A Sharper Hubble Tension, Not a Resolution: One of the week’s most consequential cosmology stories is not a breakthrough that settles the Hubble tension, but a stronger case that the problem is real. A large collaboration synthesized multiple local-distance techniques into what it describes as its most precise direct estimate yet of the nearby universe’s expansion rate, landing at 73.50 ± 0.81 kilometers per second per megaparsec. That still sits well above the lower value inferred from the early universe, meaning the long-running mismatch survives even after researchers combined Cepheids, red giant branch stars, Type Ia supernovae, and other rungs of the distance ladder into a unified framework. The implication is uncomfortable and exciting at once: the discrepancy may not be a bookkeeping problem inside one method, but a sign that standard cosmology is missing something important. (EurekAlert!)

TRAPPIST-1’s Inner Worlds Look Even Harsher Than Hoped: James Webb observations have now pushed one of exoplanet science’s most tantalizing systems in a sobering direction. Researchers studying TRAPPIST-1b and TRAPPIST-1c report the first climate mapping of rocky, Earth-mass-class exoplanets in this system, and the result is not friendly: the two worlds appear to lack dense atmospheres. The key clue is the enormous day-night temperature contrast, exceeding roughly 500 degrees Celsius, which suggests these tidally locked planets are not redistributing heat with thick air envelopes. That matters far beyond two planets. Red dwarfs dominate the galaxy, and many Earth-size worlds orbit close to them, so TRAPPIST-1 remains a crucial laboratory for habitability. This does not doom all red-dwarf planets, but it sharpens the case that stellar activity and tidal locking can strip or prevent atmospheres on some of the most discussed potential Earth analogues. (EurekAlert!)

COLIBRE Gives Galaxy Formation a More Realistic Universe to Live In: A new set of COLIBRE simulations offers one of the week’s most important theory-meets-observation stories. The claim is not just better graphics or bigger computing power. These simulations incorporate cold gas and cosmic dust inside galaxies much more realistically than many earlier large runs, allowing researchers to model the actual raw material of star formation and how galaxies would look to telescopes across cosmic time. The team argues that once these neglected ingredients are treated properly, the standard cosmological model does a far better job reproducing galaxies both today and in the early universe seen by JWST. That matters because some early Webb observations were widely interpreted as possible trouble for standard cosmology. COLIBRE’s message is more conservative but scientifically useful: before rewriting the universe, improve the astrophysics inside the simulations. (EurekAlert!)

Self-Interacting Dark Matter Gets a Three-For-One Test: Dark matter stories are often heavy on speculation, but this one stands out because it tries to explain three separate anomalies with one mechanism. A UC Riverside-led study proposes that dense clumps of self-interacting dark matter, each roughly a million solar masses, could account for odd gravitational signatures in a strong lens system, the GD-1 stellar stream, and the unusual Fornax 6 star cluster. The idea hinges on gravothermal collapse: if dark matter particles can collide and exchange energy, their halos can become much denser than in the usual cold-collisionless picture. What makes the paper notable is the cross-environment argument. It is not saying one weird object might fit a new model; it is arguing that distant lenses, Milky Way substructure, and a neighboring satellite all show behavior that emerges naturally from the same physics. That makes SIDM newly hard to ignore. (EurekAlert!)

Starquakes Revive the Case for Ancient ‘Fossil’ Magnetism: One of the more elegant astronomy stories this week links two stages of stellar life that are usually studied apart. New theoretical work from ISTA connects magnetic fields seen at the surfaces of old white dwarfs with recent evidence for magnetism inside red giants, their evolutionary predecessors. The bridge comes from asteroseismology, or “starquakes,” which probe stellar interiors through oscillations. The team argues that magnetic fields formed early in a star’s life can survive for billions of years, later re-emerging as fossil fields at the surfaces of white dwarfs. That helps explain why older white dwarfs often appear more magnetic than younger ones, and it gives stellar magnetism a much longer memory than some models allow. The story is not merely about dead stars; it also feeds into broader questions about stellar evolution and even the long-term future of the Sun. (EurekAlert!)

