OrbitalHub

On the morning of August 4, 2026, a heliophysics team gathered at the Committee on Space Research Scientific Meeting in a windowless conference room and ran a video. The video showed a cloud of charged plasma leaving the Sun on May 31, 2025, and then kept watching it, frame by frame, as it crossed the inner solar system. Twelve hours after the eruption, a basic tracking model settled on an arrival time. Eight hours later, the cloud actually showed up. The forecast was accurate to within thirty minutes, an order of magnitude better than what operational forecasters can currently hand to a satellite operator or a power grid manager. The image stream that made it possible came from a constellation of four small NASA satellites that almost no one was talking about a year ago, called PUNCH, the Polarimeter to Unify the Corona and Heliosphere.

Solar storms are the part of space weather that hits infrastructure. A coronal mass ejection that reaches Earth compresses the magnetosphere, drives geomagnetic currents through long conductors, and can knock out high-voltage transformers, satellite electronics, and GPS-based timing. The 1989 Hydro-Québec blackout, which left six million Canadians without power for nine hours, began with a CME. The 2003 Halloween storms disrupted GPS, aviation, and the Japanese ADEOS-2 spacecraft. Satellites in low Earth orbit experience increased atmospheric drag during geomagnetic storms, and astronauts on the way to the Moon or Mars need to know when to take shelter.

The forecasting problem is that the Sun is 93 million miles away and a CME traveling at a million miles per hour takes about 15 to 18 hours to reach Earth. That is a long enough lead time to act, but only if you know when the cloud will arrive. The current operational model, called WSA-ENLIL, was put into service by NOAA’s Space Weather Prediction Center and uses a 1-to-4-day cone projection that gives a forecast window of about 5 hours. The 30-minute result from PUNCH is roughly ten times tighter, and it came from a deliberately simple model that the team describes as the “steam engine” version of what could be built on top of the same data.

PUNCH launched on March 11, 2025, from Vandenberg Space Force Base in California, sharing a Falcon 9 ride with the SPHEREx sky mapper. All five satellites separated from the same upper stage, and the four PUNCH spacecraft (three carrying Wide Field Imagers and one carrying the Narrow Field Imager) began climbing into a polar, low Earth orbit (Wikipedia: PUNCH; SwRI mission page). First light came on April 14, 2025, with the NFI and one WFI snapping their inaugural images, and the other two WFIs following two days later (NASA SVS PUNCH first-light CME images). By late May the spacecraft were returning daily mosaics wide enough to track a single CME from the corona all the way out to where Earth sits.

The team chose a specific event as their test case: a coronal mass ejection that left the Sun on May 31, 2025. The leading edge of the cloud moved through the inner solar system, and PUNCH’s three WFIs captured it every four minutes throughout the journey. The researchers fed those images into a basic forward model that had no deep learning, no physics-specific tuning, and no prior knowledge of the speed or geometry of the cloud. The model extracted the position and motion of the leading edge from the imagery and converged on an arrival time forecast roughly twelve hours after the eruption. That settled forecast was accurate to within 30 minutes of the actual arrival, a 10× improvement over the 5-hour window from the current operational approach, which uses the WSA-ENLIL cone model (NOAA SWPC WSA-ENLIL; NASA Science release).

“We thought PUNCH would be good at this, but it’s a stunning result,” said Craig DeForest, the principal investigator at Southwest Research Institute’s Solar System Science and Exploration Division in Boulder. “To put it in perspective, this could be the space weather equivalent of going from a steam engine to a modern internal combustion engine.” The model also revealed when its own estimate had stabilized, which is a useful property for forecasters because it tells them when the prediction is safe to act on.

PUNCH is built to do something the previous generation of coronagraphs could not: keep its eyes on a single coronal mass ejection for the entire Sun-to-Earth journey. The big European-NASA SOHO spacecraft, launched in 1995, carries the LASCO coronagraph that has been the workhorse of CME forecasting for three decades, but LASCO’s field of view cuts off at about 32 solar radii (NOAA SWPC CME overview). Beyond that, a CME becomes too faint and too far from the Sun’s bright disk for a coronagraph to track. The gap between LASCO’s edge and Earth is roughly 80% of the journey, and most of the guessing in the current 5-hour forecast window comes from that gap.

PUNCH’s three Wide Field Imagers extend that view out to 180 solar radii, while the Narrow Field Imager, a coronagraph similar in spirit to LASCO C3, covers 6 to 32 solar radii. Where the design is unusual is in the polarimetry: rather than just taking pictures, the WFIs measure the polarization of the sunlight scattered by free electrons in the corona and solar wind, which lets the team separate the K-corona (the part of the corona made of solar plasma) from the background starfield, zodiacal light, and Milky Way. The reduction pipeline aligns images from all four spacecraft to within 0.03 pixels of each other and produces a single 4-minute-cadence polarimetric image covering a 90° field of view centered on the Sun (NASA SVS PUNCH Instruments).

The forecasting work uses that data in a deliberately simple way. The model segments the moving leading edge of the CME, fits kinematics to its position over time, and projects the arrival by extrapolating the speed and direction. It does not currently include physics for how a CME decelerates against the ambient solar wind, rotates as it expands, or interacts with earlier ejections. The fact that a basic kinematic model still beats the operational cone model by a factor of ten is the headline: more physical realism, and more PUNCH data, will only sharpen it. DeForest’s team has also begun using the high-resolution imagery to see that CMEs are clumpier than previously thought and continue to evolve as they travel, which is itself new physics for the forecast models to absorb.

