OrbitalHub

Image credit: NASA.

The James Webb Space Telescope, the NASA/ESA/CSA observatory at the Sun-Earth L2 point, has caught an exoplanet doing something a planet that close to its star really should not be able to do. HD 3167 b is a rocky world roughly one and a half times the size of Earth, and it zips around a K-type star in the constellation Pisces once every 0.96 Earth days. At that distance, the dayside should be glowing red-hot bare rock, the kind of surface where silicates are molten and any gas should have been stripped away by stellar wind and high-energy photons long ago. Instead, the dayside is noticeably cooler than the theoretical maximum, and a new analysis of a JWST secondary eclipse says the most likely reason is an atmosphere. It is the coldest lava world with evidence of an atmosphere on record, and the first result from a survey of ten such worlds led by astronomer Megan Weiner Mansfield. The team’s writeup, as covered by Space.com, lays out what makes the detection hard to explain any other way.

That word cool does not mean comfortable. The planet’s equilibrium temperature sits at about 1786 K, somewhere between a slow oven and molten glass. Lava worlds previously caught with atmospheres have all been hotter than roughly 2200 K. HD 3167 b is hot enough that the rock on its star-facing side is almost certainly molten, and cool enough that something other than bare rock is controlling its dayside temperature.

The result, published in The Astrophysical Journal Letters, comes from a single JWST observation using the Mid-Infrared Instrument’s Low Resolution Spectrometer, the team that has been doing most of the heavy lifting on small rocky exoplanets for the last two years. The team watched HD 3167 b slip behind its host star, a maneuver called a secondary eclipse, and measured how much mid-infrared light disappeared. They measured the white-light eclipse depth at 38 plus or minus 11 parts per million. That number is more than five standard deviations shallower than a dark bare rock with no heat redistribution would produce at this distance from the star. The only good explanations are an atmosphere that reflects some incoming starlight back into space, an atmosphere that moves heat from the day side to the night side, or some combination of the two.

The lead author is Brandon Park Coy, a graduate student at the University of Chicago working in planetary scientist Edwin Kite’s group. Kite is the second author and a co-author on a long line of papers trying to figure out which rocky exoplanets hold onto their air. The HD 3167 b paper, described in a University of Chicago news release, is the first published result of a survey that Megan Weiner Mansfield, who did her PhD at Chicago and is now at the University of Maryland, is running. The program is looking at ten lava worlds with JWST and asking a single question. Below what temperature do rocky planets start losing their atmospheres, and above what temperature do they keep them? The published sample so far suggested a gap. Ultra-hot lava worlds such as 55 Cancri e kept their air. Cooler rocky worlds, the ones too cold to be lava worlds at all, often did not. The boundary lived somewhere in the middle, and nobody had measured it.

HD 3167 b sits right at that boundary. Its dayside is too cool for a bare rock, so it has an atmosphere. Its equilibrium temperature is far below the ultra-hot threshold, so it is the first cool end of the population in question. The boundary should sharpen from a guess into a measured curve as the program keeps adding worlds to the sample.

The detection technique itself is worth slowing down on. A secondary eclipse is the small dip in light that happens when a planet passes behind its star as seen from Earth. The dip is small because the planet is much cooler than the star and emits much less light at the wavelengths being observed, but it is measurable, and the depth of the dip tells you how much of the observed light is the planet’s own thermal emission. Doing this in mid-infrared light, around 15 micrometers for this observation, is what lets JWST see the heat of a planet whose dayside is below 2000 K. The same measurement in visible light would be much less informative, because at those wavelengths the planet contributes essentially nothing.

Why does the dayside being cooler than the maximum matter? On a bare rock world with no atmosphere, the side facing the star absorbs starlight, heats up, and re-radiates that heat as infrared light. The temperature that produces is set by the rock’s reflectivity and the distance to the star, and it is the highest possible dayside temperature for that orbit. Add an atmosphere, and two things change. First, the atmosphere can carry heat from the day side to the night side, evening out the temperature. Second, clouds or hazes can reflect some starlight back into space before it ever reaches the surface, lowering the dayside temperature below the bare-rock maximum. Venus is the textbook example of the first effect, with almost no temperature difference between its equator and poles or between its day and night sides. Earth is the textbook example of the second effect. HD 3167 b is showing one or both on a world whose dayside is liquid rock.

What the atmosphere is actually made of, the team is careful to say, is not known. The single JWST spectrum is not precise enough to pick out individual molecules. The paper notes that the dayside emission spectrum is compatible with a silicate-rich composition consistent with vaporized rock, but also with heavier gases like carbon dioxide, carbon monoxide, or water. Picking among those will take follow-up spectroscopy, ideally with JWST’s Near-Infrared Spectrograph, which covers a different wavelength range. The team is also hoping that the rest of the ten-planet program will start to fill in a statistical picture, where several planets measured the same way start to show consistent or inconsistent composition patterns.