Mercury’s Sulfur-Rich Interior May Rewrite How We Picture the Planet: Mercury is still one of the least intuitive rocky planets in the solar system, and new lab work from Rice adds a useful twist. Researchers recreated Mercury-like rocks using the meteorite Indarch as an analogue and found that sulfur-rich magmas on Mercury likely behave very differently from magmas on Earth. Because Mercury is iron-poor, sulfur is not mostly tied up with iron the way it often is on Earth and Mars. Instead, sulfur can alter the mineral framework more directly, lowering crystallization temperatures and changing how the planet’s mantle solidified. That means Mercury’s magmatic evolution cannot simply be treated as a drier or smaller version of Earth’s. The larger importance is conceptual: comparative planetology works best when worlds are allowed to be chemically themselves, not when they are forced into terrestrial assumptions. (EurekAlert!)

A Possible Close Pair of Supermassive Black Holes Comes Into View: Black-hole mergers are central to how galaxies grow, but catching two supermassive black holes in a truly close pairing has been difficult. This week brought a strong candidate from Markarian 501. Radio observations analyzed by a team led from the Max Planck Institute for Radio Astronomy suggest the galaxy’s core may host not one but two supermassive black holes in an unusually tight orbit, potentially close enough to merge on a timescale of about a century. That is astonishingly fast by galactic standards. The report matters because the final stages of supermassive black hole pairing are one of the least directly observed parts of hierarchical galaxy evolution. If confirmed, this would become an important system for testing models of black hole inspiral, jet behavior, and the long-suspected pathways by which the largest black holes bulk up over time. (Max Planck Institute for Radio Astronomy)

Astronomers Finally Find the Hydrogen Reservoirs Cosmic Noon Needed: For years, astronomers have inferred that galaxies during “Cosmic Noon” had access to huge stores of hydrogen gas, because star formation was booming. The puzzle was where that gas was hiding. A HETDEX-based study now claims a dramatic leap forward: the number of known giant hydrogen halos, or Lyman-alpha nebulae, around galaxies 10 to 12 billion years ago has jumped from about 3,000 to more than 33,000. That turns a suggestive picture into a much richer statistical landscape. The finding matters because hydrogen is the fuel for star formation, and Cosmic Noon was the era when galaxies were building themselves most rapidly. Rather than a universe where vigorous growth somehow lacked visible supply lines, astronomers are starting to see the reservoirs directly. It is a quiet but foundational result about the gas ecology of the young universe. (EurekAlert!)

The Milky Way’s Outer Halo Suddenly Looks Much Busier: A new search method applied to Gaia data has revealed 87 stellar stream candidates in the outskirts of the Milky Way, more than quadrupling the number previously known. That is a big deal because stellar streams are not just decorative debris trails. They are sensitive tracers of the galaxy’s gravitational field and therefore of the dark matter structure shaping that field. Many streams are faint, short, misaligned, or morphologically messy enough to slip past visual searches, so the use of a model-based algorithm called StarStream could mark a methodological shift as much as a discovery one. The haul still needs confirmation, but even at this stage it suggests the halo may be threaded with far more shredded clusters and merger leftovers than astronomers had cataloged. In Milky Way archaeology, this is the kind of hidden structure that changes the map. (Space)

Artemis II Returns, Turning a Symbolic Mission Into a Real One: The biggest spaceflight story of the week was not a telescope paper but a mission milestone. NASA’s Artemis II crew returned to Earth on April 10, ending the first human voyage to the Moon in more than half a century. That makes this more than a public-relations triumph. Artemis II was the first crewed test of Orion in deep space, a systems-level demonstration that matters for future lunar operations and for the credibility of NASA’s broader human-spaceflight architecture. In practical terms, the mission tested spacecraft performance, communications, re-entry, recovery, and operational coordination under real deep-space conditions. In symbolic terms, it restored crewed lunar flight from aspiration to present reality. Science-heavy news cycles can underplay such missions, but this one belongs on the list because astronomy, planetary science, and exploration strategy all rest partly on whether ambitious space infrastructure actually works. (NASA Science)