PUNCH’s first forecast result is a proof of concept rather than a finished system. The model that produced the 30-minute window is not yet integrated into NOAA’s operational forecasting pipeline, and the August 4 announcement at the Committee on Space Research Scientific Meeting is paired with a paper currently under review at the journal Space Weather (NASA Science release). The next steps are obvious and on the team’s roadmap: refine the model, run it on a larger sample of CMEs, and hand it to SWPC for testing. If the gain holds across more events, the practical effect is that satellite operators can keep a spacecraft in safe mode for a shorter window, power grid dispatchers can stand down earlier, and crewed deep-space missions can plan around tighter storm arrival predictions. The CMEs that PUNCH is now watching arrive and evolve across the inner solar system will keep teaching the team how the Sun connects to the space weather we feel on Earth.

The source flagged on December 10, 2023 looked ordinary at first: a flat-spectrum radio quasar in the constellation Canes Venatici, sitting just shy of a redshift of 1, where most extragalactic work stops being feasible. Within four nights of follow-up, the prototype Large-Sized Telescope (LST-1) on La Palma had pulled it out of the background with a statistical significance of 12 standard deviations, and a few nights later the MAGIC telescopes at the same observatory confirmed the detection at 6 standard deviations. The result, published in August 2026 in Astronomy & Astrophysics by the CTAO LST and MAGIC collaborations, makes OP 313 the most distant active galactic nucleus ever detected at very-high-energy gamma rays (above 100 GeV) and only the tenth flat-spectrum radio quasar (FSRQ) ever caught at those energies (Abe et al. 2026, A&A).

Blazars are what happens when a supermassive black hole happens to be pointing one of its relativistic jets almost directly at Earth. The jet accelerates particles to extreme energies, and the blazar we see is the Doppler-boosted glow of that jet. The lower-energy bump of that glow peaks somewhere in the optical or X-ray range, and a second, much higher-energy bump sits in the gamma-ray range. For BL Lacertae objects, the second bump can be tracked cleanly all the way up to tens of tera-electron-volts with imaging atmospheric Cherenkov telescopes (IACTs). For FSRQs, where the jet is embedded in bright gas clouds and a dusty torus, that same very-high-energy glow is much harder to produce and gets eaten on the way out.

The “eaten on the way out” part is what makes OP 313 a hard target. Every gamma-ray photon at, say, 300 GeV that leaves an FSRQ has to traverse roughly seven billion light-years of space to reach us, and along the way it can pair-produce on infrared and optical background photons left behind by every star that has ever lived. That fog, the extragalactic background light (EBL), gets thicker as you look deeper into the universe, and very-high-energy photons from distant blazars usually arrive at Earth with their high-energy tail statistically removed. OP 313 at z=0.997 sits deep enough in this fog that detecting its very-high-energy emission at all was the main challenge; using it to constrain the fog itself is the secondary prize (phys.org news writeup, 24 August 2026).

The detection was triggered by a high state reported by the Fermi-LAT and optical monitoring networks in late November 2023. Once the daily Fermi analysis (the FLaapLUC pipeline) flagged the rising flux, two follow-up alerts went out on December 10, and both LST-1 and MAGIC began observing that same night. Between December 10 and December 19, LST-1 accumulated 14.6 hours of good-weather data and detected the source at 12.0 standard deviations above ~10 GeV, the highest single-instrument significance the campaign produced. The MAGIC stereo system collected 10.4 hours during the same flare window and confirmed the detection at 6.0 standard deviations. Follow-up in January 2024, when the source had dropped back into a low state, returned only upper limits, consistent with a flaring source that had settled back down (Abe et al. 2026, A&A).

The paper’s value goes beyond confirming one more extragalactic source. OP 313 had been observed before in the very-high-energy range by MAGIC alone and produced only upper limits, so the new detection, which doubled as a first-light demonstration for the LST-1 prototype that will seed the Cherenkov Telescope Array Observatory (CTAO) in the Northern Hemisphere, slots the source into the small club of VHE-detected FSRQs (TeVCat catalogue for OP 313). The previous record-holder at this kind of energy was a different FSRQ called PKS 0346-27, at redshift 0.991. Pushing that mark to 0.997 by no more than a sliver of z amounts to several extra billion years of lookback time at this distance, where each tick of z adds roughly a billion light-years of optical depth through the EBL.

The detection also slots into a wider multimessenger story. In May 2012, the IceCube Neutrino Observatory at the South Pole recorded a high-energy track-like event whose reconstructed direction was consistent with the position of OP 313. The neutrino was not temporally coincident with the gamma-ray flare, so this paper cannot claim a coincident detection; but the fact that the same source is now visible at the highest gamma-ray energies, in the same sky region IceCube flagged, raises the long-term odds of catching a genuine neutrino-blazar coincidence during a future high state (LAPP press release, 2024).