The planet itself is also interesting in detail. Its host star, HD 3167, is a K-type main-sequence star slightly smaller and cooler than the Sun, and the planet was first spotted in 2016 in data from the Kepler space telescope’s extended K2 mission, then confirmed by Vanderburg and collaborators in a dedicated follow-up. Like most ultra-short-period rocky worlds, it is tidally locked, with one side permanently facing the star and the other side in permanent night. The new paper refines the planet’s radius to roughly 1.6 Earth radii and confirms the bulk density is slightly lower than a pure Earth-composition planet would suggest, consistent with the planet having a substantial gas layer on top of the rock.

For the broader exoplanet field, the result is a small but real data point in a much larger argument. Most rocky exoplanets found so far, the ones that orbit small cool stars and sit at Earth-like distances, do not have atmospheres. JWST has now measured enough of them to know that, and that has driven a lot of the conversation about whether Earth-like planets are rare or common. Lava worlds are the opposite case. They are easy to observe because they are hot, and the evidence so far is that most of them have something on top of the rock. HD 3167 b extends that trend. It does not change the picture for habitable-zone rocky worlds, but it does sharpen the boundary case where atmospheres start to fail.

There is one quote in the paper and its accompanying press release that captures why a team would spend JWST time on a planet that cannot possibly host life. Lava worlds are useful because they let you watch the processes that matter for all rocky worlds at the extreme end of their temperature range. A planet that is too hot for life can still tell you something about how its rock interacts with its air, how heat moves around, and how clouds form. None of that is unique to lava worlds. All of it shows up in the physics of habitable worlds too. The difference is that on a lava world you can measure it directly, and on a habitable world you mostly have to guess.

A planet heavier than Neptune but the size of Earth should not, by the rules of how planets form, be a rock. Anything above roughly ten Earth masses is supposed to grab gas from the protoplanetary disk and become a sub-Neptune or larger. Yet a small catalog of worlds has long carried the label “Mega-Earth,” rocky objects sitting above that ten-Earth-mass line, and that label itself colors what people assume about planet formation at the upper end of rocky worlds. A paper published today by Casey Brinkman and Nicolas Cowan at McGill’s Trottier Space Institute argues that the entire category may be a measurement artifact (Brinkman & Cowan 2026, arXiv:2610.12600, reported on by Astrobiology.com the same day). Every candidate Mega-Earth in the literature, the authors show, orbits a magnetically active star. Active starspots and plages mimic and inflate the radial-velocity signal of an orbiting planet, and the chance that all of these outliers would land on active hosts by coincidence is below one percent. The implication is uncomfortable but specific. The Mega-Earths were never there. The detection technique was just seeing starlight flicker, and the label stuck because the underlying objects were just hard enough to disprove.

The category was supposed to mark the upper edge of rocky planet formation. When Xavier Dumusque and colleagues at the Harvard-Smithsonian Center for Astrophysics used the HARPS-N spectrograph on La Palma in 2014 to weigh Kepler-10c, the result landed at seventeen Earth masses packed into a radius only 2.35 times Earth’s (Harvard Gazette, June 2014). That density, on the order of seven grams per cubic centimeter, was consistent with a compressed rocky interior under extreme pressure. The team coined the term “Mega-Earth” (Wikipedia: Mega-Earth) on stage at the Boston meeting of the American Astronomical Society, and Dimitar Sasselov called Kepler-10c the “Godzilla of Earths.” The discovery paper was published in The Astrophysical Journal in June 2014. Subsequent surveys added more candidates with apparent masses between ten and forty Earth masses and radii sitting inside the rocky planet regime, and at various points the literature has listed six to eight such worlds, depending on which mass-radius cuts are applied. Each one pressed against a theoretical limit set by collisional mantle stripping and post-formation erosion that no primordial rocky planet should be able to cross.

What jumps out of the resulting scatter plot is that every white-circle Mega-Earth candidate lies on the active side, while the gray-circle population of ordinary rocky and sub-Neptune-mass planets spans inactive through quiet. The four Mega-Earths the authors identify, WASP-84 c, TOI-1347 b, TOI-2322 c, and HD 63433 b, all orbit stars with log R prime HK above negative four point seven five. Three additional planets sit close to the Mega-Earth density regime: GJ 523 b, TOI-815 c, and HD 18599 b. All seven orbit active stars. The probability of that alignment by chance, given how many inactive and quiet-host rocky systems exist in the same sample, comes out below one percent. The authors also note that a previously Mega-Earth-classified world, HD 119130 b, was already re-measured by another group and found to have an inflated mass caused by constructive interference between the planet’s orbital signal and the star’s rotational modulation.

