Gaia measurements of 7,426 massive stars in the Small Magellanic Cloud reveal opposing motions across the galaxy, with eastern regions generally moving southeast toward the Large Magellanic Cloud while western regions move northwest. The pattern does not resemble ordinary galactic rotation and instead supports the idea that tidal forces, possibly combined with ram pressure, are stretching and disrupting the smaller galaxy. If the Small Magellanic Cloud is not rotating as previously assumed, estimates of its mass and reconstructions of its past interactions with the Large Magellanic Cloud and Milky Way may need to be reconsidered. A small galaxy on the Milky Way’s doorstep may be slowly coming apart under the influence of its larger neighbor. Astronomers tracking thousands of massive stars across the Small Magellanic Cloud, or SMC, found that stars on opposite sides of the galaxy are moving away from each other rather than following the orderly rotational pattern expected for a disk. The eastern side generally moves toward the Large Magellanic Cloud, or LMC, while the western side moves in the opposite direction. …

Astronomers detected five ion species simultaneously in the plasma tail of interstellar comet 3I/ATLAS, including ionized molecular nitrogen, using the WEAVE instrument on the William Herschel Telescope. The unusually strong nitrogen signature relative to carbon monoxide points to formation at temperatures of roughly 30 kelvins or below, suggesting the comet assembled in the frigid outer reaches of another planetary system. Measurements along the tail also showed that most ion ratios remained stable over the observed distances, while CH+ appeared to decrease slightly, offering an unusually detailed look at plasma chemistry in an interstellar comet. The third known object to enter our solar system from interstellar space appears to have been born in an environment far colder than the region where many familiar comets formed. Astronomers studying 3I/ATLAS detected an unusually strong signature of molecular nitrogen in its plasma tail, alongside four other ionized species. The chemical mixture points toward formation in temperatures around 30 kelvins or lower, roughly minus 243 degrees Celsius. “This object gives us a rare chance to study material that formed somewhere …

Cosmic rays and collisions with interstellar gas may erode icy interstellar objects much faster than some earlier estimates suggested, limiting how long small frozen bodies can survive between stars. The model found that a nitrogen-ice version of ‘Oumuamua traveling through interstellar space for about 500 million years may have needed an initial radius of at least roughly 0.5 kilometer, substantially larger than the object eventually observed. Because erosion depends on an object’s composition, speed and the cosmic-ray environment it crosses, future interstellar visitors could potentially help astronomers place limits on where in the Milky Way they originated. Interstellar space may look empty, but an icy object drifting between the stars faces a relentless bombardment that can slowly erase it. Cosmic rays and collisions with thin interstellar gas could strip material from frozen bodies much faster than previously estimated, according to theoretical work examining how objects such as ‘Oumuamua survive journeys lasting hundreds of millions of years. When the work was written, only two confirmed interstellar objects had been detected, ‘Oumuamua and comet 2I/Borisov. That tiny …

New simulations suggest gas giants can build roughly 10-Earth-mass solid cores in about 200,000 years when icy pebbles drifting inward from the outer disk grow into planetesimals before being swept up by embryos. Instead of relying mainly on inefficient direct pebble capture, the process concentrates solid material between roughly 6 and 9 astronomical units, where relatively small planetesimals can feed planetary cores rapidly. The model offers a possible solution to the long-standing problem of forming Jupiter-like planets before their gas disks disappear or their growing cores migrate too close to their stars. Building something as massive as Jupiter presents planetary scientists with a timing problem. A giant planet must assemble a large solid core while plenty of hydrogen and helium still surrounds its young star, yet conventional planet-building processes can take too long. Computer simulations now suggest a possible shortcut. Icy particles born far from a young star can drift inward, collide and grow into larger bodies that pile up in a relatively narrow region of the protoplanetary disk. Planetary embryos there can then consume …

MeerKAT radio observations produced the first direct detection of the neutral-hydrogen intensity autopower spectrum at redshifts of about 0.32 and 0.44 without relying on an overlapping optical galaxy survey. The researchers extracted the extremely faint 21-centimetre hydrogen signal from about 96 hours of 2018 observations despite contamination from bright foreground radio emission, weak radio-frequency interference and instrumental effects. The result shows that hydrogen intensity mapping can begin functioning as a standalone cosmological tool for tracing gas, galaxies and the underlying matter distribution across enormous volumes of the Universe. A whisper of hydrogen that traveled across the Universe for billions of years has been pulled directly from radio observations, giving astronomers a new way to map the cosmic structures that surround galaxies. Using South Africa’s MeerKAT telescope, astronomers detected the collective radio glow of neutral hydrogen at two periods in cosmic history. Instead of identifying individual distant galaxies, they measured the statistical pattern created by hydrogen spread across enormous volumes of space. “This is a very exciting milestone,” said lead author Sourabh Paul. “Hydrogen intensity mapping …