LST-1 is the first of four Large-Sized Telescopes planned for the northern Cherenkov Telescope Array Observatory (CTAO) array, situated next to MAGIC at the Roque de los Muchachos Observatory on La Palma in the Canary Islands. Its 23-metre segmented mirror dish and its 1,855-pixel camera of high-quantum-efficiency photomultiplier tubes give it a low energy threshold of roughly 20 GeV, low enough that any VHE source that drifts overhead is within reach. MAGIC, the older neighbour, is a stereo pair of 17-metre dishes; together they cross-check each other’s energies and directions, which is why the LST-1 paper and its Table 1 quote both sets of numbers.

Detecting OP 313 was a threshold problem on both instruments. LST-1 reached 12.0 sigma in the December window but with an analysis threshold of about 60 GeV, where the gamma/hadron separation is intrinsically harder for a single dish; the per-cent signal-to-background level reflects that the measurement is background-limited near threshold. MAGIC, with stereoscopic reconstruction, ran warmer at a threshold of about 70 GeV and reached 6.0 sigma, but its higher absolute flux above 100 GeV put it above background-systematic-limit. The two spectra agree, within their stated uncertainties, on a simple power law with no strong sign of intrinsic curvature (Abe et al. 2026, A&A HTML).

A common background light hides in those measurements. The cumulative infrared-to-ultraviolet glow of every star that has ever existed, the EBL, attenuates very-high-energy photons in a way that grows with redshift. To turn the OP 313 detection into an EBL measurement, the team fit the joint Fermi-LAT and LST-1 spectrum with a spectral model multiplied by exp(-α τ), where τ is the optical depth predicted by a reference EBL model (Saldana-Lopez et al. 2021) and α is a free scaling factor. They then constrained α by likelihood ratio testing. The result: α(95%) < 1.14 from the LAT plus LST-1 dataset, and tighter upper limits in the optical band, with the most stringent constraint coming between about 0.325 and 1.069 micrometres, the so-called Cosmic Optical Background. At 0.6 micrometres, the upper limit lands at 6.72 nanowatts per square metre per steradian (statistical, 95%), or 8.74 with energy-scale systematics included (Abe et al. 2026, A&A).

OP 313 has a separate history worth noting. Originally catalogued as a variable star in 1959 (the OP 313 designation is a positional reference), it was later identified with a flat-spectrum radio source (B2 1308+326) and reclassified as a quasar at z ≈ 0.997. The early literature sometimes labelled it a BL Lacertae object; current multi-wavelength studies favour the FSRQ classification because its emission lines and broad-line-region signatures are visible when the source is in a high optical state (Wikipedia – B2 1308+326, companion A&A study, March 2026).

OP 313 is now the highest-redshift AGN detected at very-high-energy gamma rays, the tenth FSRQ caught at those energies, and a useful lever on the optical part of the extragalactic background light. LST-1’s first confirmed contribution to extragalactic astronomy came with the same paper that moved the VHE distance record. The CTAO Consortium plans to complete the northern array over the next several years; with four LSTs at low threshold and several mid-sized telescopes at higher energies, the arrival-time window for catching the next record-breaker will keep getting shorter.

At 60.14 parsecs from Earth, a red dwarf no bigger than Jupiter hosts the most-photographed protoplanetary disk in the night sky. TW Hydrae, or TW Hya, has been a fixture of circumstellar astronomy since the 1980s, because its nearly face-on geometry makes its rings, gaps, and shadows easier to see than almost any other system. On July 27, 2026, a team led by Yu-Chia Lin of the University of Arizona submitted the deepest look yet at this benchmark disk: a four-filter JWST/NIRCam coronagraphic campaign spanning 1.87 to 4.44 microns. The result, published in arXiv:2607.23992 and accepted for The Astronomical Journal, does not yet reveal a hidden planet. What it does is reshape the geometric picture of the disk itself, with tentative but consistent evidence that the outer disk of TW Hya bends out of the plane traced by the inner disk.

Protoplanetary disks are the construction sites of planetary systems. Their rings, spirals, and shadows are the indirect signatures of forming worlds, and reading them correctly requires a precise model of how the disk sits on the sky. A warped geometry implies either an unseen inclined companion tugging the inner disk, a misalignment between the host star’s rotation axis and the disk’s angular momentum, or a past gravitational encounter that left the outer disk bent. For TW Hya specifically, where observers have spent decades trying to identify the planet or planets responsible for the system’s famous moving shadows, a confirmed warp would shift the conversation away from “is the disk flat” and toward “what is bending it.”

The JWST result is also a methodological milestone. Coronagraphic imaging of a face-on disk near the diffraction limit of a 6.5-meter mirror is technically punishing, because the coronagraphic mask hides the inner disk and point-spread-function residuals can masquerade as faint disk structures. Lin and colleagues addressed both problems with a custom PSF-subtraction routine (HPFRDI), a deconvolution algorithm tuned to the NIRCam PSFs, and an MCMC geometric fit with a non-trivial noise model. The same pipeline, applied to other nearby disks in the JWST cycle, is now an off-the-shelf tool.

The TW Hya system has been studied in enough wavelengths to fill a textbook chapter. The first clear evidence for an inner cleared region came from Hubble in the 2000s, when a near-infrared image revealed a dark gap at roughly the orbital distance of a Saturn-mass planet. Subsequent ALMA observations resolved the dust continuum and showed the gap was real, not an artifact of scattered-light modeling. The system also exhibits a moving shadow pattern, first characterized by Debes et al. and refined over multiple epochs since then, with the shadow’s apparent drift suggesting a precessing inner disk that casts a rotating silhouette onto the outer regions.

