first on AAS Nova. ]]> Not available Catching the Culprit Behind Globular Clusters’ Disappearing Binaries 2026/10/14/catching-the-culprit-behind-globular-clusters-disappearing-binaries/?utm_source=rss&utm_medium=rss&utm_campaign=catching-the-culprit-behind-globular-clusters-disappearing-binaries Wed, 14 Oct 2026 16:00:08 +0000 ?p=16368 Globular clusters have far fewer binary stars than the solar neighborhood. New research identifies black hole burning as the culprit. The post Catching the Culprit Behind Globular Clusters’ Disappearing Binaries appeared first on AAS Nova. ]]> Roughly one-third of stars in the Milky Way are in binary or multiple systems, but only ~1–10% of stars in globular clusters have a companion. Did globular clusters start with fewer binaries than the solar neighborhood, or have they since been wiped out? Survival of the Tightest Map of the semi-major axis–primary mass parameter space for binary systems. Solid lines show the boundary between hard (below the line) and soft (above the line) binaries for a variety of models. Models A–K span a variety of cluster masses and virial radii (a proxy for cluster density). [O’Connor et al. 2026]Globular clusters (GCs) are dense, ancient, gravitationally bound groups of stars. A team led by Christopher O’Connor at Northwestern University explored whether the lack of binary systems could be the result of some process unique to GCs. First, the team developed an analytical formalism to understand how binaries in a GC evolve depending on the binary stars’ masses, distance from each other, and interactions with other stars in the cluster. It turns out that the fate of a binary system depends on whether it is dynamically “hard” or “soft.” Hard binaries are generally tightly bound, and they tend to get “harder” from stellar flybys, which are common in a crowded cluster environment. Soft binaries are the opposite — they have much shorter lifetimes since encounters with other stars tend to loosen them. The team found that, assuming GCs have the same initial distribution of binaries as the solar neighborhood, the dissolution of soft binaries is sufficient to explain the present-day scarcity of binaries in GCs. Burning Away the Binaries What actually tears the soft binaries apart? The answer is a process called “black hole burning.” As some of the most massive objects in a globular cluster, black holes in binary systems can transfer energy when they interact with passing stars. This influx of energy can excite soft binaries to the point of dissolution, the study shows. Black hole burning can also prevent core collapse in GCs. Left to itself, a cluster’s core gradually loses energy to its outskirts, causing the core to grow hotter and denser with stars. This leads to more dynamical interactions between stars that can then get flung from the core or enter new tight binaries. Black hole burning pumps energy back into the core and prevents this from happening. Putting the Theory to the Test The total number of black holes in a cluster (top) and the binary fraction (bottom) as a function of time for three different cluster models. In the densest cluster (blue), binary dissolution starts early on, mainly driven by stellar collisions. For the other two models, binary dissolution mainly occurs after the number of black holes reaches its peak and black hole burning commences. [Adapted from O’Connor et al. 2026]To validate their analytical results, the team performed N-body simulations of GC dynamics with the Cluster Monte Carlo code. They found that, in moderate-to-low-density clusters, the decline of binary systems is powered mainly by black hole burning. In more compact clusters, however, stellar collisions also play an important role in the dissolution of binary systems, and at earlier times than the onset of black hole burning. In general, the final binary fractions of the simulated clusters agree with those predicted by the team’s analytical formalism. This further supports the theory that there is a universal initial binary distribution between galactic GCs and our solar neighborhood. Constraining this distribution is pivotal for refining dynamical models of GCs. In short, GCs and the solar neighborhood likely started with the same amount of binary systems, and interstellar dynamics handled the rest. Citation “A Common Origin for Binary Fractions in the Field and in Dense Clusters,” Christopher E. O’Connor et al 2026 ApJ 1009 L80. doi:10.3847/1538-4357/aea078 The post Catching the Culprit Behind Globular Clusters’ Disappearing Binaries appeared first on AAS Nova. ]]> “A Common Origin for Binary Fractions in the Field and in Dense Clusters,” Christopher E. O’Connor et al 2026 ApJ 1009 L80. doi:10.3847/1538-4357/aea078 The Properties of Globular Clusters and Elqui Associated with the Sagittarius Dwarf Galaxy Tue, 13 Oct 2026 16:00:28 +0000 ?p=16307 P. Wang et al 2026 AJ 172 102 After identifying a new globular cluster, HSC 61, belonging to the Sagittarius dwarf galaxy, researchers have mapped the stellar stream, determined its metallicity, and analyzed the Sagittarius merger event. The post The Properties of Globular Clusters and Elqui Associated with the Sagittarius Dwarf Galaxy appeared first on AAS Nova. ]]> P. Wang et al 2026 AJ 172 102 After identifying a new globular cluster, HSC 61, belonging to the Sagittarius dwarf galaxy, researchers