NASA's Chandra X-ray spacecraft has detected the supernova wreckage of a dead star that erupted 1,700 years ago and ejected debris at 2 million miles per hour.

On June 12, 2021, Nova Herculis 2021 (V1674 Herculis) erupted, and was discovered by amateur astronomer Seiji Ueda of Japan. The white dwarf quickly became visible to the naked eye, surging to 10,000 times brighter than it originally had been. Its speed was unprecedented: V1674 Herculis faded from that peak brightness in just over oneContinue reading "June 12, 2021: Seiji Ueda discovers Nova Herculis 2021"

The post June 12, 2021: Seiji Ueda discovers Nova Herculis 2021 appeared first on Astronomy Magazine.

Eyes on Exoplanets Tutorial

Welcome to NASA’s Eyes on Exoplanets! Use this tutorial to start exploring worlds beyond our own. With this 3D interactive tool, you can visit all the stars beyond the Sun where we’ve found other planets, called exoplanets. 

Choose a star or exoplanet and see an artist’s concept of what it might look like. Spin it around to see its sun and planetary system. Learn how long a trip there from Earth would take at light speed — or by jet plane, or family car!

Study the real versions of planets and stars cited in your favorite science fiction. See which planets reside in habitable zones, where liquid water could exist on their surfaces. Or, search “Where We Explore,” stars that future space telescopes will target when looking for Earth-like planets. You can also choose your location on Earth and see what’s in the sky above you right now.

Select any of the stars shown to see how many planets have already been found there. Examine how those star systems compare to the layout of our solar system, or check the sizes of individual planets — are they as small as Earth, or as big as Jupiter? 

See all the different techniques we’ve used to confirm the 6,000+ exoplanets discovered so far — among the billions we believe exist in the galaxy — and the many observatories, on Earth and in space, that have detected them. You can also browse some of our favorite weird worlds, or destinations featured in our Exoplanet Travel Bureau.

Where will you explore?

Transcript

Welcome to NASA’s Eyes on Exoplanets. With this interactive tool, you can explore all of the stars beyond the Sun where we’ve discovered planets known as exoplanets. When you enter the site, the default is this view from space. You can start your exploration here. Or if you know of a specific star or exoplanet you want to visit, enter that in the search bar at upper right. 

You can also select View from Earth. Choose your location and see what’s in the sky above you right now. Click and drag to explore different parts of the sky. In the lower right corner, you can choose different display options. You can see the constellations, view only stars that are visible to the naked eye, or see the stars that are good places for future telescopes to search for planets like Earth. 

These future target stars are shown as filled-in circles. If you click the gear symbol and switch from the star symbol to the circled number, you will see how many exoplanets have already been found around the star shown. 

When you select a star, you have three different view options. Starting in System View, you will see the star and where planets are located around it. The shaded green area marks the habitable zone, the region around a star where a planet could have liquid water on the surface, a key to the search for life beyond Earth. You can also see how this system compares to our solar system by selecting that feature in the lower right. The star view will show a hypothetical view of what the star might look like. 

Click “Learn More” to see basic information about the star, including its history and pop-culture references. You can see how it compares to our Sun and solar system and what we found so far. Under “How to Detect a Planet in the System,” you can learn about the different ways to discover an exoplanet and see how many planets have been found with each technique, as well as the prospects for discovering more. Finally, the planet view allows you to explore each planet in the system. 

For each confirmed exoplanet, you’ll see an artist’s concept of what it might look like and see how it compares to other planets. Planets also have an option to learn more, where you can see how far away it is, how long it would take to get there, how it was discovered, and which observatory found it. 

To see other discoveries made by that observatory, click “Browse Destinations” in the upper right menu. There you can also find curated lists of featured discoveries and truly weird worlds. 

As you can see, there are so many worlds to discover. Where will you explore?

The post Eyes on Exoplanets Tutorial appeared first on NASA Science.

A new study has taken a fresh look at a late 2025 Yonsei University study claiming the universe’s expansion is stalling out and instead has found that the universe is still expanding as previously believed.

Led by researchers from the University of Southampton, the team behind the new analysis acknowledged the scientific value of the 2025 team’s work, noting that their calculations were not wrong but lacked the additional data needed to confirm the universe’s expansion rather than refute it.

The lead author of the 2025 study, Dr. Chul Chung, told The Debrief that he and his colleagues “have already submitted our response to Wiseman, Riess et al. 2026 on May 14,” adding that the paper, “Still accelerating: age bias correction in supernova cosmology is robust to host-progenitor age mapping,” has also been posted on arXiv.

“The abstract summarizes the two main issues we identify in Wiseman et al., so I think it provides a concise overview of our position,” Chung told The Debrief.

Challenging Universal Expansion

According to a statement announcing the findings, scientists first confirmed the universe’s expansion was accelerating in 2011, a discovery that won astrophysicists Professor Adam Riess and Professor Brian Schmidt the Nobel Prize in Physics. Since that discovery, cosmological models have incorporated this accelerating expansion, with experiments on dark matter and dark energy attempting to explain it.

Then last year, a separate team of astronomers announced that a new analysis of stellar phenomena indicated that the universe was no longer expanding. Adding to the controversy was the team’s claim that dark energy may not exist, citing the lack of concrete evidence for a universe undergoing accelerating expansion.

According to the Southampton-led team behind the new study, the 2025 study suggested that previous methods used to measure the universe’s expansion, such as measuring supernovae, “were fundamentally flawed.”

“This points to a time-varying dark energy and a universe that is no longer accelerating, representing a potential paradigm shift in cosmology if confirmed,” explained Professor Chul Chung, co-lead author on the study, in a 2025 email to The Debrief.

The claims sent shockwaves through the scientific community, a result that the researchers note could have dismantled the Nobel Prize-winning team’s historic findings, and “nearly three decades of astronomical progress.”

When discussing the 2025 team’s work, the lead author of the new study, Dr Phil Wiseman, said the team’s findings and the resulting debate were not necessarily incorrect. Instead, the Southampton researcher said it was primarily a result of a scientific understanding.

“The previous and well-accepted measurements were, in fact, fine and our current understanding of the fate of the universe remains robust.”

Recalculating Galaxy Masses and White Dwarf Star Ages Reestablishes Expansion

In their reanalysis, the Southampton-led team recalibrated the original data to account for variables not in the original study. According to Wiseman, these included “different host environments and populations.”

For example, the research team looked at Type 1a supernovae, which are violet, extremely bright explosions of white dwarf stars. The authors of the 2025 study claimed that this class of supernova had “different maximum brightness,” which had tricked astronomers into thinking the cosmos was accelerating, when their analysis said it was actually slowing down.

When they took a fresh look at the data, the Southampton team found that they had incorrectly estimated the age of these stars. The new study also says the 2025 team didn’t account for the mass of the galaxies hosting these cosmological phenomena, which they described as “a standard correction used in modern cosmology to prove accuracy.”

When his team factored those data points in, Wiseman said the evidence for a stalling expansion was not supported. Instead, the researcher observed that “the evidence for cosmic acceleration remains remarkably consistent.”

In their reply on ArXiv, the Yonsei University team said the new research failed to factor in two variables of their own, adding that “when these two effects are consistently combined in computing the redshift-dependent magnitude correction, the final correction, and hence the resulting cosmological impact, remain largely unchanged,” from the original 2025 calculations.

“Extraordinary Claims Require Especially Careful Testing”

When discussing the new study’s findings, Southampton Professor Mark Sullivan highlighted the benefits of scientific review, noting that “this is how progress is made.”

“Although this idea did not turn out correct, it has opened up new ways of thinking about how supernovae explode and how we can measure dark energy more accurately,” the researcher added.

Paper co-author, Dr Brodie Popovic agreed, noting that the 2025 study provided astronomers a good opportunity to “go back over all of our assumptions,” adding that “it turns out, yes, we do understand this stuff, and we’re accounting for it in our cosmology measurement.”