Against this backdrop, the JWST team designed a four-coronagraph campaign in NIRCam filters F187N, F200W, F356W, and F444W. F187N is a narrow-band Pa-alpha filter designed to catch hydrogen recombination emission; it produced a non-detection of the disk. F200W, F356W, and F444W caught the disk in scattered light. The team stacked two epochs in F200W and two in F444W, then ran the result through HPFRDI to subtract the stellar PSF and the coronagraphic mask transmission, then through a deconvolution code called winnie (200 Richardson-Lucy iterations for the F200W stack, 129 for F444W, with a forward-modeled synthetic disk as the stopping criterion).

The resulting images show what previous instruments could only hint at. The disk’s nearly face-on geometry means that even small inclination differences between inner and outer regions are detectable when the data are deep enough. An MCMC fit to the deconvolved F200W image, splitting the disk into inner (0.675 to 1.44 arcsec) and outer (1.44 to 2.98 arcsec) annuli, yields inclination values that overlap but tend to differ at the 1-sigma level, with the outer annulus showing a broader, asymmetric posterior. Position angle drifts slightly between inner and outer fits. The team’s cautious language is “tentative evidence consistent with a disk warp,” but the trend is the same direction across both parameters.

The companion search sets the deepest mass limits yet on potential planets in the gap region: no new point sources detected in the F444W data, reaching approximately 0.4 Jupiter masses at 1 arcsec (60 AU) under clear-atmosphere assumptions, and sub-Jupiter masses beyond 2 arcsec when local extinction is accounted for. The dust gaps in TW Hya are either being carved by planets smaller than Jupiter, or by a process that does not require a planet at all.

The disk’s near-face-on orientation makes it both a gift and a problem. With the disk inclined at only ~8.74 degrees from our line of sight, scattered-light rings and gaps are not foreshortened, so the structure stays visible across the entire field. The cost is that any inclination variation produces a small but detectable effect on the projected geometry. The team formalized this by computing brightness variance as a function of trial inclination and position angle, weighted by an empirical variance model derived from the data itself. The relationship between log-mean intensity and log-variance was fit with a second-order polynomial with R-squared of 0.98, giving the MCMC walker a well-behaved likelihood surface.

The deconvolution step matters more than is obvious. A Richardson-Lucy algorithm with too few iterations leaves the disk blurry; with too many, it amplifies noise and produces a fake central peak. The team’s solution was synthetic injection and recovery: they simulated a face-on disk with the same noise properties, ran the same pipeline, and used the residual statistics to choose iteration counts that recovered radial profiles without over-fitting the core. This kind of forward-modeled stopping criterion is becoming standard practice in high-contrast imaging, but it is unusual to see it documented so carefully in a peer-reviewed publication.

The detection of the bifurcation at 120 AU is a structural find rather than a kinematic one. The team did not measure orbital velocities, so they cannot say whether the bifurcation is a single spiral arm unwinding from a planet, dust streams from a recent collision, or a shadow projected by the inner disk onto a slightly tilted outer disk. They explicitly list all three in their discussion. The 2-degree logarithmic spiral pitch is most easily explained by gravitational interaction with a planet, but a planet of the mass implied by the spiral pitch (around 1 Neptune mass, depending on disk viscosity assumptions) would, if present at 120 AU, sit at the very edge of what JWST can detect in this dataset. The detection limits at F444W do not quite reach there, which the team acknowledges.

JWST’s coronagraphic modes, combined with careful reference-star differential imaging and iterative deconvolution, are now routinely producing sub-arcsecond views of nearby disks that were not feasible with HST or ground-based adaptive-optics instruments. The team’s PSF library (built with STPSF, the successor to WebbPSF) and their MCMC geometric fit are reusable for the next round of JWST disk-imaging programs.

TW Hya, after 40 years of study, has revealed another layer of structure to a team willing to push JWST’s coronagraphic modes to their limits. The headline result is geometric: a tentative radial warp between inner and outer disk, captured across three near-infrared filters and quantified with an MCMC fit that distinguishes real inclination drift from noise. The structural result, a confirmed bifurcation at 120 AU along a 2-degree logarithmic spiral, adds a specific observational target for any future search for the disk’s hidden planets. The companion search, which sets 0.4 Jupiter-mass limits at 60 AU, rules out a gas-giant explanation for the gap-clearing but leaves room for smaller worlds.

The paper is Lin et al. 2026, accepted for The Astronomical Journal, arXiv:2607.23992, with figures in the HTML build at arxiv.org/html/2607.23992v1. For the moving shadow history that frames the warp hypothesis, see Debes et al. 2023 in The Astrophysical Journal. The next step is a coordinated multi-epoch program: re-imaging TW Hya at F200W and F444W every six to twelve months would test whether the inferred warp precesses on a timescale consistent with a misaligned inner disk, and a single deep ALMA cycle at matched resolution would pin down whether the gas disk shares the same geometric tilt as the dust. The disk is closer than any other, so any future detection will be the cheapest JWST cycle to write and the most consequential for planet-formation theory.

