Show notes
Today's episode — S05E190, Thursday September 10, 2026: Main story: 109 fast radio bursts have been used to measure how much galactic feedback has smoothed out the matter in the universe. A fast radio burst lasts about a millisecond, and on its way to us it is dispersed — low radio frequencies slowed more than high ones by free electrons along the path, exactly the way a prism separates white light. The size of that delay counts the ordinary matter the burst passed through. Writing in Nature Astronomy on 8 September, a team led by Kritti Sharma at Caltech, with Vikram Ravi, Liam Connor and Elisabeth Krause (University of Arizona), used 109 bursts localised to host galaxies out to redshift ~0.3 — most of them from Caltech's DSA-110 — to constrain the suppression of matter clustering by feedback, and the gas fractions of groups and clusters between 10^13 and 10^15 solar masses. They find more gas retained than the X-ray picture implies: gas fractions about 1.9σ above stacked eROSITA measurements, and slightly above the Atacama Cosmology Telescope's kSZ constraints, consistent with the bursts counting cool gas that X-rays miss. The constraint is already competitive with both of those far larger experiments, cutting the uncertainty on clustering at these scales by roughly a factor of eight. That matters because feedback is the confound sitting under the S8 tension — it mimics the signature of massive neutrinos and of some dark energy and dark matter models. The technique's foundation is Australian: the Macquart relation, established with ASKAP in Western Australia in 2020, is what found the universe's missing ordinary matter in the first place. The rest of the news: · Hypersoft X-ray sources: NASA and the Chandra X-ray Center announced a new class of object on 9 September — 84 sources across six galaxies (M31, M101 and four ellipticals) that emit more than eight times as many photons below 0.3 keV as just above it, exceeding 10^38 erg/s in that narrow band and more again in the extreme ultraviolet. Led by Mustafa Muhibullah (University of Alabama) with Jimmy Irwin and Rosanne Di Stefano (CfA), published in Nature Astronomy. They are likely compact objects accreting from companions, and may be both the long-sought progenitors of Type Ia supernovae and a significant unaccounted source of ionising radiation. · A rendezvous with Halley's Comet: a trajectory study circulated on 6 September by Roberto Flores and Elena Fantino (Khalifa University), Mauro Pontani (Sapienza), and Ivano Bertini and Cesare Barbieri (Padua) sets out the first Halley rendezvous achievable with proven hardware — unpowered Jupiter and Saturn gravity assists plus deep-space low-thrust arcs, a Hall-effect thruster on a standard RTG, ~2,000 kg launch mass with ~750 kg of instruments, launching August 2036 or September 2037 and arriving in 2060, about a year before Halley's 2061 perihelion. Months alongside the comet instead of Giotto's minutes at 68 km/s. · Apollo Maneuvers 2026: US Space Command announced on 8 September that it had completed the first live-fly orbital manoeuvre exercise of its kind, moving real operational satellites across low, medium and geosynchronous orbits with Operation Olympic Defender allies (Australia among them) and commercial operators via its Commercial Integration Cell. Named for the US Army's 1941 Louisiana Maneuvers. The practical consequence is more unpredictable objects in an already crowded region, and in-orbit refuelling becoming load-bearing. · Skywatch: New Moon on 11 September at 14:27 AEST (04:27 UTC) makes tonight and tomorrow the darkest nights of the month. Southern Hemisphere — the galactic core still high after dark, and Venus well placed low in the west-south-west, 7.4° from Spica and building to greatest brilliancy on 18 September at magnitude −4.8. Saturn rises about an hour after sunset for everyone, heading for its 4 October opposition with the rings about 7° from edge-on. North America — the pre-dawn sky, with Mars in Gemini passing Castor on the 12th and Pollux on the 17th, and Jupiter below it in Cancer. Plus a convoy of CMEs from AR4524 arriving since 8 September, two G1 storms already recorded and G2 possible: aurora chances at both ends of the planet, including Tasmania, coastal southern Victoria and New Zealand's South Island. Links & sources · Caltech — Fast Radio Bursts Poised to Help with Biggest Cosmic Mysteries (8 Sept 2026) — https://www.caltech.edu/about/news/fast-radio-bursts-poised-to-help-with-biggest-cosmic-mysteries · Sharma, Krause, Ravi, Connor et al., 'Signatures of Suppressed Matter Clustering revealed by Fast Radio Bursts', Nature Astronomy (8 Sept 2026) — https://arxiv.org/abs/2604.17162 · NASA — NASA's Chandra Unveils Mysterious X-ray Objects (9 Sept 2026) — https://science.nasa.gov/missions/chandra/nasas-chandra-unveils-mysterious-x-ray-objects/ · Muhibullah, Irwin & Di Stefano, 'Hypersoft X-ray Sources: A New Class of Luminous Cosmic Emitters', Nature Astronomy (9 Sept 2026) — https://arxiv.org/abs/2602.06192 · Flores, Beolchi, Pozzi, Pontani, Bertini, Barbieri & Fantino, 'Double Gravity-Assist Rendezvous Trajectory to Halley's Comet Using Deep-Space Low Thrust' (arXiv, 6 Sept 2026) — https://arxiv.org/abs/2609.02189 · Air & Space Forces Magazine — SPACECOM Maneuvers Satellites Across Orbits in New Exercise (9 Sept 2026) — https://www.airandspaceforces.com/space-command-maneuvers-satellites-across-multiple-orbits-in-new-exercise/ · EarthSky — Sun news: series of sun blasts arriving, auroras to come — https://earthsky.org/sun/sun-news-activity-solar-flare-cme-aurora-updates/ · EarthSky — Visible planets and night sky guide for September — https://earthsky.org/astronomy-essentials/visible-planets-tonight-mars-jupiter-venus-saturn-mercury/ · TheSkyLive — Moon calendar, September 2026 — https://theskylive.com/moon-calendar?year=2026&month=09
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