The mechanism behind the contamination is well known but tricky to remove. Starspots and the brighter magnetic regions called plages move across the disk of a rotating star and produce Doppler shifts in the integrated starlight that are indistinguishable, in many pipelines, from the reflex motion of a planet. Starspots suppress local convection and produce false radial-velocity signals at the star’s rotation period. Plages do the same at somewhat different amplitudes. When a planet’s orbital period happens to land near an integer or half-integer multiple of the star’s rotation period, the two signals can constructively interfere and inflate the inferred planet mass by a factor of two or more. That is the situation for several of the candidate Mega-Earth hosts, whose TESS light curves show clean rotational modulation at periods from roughly four to fourteen days. The full radial-velocity datasets that yielded the published masses came from public archives including the NASA Exoplanet Archive, which compiled discovery spectra from HARPS, PFS, and TESS follow-up campaigns. Gaussian-process regression, the tool most often used to handle stellar activity in radial-velocity fits, is only as good as its kernel choices and its priors. When the kernel is too smooth, the process absorbs genuine planetary motion as activity noise. When it is too wiggly, activity noise leaks into the planetary model and inflates the mass.

What the paper does not do is rule out rocky planets above ten Earth masses on theoretical grounds. The runaway gas accretion argument sets ten Earth masses as the threshold above which a core cannot avoid grabbing gas during formation, but it is a threshold, not a wall. Collisional mantle stripping after disk dispersal or photoevaporation of a once-larger planet’s envelope can, in principle, leave a bare rocky remnant. The authors are explicit that those pathways remain possible, just unproven. The Mega-Earth label, in their framing, has been applied to planets whose mass measurements cannot yet distinguish between a real ultra-dense rocky world and a noisy radial-velocity fit around an active star. Re-observing these systems with ESPRESSO on the Very Large Telescope, with HARPS on the TESS-Keck Survey infrastructure, or with NIRPS at La Silla, all of which have the spectral resolution to see activity-induced line-profile variations directly, would settle the question. Several of the candidate Mega-Earths have already been on those queues. The paper, which appeared on the arXiv preprint server on 8 October 2026 and is now in the resubmission cycle for The Astrophysical Journal Letters, lands in a catalog of corrections that have repeatedly eaten specific claimed populations of extreme exoplanets. Stellar contamination has eaten mini-Neptunes hiding inside hot-Jupiter mass measurements, cold Jupiters past ice lines that were artifacts of magnetic cycles, and small-radius planets that turned out to be diluted binaries. Each time, the underlying detection method is sound for inactive host stars and quietly wrong for active ones. Adding Mega-Earths to that list is, in a way, an expected move. The catalog of rocky worlds stays grounded. The Ultra-Massive Rocky Planet threshold, if it exists at all, moves somewhere more difficult to measure from the ground, perhaps requiring JWST transmission spectroscopy of these same systems to constrain atmospheric mass, or years of radial-velocity monitoring as activity cycles rotate through minimum phases. For now the simple chart is enough: a horizontal line at ten Earth masses, with seven suspected outliers sitting on the active side and zero on the quiet side. Pattern recognition cut the question in half.

A flare appeared in November 2025 near the outer edge of a galaxy in Cetus. It shone in ultraviolet light with roughly the output of 10 billion Suns and, for a few months, outshone the galaxy itself. That sounds like the sort of event astronomers would notice immediately. The awkward part was its address.

The flare sat more than 30,000 light-years from the galaxy’s center, nowhere near the central supermassive black hole that should have been capable of producing it. Follow-up observations nevertheless showed the signature of a star pulled apart by a massive black hole. The event, named TDE 2025abcr, had exposed an otherwise dark object wandering through the galactic outskirts.

The NASA account of the discovery describes it as the most distant-from-center example of its kind. More important than the record is how it was found: a search deliberately stopped assuming that a galaxy’s biggest black holes must stay in the middle.

Artist’s concept of a tidal disruption event. Credit: NRAO/AUI/NSF/NASA. NASA JPL image page.

Supermassive black holes are usually found through their effects rather than by seeing the objects themselves. At a galaxy’s center, the surrounding stars and gas provide several ways to measure an unseen mass. Far from the nucleus, a quiet black hole can disappear against the sky. It may reveal itself only when matter falls in.

Tidal disruption events offer that brief illumination. NASA estimates that one occurs in a given galaxy about once every 100,000 years, while surveys find roughly 30 across the sky each year. Until recently, optical searches concentrated on galactic nuclei. That was a reasonable filter because known supermassive black holes lived there, but it also built the expected answer into the search.