In a salute to the Sagan Standard established by astronomer Carl Sagan, which says “extraordinary claims require extraordinary evidence,” Reiss seemed to celebrate the new findings that reestablish his original work by quipping that “extraordinary claims require especially careful testing.”

With the accelerating expansion of the universe seemingly reestablished, at least for now, Dr Wiseman said: “we can get back to trying to understand what dark energy actually is, rather than wondering if it exists at all.”

“Thankfully we have averted this crisis, but the mystery about why the universe is still accelerating in size remains,” he added. 

The study “Still Accelerating: Type Ia supernova cosmology is robust to host galaxy age evolution” was published in Monthly Notices of the Royal Astronomical Society.

Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.

Zooming through the galaxy faster than they should, hypervelocity stars are a curious population of stars whose origins are often difficult to determine. A recent study presents the first evidence of an old, low-mass hypervelocity star launched from the Milky Way’s center, providing clues into this elusive set of fast-moving stars.

Flinging Fast Stars

Astronomers have caught a number of hypervelocity stars zipping through the Milky Way since their first discovery in 2005. With speeds fast enough to escape the galaxy, hypervelocity stars were launched off course by some strong dynamical interaction. One such method, known as the Hills mechanism, predicts that when a binary star system approaches the Milky Way’s central supermassive black hole, one binary member is captured by the black hole and the other is flung away with high velocity.

However, constraining a hypervelocity star’s origin to the galactic center is limited by uncertainties in distances and proper motions, muddling how well researchers have been able to trace their orbits backward. Among a number of candidate galactic center–origin hypervelocity stars, only one has been confidently identified as having been kicked from the galaxy’s center. Intriguingly, this hypervelocity star and most galactic center–origin candidates are young, massive stars — old, low-mass hypervelocity stars from the galactic center have yet to be identified.

What does this dearth of old, low-mass zooming stars mean? Either stars in the galactic center are preferentially young and massive, with fewer than expected old and small stars, or low-mass hypervelocity stars are missed by selection effects, challenging to detect in current surveys. Searching for hypervelocity stars with higher precision and sensitivity may allow astronomers to tease out this missing population and trace back more zooming stars to a Hills mechanism origin.

Discovering An Old Hypervelocity Star

Leveraging high-quality spectra from the Dark Energy Spectroscopic Instrument (DESI) survey and precise astrometry from Gaia, Shunhong Deng (University of Chinese Academy of Sciences; China West Normal University) and collaborators reported the discovery of the hypervelocity star DESI-HVS1. From the spectroscopic and astrometric analyses, the authors determined that DESI-HSV1 is a ~14-billion-year-old low-metallicity star with a mass about 80% that of the Sun’s, moving through the galaxy at 523 km/s.

Exploring the possible origins of this hypervelocity star, the authors integrated the star’s orbit backward in time for one billion years. The backward orbit integrations show the star approaching the galactic center where it then turns around, traveling away faster than the local escape velocity of the galaxy. Even when varying the galactic potential and constants, all orbit integrations suggest DESI-HVS1’s motion through the galaxy is most naturally explained by the Hills mechanism.

While more refined galaxy models and comparison to other candidate galactic center–origin hypervelocity stars are necessary to fully confirm its origins, DESI-HVS1 provides the first compelling evidence for an old, low-mass hypervelocity star candidate consistent with a galactic center launch. This suggests that the observed lack of such stars is likely not a reflection of the Milky Way’s central stellar population, but rather a consequence of observational constraints making such small hypervelocity stars particularly difficult to detect. As large spectroscopic and astrometric surveys continue to advance, the sample of galactic-center hypervelocity star candidates will grow, enabling further exploration of the stellar environment and dynamical processes at the Milky Way’s core.

Citation

“An Old, Low-mass, Metal-poor Hypervelocity Star Candidate Consistent with Galactic Center Origin,” Shunhong Deng et al 2026 ApJL 1003 L9. doi:10.3847/2041-8213/ae6505

The post Shot from the Heart of the Milky Way: Discovery of an Old Hypervelocity Star 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: Hunting for the First Explosions at the High-Redshift Frontier
Authors: Junehyoung Jeon et al.
First Author’s Institution: The University of Texas at Austin
Status: Published in ApJ

Back in the 1920s, astronomers discovered that we live within just one of many, many galaxies in the big, wide universe. Since then, we’ve been racing to search for the most distant galaxy that can be observed — in other words, searching for the oldest starlight we can see, since the light from these distant sources has been travelling towards us for most of the age of the universe. (Remember: more distant = higher redshift = longer lookback time.)

This race to the redshift frontier has had a pretty eventful history (see a great overview video here), which became even more eventful with the launch of JWST. JWST rapidly smashed the previous redshift (z) record of z = 10.6 by discovering a galaxy at z = 13.2, and then it broke its own record twice more. The current title holder sits at z = 14.4, observed less than 300 million years after the Big Bang.

Several galaxy candidates (to date unconfirmed) have now even been proposed at z ~ 25–32 (e.g., Capotauro), only 100 million years after the Big Bang! If real, these sources would pose a serious challenge to our understanding of the formation of the first galaxies, as galaxies shouldn’t really be observable at such early times. In today’s article, the authors put forward an intriguing alternative: what if some of these ultra-high-redshift candidates aren’t galaxies at all, but transient explosions from the universe’s first stars?

The First Stars and Their Explosive Endings

The earliest generation of stars (Population III; see my previous bite on these here) formed from pristine hydrogen and helium gas. Without metals to cool the gas efficiently, theory predicts that these stars were extremely massive, often exceeding 100 solar masses. While such stars would be short-lived, their deaths could be spectacular.

Population III stars of sufficient mass are predicted to end their lives as hyper-energetic pair-instability supernovae (PISNe). This is a long-winded name for a rapid, intensely hot explosion that leaves no remnant behind — not even a trace of the pre-existing star. Whilst nothing would remain of the star, the light emitted in that explosion could be bright enough to masquerade as a high-redshift galaxy candidate in current JWST surveys, but only if three key conditions are met:

1. JWST must observe a sufficiently overdense region, where lots of Population III stars can form very early.
2. A PISN must occur while JWST is “watching.”
3. The explosion must be bright enough to rise above JWST’s detection limits.

Simulating a (Biased) Universe

To address the likelihood of these conditions having already been met by existing JWST observations, the authors turn to cosmological simulations. Rather than simulating an “average” patch of the universe, they focus on an extremely overdense region (Fig. 1). This creates a rare but important environment where structures collapse earlier than usual. These regions are exactly where large numbers of Population III stars are expected to form at the highest redshifts.

In their simulations, star formation begins as early as z ~ 30–40 (within the first hundred million years after the Big Bang), producing Population III stars and, by extension, potential PISNe very shortly afterwards. While such overdense regions are rare, the authors show that the total area already surveyed by JWST (including large surveys such as CEERS, JADES, PRIMER, and COSMOS-Web) is large enough that it is plausible JWST has already observed at least one such region.

Catching a Cosmic Explosion in the Act

So, we can tick off condition #1: it’s possible that a sufficiently overdense region has already been observed by JWST. Next up, how lucky do we have to be to catch an explosion in the act (condition #2), so to speak? For this condition, cosmic time dilation actually works in our favour. A PISN explosion at z > 20 that lasts only months in its own rest frame can last for decades in the observed frame. (This whole time-being-relative thing sounds wacky because it is — please join me, Neil deGrasse Tyson, and countless others in struggling to imagine this.)

But would any such explosion be bright enough (condition #3)? Using theoretical PISN spectra, the authors show that these explosions could reach observed magnitudes of ~28–29 at z ~ 30 — right at the depth of current JWST deep surveys (Fig. 2). In fact, the predicted brightness and colours are somewhat comparable to those of some proposed z ~ 30 candidates (Fig. 3), raising the possibility that these objects could be PISNe rather than galaxies.