For most of its 6.42-hour rotation, asteroid 44 Nysa is just a bright point in a telescope image. On the best nights, though, that point opens into something much stranger: a broad primary body with deep, wraparound valleys and a faint speck moving nearby. The new observations do not show a tidy, single rock. They suggest that Nysa may be a contact trinary, three pieces that came together slowly enough to remain joined, with a small moon circling the outside.

That conclusion is still provisional. The paper is a preprint, and the authors leave room for a different answer: Nysa could be one unusually strong, heavily fractured body whose surface only looks divided into lobes. Either way, the result is a reminder that many asteroids are known from their changing brightness long before their actual shapes can be resolved. In Nysa’s case, a century of indirect clues has finally been paired with images sharp enough to test them.

Figure adapted from Minker et al., “Unmasking (44) Nysa: Evidence for a trilobate structure”, used under the arXiv-hosted CC BY-NC-ND 4.0 license; labels and layout are unchanged.

Asteroids are fragments, but “fragment” does not mean simple. Their shapes retain evidence of collisions, gravitational settling, rotation, and the weak forces that bind rubble together. A contact binary, such as the two-lobed objects visited by spacecraft, can form when separate bodies collide at low speed and stay together. A three-lobed contact object would add another step to that history. It would give researchers a particularly clear test of whether several pieces can remain attached through later impacts and through the long-term stresses of rotation.

Nysa is also useful because its composition is unusual. It is one of the larger E-type asteroids, a rare group associated with enstatite-rich meteorites. Those meteorites resemble material thought to have formed in the hot inner part of the young solar system. The link is not a direct sample return, and the authors are careful about what can be inferred from a spectrum, but the object offers a chance to connect surface chemistry with internal structure. If its three lobes came from one parent body, their similar appearance may preserve a record of how that parent was broken and reassembled.

The moon matters for a more practical reason: its orbit can eventually provide Nysa’s mass. Shape and brightness alone leave density uncertain. A measured mass combined with the paper’s size estimate would help distinguish a coherent, dense object from a looser aggregate of fragments. That number could turn an intriguing silhouette into a physical model.

Nysa has been observed for more than a century. Earlier work used light curves, stellar occultations, radar, and the Hubble Space Telescope’s Fine Guidance Sensor to look for clues about its form. Those methods pointed toward an elongated body, perhaps with a large companion or a pronounced concavity, but they could not settle the question. A spinning asteroid changes brightness as different faces rotate into view; converting that change into a three-dimensional shape is useful, but several shapes can produce similar light curves.

The new campaign attacked the problem directly. The team led by Kate Minker of Lowell Observatory observed Nysa with SHARK-VIS on the Large Binocular Telescope on February 15 and March 21, 2026. They also used SPHERE/ZIMPOL on the European Southern Observatory’s Very Large Telescope during ten observing epochs between March 9 and April 5. The instruments work at visible wavelengths, where the asteroid is bright, and combine high-speed imaging with adaptive optics to correct for turbulence in Earth’s atmosphere. The Lowell Observatory release and the study describe these as the highest-resolution images yet obtained of Nysa. (Lowell Observatory research release)

The images show two shadowed valleys that appear to run around the asteroid’s narrowest directions. The researchers call these structures colli, using a geological term for neck-like connections. In their preferred reading, one neck joins two larger lobes and a second divides the smaller lobe, producing a three-lobed primary. The paper’s shape model has a volume-equivalent diameter of about 75 kilometers and reproduces the disk-resolved images, light curves, and several stellar occultation silhouettes. (Nysa preprint)

The same processing uncovered a satellite. It appears in residual images left after the bright halo around Nysa was modeled and removed, and it was recovered independently in data from both LBT observing nights. The point source moved across the sky while remaining fixed relative to Nysa for more than three hours on each night, which argues against a background star. The authors estimate a diameter of about 1 +/- 0.5 kilometers and projected separations of about 180 and 170 kilometers in February and March. The provisional designation is S/2026 (44) 1.

Those measurements support the binary-system conclusion, but not yet a final origin story. The authors discuss a battered single body, a contact trinary, and a hit-and-run collision followed by slow reaccumulation. They also note that an impact capable of making several large pieces in Nysa’s present orbital neighborhood should leave more enstatite-rich debris than has been observed. Further orbital work is therefore not a footnote. It is the part that may decide which history survives.

The central engineering problem is angular resolution. A telescope does not see an asteroid’s surface directly; it sees a blurred pattern set by diffraction and by the atmosphere. The angular scale of diffraction is roughly 1.22 lambda/D, where lambda is the observing wavelength and D is the telescope aperture. Larger apertures help, shorter wavelengths help, and a turbulent atmosphere can erase both advantages unless its distortion is measured and corrected.

Adaptive optics uses a wavefront sensor to estimate that distortion and a deformable mirror to compensate for it many times per second. SHARK-VIS works with the LBT’s adaptive-optics system for high-contrast visible imaging. SPHERE is an extreme adaptive-optics and coronagraphic facility; its ZIMPOL camera is designed for sharp visible-light images and polarimetry. (LBTO instrument overview) (ESO SPHERE description)

Even corrected images contain a problem that is especially severe for a small moon: Nysa is much brighter than its satellite. The team used short exposures, image stacking, lucky-imaging selection, blind deconvolution, and a version of principal-component angular-differential imaging adapted from exoplanet searches. Blind deconvolution estimates both the object and the point-spread function, allowing the bright adaptive-optics halo to be subtracted. PCA-ADI builds a model of quasi-static background structure from images taken as the sky rotates, then looks for a source that moves with the target rather than with the detector.

