Half the Neutron Stars

Today's episode — S05E191, Friday September 11, 2026: Main story: A population-synthesis study published in Nature Astronomy on 10 September argues that magnetars make up roughly half of all neutron stars, not the one-in-a-hundred implied by the catalogues. Celsa Pardo-Araujo and Nanda Rea (Institute of Space Sciences, ICE-CSIC, Barcelona) with Michele Ronchi (ASTRON) and Vanessa Graber (Royal Holloway) modelled the whole isolated-neutron-star population as one family rather than four separate classes, evolving spin-down, magneto-thermal decay and Galactic dynamics together, then filtering the simulated population the way real surveys filter the sky. Of the 24 known neutron stars younger than 2,000 years, magnetars and central compact objects are about 59%; the derived birth fraction averages ~50% (40–70% or 30–50% depending on the assumed birth-field distribution, which peaks at 1–2.5 × 10^14 gauss). Two consequences: the Galactic core-collapse supernova rate has to be higher than assumed, around two per century, and magnetar central-engine models for superluminous supernovae, gamma-ray burst plateaus and fast radio bursts finally have the supply to work. Caveats: it is a model rather than a census, the anchor sample is 24 objects, and 'magnetar' is defined by a field threshold. Southern thread: the field began with SGR 0526−66 in the Large Magellanic Cloud on 5 March 1979, and the same Barcelona group modelled GLEAM-X J162759, found with the Murchison Widefield Array in Western Australia. The rest of the news: · Chariklo's rings: The first stellar occultation ever planned specifically for JWST — 18 October 2022 — has been published in Science Advances, led by Yücel Kılıç, Pablo Santos-Sanz and Celia Navas (IAA-CSIC) with Nicolas Rambaux, Bruno Sicardy and Josselin Desmars (LTE) and Damya Souami (LIRA). Against the 2017 ground-based occultations, the inner ring C1R is about 50% more opaque and the outer ring C2R about 60% less, with the ring positions unchanged. Chariklo is the largest known centaur at ~125 km radius; the rings sit at 390 and 405 km and are a few km wide. Candidate explanations: material loss from C2R, material arriving at or collisions grinding down C1R — or a wavelength effect, since infrared is being compared with visible light. The rings were discovered in 2013 by an occultation campaign across Chile, Brazil, Argentina and Uruguay. · Mercury under bombardment: Kilpua et al. report in Nature Astronomy (8 September) that BepiColombo's fourth Mercury flyby in September 2024 — 165 km above the surface, closer than its eventual science orbit — coincided with a major solar particle eruption. The Finnish-built SIXS instrument watched energetic electrons and protons penetrate Mercury's magnetosphere and precipitate onto the surface over a wide area. That bombardment both sputters atoms off the surface and drives the X-ray fluorescence used to read its composition, and Mercury's small, weak magnetosphere makes it a stand-in for Earth during an extreme solar storm. The spacecraft separated its transfer module on 3 September; gravity capture is 21 November. · Europe buys a way home: ESA has awarded The Exploration Company a contract worth up to €760M under ALADDIN (Autonomous LEO Accelerated Demo Docking to ISS Node) — €310M for the demonstration mission, with ESA funding 60% and the company 40%, plus €450M in options for two further flights. The Nyx capsule flies on Ariane 6 and must dock with the ISS no later than Q2 2029, with up to €50M in additional incentive for using European launch vehicles. Europe has flown cargo up before, with the five ATVs, but has never returned anything from orbit. CEO Hélène Huby: 'It is the first time in Europe that a five-year-old space startup wins a contract worth hundreds of millions of euros.' The company's Mission Possible capsule survived reentry in June 2025 but was lost before splashdown — a partial success in its own words. Thales Alenia Space Italy remains in a parallel tender. · Parker Solar Probe: NASA reports the spacecraft completed its 29th close approach on 4 September, again matching the record set on Christmas Eve 2024 — 430,000 mph and 3.8 million miles from the solar surface, for the eighth time. The encounter ran 30 August to 9 September with nine days of autonomous operation and a beacon tone on the 7th; this pass targeted structures near the Sun's north pole, sampling nearly 40% of the solar circumference in a day. Telemetry began flowing on 11 September, science data 13–27 September. The mission is extended through 2029. · Skywatch: New Moon on 11 September at 14:27 AEST makes tonight and tomorrow the darkest nights of the month. Southern Hemisphere — Venus low in the west after sunset, building to greatest brilliancy on 18 September at magnitude −4.8, with a very thin crescent Moon sweeping past on the 13th and 14th (about half a degree apart on the 14th, near Spica); EarthSky notes the Southern Hemisphere gets the better view. Saturn...