Solar Orbiter crossed the heliospheric current sheet only about 0.3 astronomical units from the Sun, giving researchers an unusually fresh look at solar wind before its original signatures were heavily altered in transit. The spacecraft found that the iron-to-oxygen ratio fell sharply at the magnetic sector boundary, showing that the current sheet carries a distinctive chemical signature as well as a reversal in magnetic polarity. The observations came from a single crossing, so they do not establish how the current sheet forms, but they give future models specific measurements of composition, heating and magnetic structure that they must explain. An enormous magnetic boundary stretching outward from the Sun is turning out to be more complicated than a simple dividing line. Measurements from the European Space Agency’s Solar Orbiter show that the heliospheric current sheet, or HCS, contains organized changes in the composition and temperature of its particles. Those chemical fingerprints may help scientists trace solar wind back toward the processes that released it from the Sun. The results appear in The Astrophysical Journal in the …

Mars’s mantle beneath the southern highlands appears to be about 200 to 400 degrees Celsius warmer than the mantle beneath the northern lowlands. Nearly two decades of spacecraft tracking data revealed gravity changes that suggest the planet’s deep interior is far less uniform than scientists often assume. The thermal divide could help explain differences in Mars’s crust, ancient magnetism and seismic behavior, but its origin remains uncertain. Mars has long looked like a planet divided in two. Its southern hemisphere rises into rugged, heavily cratered highlands, while broad, relatively flat lowlands dominate the north. That contrast may extend much farther beneath the surface than scientists realized. An analysis of subtle changes in Mars’s gravitational field indicates that the mantle beneath the southern highlands is roughly 200 to 400 degrees Celsius warmer than the mantle beneath the northern lowlands. The finding suggests one of the planet’s defining surface differences may have roots deep inside Mars that have survived for billions of years. The research, published in Nature was led by Caltech alumnus Alexander Berne, now a …

Powerful magnetic fields around active stars may trap huge coronal mass ejections before they can escape into space. Laboratory plasma experiments found that stronger magnetic fields caused CME-like flows to fragment, bend and eventually stop. The results could help explain why astronomers rarely detect stellar CMEs despite seeing powerful flares on stars far more active than the Sun. Some of the most active stars in the galaxy appear capable of producing enormous eruptions, yet astronomers rarely see those blasts escaping into space. Experiments recreating part of that process in a laboratory now offer a possible explanation. Strong stellar magnetic fields may act as a cage, destabilizing massive flows of plasma until they break apart and stop. An international team of astrophysicists and plasma physicists from the Leibniz Institute for Astrophysics Potsdam (AIP), Germany, École Polytechnique and the Technion-Israel Institute of Technology, combined stellar simulations, high-energy laser experiments and three-dimensional magnetohydrodynamic modeling to investigate why coronal mass ejections are so difficult to find beyond the Sun. The results provide experimental evidence that sufficiently strong magnetic fields …

Tokyo Metropolitan University researchers built a pulsed electromagnet system that can test magnetic aerobraking under shockwaves traveling about 7.7 kilometers per second. The system produced magnetic fields of 1.24 and 1.58 tesla, reaching roughly 1.7 and 2.1 times the strength of the permanent magnet used for comparison. Applying the magnetic field expanded the glowing shock layer by about 16%, supporting the idea that magnetic forces could someday help protect and slow spacecraft during atmospheric reentry. A spacecraft plunging into an atmosphere faces an environment violent enough to heat the gas around its surface to thousands of degrees. Engineers have traditionally dealt with that punishment by putting something tough, expendable or both between the vehicle and the heat. A different approach could eventually use magnetic fields to push some of that superheated gas away. Researchers at Tokyo Metropolitan University have developed an experimental system that produces unusually strong magnetic fields inside miniature spacecraft models while exposing them to shockwaves traveling at roughly 7.7 kilometers per second. The setup allows engineers to study magnetohydrodynamic aerobraking, or MHD …

JWST observations of 72 young planetary systems suggest powerful magnetic winds dominate early disk evolution before giving way to gentler atomic winds. Molecular hydrogen winds were common around younger, more actively accreting stars, while ionized neon increasingly traced slower winds as disks evolved. The findings help explain how planet-forming disks lose their gas and why giant planets such as Jupiter must assemble before that material disappears. The solar system looks calm today, but its earliest years were anything but empty. Around the newborn Sun, a dense disk of gas and dust churned with the raw material that would eventually become planets. That young disk contained about 100 times more gas than dust. Most of that gas disappeared within the first 10 million years, setting a deadline for planets such as Jupiter to gather their enormous atmospheres. A new analysis of James Webb Space Telescope observations now provides one of the clearest pictures yet of how that disappearance may have unfolded. The results suggest that powerful magnetic winds dominated first, followed later by gentler winds driven …