So… Are We Seeing the First Stars Die?

It’s not time to throw a party just yet. The authors note there are several caveats and uncertainties. The nature of Population III stars is still highly uncertain, JWST does not continuously monitor the same patch of sky, and identifying a PISN at such high redshift would be extremely challenging. Thanks to time dilation, these explosions would fade very slowly, making them hard to distinguish from steady sources using photometry alone. Alternatively, there are other plausible explanations for these ultra-high-redshift candidates: lower-redshift interlopers (a rather infamous example is CEERS-93316), local brown dwarfs, or even nearby exoplanets.

Still, the idea is exciting. If JWST were to detect a genuine PISN at z > 20, it would represent a direct glimpse of the very first stars, pushing observational astronomy into truly uncharted territory. For now, the most distant explosions in the universe may already be hiding in JWST images; we just have to learn how to recognise them.

Original astrobite edited by Nathalie Korhonen Cuestas.

About the author, Lucie Rowland:

I’m a fourth (and final!) year PhD student at Leiden Observatory in the Netherlands, studying massive, star forming galaxies in the early universe with ALMA and JWST. It’s a really exciting time to be interested in astronomy, so I hope to make groundbreaking new research more accessible!

The post The Oldest Starlight 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: GLIMPSE: An Ultrafaint ≃10⁵ M_⊙ Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at z ≃ 6–7
Authors: Seiji Fujimoto et al.
First Author’s Institution: University of Toronto; The University of Texas at Austin
Status: Published in ApJ

You, me, your laptop, my $8 matcha, and just about everything else on Earth was forged in the fiery bellies of dying stars. Generations of stars had to live and die before the universe became enriched with any elements heavier than helium (what astronomers call “metals”). The first stars to undergo this cosmic cycle are known as Population III (Pop III) stars. Though their existence has been hypothesized since the 1960s, astronomers have failed to observe these distant metal-free stars or the faint, low-mass galaxies that host them.

The first Pop III stars likely formed around 100 million years after the Big Bang in pristine pockets of hydrogen gas. Although these are too distant for us to observe, we expect that as the universe started to become metal enriched, there were still existing pockets of gas introverted enough to survive unpolluted and form metal-free Pop III stars up to a redshift of z ~ 6–7 (when the universe was around 900 million years old)!

JWST is the perfect instrument to search for these systems. You can read other astrobites on the search for possible Pop III systems with JWST here and here. The authors of today’s article seek to develop the most efficient way of using JWST’s Near-Infrared Camera (NIRCam) to find the galaxies hosting Pop III stars. Using their selection method on existing NIRCam data, the authors identified one promising Pop III galaxy candidate.

I’m Not Like Other Galaxies

In order to find a Pop III galaxy, we need to take a look at galaxies’ spectral energy distributions (SEDs). These are graphs that show the energy emitted by a galaxy at different wavelengths of light. Pop III galaxies are expected to have SEDs that differ from your everyday, metal-enriched galaxy. NIRCam will be especially sensitive to three key spectral features that show up in the SEDs of Pop III galaxies: an absent [O III] line (light emitted by doubly ionized oxygen atoms), a strong H-alpha line (light emitted when a hydrogen atom transitions from its third to its second energy level), and a significant Balmer jump (light absorbed to ionize electrons in the second energy level of a hydrogen atom). To identify these key SED characteristics, the authors use SED fitting and color–color diagrams to execute an efficient Pop III search with NIRCam.

The first selection method involves SED fitting. Astronomers create template SEDs that represent different types of galaxies and then compare these templates to the observed SEDs to see which one matches best. In this work, the authors use metal-rich galaxy templates and Pop III templates to fit the galaxies observed with NIRCam. They then calculate the chi-squared χ² (a statistical measure of best fit) between the data and all the SED templates. A galaxy is selected as a Pop III candidate if the Pop III model provides a good fit (χ² < 10) to the photometry and is significantly better than any metal-rich model. It’s kind of like looking for Cinderella by making every woman in the kingdom try on the glass slipper.

A color–color diagram plots the difference in magnitude between two filters on each axis. NIRCam filters are specially chosen to emphasize the SED characteristics above. When these filters are chosen, Pop III galaxies occupy a distinct region of this diagram as compared to metal-rich galaxies. For example, subtracting the F356W filter from the F277W filter is sensitive to the presence of the [O III] line and the Balmer jump. Figure 1 demonstrates how this color selection separates Pop III galaxies from typical galaxies.

O Pop III, Pop III, Wherefore Art Thou?

The authors apply their fresh new selection criteria to publicly available NIRCam data from large surveys. And (drum roll please) the slipper fits! The Pop III galaxy candidate GLIMPSE-16043 is an ultra-faint galaxy at z = 6.5. It was imaged in the GLIMPSE survey, which uses the technique of gravitational lensing to observe faint and distant galaxies.

The GLIMPSE survey targeted a massive galaxy cluster, Abell S1063. The cluster bends the light from distant galaxies and, like a giant lens, magnifies faraway objects, providing some of the deepest JWST imaging to date. The Pop III candidate passes both tests: it resides in the Pop III region of the color–color diagram, and its SED is best fit by a Pop III model, not a metal-rich galaxy model (see Figure 2). Next, spectroscopic follow-up is needed to ensure that this galaxy is truly metal free and not just extremely metal poor.

The authors conclude that our best shot at identifying additional Pop III galaxy candidates is using NIRCam to image large numbers of gravitationally lensed clusters. Without magnification from gravitational lensing, it may be impossible to see these ultra-faint Pop III galaxies. Once candidates have been identified, they can be followed up with deep spectroscopy to confirm their redshift and their lack of metals. Who knows? With these new methods, we may soon get a glimpse of the universe’s very first stars.

Original astrobite edited by Chris Layden and Margaret Verrico.

About the author, Madison VanWyngarden:

I am a first-year PhD student in astronomy and NSF Graduate Research Fellow at the University of Arizona. I study galaxy formation and evolution in the distant universe and am particularly interested in dusty star-forming galaxies. In my free time, I love reading, hiking, and baking bread!

The post A Possible GLIMPSE of the Universe’s First Stars appeared first on AAS Nova.

This image shows one W51A, of the most active star-forming regions in our galaxy. A research team led by Taehwa Yoo (University of Florida) recently observed this region with JWST, using the telescope’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) to record fine structures in the swirling, dusty gas and reveal deeply embedded protostars. The JWST data enabled the team to study two protoclusters that are busily sculpting roughly 10,000 solar masses of gas — each! — into new stars. One protocluster, W51-IRS2 (containing the brightest source in the image above), has excavated a bubble around itself through intense stellar feedback, while the other, W51-E (down and to the right of W51-IRS2, where multiple dust lanes converge), is still being fed by dusty tendrils. For more details on this star-forming region, be sure to check out the full research article linked below.

Citation

“A JWST NIRCam/MIRI View of the W51A High-Mass Star-Forming Region,” Taehwa Yoo et al 2026 AJ 171 208. doi:10.3847/1538-3881/ae40b7

The post Featured Image: Massive Stars in the Making appeared first on AAS Nova.

Neutron stars are composed of some of the most extreme material in the universe, and their internal properties are challenging to determine. Recently, researchers investigated an unusual spectral feature that may help to probe the interiors of neutron stars.

Examining Extreme Matter

When a massive star expires in a supernova explosion, it can leave behind its condensed core in the form of a neutron star: an exceptionally dense sphere roughly as wide as Manhattan is long, composed almost entirely of neutrons. Neutron stars represent an extreme state of matter and contain some of the densest and strongest material in the universe.