TDE 2025abcr shows what happens when that positional filter is relaxed. The accepted paper and open preprint calls it the first optical tidal disruption event discovered in the outskirts of a host galaxy. Its inferred black hole mass is about 10^6.09 solar masses, far below the roughly 10^8.82-solar-mass black hole estimated at the host’s center. One galaxy may therefore contain two massive black holes with very different histories and locations.

Finding more such objects would put numbers on a poorly measured population. Wandering black holes preserve evidence of galaxy mergers, stripped dwarf galaxies, and gravitational encounters among black holes. They also test whether catalogs built around bright galactic centers have missed a class of massive objects hiding in plain sight.

The Zwicky Transient Facility, or ZTF, first flagged the brightening in November 2025. ZTF surveys the northern sky from Palomar Observatory and produces an enormous stream of changing points. According to NASA, about half a million flashes are detected each night. A custom version of the machine-learning classifier tdescore examined that stream without requiring candidates to coincide with a galaxy nucleus. It recognized the light curve of TDE 2025abcr even though the source was well off-center.

That initial match was only a prompt for more observing. The galaxy WISEA J014656.04-152214.7 lies about 750 million light-years away. The transient was separated from its nucleus by 9.5 arcseconds, corresponding to a projected distance of 9.3 kiloparsecs. Spectra from ground-based telescopes, including the SOAR telescope in Chile, showed hydrogen and helium emission associated with a tidal disruption event. NASA’s Neil Gehrels Swift Observatory then supplied ultraviolet and X-ray measurements unavailable from the ground. Swift’s ultraviolet telescope measured a temperature near 30,000 degrees Celsius.

Together, the light curve, spectrum, temperature, and location ruled out more ordinary explanations. The researchers classified the source as a hydrogen-and-helium tidal disruption event. Scaling relations between peak luminosity and black hole mass gave an estimate of 10^6.09 solar masses, with an uncertainty of 0.53 dex. That uncertainty is broad, but the result still separates the wandering object from the much heavier black hole expected in the main galaxy’s nucleus.

How did it get there? The team offers two possibilities. In one, several galaxies merged and the interaction among their central black holes ejected the lightest one toward the outskirts. In the other, the black hole remains at the center of a faint dwarf galaxy now being stripped during a minor merger. The dwarf’s stars may be too dim or too dispersed to stand out in current images.

Those explanations can be tested. Deep late-time imaging, after the flare fades, could expose a faint stellar system around the black hole. More off-nuclear events would reveal whether large offsets favor one merger history over another. The paper places the rate of events more than 3 kiloparsecs from a nucleus below 10 percent of the nuclear TDE rate, while predicting that the Vera C. Rubin Observatory could find dozens with resolvable offsets each year.

The timing has an engineering wrinkle. Swift’s pointed observations are temporarily suspended while the mission awaits an orbit boost. Its primary mission ran from 2004 to 2006, yet it has continued watching the changing sky for more than two decades. Rubin can supply a much larger optical sample, and NASA’s Roman telescope can extend the search to greater distances. Swift, once normal operations resume, remains useful for the ultraviolet and X-ray follow-up that turns an unusual point of light into a physical diagnosis.

A tidal disruption begins with a gradient. Gravity is stronger on the side of a star facing a black hole than on the far side. If the star passes close enough, that difference overwhelms the star’s self-gravity. The star stretches, breaks apart, and becomes a stream of gas. As the NASA tidal disruption explainer shows, some debris escapes while some returns, collides, heats up, and gathers around the black hole.

The rough boundary is the tidal radius, often written as r_t approximately equal to R_star times (M_BH/M_star)^(1/3). A larger star is disrupted farther out. A more massive black hole also raises the tidal radius, but only with the cube root of its mass. The event horizon, by contrast, grows directly with black hole mass. This difference explains why a million-solar-mass black hole can tear a Sun-like star apart outside its horizon, where the hot debris remains visible.

The flare is not a photograph of the black hole. It is radiation from gas responding to extreme gravity. Ultraviolet temperature constrains the hot emitting region. Spectral lines identify elements and track changing velocities. X-rays probe hotter material closer to the compact object. None of these measurements alone settles the case; their agreement does.

The classifier solves a different problem. A survey camera records real transients alongside variable stars, supernovae, moving objects, and instrumental artifacts. A model trained on known tidal disruption light curves can rank candidates, but a model trained only on nuclear examples may learn location as a shortcut. The off-nuclear version of tdescore removed that shortcut. Its success is a clean lesson in survey design: changing a selection rule can reveal objects the telescope had already become capable of seeing.

TDE 2025abcr did not make a wandering black hole appear. It made one observable for a few months. A star supplied the fuel, ZTF caught the changing light, and Swift helped establish what produced it. The result is a black hole of roughly a million solar masses projected 9.3 kiloparsecs from the center of a massive galaxy.

