Combining strongly lensed gravitational wave signals with luminosity distances from their host galaxies, the Hubble constant could be measured in a way that is complementary to electromagnetic methods.
The post The Impact of Strong Lensing on Hubble Constant Measurements with Gravitational-Wave Dark Sirens appeared first on AAS Nova.
Modeling suggests that even planets within their stars’ habitable zones may become uninhabitable if they do not have a sufficient water inventory to balance their carbon cycle.
The post Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus appeared first on AAS Nova.
What’s the story behind the longest gamma-ray burst ever observed? Researchers explore how repeated interactions between a white dwarf and an intermediate-mass black hole could explain GRB 250702B’s unusual properties.
An image of GRB 250702B’s location within its host galaxy. [NASA, ESA, CSA, H. Sears (Rutgers). Image Processing: A. Pagan (STScI)]
These characteristics have been challenging to explain with typical models of long gamma-ray burst formation, such as collapsing massive stars, but researchers have developed numerous promising alternatives. In a new research article, astronomers have shown how GRB 250702B’s behavior might be explained by repeated close encounters between a white dwarf and an intermediate-mass black hole.
Yuri Sato (Tohoku University) and collaborators modeled the source of GRB 250702B as a white dwarf that has been captured into orbit around an intermediate-mass black hole. In their model, the white dwarf travels on an extremely eccentric orbit, drawing close to the black hole roughly once an hour. Each time the white dwarf ventures close, the black hole’s tidal forces strip away part of the star until, after about 40 such encounters, the white dwarf is completely destroyed.
Schematics showing the orbit of the white dwarf (WD; left) and the geometries that produce observable and unobservable jets. Click to enlarge. [Sato et al. 2026]
The discrepancy can be resolved if the angle between the jet and the black hole’s spin axis precesses over time so that only some of the jets are pointed toward us. This can occur if the accretion disk is misaligned relative to the black hole’s spin. As an alternative, disk instabilities or other processes could keep all but a few of the expected jets from being launched.
Predicted strength of the radio afterglow for the jet precession case (maximum case) and the case in which only four jets were launched due to disk instabilities or jet choking (minimum case). The x-axis shows the time since the burst was detected in X-rays by the Einstein Probe (EP). [Sato et al. 2026]
This work by Sato and collaborators demonstrates how the repeated partial tidal disruption of a white dwarf by an intermediate-mass black hole can match the properties of one of the most remarkable recent transient sources — one that has pushed astronomers to consider new ways of producing gamma-ray bursts.
“Successive Partial Disruptions with Orbital Precession in a White Dwarf–Black Hole System for Repeating GRB 250702B,” Yuri Sato et al 2026 ApJL 1003 L44. doi:10.3847/2041-8213/ae6a8f
The post Could a White Dwarf–Black Hole Pair Explain the Longest Gamma-Ray Burst Ever Seen? appeared first on AAS Nova.
ZTF19acnskyy may be the first X-ray quasiperiodic eruption source to display correlated ultraviolet emission — another strange behavior that researchers must explain for this already unique source.
The post Evidence for a Delayed Ultraviolet Counterpart to X-Ray Quasiperiodic Eruptions in Ansky appeared first on AAS Nova.
Simulations suggest that tidally locked planets have similar atmospheric escape rates to Earth analogs despite having cooler and drier atmospheres near their surfaces.
The post The Response of Planetary Atmospheres to the Impact of Icy Comets. III. Impact Driven Atmospheric Escape appeared first on AAS Nova.
Using the Five-hundred-meter Aperture Spherical radio Telescope, researchers have discovered and measured the spins and masses of a pair of neutron stars using the pulsar timing method.
The post Mass Measurements of the Double Neutron Star System PSR J0641+0448 appeared first on AAS Nova.
A survey of six gas giants orbiting F-type stars suggests that atmospheric escape of these planets is determined by the X-ray and extreme-ultraviolet output of their host stars as well as the Roche filling factor.
The post The First Dedicated Survey of Atmospheric Escape from Planets Orbiting F Stars appeared first on AAS Nova.
Planets that get too close to their host stars are liable to be engulfed and consumed. New research explores how to identify stars that have had a planetary snack.
Being a planet that closely orbits its star is dangerous, and various dynamical processes can draw a planet inward past the point of no return. When a planet vanishes beneath the surface of its host, it eventually disintegrates within the star, its atoms mixing into the blazing stellar soup.