By observing neutron stars, astronomers attempt to pin down their equation of state, or the relationship between their interior density and pressure. In a recent research article led by Rosario Iaria (University of Palermo) described a promising way to probe the interior of a neutron star.

This method relies on measurements of a spectral line that originates near the neutron star’s surface and is gravitationally redshifted as it escapes from the intense gravitational pull of the star. The gravitational redshift provides a direct measurement of the compactness of the neutron star, or the ratio of its radius to its mass. Despite the promise of this method, definitive identification of gravitationally redshifted absorption lines has been challenging.

Directly Measuring Compactness

Iaria’s team identified potential evidence of this phenomenon in Neutron star Interior Composition Explorer (NICER) observations of 4U 1820-30, a close binary system containing a neutron star that is accreting matter from a white dwarf companion. (4U 1820-30 is famous for having one of the most rapidly rotating neutron stars known, with a blistering rate of 716 rotations per second.)

Iaria and collaborators focused on a strong iron absorption line at 3.8 keV, which arose three hours after a carbon superburst: a rare burst of high-energy radiation from thermonuclear burning of carbon deep in the neutron star’s atmosphere. The signal persisted for nearly 17 hours before subsiding.

The team proposed that the rare superburst paved the way for the gravitationally redshifted absorption line to appear. During the superburst, a powerful radiation-driven wind swept away most or all of the neutron star’s corona, a diffuse cloud of plasma floating above and below the accretion disk. After the superburst ended and the wind subsided, but before the obscuring corona reformed, the tell-tale absorption line was visible for a short time.

Cracking the Mystery of Neutron Star Structure

By interpreting the 3.8 keV absorption feature as a gravitationally redshifted spectral line arising near the neutron star’s surface, Iaria and collaborators measured a redshift of 1 + z ≅ 1.72. This corresponds to a compactness of 4.46 kilometers per solar mass, which translates to a radius of 6.4 km for a typical mass of 1.4 solar masses or a mass of 2.2 solar masses for a typical radius of 10 km.

The interpretation of the 3.8 keV absorption line as a gravitationally redshifted iron line is still tentative. Further measurements with NICER, or with future facilities like the Advanced Telescope for High-ENergy Astrophysics (Athena) X-ray observatory (planned launch in 2037) or the enhanced X-ray Timing and Polarimetry (eXTP) mission (planned launch in 2030), may help to advance the study of neutron star interiors using this technique.

Citation

“A Mysterious Feature in the NICER Spectrum of 4U 1820-30: A Gravitationally Redshifted Absorption Line?” R. Iaria et al 2026 ApJ 998 58. doi:10.3847/1538-4357/ae2758

The post A Mysterious Spectral Feature Could Help Crack the Case of Neutron Star Structure 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: Protostars at Subsolar Metallicity: First Detection of Large Solid-State Complex Organic Molecules in the Large Magellanic Cloud
Authors: Marta Sewiło et al.
First Author’s Institution: NASA Goddard Space Flight Center
Status: Published in ApJL

Stars and planets form when clouds of molecules collapse in on themselves due to the overwhelming force of gravity (which, relatable). This process is quite mysterious, as these clouds will only live for a couple million years before collapsing, and the newly forming protostars only live for about half a million years before becoming main-sequence stars.

But we are able to find some protostars in the Milky Way and in the Small and Large Magellanic Clouds near us, and observing the molecules around these protostars can help us understand how protostars form.

To look for molecules around protostars, astronomers take spectra of the protostars in the infrared, which is a wavelength region where molecules emit a lot of light. As better instruments are being built, astronomers are more often able to look for what are called complex organic molecules, which are carbon-bearing molecules with at least six atoms.

These complex organic molecules can be detected in different states: most detections have been of gaseous molecules in and around protostars or planet-forming disks, but they can also be found in a solid state on the surfaces of dust grains in the interstellar medium in a galaxy. In this state, they are called complex organic molecule “ices.” These “ices” were rarely found pre-JWST, but since its launch, detections have been more numerous, mainly in the Milky Way. Observing these complex molecules on the surfaces of dust grains tells us more about protostellar dust chemistry, which is an important but still mysterious aspect of star formation.

In this study, researchers look outside of our own galaxy to explore the complex organic molecules in the Large Magellanic Cloud (LMC). The LMC is an interesting place to look for these molecules because it has lower metal content (i.e., elements heavier than hydrogen and helium) than the Milky Way, as well as a harder radiation field. This means photons flying around in the LMC generally have higher energies than photons flying around in the Milky Way, and elements like carbon, oxygen, and nitrogen are less abundant. This is important because these conditions are more similar to what typical galaxies were like in the early universe. Thus the LMC is a better test bed to look at protostars than the Milky Way if we want to understand how stars formed in the early universe.

The authors of this study have found signatures of complex organic molecules in protostars forming in the LMC. They focus on the protostar ST6 in the LMC, shown in the right image in Figure 1. They used JWST’s Mid-Infrared Instrument to take spectra of the region around ST6.

Spectroscopic Signatures of Molecules on Dust Grains

The researchers used the Python tool called dEcompositioN of Infrared Ice features using Genetic Modelling Algorithms (ENIIGMA) to fit the spectroscopy. This code compares the spectra to laboratory data of these complex organic molecules at the temperatures we see in the LMC. The authors fit for complex organic molecules they might expect to see, and they detect methanol (CH₃OH), acetaldehyde (CH₃CHO), ethanol (CH₃CH₂OH), methyl formate (HCOOCH₃), and acetic acid (CH₃COOH); of these, acetaldehyde, ethanol, and methyl formate have never before been detected outside of the Milky Way. Interestingly, this is the first time acetic acid has been definitively detected in any astrophysical environment. The spectral contribution from each molecule is shown in Figure 2; all the individual contributions added together make up the observed spectrum.

These detections provide evidence that these complex organic molecules can be produced on the surfaces of dust grains. Further, their detection in the LMC provides evidence that these molecules can be produced in “harsh” environments like the LMC, with lower metal content and harder radiation fields.

When the authors compared the abundances of these ices to other protostars in the Milky Way galaxy, they found that the abundances are slightly lower around the LMC protostar. This may happen because the dust temperatures are generally higher in the LMC due to the higher-energy photons, which affect the chemistry happening on the dust. Some species they found, however, do have similar abundances to the Milky Way protostars, indicating that the harder radiation field of the LMC does not affect how these species form. Finding more complex organic molecules in the Magellanic Clouds will help us understand further how these compounds form on dust grains and how the galactic environment may affect their formation.

Original astrobite edited by Shalini Kurinchi-Vendhan.

About the author, Caroline von Raesfeld:

I’m a third-year PhD student at Northwestern University. My research explores how we can better understand high-redshift galaxy spectra using observations and modeling. In my free time, I love to read, write, and learn about history.

The post Detecting New Icy Molecules Around a Newly Forming Star with JWST 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: Supernova Ia Remnants with M-Dwarf Surviving Companions
Authors: Kuo-Chuan Pan (潘國全), Pilar Ruiz-Lapuente, and Jonay I. González Hernández
First Author’s Institution: National Tsing Hua University
Status: Published in ApJ

Type Ia supernovae are important tools astronomers use to measure distances in space. Despite their important role as “standardizable candles,” their origins remain hotly debated. It’s long been theorized that a Type Ia supernova can develop from one of two pathways: the single-degenerate channel or the double-degenerate channel. In the single-degenerate channel, a white dwarf and a non-degenerate star (such as a red giant or main-sequence star like our Sun) orbit each other in a close binary system. The white dwarf accretes material from the outer surface of the non-degenerate star until it reaches a critical mass and explodes. The double-degenerate channel begins instead with two white dwarfs orbiting each other. Most explosion mechanisms from this channel result in the complete obliteration of the secondary, less-massive white dwarf. However, one theoretical explosion mechanism, called the dynamically driven double-degenerate double-detonation (D⁶) channel, might allow the secondary companion star to survive an explosion from a double-degenerate Type Ia supernova.

