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KPNO

After AAS 247 in Phoenix, Arizona, AAS Nova Editor Kerry Hensley and I had the chance to travel about 150 miles south for a tour of Kitt Peak National Observatory.

A Window into Kitt Peak

Located 60 miles southwest of Tucson, Kitt Peak National Observatory (KPNO) resides on a mountain top within the Tohono O’odham Nation reservation. Founded in 1958, Kitt Peak is home to nearly two dozen active telescopes ranging in wavelength coverage and scientific objectives. Ronald Proctor, Lori Allen, and Jacelle Ramon-Sauberan, all serving in crucial roles for the observatory, led our tour around the mountain.

Windows Center Lobby

The Windows On the Universe Center’s lobby exhibit displaying the Tohono O’odham language with words describing the land and astronomy. Jacelle Ramon-Sauberan, the Tohono O’odham Nation Education Liaison, is seen to the left. [KPNO/NOIRLab/NSF/AURA/R. Proctor; CC BY 4.0]

Our visit began in the new Windows on the Universe Center — the first science center inside of a telescope. Situated inside the retired McMath-Pierce Solar Telescope, the Windows Center takes visitors through exhibits exploring the universe, the telescope’s original control room, and the observatory’s connection to the Tohono O’odham Nation.

The center’s lobby introduced visitors to the beautiful land KPNO calls home. Working with Tohono O’odham linguists, Jacelle, the observatory’s Tohono O’odham Nation Education Liaison, curated the lobby exhibit that features the native language and the Nation’s connection to astronomy and the observatory. The science center serves as an educational resource and place of cultural exchange, expanding the relationship between the observatory and the Tohono O’odham Nation. 

Astronauts

Apollo astronauts in the control room of the McMath-Pierce Solar Telescope in 1964. [United States Geological Survey; CC BY 4.0]

After walking through an introduction to the universe exhibit, visitors enter the original control room of the telescope. Mirrors across the room’s ceiling focus the Sun’s light onto table screens where visitors can observe the Sun in real time without burning their eyeballs. In addition to observing the Sun, the solar telescope allowed astronauts in the 1960s to view a projection of the Moon’s surface and plan their landing site for the Apollo 11 mission. Visitors can stand in the same place and witness the instruments that made the moon landing possible.

At the end of the Windows Center is a Science On a Sphere Theater — a spherical display system that allows visitors to see planets, stars, moons, and even large-scale structures of the universe in 3D. Featuring multiple programs, the theater takes visitors through the universe and displays data collected right there on the mountain!

WIYN

The WIYN 3.5-meter telescope at sunset. [KPNO/NOIRLab/NSF/AURA/P. Marenfeld; CC BY 4.0]

A WIYN for Exoplanetary Science

Though not typically open to the public for tours, our next stop took us to the WIYN 3.5-meter telescope. This telescope is operated and owned by the WIYN Consortium, a partnership between the University of Wisconsin, Indiana University, NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory; formerly NOAO), Pennsylvania State University, and Princeton University. Operating since 1994 with a strong collection of instruments, WIYN has observed galaxies near and far, stars across their lifetimes, and exoplanets tugging on their host stars.

Lexi at WIYN

Me, Lexi Gault (AAS Media Fellow), in front of the WIYN 3.5-meter telescope. I have used WIYN’s SparsePak spectrograph to collect data for my dissertation research! [AAS Nova/Kerry Hensley]

WIYN’s newest instrument, NEID (pronounced “NOO-id”), has been advancing exoplanetary science since its first light in early 2020. Derived from the word meaning “to see” in the Tohono O’odham language, NEID is a high-resolution spectrograph that uses the radial velocity method to detect exoplanets. As a planet orbits its host star, its gravitational pull induces a wobble in the star, and NEID can detect these wobbles with unprecedented precision. This instrument allows astronomers to find exoplanets that were previously undetectable.

The partnership between public and private universities and a government institution was the first of its kind. Through this consortium, hundreds of undergraduate and graduate students have conducted research with WIYN, and the telescope’s suite of instruments have enabled early career astronomers to explore the universe both near and far.