The remaining question is whether this object was kicked out of a galactic nucleus or still occupies the fading core of a stripped dwarf. Late-time imaging may answer that for this system. Rubin’s larger alert stream can answer the population question by finding enough examples to compare.

The useful change was modest: researchers searched outside the place where theory and habit told them to look. If Rubin finds the predicted dozens of resolvable off-center events each year, TDE 2025abcr will become less of an oddity and more of a map marker for a hidden population moving through galactic outskirts.

In the constellation Cassiopeia there is a small, oddly symmetrical puff of gas that, on the best nights, looks like a firework frozen at the instant it bursts. Astronomers call it Pa 30, and it is the leading candidate for the remains of a supernova that flared over China, Japan, and the medieval Middle East in the summer of 1181. New narrowband imaging from the Gemini North telescope on Maunakea, published on 6 October 2026 in The Astrophysical Journal, shows that Pa 30’s famous radial filaments are not smooth streamers at all. They are chains of small, evenly spaced knots of gas, lined up like beads on a string along every spoke of the nebula, and the new observations resolve about ten times more of them than any previous study had seen (Cunningham et al. 2026 ApJ; NOIRLab press release). That changes what astronomers thought they were looking at, and it gives the field a way to measure how the ejecta of an 850-year-old failed thermonuclear supernova actually broke up as it ran outward.

Pa 30 was nothing more than an entry in a star catalogue until 2013, when an American amateur astronomer named Dana Patchick, sorting through Wide-field Infrared Survey Explorer data for a citizen-science hunt for planetary nebulae, picked out a previously unrecognized infrared source he labelled “Pa 30” (Sci.News). Follow-up imaging on the 2.1-metre telescope at Kitt Peak and then the 2.4-metre Hiltner telescope revealed a faint nebula threaded by remarkably straight radial filaments, almost perfectly circular in outline, with a hot blue star at the centre (Cunningham et al. 2026 arXiv:2610.06424). The reason that matters is that a normal Type Ia supernova is the catastrophic disruption of a white dwarf that has been pushed over the Chandrasekhar mass limit by accretion from a companion. The white dwarf is destroyed completely; no central star survives; the expanding debris forms a roughly spherical shell with no heartbeat. Pa 30 has a star at its centre that is still very much alive and very hot. Spectra put its surface temperature at roughly 200,000 kelvin and its stellar wind at about 16,000 kilometres per second (Cunningham et al. 2026 ApJ). That is the calling card of the much rarer Type Iax class, a family of faint thermonuclear explosions in which the white dwarf survives the blast, sometimes barely. Only a handful of Type Iax events have been catalogued, and Pa 30 is the only confirmed one whose remnant we can resolve in detail.

The 1181 identification is what turns Pa 30 from a curiosity into a calibration point. Eight separate texts record that a “guest star” appeared in Cassiopeia between 4 and 6 August 1181 and remained visible to the naked eye for 185 days. For decades the historical remnant was confused with the radio pulsar wind nebula 3C 58, but 3C 58 turned out to be too old to match. In 2021, Andreas Ritter and a team at Queen’s University Belfast identified Pa 30, with its associated central star (which they dubbed Parker’s Star after the Hong Kong astronomer Quentin Parker), as the much more plausible remnant of the 1181 event (Sci.News). The geometry fit: an age of roughly 850 years, a position consistent with the historical records, and an ejecta velocity near 1,000 kilometres per second. The 2026 Gemini North campaign, led by Tim Cunningham, then at the Center for Astrophysics at Harvard and Smithsonian and now at the University of Warwick, with Ilaria Caiazzo at the Institute of Science and Technology Austria, John Raymond, and Scott Kenyon, set out to see what was hidden in the filaments at the highest resolution available from the ground. They used the Gemini Multi-Object Spectrograph (GMOS) in narrowband filters tuned to the [S II] and [O III] emission lines of low-ionization gas, and took very long exposures to pull faint substructure out of the background. Each radial spoke resolved into a string of small bright knots separated by fainter gaps, marching outward from near the central object, and the [O III] imaging produced the first confirmation that the diffuse oxygen emission in the nebula is co-spatial with the sulphur filaments rather than being a separate, smoother component (Cunningham et al. 2026 ApJ).