Generally, due to the immense energy from a supernova explosion, we expect these surviving companion stars to be “kicked” away from the blasts at high velocities. Fortunately, astronomers have found evidence of these surviving companion stars. As covered in a previous Astrobite, three hypervelocity white dwarfs have been found in Gaia data and traced back to the locations of double-degenerate Type Ia supernovae. Given the prevalence of Type Ia supernovae, however, astronomers are led to question why we haven’t seen many more of these candidates. It’s additionally important to wonder what similar “runaway” companions might look like for the single-degenerate channel.

Recent observations by the Gaia spacecraft near the supernova remnant G272.2-3.2 show an M-dwarf star, MV-G272, with an unusually high velocity around 240 km/s and a trajectory tracing back to the center of the supernova remnant. Is it possible for this M dwarf to be the runaway companion to the remnant’s original supernova? The authors of today’s article look at simulations of potential companion stars from single-degenerate Type Ia supernovae and compare their results to this observed potential companion candidate.

Because this work focuses on the potential for M-dwarf companions, the authors explored a range of simulated companion-star masses and radii characteristic of M dwarfs: 0.5, 0.6, and 0.7 solar mass and 0.396, 0.454, and 0.483 solar radius, respectively. To make these models, they used the stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA) to construct and evolve a number of simulated stars with these specifications.

After setting up the models in MESA, they used the magnetohydrodynamics code FLASH to perform 2D and 3D simulations of the supernova explosion and the subsequent impact of the exploding star’s ejecta (or hot material) on its M-dwarf companion. After the explosion and impact were modeled, the companion star’s evolution was further followed in MESA.

Figure 1 shows the density of the supernova’s ejecta, or exploding material, as it impacts the companion star. (You can think of this figure as if you were looking at the companion star out in space.) After roughly 100 seconds, you can see a bow shock develop around the top of the companion (or the “front” of the star) as it wraps around the companion. This impact causes significant compression of the companion star and rips away upwards of 50% the companion’s mass. The impact of this shock is what gives the companion star its “kick,” sending it hurtling through space.

Because the authors explored a range of initial companion masses and distances between the primary and companion star, their results show some range. Figure 2 shows two important results: the evolution of the companion’s mass before and after the explosion (left plot), and the evolution of the companion’s kick velocity (right plot). The dip in mass around 100 seconds (10² s) indicates the impact of the bow shock. Even though the simulations model companions with a relatively narrow mass range (0.3–0.7 solar mass), there is considerable variation in the final masses after explosion. For example, the initial 0.5-solar-mass model ends up with anywhere between 0.07 solar mass (just 14% of its initial mass) and almost its full initial mass of 0.5 solar mass, depending on the distance between the companion and its exploding star. The results from this work generally show, predictably, that a companion closer to its primary star gets a bigger kick in velocity. These “kicks” range from about 50 km/s to 150 km/s. When added to the system’s initial velocity in space, it brings the total velocity of these companions into the 150–200 km/s range. This result is generally well aligned with the observed velocity of MV-G272, which was roughly 240 km/s.

Notably, runaway companion stars of these Type Ia supernovae seem to retain information from the initial explosion. Given the final velocities of these companions, astronomers might be able to figure out the companion’s initial mass and trace back its trajectory to the system it originated from. Overall, the fact that MV-G272 has a trajectory that tracks back to the center of a supernova remnant makes it a good companion candidate. These results support the feasibility of M-dwarf runaway companions from single-degenerate Type Ia supernova systems. Now that we know what these companions might look like — and how fast they can be going — astronomers can hopefully better search for these high-velocity stars in the future.

Original astrobite edited by Catherine Slaughter.

About the author, Mckenzie Ferrari:

I’m currently a PhD student in the geophysical sciences program at the University of Chicago. While I now study the atmosphere and oceans of Earth, most of my previous research focused on simulations of Type Ia supernovae and galaxy formation and evolution. In my free time, I foster cats for a local organization, enjoy cooking, and can often be found running along Lake Michigan.

The post I Survived a Type Ia Supernova, and All I Got Was This Kick Velocity appeared first on AAS Nova.

One of the most luminous supergiant stars in the Andromeda Galaxy, M31-2014-DS1, has disappeared, potentially leaving behind a black hole shrouded in dusty gas. What do new infrared and X-ray observations tell us about this event?

Failure to Explode?

Massive stars are famous for going out with a bang. After swelling into supergiants, these stars bring their brief lives to a close in a cosmic fireworks show: a supernova explosion that creates a neutron star or a black hole.

But a splashy supernova explosion may not be the only way for a massive star to go out. As observations have begun to suggest, some massive stars may — for reasons not yet fully understood — quietly collapse in upon themselves, going out with a whimper rather than a bang. Though less spectacular and far harder to spot, these “failed” supernovae highlight a possible pathway for the formation of stellar-mass black holes.

A Newborn Black Hole in a Dense, Dusty Blanket

Just last month, researchers reported their discovery of a potential failed supernova. The supergiant M31-2014-DS1 suddenly brightened in 2014 before fading to obscurity, leading researchers to suspect that the star had experienced a failed supernova and created a black hole. The event shared similarities with another failed supernova candidate, NGC6946-BH1.

In a new article published in the Astrophysical Journal Letters, Kishalay De (Columbia University; Flatiron Institute) and coauthors have used JWST and the Chandra X-ray Observatory to learn more about what remained after M31-2014-DS1 disappeared. The JWST observations show an extremely red object that has faded considerably in just a few years, with a deep absorption feature from silicate dust and numerous narrow molecular absorption lines. Chandra did not detect any X-rays.

Together, these observations support a model in which the collapsing star ejected its outer layers in a relatively low-energy event (somewhere in the broad ballpark of one hundred-millionth to one ten-thousandth the energy of a typical core-collapse supernova) and formed a black hole. Some of the ejected material fell backward and fed the newborn black hole, while the remainder created a dense blanket that blocked the light from the accreting black hole from view.

Continued Evolution

In observations from 2024, the source had faded to just 7% of the progenitor star’s luminosity, supporting the conclusion that the star has disappeared and what lies beneath the dusty ejecta is a black hole. De’s team expects that as time goes on, the gas that obscures the accretion-powered luminosity of the newborn black hole will expand and become less dense along our line of sight. At some point — estimated to be no sooner than about 27 years from now — the X-ray emission from the accreting black hole should pierce the dusty shroud and become visible to sensitive X-ray observatories. In the infrared, JWST will be able to track the source’s evolution caused by continued dust creation in the expanding shell.

Thanks to its location in a neighboring galaxy, M31-2014-DS1 has granted astronomers a front-row seat to a poorly understood pathway for black hole formation. Going forward, we can expect further insights into M31-2014-DS1 and, hopefully, the discovery of many more sources like it.

Citation

“Fading into Darkness: A Weak Mass Ejection and Low-Efficiency Fallback Accompanying Black Hole Formation in M31-2014-DS1,” Kishalay De et al 2026 ApJL 999 L25. doi:10.3847/2041-8213/ae468d

The post Black Hole Baby Photos: JWST and Chandra Observe M31-2014-DS1 appeared first on AAS Nova.

JWST images of galaxy clusters are rich with gravitationally lensed galaxies. Recent work examines a source in a lensed galaxy that may offer a glimpse into the lives of massive stars billions of years ago.

Glimpses of Single Stars

Galaxy clusters, the largest gravitationally bound structures in the universe, create the conditions necessary for astronomers to perform an extraordinary feat: examine individual massive stars and star clusters at far greater distances than our telescopes can typically achieve. This is possible thanks to gravitational lensing, the bending of spacetime by an immense mass, which warps and magnifies the light from more distant objects.