Mysteries of Dark Energy at Mayall

We concluded our tour at the Mayall 4-meter Telescope, the tallest telescope dome on the mountain at a staggering 18 stories high. This iconic telescope saw first light in 1973, and at the time, was the second-largest (in diameter) telescope in the world. Originally built for wide-field optical and infrared studies of the universe, the Mayall has enabled decades of critical scientific research.

Mayall dome

The Mayall dome across the mountain as seen from inside the WIYN dome. [AAS Nova/Lexi Gault]

Mayall is now home to the Dark Energy Spectroscopic Instrument (DESI), the most powerful multi-object survey spectrograph in the world. The DESI survey measures the impact of dark energy on the expansion of the universe through creating the largest ever 3D map of the universe. Mapping the distances to hundreds of millions of galaxies, DESI has revolutionized cosmology and enabled groundbreaking research into the origins of the universe. 

From the telescope’s massive dome, to the busy DESI control room, to the gallery floor with a nearly 360 degree view of the surrounding desert, the Mayall offers visitors a unique glimpse into Kitt Peak’s history and its future. While WIYN is a hidden gem, the Mayall 4-meter Telescope is open to the public for tours daily, so you can experience the exciting era of research and discovery at KPNO. 

Visit Kitt Peak

Interested in getting a peek yourself? KPNO is open to the public daily with multiple tour types to choose from, including both daytime and nighttime visits! Plan your visit to Kitt Peak here.

illustration of a gamma-ray burst

Discovered in July 2025, GRB 250702B is unlike any other gamma-ray burst astronomers have seen. New follow-up observations of the burst’s location have underscored the strangeness of this event.

Not Like Other GRBs

Gamma-ray bursts (GRBs) are intense flashes of gamma rays lasting anywhere from milliseconds to hours. The shortest of these bursts are thought to come from colliding neutron stars, while bursts lasting longer than a few seconds tend to come from collapsing massive stars, though notable exceptions have been discovered.

Even with known GRBs spanning such a broad range of timescales and arising from different sources, some bursts are truly exceptional. Such is the case for GRB 250702B, which was discovered on 2 July 2025 by the Fermi Gamma-Ray Burst Monitor. This event featured three separate bursts spread across several hours, as well as never-before-seen X-ray emission in the day leading up to the gamma-ray emission.

JWST on the Case

rest-frame spectrum of GRB 250702B

Rest-frame spectrum of GRB 250702B (blue) with the host galaxy spectrum of another burst, GRB 240825A, for comparison (orange). Click to enlarge. [Adapted from Gompertz et al. 2026]

Benjamin Gompertz (University of Birmingham) and collaborators used JWST to investigate GRB 250702B’s birthplace roughly 51 days after the burst was first detected. JWST spectroscopy revealed that GRB 250702B emerged from a galaxy at a redshift of z = 1.036, when the universe was roughly 6 billion years old.

This precisely measured redshift allowed the team to estimate the burst’s energy; in gamma rays alone, the event released at least 2.2 × 1054 ergs. This places GRB 250702B in the top 20 most energetic GRBs known, and the team estimates that events of this kind are 1,000 times less common than other long-duration GRBs and more than 100,000 times less common than typical core-collapse supernovae.

The burst’s host galaxy is also unusual. It’s larger, brighter, and dustier than other galaxies of similar redshift, and it’s unusually massive among GRB host galaxies. In the wavelength range studied here, it also appears to be the most luminous galaxy known to host a GRB.

What Caused GRB 250702B?

Now, to the cause of this unusual burst: is GRB 250702B just a very strange example of a long-duration burst arising from the collapse of a massive star into a black hole, or could it have an entirely different cause, like a star being ripped apart by a black hole?

plot of host galaxy subtracted spectra of GRB 250702B

The team placed limits on the supernova emission by subtracting a spectrum of the host galaxy from the event. The green lines show this subtracted spectrum under two different normalization conditions. The black lines show for comparison the emission from the bright supernova SN 2023lcr using two possible extinction values. Click to enlarge. [Adapted from Gompertz et al. 2026]

In the collapsing-massive-star scenario, the GRB would be accompanied by a supernova. Gompertz’s team was able to rule out bright supernova emission, but uncertainties in the level of dust within the host galaxy prevented them from excluding the possibility of a significantly fainter supernova hiding within the dust.