have mapped the stellar stream, determined its metallicity, and analyzed the Sagittarius merger event. The post The Properties of Globular Clusters and Elqui Associated with the Sagittarius Dwarf Galaxy appeared first on AAS Nova. ]]> Not available Drawing Back the Curtain on Solar Spicules 2026/10/13/drawing-back-the-curtain-on-solar-spicules/?utm_source=rss&utm_medium=rss&utm_campaign=drawing-back-the-curtain-on-solar-spicules Tue, 13 Oct 2026 16:00:19 +0000 ?p=16363 Why do spicules — tiny spikes of plasma on the Sun — appear to rotate, split, and merge? New simulations reveal the possible cause of these motions. The post Drawing Back the Curtain on Solar Spicules appeared first on AAS Nova. ]]> The Sun’s surface is peppered with spikes of plasma called spicules that appear to shift and twist over time. Recent simulations suggest a new explanation for the motion of solar spicules. Solar spicules as seen by the Hinode mission. [Adapted from Dey et al. 2026] Jets in Motion Solar spicules are tiny jets of solar plasma that last just a few minutes. When viewed along the solar limb, spicules resemble blades of grass blowing in the wind. Observations show these structures moving in a variety of ways: twisting, shifting side to side, splitting, and joining together. Though spicules were first identified more than a century ago, where these motions come from is still up for debate. In a recent research article, Sahel Dey (University of Newcastle; Indian Institute of Astrophysics; Indian Institute of Science) and collaborators performed 3D magnetohydrodynamics simulations to investigate the source of solar spicules’ motion. The team’s simulations encompassed a volume of 6,000 × 9,000 × 37,000 kilometers that stretched from beneath the visible surface of the Sun up to the lower region of the Sun’s outer atmosphere, or corona. In this region, they applied a uniform vertical magnetic field, mimicking the conditions within a coronal hole, where the Sun’s magnetic field streams outward into the solar system A) A three-dimensional view of simulated solar spicules, showing curtain-like structures. B) Intensity of synthetic emission from the spicules in panel A, integrated along the line of sight. The cyan circle indicates the same region in both panels. [Adapted from Dey et al. 2026]Convection low in the simulation region generates slow magnetohydrodynamic waves, which create pockets of hot, upward-moving plasma and launch the spicules. When looking at the 3D structure of the spicules, Dey and collaborators found that they are not individual jets as they appear to be in photographs of the Sun. Instead, the sea of spicules creates an interconnected structure similar to a folded curtain. Simulating Spicules The jet-like appearance arises when this arrangement is viewed from the side; the team created synthetic images of their simulated spicules that show individual jet-like features. These “jets” have properties similar to those of real spicules, lasting just 5–10 minutes, journeying upward at 20–70 kilometers per second, and reaching heights of 6,000–16,000 kilometers. These simulations clearly demonstrate that what appear to be individual jets can arise from curtain-like plasma structures. Dey and collaborators showed that this network of spicules evolves over time, buoyed upward from below by a series of shocks, pulled down gradually by gravity, and buffeted by adjacent plasma. Three-dimensional view of spicules (purple–yellow regions) and coronal swirling conduits (represented by spiraling black lines). [Adapted from Dey et al. 2026]The team showed that when spicules seem to rotate, merge, or split, these are largely apparent motions. For example, when two spicules appear to merge, this could be caused by different sections of a plasma curtain aligning along the line of sight. Some of the spicule rotation is due to what the authors term coronal swirling conduits: columns of rotating plasma interspersed within the network of spicules. These swirling plasma columns can transfer some of their motion to the spicules, especially when the spicules are falling back toward the solar surface. This work demonstrates that a curtain-like configuration provides a viable explanation for the observed variety of spicule motions. Going forward, it will be critical to test this possibility further, as correctly interpreting the underlying structures of solar spicules is key to understanding how mass and energy are transferred to the solar corona. Citation “Solar Spicule Rotation Driven by Plasma Curtain–Vortex Interactions,” Sahel Dey et al 2026 ApJ 1008 132. doi:10.3847/1538-4357/ae8999 The post Drawing Back the Curtain on Solar Spicules appeared first on AAS Nova. ]]> "Solar Spicule Rotation Driven by Plasma Curtain–Vortex Interactions," Sahel Dey et al 2026 ApJ 1008 132. doi:10.3847/1538-4357/ae8999 The Invisible Architecture Between the Stars 2026/10/12/the-invisible-architecture-between-the-stars/?utm_source=rss&utm_medium=rss&utm_campaign=the-invisible-architecture-between-the-stars Mon, 12 Oct 2026 16:00:58 +0000 ?p=16341 Astrobites reports on why interstellar magnetic fields can appear ordered or tangled, depending on which gas clouds you measure and how. The post The Invisible Architecture Between the Stars appeared first on AAS Nova. ]]>

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