These glimpses of single stars and star clusters offer a rare chance to study massive stars in our universe’s distant past directly. In particular, these observations allow us to probe whether factors like the multiplicity fraction — how many massive stars are in binary or multiple systems — have changed over cosmic time.

Peering Through a Gravitational Lens

In a recent research article, a team led by Hayley Williams (University of Minnesota) reported on their examination of an intriguing source in a gravitationally lensed galaxy called the “Warhol arc.” This galaxy, located at a redshift of z = 0.94 (when the universe was roughly 6 billion years old), is gravitationally lensed by the massive galaxy cluster MACS J0416.1−2403. The cluster is located at a redshift of z = 0.396, corresponding to when the universe was about 9.4 billion years old.

Using data from the JWST Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) program and the Canadian NIRISS Unbiased Cluster Survey (CANUCS), Williams’s team analyzed a source in the Warhol arc called W2, which previous work suggests is either a binary star system or a small star cluster.

Multiplicity and Microlensing

Across four epochs spanning 126 days, the JWST observations show the source W2 within the Warhol arc. Williams and collaborators performed spectral fitting of the JWST light curves to investigate the multiplicity of the source. They found that the data are best matched by a binary system containing stars with temperatures of 3500K and 12600K.

W2 varies between observations in both brightness and color, a fact that the authors suggested is due to microlensing by a star within the lensing galaxy cluster, rather than variability within the binary system itself. Under this hypothesis, the orbital motions of the binary bring the stars across the microlensing caustic — a region in which the magnification is exceptionally high — and the brightness and color of W2 vary as the components of the binary approach and recede from the caustic.

Williams and collaborators also performed stellar population modeling to explore the binary configurations that could match the observations. They found that the stars likely have masses of 21–24 solar masses, with one being a cool red supergiant and the other a hot, main-sequence companion. Depending on the precise evolutionary stage of the binary, it’s possible that one of the stars is nearing a supernova explosion. Lending more support to the binary system hypothesis, the microlensing measurements constrain W2 to be no larger than 90 au — too small for even a compact star cluster.

The team closed by proposing further observations of W2’s position to rule out the possibility that the microlensing rate there is unusually high, an outcome that may suggest that microlensing of two unrelated stars, rather than a binary system, is responsible for these observations.

Citation

“JWST’s PEARLS: A Candidate Massive Binary Star System in a Lensed Galaxy at Redshift 0.94,” Hayley Williams et al 2026 ApJ 997 292. doi:10.3847/1538-4357/ae2003

The post JWST Spies a Potential Microlensed Massive Binary Star System appeared first on AAS Nova.

Researchers have recently discovered a number of ultra-long-period pulsars that are difficult to explain with typical pulsar models. A new article explains how these pulsars might arise from massive stars in close binary systems.

Strangely Slow Sources

When massive stars go supernova, the explosion can leave behind the condensed stellar core in the form of a neutron star. Neutron stars that spin rapidly become pulsars, whose fast rotation powers beams of radio emission along the star’s poles.

Until not too long ago, pulsars appeared to have periods no longer than 12 seconds. Above that “sluggish” rotation rate, researchers suggested, pulsars could no longer produce electron–positron pairs and channel them along polar magnetic field lines to generate their characteristic radio signals.

So it seemed, until unexpectedly slow pulsars began to crop up. The first trend-breaking pulsars had periods of a few dozen seconds, and objects with pulse periods of minutes or hours have now been found. What could these strange objects be?

Neutron Star Origin Story

In a recent article led by Savannah Cary (University of California, Berkeley), researchers proposed that these strange radio sources are pulsars, but pulsars that rotate slowly and have magnetically powered (rather than rotationally powered) radio emission.

The proposed origin story for these ultra-long-period pulsars begins with a binary system containing a massive star and a close stellar companion. As the massive star evolves, it transfers its outer layers to the companion and expires as a stripped-envelope supernova that births a rapidly spinning neutron star. As the supernova ejecta crashes into the companion star, the star heats up and expands to 5–100 times its original radius.

Meanwhile, the explosion delivers a ferocious kick to the newborn neutron star, likely unbinding the binary system. This sets the neutron star on a new course that could take it through the puffed-up outer layers of its former companion, where it may collect gas from the star and ejected material from the supernova into an accretion disk.

Slowing Down

Cary’s team explored the outcomes of this scenario with a trio of simulations: hydrodynamical models for the shock heating of the companion star, numerical models for the formation of the disk around the neutron star, and analytical models for the interaction between the disk and the neutron star.

For a binary system containing stars of 6.4 and 4.0 solar masses and a separation of 20 solar radii — values drawn from observations and simulations — the resulting unbound neutron star collects a disk in 8–10% of cases. The neutron star’s mass, radius, rotation rate, and magnetic field strength determine whether the neutron star and the disk will interact. If they don’t, the neutron star remains rotating rapidly like a typical pulsar. If they do, the neutron star’s rotation will slow to a relative crawl over about a million years. For modest magnetic fields between 10¹³ and 10¹⁴ Gauss, this means rotation periods in the realm of 10² seconds, whereas stronger magnetic fields, above 10¹⁵ Gauss, yield periods of roughly a day.

This work suggests that close binary systems could be the source of ultra-long-period pulsars, of which Cary’s team estimates there may be 10–1,000 in the Milky Way. Future work will explore this possibility further, examining broader swaths of parameter space to learn more about how this scenario could contribute to the population of ultra-long-period pulsars in our galaxy.

Citation

“Accretion from a Shock-Inflated Companion: Spinning Down Neutron Stars to Hour-Long Periods,” Savannah Cary et al 2026 ApJ 996 141. doi:10.3847/1538-4357/ae1d43

The post Supernovae, Shocks, and Spindown: A Possible Origin Story for Ultra-Long-Period Pulsars appeared first on AAS Nova.

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

The SOFIA Massive (SOMA) Star Formation Survey. V. Clustered Protostars

Published June 2025

Main takeaway:

A team led by Zoie Telkamp (University of Virginia) used the Stratospheric Observatory for Infrared Astronomy, SOFIA, to study massive protostars and test theories of high-mass star formation. Contrary to the predictions of some star-formation models, the team found no evidence that massive protostars require a certain surface mass density to form. Formation in a cluster environment, however, may limit the formation of the most massive protostars.

Why it’s interesting:

Massive stars are rare, short-lived, and luminous. They influence their environments across a vast range of spatial and temporal scales, from advancing the epoch of reionization in the early universe to impacting the formation of individual planetary systems in the present-day universe. The fundamental question of how high-mass stars form is still unsettled. Theories of high-mass star formation range from scaled-up versions of low-mass star formation to scenarios involving collisions between protostars.

More about this massive-star study and the potential impact of a cluster environment:

Researchers developed the SOFIA Massive Star Formation Survey to investigate the origins of massive stars, targeting roughly 50 high-mass and intermediate-mass protostars in a wide variety of environments in our galaxy. This particular work, the fifth in a series of articles reporting the survey’s findings, described the team’s study of massive protostars forming in cluster environments. Using the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST), Telkamp and collaborators identified 34 protostars in seven star-forming regions and estimated their masses and other physical properties. The team noted a lack of protostars above 30 solar masses in these cluster regions, which might be evidence that competition for gas in dense environments can prevent the formation of more massive protostars. More work is needed to confirm this finding.

Citation

Zoie Telkamp et al 2025 ApJ 986 15. doi:10.3847/1538-4357/adcd79

The post Selections from 2025: The Formation of Massive Stars appeared first on AAS Nova.

A discovery that linked a fast radio burst to a magnetar in the Milky Way showed that certain fast radio bursts come from magnetars. A new study explores whether all fast radio bursts could have magnetar origins.