The other headline from the same campaign is a quiet one: the centre of the nebula sits almost exactly where the central star sits. Surviving supernova remnants are expected to recoil, and models of double-white-dwarf mergers predict a kick of anywhere from a few to several hundred kilometres per second for whatever survives the blast. Cunningham and colleagues used their imaging to pin the geometric centre of Pa 30 with a Monte Carlo Markov chain and compared it to the position of the central star, concluding that any transverse kick must be under about 100 kilometres per second at the 3-sigma level (Cunningham et al. 2026 arXiv:2610.06424). That is unusually small for a merger survivor. It tightens the constraint on how energetic and asymmetric the explosion could have been, and it adds another piece of evidence that the 1181 event really was a Type Iax: a comparatively gentle thermonuclear runaway in which much of the white dwarf’s mass was ejected but a substantial core remained intact, sitting nearly where it began. What the knots themselves are made of is the open question the new data sets up. If the filaments were once smooth, their beaded structure implies either that the ejecta itself was clumpy on small scales when it was launched, or that the interstellar or circumstellar material the ejecta ran into was inhomogeneous enough to break the flow up into discrete radiative-cooling zones. The characteristic spacing Cunningham’s team measures, around 10^16 centimetres per knot, is roughly the size scale that Rayleigh-Taylor fingers in supernova remnants are expected to produce, and strings of similar knot cascades can be seen in the core-collapse remnant Cassiopeia A, although without Pa 30’s strict radial geometry (Cunningham et al. 2026 ApJ).

Follow-up is already in the queue. STScI program 18082, accepted in June 2026, will pair the Gemini narrowband imaging with a 16-orbit Hubble WFC3 campaign in [S II] to map Pa 30’s filaments across their full length, and JWST program 9111, in parallel, is using MIRI’s integral-field unit to obtain mid-infrared spectra of six bright filaments to measure their dust content and cooling balance. The combination should let the team tie the optical knots to specific ejecta species (oxygen, neon, sulphur) and to the dust that survived the explosion, and to test whether the beading is consistent with a clumpy progenitor or a clumpy medium. There is also a separate, very recent coda to the Pa 30 story: a separate team announced in early October 2026 that the central star, IRAS 00500+6713, has a measurable green tint in its visible-light spectrum, the first white dwarf to show one, painting it with the same mechanism that gives oxygen-rich Wolf-Rayet stars their colour (NASA APOD 2026 October 7). The 1181 supernova is the only historical Milky Way Type Ia-class event whose remnant we can resolve and the only Type Iax remnant at all, and with knots now measurable one by one, a quiet central star that did not fly away, and a Hubble and JWST follow-up in flight, it is the closest thing the field has to a benchmark for what a failed-but-not-quite thermonuclear supernova looks like 850 years after it happened.

SETI has spent decades listening for narrowband radio signals, mostly below a few gigahertz. Most of that listening has been concentrated in a small slice of the radio dial. A new analysis from the University of Manchester points at a different slice and asks what has been there the whole time.

Louisa Mason, a PhD researcher at Manchester, used four archived observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to run the telescope’s first SETI survey. The work, published in the Monthly Notices of the Royal Astronomical Society, focuses on ALMA’s Band 3 receivers and two narrow frequency windows near 90.642 GHz and 93.151 GHz. Those frequencies sit well above the traditional SETI bands and have barely been searched for narrowband technosignatures.

No candidate signals exceeded the survey’s detection thresholds. That is the expected result for a first pass, and the researchers describe the result as an opening of parameter space rather than a discovery.

SETI is shaped as much by instrumentation as by theory. Most narrowband technosignature work has relied on telescopes such as the Green Bank Telescope, the Parkes Murriyang telescope, and the Allen Telescope Array. Those instruments are excellent in their ranges but were not built for the millimeter and submillimeter bands. ALMA is sensitive above 35 GHz in a way few other facilities can match, and it has been producing archived data since 2011.

The implication is straightforward. A signal at 90 GHz could be present in ALMA data right now without anyone having looked. The new analysis is the first structured attempt to check.

There is a secondary finding, also presented at the Royal Astronomical Society’s National Astronomy Meeting in 2026. The same team used Gaia stellar catalogues to revisit the number of stars that earlier SETI surveys actually covered. ScienceDaily’s summary notes that the Manchester group found prior published counts may have understated the real coverage by more than an order of magnitude, with one estimate moving from roughly 288,000 stars to over 6 million once Gaia cross-matching was done properly.

The headline numbers are different from the search itself, but they are linked. Both findings argue that SETI has been sampling the sky less carefully than the literature suggests.

Mason did not request new ALMA time. The survey pulled four archived calibrator scans from the ALMA archive. Calibration observations are short, pointed at bright reference sources, and usually discarded after the data are reduced. Mason treated each scan as a science observation in its own right, looked at the stars that happened to fall in each antenna’s field of view, and searched for narrowband signals inside two narrow windows in Band 3.

The search covered 28 stars in total. They are a mix of main-sequence stars and white dwarfs, drawn from Gaia cross-matches. For each star, the analysis looked for narrowband emissions that would not be consistent with known natural processes in the band. Carbon monoxide, hydrogen cyanide, and diazenylium all produce molecular lines in this frequency range, so a SETI search needs to avoid flagging those as candidates.