The observations also place constraints on a tidal disruption event scenario, in which a star is ripped apart by a black hole. The data strongly favor a jetted, relativistic tidal disruption event, which makes it difficult to pin down the mass of the black hole involved. The timescales are consistent with a white dwarf spiraling around an intermediate-mass black hole, and other factors suggest that the black hole could be no more than a million solar masses, placing it firmly in the intermediate-mass regime, should this explanation prevail.

With GRB 250702B’s source still unsettled, astronomers will continue to study the burst and its unusual host galaxy. Gompertz and collaborators anticipate that follow-up spectroscopy will provide more clues in this case.

Citation

“JWST Spectroscopy of GRB 250702B: An Extremely Rare and Exceptionally Energetic Burst in a Dusty, Massive Galaxy at z = 1.036,” Benjamin P. Gompertz et al 2026 ApJL 997 L4. doi:10.3847/2041-8213/ae2ed9

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

Crab Nebula

A multi-wavelength view of the Crab Nebula, the remnant of a supernova that birthed a neutron star. The neutron star powers a pulsar wind nebula, shown in blue. [X-Ray: NASA/CXC/J.Hester (ASU); Optical: NASA/ESA/J.Hester & A.Loll (ASU); Infrared: NASA/JPL-Caltech/R.Gehrz (Univ. Minn.)]

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.

simulation of supernova ejecta colliding with a star

Simulation snapshot taken one hour after the supernova explosion. The black dashed line shows the path the neutron star (NS) will take through the companion star’s outer layers. Click to enlarge. [Adapted from Cary et al. 2026]

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

Illustration of the solar wind interacting with Earth's magnetic field

What happens when pileups of solar wind plasma collide with Earth’s protective magnetosphere? New work uses machine learning to examine how strongly these events affect our planet’s magnetic field.

Plasma Pileups

photograph of a coronal mass ejection

The Solar & Heliospheric Observatory (SOHO) took this coronagraphic image of a coronal mass ejection on 20 April 1998. [SOHO (ESA & NASA)]

Geomagnetic storms driven by solar activity paint night skies with glowing aurorae, but they also threaten spacecraft electronics with showers of high-energy particles. While immense eruptions of solar plasma and magnetic fields called coronal mass ejections are the most infamous example of solar activity, a team led by Yudong Ye (Sun Yat-Sen University) recently focused on another, less destructive form of activity: stream interaction regions.

Stream interaction regions arise when slow-moving solar wind is struck from behind by faster-moving solar wind emitted later. The collision of the two solar wind streams creates a tangle of compressed plasma and strong magnetic fields capable of peeling back Earth’s protective magnetosphere and dumping in high-energy charged particles, with beautiful yet harmful results.

Machine Learning Method

Though stream interaction regions are less disruptive than coronal mass ejections, they’re far more common; they frequently needle Earth’s magnetosphere, especially during the calmer years of the Sun’s activity cycle. Predicting how strongly a stream interaction region will influence Earth’s magnetosphere — in other words, how geoeffective it is — is challenging, however. When two streams of solar wind collide, their properties combine in complex and nonlinear ways that traditional statistical investigations have struggled to pin down.

Now, Ye and collaborators have used machine learning to study the properties and impact of stream interaction regions in a physically meaningful way. They performed their study on a sample of 879 stream interaction events for which there is abundant information, such as temperature, magnetic field strength and direction, and solar wind conditions before and after the event.

illustration of the support vector machine framework

Illustration of the authors’ support vector machine framework. The optimal hyperplane is the boundary that best divides the data by maximizing the distance between the boundary and the data points nearest to it; these points are called support vectors. Square and triangle symbols represent two classes of data. Click to enlarge. [Ye et al. 2025]

Ye’s team based their framework on a support vector machine classifier: a classical machine learning algorithm that draws a mathematical boundary between groups of data while maximizing the distance between the boundary and the data points nearest to the dividing line. The support vector machine algorithm is well-suited to the task of modeling the geoeffectiveness of stream interaction regions because it doesn’t require a particularly vast dataset, can tolerate misclassified events, and allows for a physical interpretation of the results.