Varied Bursts

Fast radio bursts — extremely bright radio blips lasting anywhere from a fraction of a millisecond to a few seconds — have provided researchers with one of the best recent astronomical mysteries. What causes these brilliant radio flashes, and why are they so varied? Most fast radio bursts seem to happen just once, while others repeat frequently or infrequently on irregular or regular timescales.

In July 2020, astronomers reported the discovery of a fast radio burst likely associated with a magnetar in the Milky Way. This discovery suggested that at least some fast radio bursts come from magnetars, the rapidly spinning, intensely magnetized remnants of certain massive stars. However, it’s still not known whether all fast radio bursts share this origin, or if their varied behaviors can be traced to equally varied origins.

Mystery Solved by Magnetars?

In a recent research article, Bing Zhang (University of Hong Kong; University of Nevada) and Rui-Chong Hu (University of Nevada) set out to explore the possibility that all fast radio bursts have magnetar origins.

Zhang and Hu examined the different pathways through which magnetars form, as well as what properties they tend to have in each of these scenarios. This analysis suggested that the vast majority of magnetars in our universe are singletons, having formed from isolated stars, disrupted binary systems, or stellar mergers. This aligns with observations of magnetars in the Milky Way, none of which appear to have companions.

The remaining few percent of magnetars reside in binary systems. These coupled-up magnetars largely have companions more than twice as massive as the Sun, though some are paired with helium stars or compact objects.

Multiple Possible Arrangements

Zhang and Hu found that both isolated and paired-up magnetars tend to form with their spin and magnetic axes in close alignment — a setup that likely enables the production of rapid-fire fast radio bursts. For isolated magnetars, these axes may become misaligned over time, sapping their ability to produce repeated bursts. In binary systems, magnetars that accrete mass from the stellar winds of a companion likely retain their alignment, creating a long-lasting engine of repeating fast radio bursts. The presence of winds from a stellar companion may also explain several curious traits of some fast radio bursts, such as rapid changes in polarization angle.

In this framework, actively repeating fast radio bursts arise from aligned magnetars in binary systems, while one-off or infrequently repeating bursts come from isolated magnetars or misaligned magnetars in binary systems. Isolated magnetars could also be responsible for some actively repeating bursts, though this ability is likely short lived.

Though this work demonstrates that magnetars could be the source of all fast radio bursts, it doesn’t rule out the possibility that fast radio bursts have diverse origins instead. Further work is needed to explore other pathways and make even more headway on the mystery of fast radio bursts.

Citation

“Magnetars in Binaries as the Engine of Actively Repeating Fast Radio Bursts,” Bing Zhang and Rui-Chong Hu 2025 ApJL 994 L20. doi:10.3847/2041-8213/ae1023

The post A Unified Explanation for Fast Radio Bursts 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: Supernova-Induced Binary-Interaction-Powered Supernovae: A Model for SN2022jli
Authors: Ryosuke Hirai (平井遼介) et al.
First Author’s Institution: RIKEN Pioneering Research Institute, Monash University, OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery
Status: Published in ApJ

There are thousands of dying stars that go bang in the night. These explosions are known as supernovae, and they are classified primarily on what spectral lines they show in the days and weeks following their initial explosion. Most broadly, they are separated into Type I (spectra that show little or no evidence of hydrogen) and Type II (spectra that show hydrogen). The physics leading to each type of supernova is different, and astronomers use all of the information at their disposal to learn about these cosmic fireworks.

One of the most useful tools for monitoring and learning about a supernovae is its light curve — the plot of the explosion’s brightness over time. This light curve usually appears as a steep incline up to a peak in brightness several days after the initial detonation, and then a shallow decline in brightness over the following weeks. There are, however, a few examples of supernovae that break this mould.

Today’s article seeks to understand the curious case of supernova SN2022jli. Unlike the typical gradual fade in brightness, the light curve of this supernova shows a periodic bump of brightness every 12.5 days (see Figure 1). The proposed mechanisms to explain this include the blown-apart supernova material interacting with concentric and regularly spaced shells of circumstellar matter, or a binary companion that interacts with the supernova remnant each orbital period. The authors of today’s article investigate the latter scenario by running 3D hydrodynamical simulations of an interacting, post-supernova binary to try to recover SN2022jli’s periodic light curve and constrain the orbital characteristics of the system.

The authors only have the supernova’s light curve to go off of, so they explore a range of orbital scenarios to explain SN2022jli. They run a series of models evolving a neutron star — the degenerate core left over after a low-mass supernova — together with a main-sequence stellar companion, varying the orbital eccentricity and companion mass, while fixing the orbital period (at the observed 12.5-day oscillatory period) and neutron star mass to 1.4 solar masses — a typical mass for a newborn neutron star.

Why a neutron star? SN2022jli is a sub-class of Type I supernovae involving a “stripped” massive star which has lost its hydrogen — most likely through interactions with a close companion. These interactions typically circularise the pre-supernova orbit, and the subsequent explosion most commonly yields neutron stars. To explain the necessarily highly eccentric post-supernova orbit that may cause the periodic oscillation in SN2022jli, there was most likely a “natal kick” — a sudden and asymmetric burst during the supernova that rockets the neutron star in a random direction — which widened the orbit and de-circularised it, giving further evidence for a neutron star remnant.

Immediately following the supernova explosion, ejecta interacting with the main-sequence companion star would heat the star and cause it to swell up. This inflated companion then feeds matter to the orbiting dense neutron star, and the accretion is most intense when the stars are closest in their orbit (called the periastron). During accretion, however, mass is not perfectly absorbed onto the neutron star, and there is some feedback onto the surrounding gas due to the complex thermal and magnetic physics around the neutron star. In this study, the authors model cases where there is no feedback, feedback from thermal radiation due to accretion, or feedback from bipolar outflows via jets or disk winds. Snapshots from the simulation involving a 5-solar-mass companion on an orbit with eccentricity of 0.5 and bipolar feedback is shown in Figure 2.

The authors evolve the simulation for several orbits and show that periodic bursts of accretion onto the neutron star are capable of producing the oscillatory behaviour seen in SN2022jli’s light curve. The scale of the brightness oscillations are best recreated if the plane of the binary’s orbit is aligned with our line of sight (shown with the +x red line on the right side of Figure 1). Still, the profile of the undulations is not exactly reproduced by the model, and the outcome is very sensitive to our viewing angle of the binary orbit.

SN2022jli is just one of an emerging class of oscillatory supernovae, with more and more being discovered with highly sensitive modern all-sky surveys. Today’s authors rigorously modelled one proposed scenario to explain this periodic oscillation in brightness and showed that it is viable. More modelling using this interacting-binary mechanism on other oscillating supernova light curves — those with longer periods and different supernova classifications — will show whether this explanation is ubiquitous, or if the population of dancing supernova light curves is due to some other process!

Original astrobite edited by Anavi Uppal.

About the author, Ryan White:

I am a masters student at Macquarie University in Australia, working mainly on binary/multiple systems with massive stars (Wolf–Rayets in particular!). Outside of study, I’m a novice film buff, baking sourdough all the time, probably drinking coffee, and trying to get more into reading and frisbee/squash. You can also find me procrastinating on Bluesky @astroryan.bsky.social.

The post Bumpy Road Ahead: Can Binary Interactions Make Supernovae Periodically Brighter? 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: Search for the Blazhko Effect in Field RR Lyrae Stars Using LINEAR and ZTF Light Curves
Authors: Ema Donev and Željko Ivezić
First Author’s Institution: XV. Gymnasium (MIOC)
Status: Published in AJ

RR Lyrae stars are a class of pulsating variable stars — similar to better-known Cepheid variables — that sit on the horizontal branch of the Hertzsprung–Russell diagram. Because of the regularity with which they pulsate, these stars are useful for a number of scientific applications, including standard-candle distancing (helping astronomers set the scale of distances in the universe) and as probes of very old star formation in nearby populations (because most RR Lyrae stars are at least 10 billion years old).