The shape model adds a separate constraint. The ADAM algorithm combines the resolved images with photometric light curves, adjusting a three-dimensional surface until its projected silhouettes and changing brightness agree with the observations. The final model used 1,600 vertices and 3,200 facets. That does not mean every facet is a mapped piece of ground. It means the model is detailed enough to reproduce the data without adding unsupported internal information. In particular, the authors note that their regularization fixes the model’s center of mass, so the reconstruction cannot reveal how mass is distributed inside Nysa.

The useful result is not that Nysa has been definitively declared a three-headed asteroid. It is that two independent kinds of evidence now meet in the same object: resolved images show two possible necks, while light curves and occultations agree with a lopsided, rapidly rotating shape. A faint satellite adds a future mass measurement.

The next step is patient work rather than a dramatic flyby. Repeated observations can refine the moon’s orbit, turn separation into mass, and test whether the apparent lobes remain dynamically stable. If the contact-trinary interpretation holds, Nysa will offer a rare ground-based laboratory for studying how large asteroid fragments join and survive. If a coherent body fits better, that would be just as interesting. Either answer would replace a century of suggestive shadows with a more constrained physical history.

For thirty years, every stellar stream an astronomer could pull out of an image has come from inside the Milky Way. The Sagittarius stream winds under the galactic plane. The tidal tail of Palomar 5 drapes across the inner halo. All of them have lived inside our galaxy. On August 12, 2026, that monopoly ended. A team led by Julie Kiel Holm at the University of Copenhagen reported in Nature the first confirmed globular cluster stellar stream identified outside the Milky Way: a thin, two-kiloparsec-long arc the team named Oyashio, after a cold Pacific ocean current, in the ultra-diffuse galaxy UGC 9050-Dw1. The find is more than a first-of-its-kind image. The stars in a stream all travel along nearly the same orbit, and that orbit lets the team weigh the host galaxy’s dark matter halo from 35 megaparsecs away, the first time anyone has done that for an ultra-diffuse galaxy.

Ultra-diffuse galaxies are an awkward class for cosmologists. They have stellar masses closer to dwarf galaxies but physical sizes closer to the Milky Way, so they should not exist in the proportions that surveys keep finding them. The dark matter halo models that explain them range from nearly empty to absurdly heavy, and the two camps have argued about it for a decade. Standard kinematic tools (stellar velocity dispersions or rotation curves) need enough light to register a velocity, and ultra-diffuse galaxies do not give them much. Stellar streams sidestep the light problem. The stream’s stars travel along nearly the same orbit, that orbit is shaped by the gravitational field they fall through, so modelling the orbit gives the field, and the field gives the halo mass. That trick has worked inside the Milky Way for two decades. Holm’s paper is the first time it has worked on a galaxy 115 million light-years away. As co-author Tjitske Starkenburg of Northwestern put it in the Universe Today writeup: “By modelling that gravity, we can estimate the galaxy’s total mass. We already know roughly how much of that mass comes from visible matter like stars, so the rest must be dark matter.”

UGC 9050-Dw1 first surfaced in 2017 in a Canada-France-Hawaii Telescope survey for low-surface-brightness dwarfs. The host galaxy, UGC 9050, is a low-surface-brightness spiral. The companion dwarf sits 35.2 megaparsecs away (close enough to image deeply with Hubble, far enough that individual stars blur into integrated light). In September 2022, a team led by David Sand at the University of Arizona imaged the dwarf under HST program 16890 using the Advanced Camera for Surveys in the F555W and F814W filters, with 2,406 and 2,439-second exposures. The 2023 analysis by Fielder et al. catalogued the dwarf’s globular cluster population and concluded that most clusters formed in a single past merger event. The images sat in the archive for three more years before Holm’s collaborators pulled the stream out of them.

The team saw the feature by eye first, then confirmed it with a Rolling Hough Transform (a standard linear-feature detector) at a signal-to-noise of 7.34 in the combined HST image. The CFHT images independently show the same feature at signal-to-noise between 2.3 and 3.9 in the g, r, and i bands. The arc measures 72.3 ± 8.9 parsecs wide and roughly two kiloparsecs long, sweeping out of a compact bright source 2.5 kiloparsecs from the dwarf’s centre. Both the arc and its compact partner have nearly identical integrated colours (F555W−F814W of 1.0 ± 0.2 for the stream, 1.1 ± 0.1 for the progenitor candidate), consistent with the same stellar population. Holm’s group named the stream Oyashio in keeping with a Milky Way tradition of naming streams after ocean currents. The width rules out a dwarf-galaxy progenitor (the Milky Way’s Orphan stream, stripped from a low-mass dwarf, runs more than 200 parsecs wide); Oyashio is narrower, and its colour matches the bluer cluster population Fielder et al. identified in this galaxy. The narrow width, the colour match, and the orbital modelling together satisfy the team that the progenitor is a globular cluster rather than a dwarf.