A Physical Interpretation

The team first reined in the model’s complexity by identifying the most important features in the dataset. They then determined which features or combination of features had the largest contribution to the output — in other words, which physical parameters most strongly determined the geoeffectiveness of the event.

illustration of magnetic reconnection in Earth's magnetosphere

Illustration of how the interplanetary magnetic field (IMF) interacts with Earth’s magnetosphere. When the IMF points southward, as it does in this diagram, the impact on Earth’s magnetosphere is increased, with magnetic reconnection occurring in the red areas. Click to enlarge. [NASA]

Ye and collaborators found that the strongest determinants of an event’s geoeffectiveness were how long the solar wind was directed southward, the strength of the solar wind electric field, and the average and minimum strengths of the southward-pointing solar wind magnetic field. These results align with the current understanding of how energy is transferred from the solar wind to Earth’s magnetosphere through magnetic reconnection, a release of magnetic energy driven by rearrangement of magnetic fields. This shows how classical machine learning methods can enhance our ability to predict the outcome of oncoming space weather while simultaneously examining the physical drivers of the event.

Citation

“Assessing the Geoeffectiveness of Stream Interaction Regions Through Physically Interpretable Machine Learning,” Yudong Ye et al 2025 ApJ 993 10. doi:10.3847/1538-4357/ae0454

star surrounded by a protoplanetary disk and wispy outflows

2025 has been a year of discovery and challenge for astronomers worldwide. In the US, even as researchers celebrated big scientific and operational wins — reveling in long-awaited first-light images from Vera C. Rubin Observatory, examining the third interstellar object to enter our solar system, and diving into a treasure trove of new gravitational wave detections, to name just a few — scientists faced existential threats to funding, and our community mobilized to advocate for our field. Here at AAS Nova, this was a big year for us, as we celebrated our 10th anniversary. Now, we’ll bring the year to a close by taking a look back at the top posts of 2025:

artist's impression of a pulsar

An artist’s impression of a pulsar — a rapidly spinning neutron star. [NASA’s Goddard Space Flight Center]

10. A Slowly Spinning Pulsar Below the Death Line

When Yuanming Wang and collaborators serendipitously discovered radio pulses from PSR J0311+1402, the object’s identity was a mystery. Its pulses were too widely spaced to come from a pulsar — an extremely dense remnant of a dead massive star — but they were also too frequent to come from a long-period radio transient. Though the object remains somewhat mysterious, several of its properties indicate that it’s an unusually sluggish pulsar.

multiwavelength image of the Crab Nebula

Composite X-ray, optical, and infrared image of the Crab Nebula, which houses a pulsar at its center. [X-ray: NASA/CXC/SAO; Optical: NASA/STScI; Infrared: NASA-JPL-Caltech]

9. Cracking Crusts Might Set a Neutron Star Speed Limit 

Neutron stars spin incredibly fast, often hundreds of times per second — but they only spin about half as fast as they could before being ripped apart by their rotation. Why don’t they spin faster? That’s the question investigated by Jorge Morales and Charles Horowitz. Morales and Horowitz hypothesized that neutron star crust (the strongest material in the universe) cracks when these stars spin at about half of their breakup rate, and once the crust splits, the star begins to emit gravitational waves and can spin no faster.

Sirius and its white dwarf companion

The tiny white dwarf Sirius B hides in the glare of its larger and brighter companion, Sirius A. [NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester)]

8. Record-Breaking Pulsating White Dwarf Discovered

The evolution of a low- or intermediate-mass star eventually leaves behind a crystallized, compressed stellar core called a white dwarf. As white dwarfs slowly cool from initial temperatures of more than a million degrees, they pass through the instability strip and begin to pulsate. These pulsations allow astronomers to peer into white dwarfs’ crystalline interiors, potentially illuminating the origins of ultra-massive white dwarfs. A team led by Francisco De Gerónimo searched for pulsating white dwarfs and discovered a record-breaking 19 pulsation modes in one ultra-massive specimen called WD J0135+5722.