Today’s article studies the Blazhko effect in RR Lyrae stars. Simply put, the Blazhko effect is a long-term change of the duration (period) or strength (amplitude) of pulsation in some RR Lyrae variables. Fig. 1 shows an example from today’s article. While this effect was first observed as early as 1907, the physical mechanism for Blazhko modulation is still formally unknown, as is the percentage of RR Lyrae stars that exhibit it. Broadly speaking, there are three explanations for this effect: 1) nonlinear resonance between a star’s primary pulsation mode and some higher-level pulsation, 2) magnetic influence, or 3) cycles in the convection activity.

Today’s article searches for and identifies a population of Blazhko stars that may be used for future research into the Blazhko effect. Using data from the Lincoln Near-Earth Asteroid Research (LINEAR) asteroid survey and the Zwicky Transient Facility (ZTF) survey, the authors analyze around 2,857 RR Lyrae stars found in both data sets. The LINEAR survey was taken over a period of about 6 years, and the ZTF survey over about 5 years. On average, there is a 15-year difference between the LINEAR and ZTF observations. Using both, therefore, allows the authors to search for Blazhko modulation in each survey individually, as well as to compare between the two over the 15-year period. They additionally require a source to have at least 150 data points in both surveys to be considered.

From this initial set of RR Lyrae stars, today’s article identifies 531 potential Blazhko star candidates that are moved on to a visual inspection step. In order to identify the candidates for visual inspection, the authors establish two pre-selection methods based on the direct light curve and periodogram for each source:

1. Light curve selection works by algorithmically assigning a score to each source, with higher scores indicating a greater expectation that the source is a Blazhko RR Lyrae star. The scores are associated with best-fit pulsation models. One way a given source could earn points was by having a very high reduced χ² statistic in one or both data sets. Blazhko modulation changes the characteristics of the pulsations over time, meaning the best-fit model will be a poor fit to many of the pulsations within one or both data sets. Generally, poorer fits mean higher reduced χ² values. In addition, candidates could earn points by having a moderately high reduced χ² statistic in one or both data sets, as well as a significant change in pulsation characteristics of the best fit model from one data set to the next. Such a change between data sets is an indication of long-term Blazhko modulation. From this 479 of the 531 candidates are identified.
2. Periodogram selection works by looking for interactions between the primary pulsation and Blazhko frequencies. First, the authors create a periodogram for the time-series data. In short, a periodogram plots a number of possible frequencies (or periods) of variability in the data versus the “power” associated with that frequency (or period), where higher power means the data vary more strongly at that frequency. When periodic data have only one associated frequency, the periodogram will show a single peak with high power. In the case where there are two effects of variation (in this case, the pulsation of the star and the Blazhko modulation) with disparate frequencies, a single, large peak will occur at the average frequency, with a smaller peak appearing to either side. Fig. 2 shows an example using simulated data. By identifying the location and strength of these side peaks, the authors are able to identify a handful of additional Blazhko sources (29), as well as estimate the frequencies of Blazhko modulation.

From here, the authors visually inspect the 531 candidates and confirm that 228 of them exhibit convincing evidence of the Blazhko effect. They are able to place a lower limit on the percentage of RR Lyrae stars that are Blazhko sources at 11.4 ± 0.8%. In addition, they report that for a certain subclass of RR Lyrae stars, those that show the Blazhko effect have pulsation periods 5% shorter on average but no significant difference in amplitude. But a less common subclass of RR Lyrae stars shows no significant difference in period or amplitude when comparing Blazhko sources to the general population. Finally, the authors highlight that some sources show Blazhko modulation in one data set, but not the other, indicating that the modulation itself may change over time. Further research into this finding may help us better identify the most likely physical mechanism(s) for the Blazhko effect.

Original astrobite edited by Kylee Carden.

About the author, Catherine Slaughter:

Catherine is a PhD candidate in astrophysics at the University of Minnesota. Her research primarily deals with stellar population astrophysics in local dwarf galaxies, with particular focus on the intersection between computational and observational research methods. Prior to moving to Minnesota, she completed her BA in Physics and Astronomy, and MSc in Astronomy Research at Leiden University.

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

Betelgeuse and Its Buddy

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

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

Spectroscopic Search

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

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

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

When Finding Nothing Tells You Something

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

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

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

Citation

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

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Astronomers have long sought evidence of the universe’s first generation of stars, and as more distant galaxies come into view, it seems these stars may finally be within reach.

Excess Metals Popping Up

Since its 2021 launch, JWST has given astronomers eyes to peer into the distant past, discovering many galaxies whose light reveals the universe’s early stages of star and galaxy formation. Within the population of newly discovered galaxies are a few with bizarre chemical properties that, upon first pass, seem to be too enriched to exist so early in the universe. These hard-to-reconcile abundances may be a sign of the universe’s first stars. 

Known as Population III (Pop III) stars, the first stars in the universe were born out of giant clouds of pristine gas (hydrogen, helium, and a little lithium) and were able to form at masses hundreds to thousands of times the mass of our Sun. Though they burned bright, they did not burn for very long, ending their lives in violent supernovae and chucking their newly enriched guts back into their surroundings. While these stars are long dead, the chemical imprints they left on their host galaxies can persist  — and understanding how Pop III stars create and distribute metals could clue us in to the odd chemical signatures recently found with JWST.

Too Much Nitrogen in GS 3073

Researchers have identified a few galaxies exhibiting high nitrogen-to-oxygen (N/O) ratios that cannot be explained by stars similar to those in the universe today. A couple of these galaxies could be explained through multiple stellar populations, rapidly rotating stars, massive explosions, or the early stages of globular cluster formation. However, GS 3073, a galaxy with a redshift of z = 5.55 (about one billion years after the Big Bang), has an N/O excess so high that is has, so far, defied explanation.

Aiming to make sense of this bizarre phenomenon, Devesh Nandal (University of Virginia; Center for Astrophysics | Harvard & Smithsonian) and collaborators used stellar evolution models to see if Pop III stars could be the culprit. Modeling stars with masses 1,000–10,000 times the mass of our Sun, the authors traced the elemental yields of these supermassive stars as they go through the various stages of nuclear burning. The analysis takes into account mixing within the stars, mass loss throughout their lifetimes, and how the eventual supernova ejecta mixes within the interstellar medium.

From this modeling, the authors found that massive Pop III stars between 1,000 and 10,000 solar masses can produce the observed elemental abundances measured for GS 3073. Stars less massive do not produce high enough N/O ratios, and stars more massive have much lower oxygen-to-hydrogen ratios — strongly suggesting upper and lower mass limits to the possible supermassive stars that could have produced GS 3073’s chemical composition.

Finally Evidence of Pop III Stars?

This study of GS 3073 is the first of its kind to confirm the chemical imprints of Pop III stars on their host galaxy at this redshift. The unique nitrogen abundance can only be produced through the evolutionary phases of Pop III stars that burn quickly enough to produce and release an excess amount of nitrogen while other elements stay consistent. From their modeling, the authors suggest that galaxies with even higher nitrogen excess could exist, and further observations with JWST may just find them. 

The search for Pop III stars is booming — another recent study (Visbal et al 2025) examines the galaxy LAP1-B. While GS 3073 shows evidence of Pop III stars through chemical abundances, the study of LAP1-B finds that the galaxy matches theoretical predictions for the formation environments and mass distributions of Pop III stars. Both of these recent research works are laying the groundwork for the wealth of discovery possible with JWST, and the universe’s first stars are no longer out of reach.

Citation

“1000–10,000 M_⊙ Primordial Stars Created the Nitrogen Excess in GS 3073 at z = 5.55,” Devesh Nandal et al 2025 ApJL 994 L11. doi:10.3847/2041-8213/ae1a63

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