This outcome is likely extremely common across the universe, and researchers have begun to see evidence for it: stars that appear to have absorbed angular momentum from their planets, white dwarfs with uncanny metals in their spectra, and stars with chemical abundances that don’t match those of their siblings. Now, in a recent publication led by Kaitlyn Lane (Vanderbilt University), researchers seek to find observational signatures of planetary engulfment of rocky exoplanets by main-sequence stars.
Lane’s team focused on main-sequence stars in the range of 0.5 to 1.4 solar masses, using one-dimensional analytical models to determine which of these stars will most readily display signs of having engulfed a planet. They simulated the stars as they consumed either an Earth-like planet or a super-Earth with the same composition as Earth but 15 times its mass.
Diagram showing a planet being engulfed by its star and beginning to disintegrate before migrating inward. The boundary between the star’s outer convective zone (CZ) and inner radiative zone is shown. Click to enlarge. [Lane et al. 2026]
After that relatively lengthy phase, the process proceeds rapidly: as the planet inches deeper into its star, the drag forces grow stronger and the planet’s demise accelerates, with the planet disintegrating over the course of hours. In the last phase, the planet makes its final plunge and is destroyed in a half hour.
Lane’s team found that the planets tended to be destroyed fully within the outer convective layer of their stars, except in the case of the most massive stars studied here. For more massive stars, the outer convective zone is shallower than it is for the less massive stars, allowing a chunk of each planet to survive the passage through the convective zone to reach the radiative zone below.
The trajectories of three example cases, showing how the planet loses mass as it spirals inward. In the 1.4-solar-mass case, part of the planet survives to reach the radiative zone, but the shallowness of the star’s convective zone means that the disintegrated planetary material is easier to observe. Click to enlarge. [Lane et al. 2026]
While the authors acknowledge that there’s more work to be done — they plan to investigate the impacts of planetary engulfment on stellar structure more closely, for example — this work represents an important foray into identifying targets for future studies of stars that have eaten their planets.
“Observable Metal Pollution in Main-Sequence Stars: Simulations of Rocky Planets Engulfed by Stars in the 0.5 to 1.4 M⊙ Range,” Kaitlyn T. Lane et al 2026 ApJ 1003 67. doi:10.3847/1538-4357/ae5b9a
The post Now That’s Metal: How to Spot Stars That Have Swallowed Their Planets appeared first on AAS Nova.
Using simulations of 20 asteroids from 0.05 to 2.4 au away, researchers demonstrate how the technique of topocentric parallax could be used to determine the distance to an asteroid in a single night.
The post Measuring the Distances to Asteroids from One Observatory in One Night with Upcoming All-Sky Telescopes appeared first on AAS Nova.
Simulations suggest that Rubin Observatory will discover 1–2 meter-size or larger imminent impactors each year, nearly doubling the discovery rate and providing an important set of eyes in the Southern Hemisphere.
The post Predictions of Imminent Earth Impactors Discovered by LSST appeared first on AAS Nova.
Researchers have found a rare example of a blue straggler star in the process of formation, providing direct evidence for the formation of these puzzling stars through ongoing mass transfer in a binary system.
The post Blue Straggler in the Making: An X-Ray Active Binary in Algol Configuration appeared first on AAS Nova.
The Antennae galaxies are a nearby pair of interacting galaxies, shown in optical light from the Hubble Space Telescope (left) and in infrared light from JWST (right) in the image above. Between the two galaxies’ bright nuclei, there is a vast and dusty molecular cloud complex that harbors a large number of massive young star clusters — and in a recent article led by Rupali Chandar (University of Toledo), researchers have worked to pin down exactly how many clusters are embedded within the dusty whorls of the Antennae galaxies. The team used JWST to search for emission from star clusters too thickly blanketed with dust to be visible in previous observations by Hubble. They ultimately identified 45 sources, 40 of which were seen for the first time in this study. These star clusters mostly inhabit the overlap region between the two galaxies, are less than 2.5 million years old, and each contain roughly 104–106 solar masses. To learn more about how JWST’s infrared capabilities unveiled young star clusters in these interacting galaxies, be sure to check out the full article linked below.
“Nowhere Left to Hide: Uncovering All of the Massive Young Embedded Star Clusters in the Antennae with JWST,” Rupali Chandar et al 2026 ApJ 1002 64. doi:10.3847/1538-4357/ae56e8
The post Featured Image: Massive Young Star Clusters, Revealed appeared first on AAS Nova.
In a sample of 171 new dual active galactic nuclei, four triplets, and one quadruplet drawn from a catalog of nearly a million quasars, researchers find that roughly 16% of targets exhibit tidal features.