The paper’s conclusion is that no candidate technosignatures passed the threshold. The survey’s sensitivity, the bandwidth of the search windows, and the relatively small star sample all limit how much can be inferred from a null result. The University of Manchester’s research record makes the same point in a more compact form.

Universe Today’s coverage walks through Mason’s quote that the millimeter and submillimeter bands “remain almost completely unexplored for SETI,” which is why the team framed the work as opening parameter space rather than confirming or refuting a particular hypothesis.

The Manchester team also pulled out a comparison with existing facilities. The figure in the MNRAS paper shows the frequency coverage each instrument could probe for narrowband SETI work. ALMA’s coverage sits in a region where other radio observatories are not conducting technosignature searches. That is both a justification for the work and an invitation to others to design complementary searches.

SETI looks for narrowband radio signals. The reasoning has not changed much since the early 1970s. Natural astrophysical sources tend to emit across broad frequency ranges, often with characteristic molecular or thermal signatures. A transmitter that uses a stable oscillator and a high-gain antenna concentrates its power into a narrow slice of spectrum. The narrower the signal, the harder it is to explain without technology.

A typical SETI pipeline breaks the recorded spectrum into fine channels, looks for narrow features, and checks that the candidate signal is consistent with the receiver’s beam shape and the motion of the telescope and the target. Drift rates, polarization, and the on-off pattern that comes from tracking a star are all used to separate terrestrial interference from real signals.

ALMA complicates this picture. ALMA is an interferometer, meaning it combines signals from many individual antennas. Each antenna has a defined field of view, and the dishes can resolve sources on the sky. At 90 GHz, that field of view is small. The good news is that any signal coming from a real source on the sky will appear in the antennas that were pointed at it, with a pattern that reflects the interferometer’s geometry. The bad news is that the same geometry creates challenges for confirming a narrowband signal across multiple baselines.

The Mason paper is explicit about these complications. Drift rates at high frequencies are larger because a transmitter of fixed velocity produces a larger Doppler shift per unit time when the carrier frequency is higher. The interferometer’s “undistorted field of view” sets a hard limit on how far off-axis a source can be and still be observed cleanly. The paper treats these as engineering constraints to design around rather than showstoppers.

The four archived scans used in the analysis were calibrator observations pointed at bright sources, not deep integrations. Each scan covers a few minutes of data. A real SETI survey would want longer integrations and a wider range of calibrator fields, but the short data are enough to demonstrate the analysis pipeline and to put a first constraint on narrowband signals at 90 GHz from a small star sample.

The Gaia cross-match that drives the higher star count is a separate but related piece of work. Previous published counts tended to use a single pointing on the sky and the simple catalog of stars within that beam. Cross-matching against Gaia, which has astrometry and stellar parameters for nearly two billion sources, lets researchers classify the targets and identify white dwarfs separately. White dwarfs are interesting for SETI because they are compact, old, and bright at optical wavelengths, and they often have stable proper motions.

The combined message is methodological. SETI can be expanded by re-examining existing archives, and existing surveys can be more ambitious about how they characterize their coverage. ALMA’s archive, described by the National Radio Astronomy Observatory as containing public data from 66 high-precision antennas in Chile, is the obvious next place to look. The European Southern Observatory’s ALMA instrument page adds the same picture from the operator side: a fifty-antenna main array plus a compact array of 12-meter and 7-meter dishes, all working as a single interferometer.

SETI’s search volume has been bounded more by receiver design than by theory. The Manchester group made that bound visible by stepping outside the usual bands and re-examining published star counts. Neither move produced a signal, but together they reset the baseline.

The next test is whether the technique scales. A follow-up that runs the same pipeline across the full ALMA calibrator archive, including longer integrations and additional Band 3 frequencies, would not require new telescope time. It would need a researcher willing to spend the weeks of compute and the careful bookkeeping the analysis demands.

Until that happens, the cleanest summary is also the most honest: SETI has more sky to listen to than it has listened to, and the millimeter bands are still open.

A new overhead image of a Martian crater floor shows branching ridges of pale bedrock winding between darker, dust-floored troughs, an arrangement that looks more like a coral reef than a piece of the red planet. The picture was captured by the High Resolution Imaging Science Experiment, HiRISE, aboard NASA’s Mars Reconnaissance Orbiter and released on September 28, 2026, by HiRISE co-investigator Cathy Weitz of the Planetary Science Institute (Space.com photo of the day for September 28, 2026; Daily Galaxy, September 28, 2026). The terrain sits inside the Arabia Terra region, a vast upland that many planetary geologists regard as one of the oldest, most heavily cratered provinces on Mars. The shapes in the image are not biological. They are layered sedimentary rocks that have been eroded into ridges and pits, and the way those layers repeat across many craters is what makes the image worth a second look. For viewers who only know Mars as a smooth red dot in the night sky, the picture is a reminder of how much texture the planet keeps when you look closely.