little red dots

JWST images of six very distant galaxies dubbed “little red dots.” [NASA, ESA, CSA, STScI, Dale Kocevski (Colby College)]

7. Distant Little Red Dot Hosts a Huge (and Growing) Black Hole

Anthony Taylor and collaborators reported their findings on CAPERS-LRD-z9, a little red dot seen by JWST as it was when the universe was just a billion years old. Using JWST, the team spotted a broad emission line characteristic of hydrogen gas moving at thousands of kilometers per second. This is a tell-tale sign of an accreting supermassive black hole, making CAPERS-LRD-z9 the earliest galaxy to show this signature.

Supernova remnant N132D

Optical image of supernova remnant N132D in the nearby Large Magellanic Cloud. [NASA, ESA, and the Hubble SM4 ERO Team]

6. Chandra Spies a Supernova Shock Front Speeding Along

N132D is a 2,500-year-old supernova remnant that holds the distinction of being the most X-ray luminous supernova remnant in the Local Group. Xi Long and collaborators turned the sensitive instruments of the Chandra X-ray Observatory toward N132D to measure the velocity of its expanding shock. Using two sets of measurements separated by 14.5 years, the team directly measured the remnant’s expansion, obtaining a much more precise measurement than previous efforts have achieved with other methods like X-ray spectroscopy and revealing differences in the expansion velocity around the remnant.

Milky Way center

Stars at the center of the Milky Way, as seen by the Very Large Telescope. [ESO/S. Gillessen et al.; CC BY 4.0]

5. Our Galaxy’s Supermassive Black Hole May Have Had a Companion in the Past

At the center of our galaxy, a supermassive black hole 4 million times the mass of the Sun holds court. Though today Sagittarius A* is a solo act, Chunyang Cao and collaborators explored the possibility that our galaxy’s supermassive black hole had a companion millions to billions of years ago. If an intermediate-black hole entered our galaxy when the Milky Way absorbed a neighboring dwarf galaxy, the presence of the smaller black hole could explain the present-day properties of the hypervelocity stars that inhabit the center of our galaxy. The two black holes likely merged 10 million years ago.

4. Examining Earendel: Is the Most Distant Lensed Star Actually a Cluster?

In 2022, researchers using the Hubble Space Telescope discovered a gravitationally lensed single-star candidate at a redshift of z = 5.926, corresponding to less than a billion years after the Big Bang. However, distinguishing between one gravitationally lensed star and many is challenging. A team led by Massimo Pascale used simple stellar population models to investigate Earendel’s identity, finding that the object’s spectrum is fit well by a variety of star cluster models. Based on this analysis, Earendel certainly could be many stars rather than one, but a single star cannot be ruled out. Variability due to stellar winds would be a smoking gun for the single-star hypothesis, but no such variability has been discovered to date.

illustration of a brown dwarf with auroral emission

Artist’s impression of auroral emission on the brown dwarf W1935. [NASA, ESA, CSA, Leah Hustak (STScI)]

3. A Strange Brown Dwarf Gets Stranger

The brown dwarf W1935 made headlines in 2024 when researchers discovered methane emission from its atmosphere, a potential sign of auroral emission. In 2025, W1935 was back in the news after Matthew de Furio and collaborators reported that the brown dwarf was actually two brown dwarfs that were closely locked into 16–28 year orbits. What delightful weirdness will we discover about W1935 next?

Artist's impression of the view from one of the planets orbiting Barnard's Star

Artist’s impression of the view from one of the planets orbiting Barnard’s Star. [International Gemini Observatory/NOIRLab/NSF/AURA/R. Proctor/J. Pollard; CC BY 4.0]

2. Confirmed at Last: Barnard’s Star Hosts Four Tiny Planets

Claims of planets orbiting Barnard’s Star have been made and disproven since the 1960s — but now, the claim has finally stuck. In 2024, researchers reported the discovery of one planet and three planet candidates around Barnard’s Star. In 2025, Ritvik Basant and collaborators confirmed the presence of all four of these planets, which appear to have minimum masses between 19% and 34% of Earth’s mass.