The post Dual Active Galactic Nuclei on 100 kpc Scales from the Million Quasar Catalog appeared first on AAS Nova.
Researchers find a system inclination of 41.8 degrees for WR 104; this result is at odds with previous interpretations of the system’s dust plume, but a new geometric model reconciles these results.
The post Can the Dust Eclipses in WR 104 Provide Constraints on the System’s Inclination? appeared first on AAS Nova.
The observed steepening of the cosmic-ray spectrum at ~4 PeV could be a global or local feature; a local feature could be explained by sources located ~1 kpc away with ages of 0.1–1 million years.
The post The Cosmic-Ray Knee as a Local Signature of Nearby PeVatrons appeared first on AAS Nova.
Where do black hole mergers happen? Recent research finds evidence that most black hole mergers occur in triple systems containing a close inner binary and a more distant third party.
Thanks to the combined efforts of the LIGO, Virgo, and KAGRA gravitational wave detectors, we’ve now collected the subtle signals from several hundred pairs of merging stellar-mass black holes. As this collection of spacetime ripples continues to grow, researchers are seeking to understand how these merging black hole pairs were assembled.
In the simplest scenario, pairs of high-mass stars independently evolve into black holes, lose momentum by emitting gravitational waves, and meld into one another. But the population of merging black holes likely contains contributions from multiple sources, including multiple-star systems, the disks surrounding accreting supermassive black holes, and black holes that have already experienced a merger. Which of these merging populations is reflected in our catalog of gravitational wave events?
A black hole binary system with aligned spins and orbit (top) and a binary with spins tilted by 90 degrees (bottom). [AAS Nova/Kerry Hensley]
So far, the increasingly large pool of gravitational wave detections tentatively points to a feature that could illuminate the sites of black hole mergers: a peak in the spin–orbit tilt distribution around 90 degrees. This feature has been most confidently extracted from nonparametric analyses, which do not make assumptions about the population of merging black holes, but it has also been hinted at in parametric analyses, which do make population-level assumptions.
To investigate this feature further, a team led by Jakob Stegmann (Max Planck Institute for Astrophysics) performed a new, astrophysically motivated parametric analysis of the most recent catalog of gravitational wave detections from LIGO, Virgo, and KAGRA.
The three populations in the team’s modeling. [Stegmann et al. 2026]
Posterior predictive distribution of black hole spin–orbit tilts. Both the authors’ modeling (solid blue line) and the nonparametric modeling performed by the LIGO–Virgo–KAGRA collaboration (solid green line) find evidence for a peak in the spin–orbit tilt distribution near cosθ = 0. [Adapted from Stegmann et al. 2026]
Stegmann and collaborators pointed out that the triple-system scenario aligns well with other properties of the observed population of black hole mergers, such as the mass and effective spin distributions. This scenario may also be necessary to explain certain merging pairs that might have had slightly eccentric orbits at the moment of merging. If future gravitational wave observations strengthen the evidence for a peak in the spin–orbit tilt distribution near 90 degrees, it will have profound implications for how and where black holes merge in our universe.
“Gravitational-Wave Observations Suggest Most Black Hole Mergers Form in Triples,” Jakob Stegmann et al 2026 ApJL 1000 L59. doi:10.3847/2041-8213/ae52ec
The post Third Star’s the Charm: Most Merging Black Holes Might Be in Triple Systems appeared first on AAS Nova.
Using three dedicated telescopes and two spacecraft in the Earth–Moon environment, researchers demonstrate the abilities of an image stacking method to detect space debris.
The post Optical Survey for Cislunar Moving Objects Using Image Stacking appeared first on AAS Nova.
Analysis of 10 nights of observations of Europa’s auroral emission suggests that optical auroral brightness may be a proxy for electron density variations, assuming a stable atmospheric composition and density.
The post Variability of Europa’s Optical Aurora on Orbital and Multiyear Timescales appeared first on AAS Nova.
Magnetothermal modeling suggests that neutron stars may remain “silent” at radio frequencies for approximately 100,000 years before activating, potentially as long-period radio transients.
The post Late-Blooming Magnetars: Awakening as Long-Period Transients After a Dormant Cooling Epoch appeared first on AAS Nova.
A newly discovered massive giant planet likely has a retrograde orbit relative to the other known planet in the system, pointing to a potentially violent dynamical history.
The post HD 164604 c: A Second Giant Planet on a 15 Yr Orbit and Constraints on the Planet–Planet Mutual Inclination appeared first on AAS Nova.
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