The story of how to do this analysis outside the Milky Way has been building for years. Nibauer and Pearson released the X-Stream sampler in 2026, a tool that turns a stream image directly into constraints on the progenitor’s mass and the host halo’s mass and density profile. Holm’s collaborators ran X-Stream on Oyashio and got a 95 percent upper limit on the progenitor mass of 2.5 × 10⁶ solar masses (comparable to Milky Way clusters like ω Centauri and to clusters in M31). The best-fit halo mass comes out at log₁₀(M₂₀₀/M☉) = 11.63 (-0.83, +0.71) within the 68 percent confidence interval, a total mass of about 1.56 × 10¹¹ solar masses, in the same neighbourhood as estimates of the Large Magellanic Cloud’s halo and consistent with the GC-count halo mass of 1.5 to 1.8 × 10¹¹ solar masses from Fielder et al. The inner density slope γ comes out at 0.92 (-0.58, +0.57) slightly steeper than 0.3 measured for UDG Dragonfly 44 and the 0.2 typical of low-surface-brightness dwarfs, but consistent with UDG AGC 242019. As co-lead Holm told Universe Today: “Our results are consistent with previous studies and what they have shown about dark matter in this ultra-diffuse galaxy. We are measuring it with a completely new tool for this type of galaxy, demonstrating that this method also works beyond our own galaxy.”

The pipeline Holm’s team ran has three pieces. They extract a stream mask from the HST and CFHT data by following a polynomial fit to points selected manually in the F814W image and duplicating it on either side to define matched background regions. The stream width is measured by collapsing perpendicular slices along the fitted track, fitting a Gaussian with a linear offset to the brightness profile, and subtracting the HST point spread function in quadrature; the final width is 72.3 parsecs. They feed the masked stream into the X-Stream sampler, which generates dynamical stream models with parameters including progenitor mass, halo mass, inner density slope, halo concentration, and line-of-sight position, and produces a posterior distribution over those parameters by comparing each model stream to the observed one. They cross-check the sampler output with a forward simulation: a Palomar 5-like cluster with twenty times Pal 5’s mass, run through the same tidal stripping, produces a stream whose surface brightness reproduces Oyashio within the 95 percent confidence region. That closes the loop between the kinematic and photometric mass estimates.

The numbers worth sitting with: a 7.34σ signal in the HST image, in a structure 72 parsecs wide and 2 kiloparsecs long, in a galaxy whose total stellar mass is in the dwarf range. The dark matter halo mass of 1.56 × 10¹¹ solar masses is roughly 30 times the dwarf’s stellar mass, unusual since most ultra-diffuse galaxies have halo masses within an order of magnitude of their stellar masses. Holm’s team does not yet have an independent kinematic confirmation, but the consistency with the Fielder et al. GC-count estimate and the agreement between the sampler mass and the forward-model mass is what makes the case strong. The inner slope of 0.92 sits in the middle of the cosmological expectation range. Cold dark matter simulations predict a cuspy halo with γ near 1 in low-mass galaxies; observed low-mass galaxies tend to look cored with γ near 0.2. Oyashio’s γ is high enough to be consistent with the cosmological prediction, low enough that the result is still compatible with feedback-driven core formation.

Holm et al. used a 2,406-second Hubble exposure from September 2022 to find the first extragalactic globular cluster stellar stream and weigh the host’s dark matter halo to about 1.5 × 10¹¹ solar masses. The paper’s arXiv preprint is the canonical worked example for extending stream-orbit dark matter inference beyond the Milky Way. Euclid is already collecting wide-field imaging, and the Nancy Grace Roman Telescope will have a field of view roughly 100 times Hubble’s. Holm’s team expects both surveys to turn up dozens of comparable streams, each one a new anchor for the dark matter halo mass function at the dwarf end of the galaxy distribution. The Milky Way is about to become one of many places to do stream-based dark matter science.

IC 1101, the dim supergiant at the center of the Abell 2029 galaxy cluster, has been called the largest known galaxy for most of the past thirty years. A new analysis by Carlos Marrero-de la Rosa of the Instituto de Astrofisica de Canarias and 14 collaborators, posted to arXiv on July 16, 2026, fixes the boundary of the main stellar body at a radius of about 260 kiloparsecs, almost 850,000 light-years from the galactic center. The full diameter comes out to roughly 520 kiloparsecs, or about 1.7 million light-years, which makes IC 1101 wider than the Milky Way by a factor of seventeen. The cluster sits about 1.07 billion light-years from Earth, in the direction of the constellation Serpens.

The number is a measurement, not a guess. The team obtained the deepest g- and r-band images of IC 1101 ever taken, reaching surface brightness limits near 30 magnitudes per square arcsecond, using the Wide Field Camera on the 2.5-meter Isaac Newton Telescope at La Palma. They then built an extended point-spread function, removed the scattered light from 250 foreground stars, deconvolved the galaxy’s own glow with a wavelet-based method, and traced the surface brightness, color, and stellar mass density profiles out to where the galaxy’s own light runs out.

Galaxies are not supposed to have edges, in the ordinary sense. They fade smoothly into the intracluster light, the loose swarm of stars that fills the space between galaxies in a dense cluster, and any sharp boundary an observer draws depends on the threshold they choose. The cleanest test of a galaxy’s true size is to identify a radial feature that is coherent across multiple independent diagnostics: surface brightness, color, geometry, and stellar mass density all change at the same radius.