What Arabia Terra offers is a stratigraphic archive. Each thin band visible in the rock records a moment in Martian climate history, and the bands stack one on top of another across hundreds of meters of relief. The rhythmic nature of those layers is the whole point. A repeating pattern across a region this large does not arise from one storm, one flood, or one impact; it implies a process that pulsed on and off again and again. The MRO camera that took the picture has been in orbit since 2006, and HiRISE has been returning 25-centimeter-per-pixel images of the Martian surface for almost the entire mission. With more than 100,000 images already on the public catalog, the September 28 release is not a new instrument result. It is a fresh reminder that some of the strongest evidence for an active, water-influenced early climate on Mars has been sitting in the MRO archive for years, waiting for someone to look at it with the right question. The 100,000-image mark was passed in October 2025 on the Syrtis Major plains, and the camera has continued adding observations since.

The deposits were first described as a regional phenomenon in a 2020 paper in JGR Planets by Stack and colleagues (Stack et al. 2020, JGR Planets), who used a combination of HiRISE stereo topography and mineral mapping from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to show that the layered rocks in many Arabia Terra craters share a common stratigraphy. Their preferred explanation was groundwater-fed evaporitic deposition, where water just below the surface cycled up, evaporated, and left behind minerals and fine sediments in regular layers. Lewis and colleagues at the California Institute of Technology had already noted in 2014 (Lewis et al. 2014, JGR Planets) that the rhythmic layering in this part of Mars matches the patterns left by air-fall dust and ash on Earth, which alternate under the influence of orbital cycles. Weitz’s own commentary for the new picture pulls those threads together. The layers are rhythmic, they are widespread, and the most plausible global drivers on Mars are dust storms and groundwater, not isolated local events. Crater counts performed by the same group suggest the layered sequence accumulated mostly during the Hesperian period, roughly 3.0 to 3.7 billion years ago, with the topmost beds stretching into the Amazonian, which is the ongoing geologic era on Mars and the one in which the planet lost most of its surface water. Earlier work by Fergason and Christensen in 2008 had already used thermal imaging to flag the same layered terrain as a candidate record of dust-driven deposition, and the 2020 paper builds on that line of argument.

The image itself is about five kilometers across. The bright ridges are bedrock that has resisted erosion longer than the surrounding material. The darker, bluer-looking troughs are a mix of wind-blown sand and what HiRISE team members call aeolian ripples, the same kind of sand patterns that form under persistent winds in terrestrial deserts. The pits, jagged edges, and crenulated rims the image shows are not the original shapes of the rock. They are erosion scars. Each one marks a layer that has been removed and a layer that has not. The contrast between the two tones is a function of the difference in composition and grain size between the original sediment that hardened into rock and the loose debris that fell on top of it later. HiRISE resolves these textures because it images through three separate color filters and stitches them together; the false-color composites that the team releases are designed to make compositional differences pop, which is why a single scene can look bluish in some places and pinkish in others. HiRISE itself is a 0.5-meter reflecting telescope on MRO, and at MRO’s 250-to-316-kilometer orbit altitude it can pick out features smaller than a meter across. Most of what we know about the fine-scale stratigraphy of Mars has come from that resolution combined with stereo imaging, which lets the team build digital terrain models and measure layer thicknesses down to a fraction of a meter.

The deeper lesson is about how scientists read climate records on a planet that does not have trees, ice cores, or ocean sediment. On Earth, the story of past climate comes from layered archives in lake beds, sea floors, and ice sheets. On Mars, the same role is played by impact craters, which act as ready-made sediment traps and which subsequently get exhumed by wind. Arabia Terra is particularly worth studying because it has been around long enough to have collected material from the Noachian period more than 3.7 billion years ago, when most evidence suggests Mars had a much thicker atmosphere and liquid water on its surface. The layered deposits in the September 28 image are younger than that, but they preserve the same kind of memory. A geologist looking at the rock can read off changes in chemistry, dust load, and water availability across hundreds of millions of years.

A few things remain unsettled. The image does not confirm a single formation mechanism, and the team has been careful not to claim it does. The rhythmic pattern is consistent with several hypotheses, and the right next step is to compare the layer thicknesses and mineralogy from one crater to the next, which the 2020 Stack analysis already started. Future observations from the Mars Reconnaissance Orbiter, and eventually from missions now in development, can sample more of these layered terrains with high-resolution spectroscopy and will be able to test whether groundwater, dust, or volcanic ash dominates the mix. Until then, the picture is best read as a working document: a region that has been taking notes on Martian climate for billions of years, and an instrument still healthy enough to read those notes from orbit.