Illustration of stellar-mass black holes embedded within the accretion disk of a supermassive black hole

Illustration of stellar-mass black holes embedded within the accretion disk of a supermassive black hole. [Caltech/R. Hurt (IPAC)]

1. Gravitationally Lensed Gravitational Waves from Black Holes Around Black Holes

Discoveries featuring black holes and gravitational waves often occupy the top spots on AAS Nova’s year-end list. This year, the most-read article features both of those topics! Samson Leong’s team explored the gravitational waves that would be produced by merging stellar-mass black holes orbiting within the disk surrounding supermassive black holes.

We wish you a safe, warm, and happy New Year, and we hope to see you in 2026 for more news from our universe!

Earth

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.

Earth Detecting Earth: At What Distance Could Earth’s Constellation of Technosignatures Be Detected with Present-day Technology?

Published February 2025

Main takeaway:

In a collaborative effort between the Search for Extraterrestrial Intelligence (SETI) Institute and the Penn State Extraterrestrial Intelligence Center, Sofia Sheikh (SETI Institute) and team turned inward to expand the search for intelligent life in the universe. Right here on Earth, humans have created a laboratory of technological signatures that can be detected from space — if another Earth-like civilization is out there, could they detect us? Using theoretical modeling, the authors determined the reaches of various human technosignatures such as radio transmissions, optical and infrared emission, satellites, and other probes sent into space. They found humanity’s strongest signals, radio transmissions, could be detected as far as 12,000 light-years away.

Why it’s interesting:

Scientists search for intelligent civilizations by hunting for signs of technology — signals or patterns that natural phenomena cannot explain. While we cannot expect other intelligent life to look exactly like Earth’s, many SETI projects have surveyed the skies for hypothetical signals far exceeding humanity’s own technological advancements. Taking a step back, Sheikh and collaborators considered where human technology is currently and what present-day instrumentation could pick up on if we were to search for ourselves. This “Earth detecting Earth” paradigm recenters the search for intelligent life and provides a multiwavelength framework for understanding the detectability of technology on far-away worlds.

Maximum detectability of Earth's technosignatures.

Maximum distances that Earth’s technosignatures could be detected by current technology. Click to enlarge. [Sheikh et al 2025]

Earth’s constellation of technosignatures:

What exactly are Earth’s many technosignatures, and how far could our current technology detect them? The most prominent and farthest detectable signal comes from radio transmissions. As the authors noted, these signals come from multiple sources: targeted radar transmissions used to characterize planets and asteroids, radio transmissions used to communicate between space probes and ground stations (e.g., space telescopes, Mars rovers, etc.), and radio leakage from Earth’s communication systems like cell towers and broadcasting stations. Additionally, there are atmospheric technosignatures from air-polluting compounds, optical and infrared emission from cities, targeted lasers from telescopes, and interplanetary and interstellar probes sent into space. All of these combined create a constellation of technosignatures detectable across a range of distances from Earth. This study underscores the importance of assessing Earth’s technology and detection capabilities, and repeating this type of study as technological advancements continue will enhance the search for intelligent life.

Citation

Sofia Z. Sheikh et al 2025 AJ 169 118. doi:10.3847/1538-3881/ada3c7

JWST image of the galaxy NGC 4141

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.

FRB 20250316A: A Brilliant and Nearby One-Off Fast Radio Burst Localized to 13 pc Precision

Published August 2025

Main takeaway:

NGC 4141

MMT observation of NGC 4141 (left) and zoomed-in on FRB 20250316A’s location. The red lines show the 1-, 2-, and 3-sigma localization ellipses of the burst. Click to enlarge. [CHIME Collaboration 2025]

Discovered in March 2025 by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Outrigger array, FRB 20250316A is one of the brightest fast radio bursts ever observed. The CHIME collaboration traced the burst to the galaxy NGC 4141, 130 million light-years from Earth, and locked in on the source’s position with a precision of just 42 light-years.