The Marrero-de la Rosa paper applies that full battery of tests to IC 1101. The team finds that a coherent change in ellipticity, position angle, color, surface brightness, and stellar mass density all happen at the same radius, around 180 arcseconds from the center, which works out to 260 kiloparsecs at the redshift of Abell 2029. That is the radius they adopt as the edge of the main body, and the paper argues that IC 1101 sits at the extreme upper end of the mass-size relation for early-type galaxies.

The result also tightens the link between a galaxy’s visible edge and the assembly history of its host cluster. Beyond the 260-kiloparsec edge, the team finds extended, asymmetric, very-low-surface-brightness features that line up with the X-ray spiral arms already mapped in the hot intracluster medium of Abell 2029. The optical and X-ray structures are tracing the same past disturbance in different wavelengths.

The deepest previous image of IC 1101 came from the early 1990s, when Juan Uson and collaborators used ground-based R-band photometry to trace stellar emission out to about 607 kiloparsecs. That paper established IC 1101 as a record-holder, but it could not say whether the system had an edge. Later work, including a 2017 Dullo MNRAS study, found that IC 1101 has the largest known galactic core, about 4.2 kiloparsecs across, but still left the outer envelope ambiguous.

The new measurement started in May 2022, when Fernando Buitrago and collaborators ran a four-night program on the Isaac Newton Telescope’s Wide Field Camera. They took 79 individual 180-second exposures in the g-band and 53 300-second exposures in the r-band, for a total of about 8.4 hours of integration. The co-added image covers a 55-arcminute by 66-arcminute patch of sky, about 0.5 kiloparsecs per pixel at the distance of Abell 2029.

The hard part was not getting the photons. It was subtracting the scattered light. Every bright star in the field spreads its image across several arcminutes, and IC 1101 itself has an extended stellar halo that smears its own light through the camera’s optics. The team built an extended point-spread function by stacking unsaturated stars in four magnitude ranges, supplemented with a bright calibration star observed in a different field. They subtracted the 250 brightest stars from the image, then applied a wavelet-based deconvolution to remove the galaxy’s own scattered light.

The result is the Figure 3 composite in the paper, reproduced here. IC 1101 is the yellowish elliptical blob slightly left of center. Around it, where the raw image looked like noise, the team now resolves a network of faint structures they label A through H. Some of those features, like the plumes labeled A, B, and C, are consistent with ongoing accretion. Others, like the broader features labeled H and G, sit exactly where a recent X-ray study of Abell 2029 has identified a cool “splash” of gas displaced by a past subcluster merger.

The contrast with the previous record is also worth noting. The 1991 Uson estimate of 607 kiloparsecs was based on R-band photometry that could not distinguish galaxy light from foreground contamination, and the 2017 Dullo MNRAS study constrained only the inner core. The new 260-kiloparsec edge sits well inside the 607-kiloparsec historical figure, but it is the first number that is anchored to a coherent physical boundary rather than a sensitivity threshold. The earlier Wikipedia entry for IC 1101 listed a similar isophotal diameter of about 400,000 to 550,000 light-years, consistent with both the Uson number and the new 520-kiloparsec figure after accounting for the different boundary definitions.

The stellar mass inside the 260-kiloparsec edge comes out to about 3.4 trillion solar masses. Including the diffuse envelope out to 475 kiloparsecs pushes the total to about 3.9 trillion, and extending to 620 kiloparsecs reaches 4.2 trillion solar masses. That is consistent with the earlier Uson estimate when the older luminosity is converted with modern mass-to-light ratios, and it is roughly a hundred times the stellar mass of the Milky Way.

Three methodological pieces make this measurement stick. The first is the extended point-spread function. The extended version captures the wide wings of the stellar image, out to half a degree from the star. Without that, the scattered light from the 250 brightest stars in the field would have added up to surface brightness levels of 27 to 28 magnitudes per square arcsecond, swamping the faint galaxy envelope the team was trying to measure.

The second piece is the wavelet-based deconvolution. Wavelets break an image into components at different spatial scales, and the team’s algorithm uses that decomposition to separate the smooth, large-scale emission of IC 1101 from the small-scale, high-frequency contamination introduced by the optics. The method is similar to the model-based deconvolution developed in earlier work, but it is run on the full image rather than on the radial profile.

The third piece is the multi-tracer edge detection. Instead of looking at one profile and drawing a line, the team looked for a radial feature that appears in surface brightness, color, and stellar mass density at the same time, with matching signatures in the ellipticity and position angle. That convergence is what justifies calling 260 kiloparsecs an edge rather than a threshold artifact. The team tested the result by varying the background subtraction and the mass-to-light conversion, and the edge location moves by less than 40 kiloparsecs across the full range of reasonable assumptions.

A preprint posted to arXiv on July 16, 2026, reports that IC 1101 has a coherent edge at about 260 kiloparsecs and a projected diameter of 520 kiloparsecs, making it the largest known galaxy by a margin wide enough that any future challenger will have to outshine a four-trillion-solar-mass central galaxy. The measurement is settled enough to cite, with a published arXiv number, a peer-reviewed acceptance in Astronomy and Astrophysics, and an independent Phys.org writeup and Debrief story describing the same numbers from the same preprint. The team is extending the analysis to other bright cluster galaxies in the same mass range and comparing the optical LSB features to the deep Chandra X-ray map of Abell 2029.