Why it’s interesting:

The origins of fast radio bursts — bright flashes of radio waves lasting on the order of milliseconds — are mysterious, despite several thousand bursts having been cataloged. Among the many questions that remain is whether one-off bursts and repeating bursts arise from the same population of objects, or if they have entirely different origins. So far, FRB 20250316A appears to be a one-off burst; while it’s still possible that the source could emit another burst, the team noted that the burst’s properties don’t mesh with those of known repeating bursts. This makes the discovery and localization of FRB 20250316A an excellent opportunity to investigate the sources of one-off fast radio bursts.

More about the potential source of this burst, and prospects for pinpointing future sources:

After homing in on FRB 20250316A’s location, the CHIME collaboration embarked on a multi-wavelength follow-up campaign to learn more about where the burst came from. This campaign placed constraints on the metallicity and gas density near the source, which lies about 600 light-years from the center of the nearest star-forming region. A separate research article, published the same day as this work from the CHIME collaboration, described the discovery of a red giant star in the FRB 20250316A source region. This star may be located near FRB 20250316A’s source by chance, or it could be in a binary system with the source. With the main CHIME array in British Columbia continuing to scan for new bursts and three newly built outrigger telescopes in British Columbia, West Virginia, and California now online, we can expect many more precise localizations in the future!

Citation

The CHIME/FRB Collaboration: et al 2025 ApJL 989 L48. doi:10.3847/2041-8213/adf62f

illustration of the TRAPPIST-1 system

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.

JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e

Published September 2025

Main takeaway:

JWST spectra of TRAPPIST-1e

JWST spectra of TRAPPIST-1e (circles) and model outputs for several different atmospheric compositions and pressures (lines). Click to enlarge. [Glidden et al. 2025]

Ana Glidden (Massachusetts Institute of Technology) and collaborators used JWST to collect transmission spectra of the exoplanet TRAPPIST-1e. The team found evidence of stellar contamination in all of their observations, and they found that the data didn’t lean strongly in favor or against the planet having an atmosphere. Venus-like or Mars-like atmospheres were disfavored, hydrogen-rich atmospheres with traces of methane and carbon dioxide were excluded, and nitrogen-rich atmospheres with traces of methane and carbon dioxide were permitted.

Why it’s interesting:

TRAPPIST-1e is one of seven confirmed planets orbiting TRAPPIST-1, a cool M-dwarf star that is just larger than Jupiter and only 41 light-years away. All of these planets are roughly the size and mass of Earth, and as many as four of them — planets d through h — are thought to lie within the tiny star’s habitable zone. Thus, this system offers an excellent opportunity for powerful observatories like JWST to characterize the atmospheres of several potentially habitable planets. This study by Glidden’s team presents JWST’s first look at TRAPPIST-1e’s atmosphere through transmission spectroscopy.

How TRAPPIST-1 complicated the observations:

When examining an exoplanet that closely orbits its host star, special care must be taken to separate the signals from the planet and the star. This is especially tricky for active stars like TRAPPIST-1, whose surfaces are peppered with dark starspots and bright faculae. TRAPPIST-1’s surface features have contaminated observations of other planets in the system, as described in previous research, and these observations of TRAPPIST-1e were not exempt from the star’s meddling. Luckily, researchers are conducting further JWST observations that should help disentangle the star’s impact; an ongoing program will capture closely spaced transits of TRAPPIST-1e and TRAPPIST-1b, which trace nearly the same track across the star’s disk. Since TRAPPIST-1b appears to be a bare rock, any features that are shared between its spectrum and TRAPPIST-1e’s are likely to come from the star. Identifying these features will allow for better characterization of TRAPPIST-1e’s spectrum and atmosphere.

Citation

Ana Glidden et al 2025 ApJL 990 L53. doi:10.3847/2041-8213/adf62e

Bullseye galaxy

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

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

Published February 2025

Main takeaway:

Bullseye galaxy rings

Red ellipses overplotted on the first eight rings identified with Hubble in the Bullseye galaxy. Click to enlarge. [Pasha et al 2025]

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

Why it’s interesting:

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

Catching the Bullseye at a lucky time in its evolution:

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

Citation

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

star-forming region AFGL 5180

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:

infrared images of massive protostars

SOFIA FORCAST and Herschel Space Observatory images of protostars in the G18.67+0.03 star-forming region. Click to enlarge. [Telkamp et al. 2025]

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

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