Is Empty Space Really Empty? A 90-Year-Old Mystery Gets Its Answer (S05E168 — The Weekend Wrap)

Show notes The Milky Way's disc settled in two stages; metal-rich gas around Sgr A*; two mirror-image simulated universes; shadows in the Orion Bar; quick hits on Hera, Uzbekistan and Artemis; Orionid-night skywatch. Sources · IAC — Milky Way's disc formed in two very distinct stages — https://www.iac.es/en/outreach/news/research-iac-reveals-milky-ways-disc-formed-two-very-distinct-stages · Mirabal et al. — ApJL 1010 L38 — https://doi.org/10.3847/2041-8213/aeb0a3 · McGill — Gas around Milky Way's central black hole is rich in metals — https://www.mcgill.ca/newsroom/channels/news/gas-around-milky-ways-central-black-hole-rich-metals-study-finds-375101 · Ford et al. — AJ (DOI) — http://doi.org/10.3847/1538-3881/ae994d · Ford et al. — arXiv 2605.13995 — https://arxiv.org/abs/2605.13995 · Argonne — Aurora powers two of the largest cosmological simulations — https://www.anl.gov/article/argonnes-aurora-supercomputer-powers-two-of-the-largest-cosmological-simulations-to-date · UDE — New 3D model reveals hidden chemistry of stellar nurseries — https://www.uni-due.de/2026-10-16-publication-aa-brandt-gaches-3d-model-en · Gaches et al. — A&A 714 A295 — https://doi.org/10.1051/0004-6361/202660769 · ESA — Finding Hera's way: Flight Dynamics team in action — https://www.esa.int/Space_Safety/Hera/Finding_Hera_s_way_Flight_Dynamics_team_in_action · Kun.uz — Uzbekistan joins Artemis Accords — https://kun.uz/en/news/2026/10/19/uzbekistan-joins-artemis-accords-on-peaceful-space-exploration · NASA — To discuss Artemis acceleration, status of upcoming Moon missions — https://nasa.gov/news-release/nasa-to-discuss-artemis-acceleration-status-of-upcoming-moon-missions · The Planetary Society — Night sky, October 2026 — https://www.planetary.org/night-sky/night-sky-what-to-see-this-month

Show notes The Moon Is Still Shrinking Watters, Banks, Nypaver and Robinson (Planetary Science Journal, 14 Oct 2026) map more than 10,000 young thrust faults — ~8,900 lobate scarps and 2,000+ small mare ridges — with LRO's camera. Together they record about 42–46 m of radial contraction over the last ~400–800 million years, at most ~11 cm per million years. That's less than thermal models predict, pointing to a thick, porous, insulating megaregolith (or a strong elastic lithosphere) that delayed faulting. The ~4 MPa stress matches Apollo shallow-moonquake stress drops, so faults may still be growing today — relevant to siting lunar bases. A Soil Map for Mars University of Sydney PhD student Daniel Irving and Prof. Alex McBratney (Catena 275) classify almost 800 million Martian locations into 10 realms, 100 assemblages and 2,000 forms of 'areths', mapping 92% of the planet. Top candidate for plant growth, Nohibareth (score 0.93; ~72% clay, pH 6.8), covers 0.14% of the surface around Tharsis, Arabia Terra and Elysium. Candidates for study, not greenhouse sites; perchlorate and nitrogen not yet included. Euclid Finds Its First Comet ESA's Euclid discovered C/2026 S1 (Euclid) in Deep Field North images from 16–24 September, flagged by Mikko Pöntinen's moving-object software and confirmed by the Minor Planet Center on 8 October. ~1.3 billion km away on a steep, thousands-of-years orbit. Uranus and Neptune: Cousins, Not Twins Briand, Hue, Mousis, Cavalié et al. (A&A 714, A364) use upper-tropospheric carbon monoxide, including ALMA data, to infer deep oxygen: Uranus ~47–177× protosolar, Neptune ~182–342×. Contrasting C/O ratios suggest Neptune's building blocks formed closer to the Sun. Accepted version online since late August. Quick hits MMX launched 04:41:03 JST 20 Oct on H3 F10; separation ~71 min 13 s; JAXA confirms the spacecraft is operating normally. Roman's Wide Field Instrument focused to 63 nm RMS against ~90 nm required. Artemis II heat shield: 9 char-loss spots vs 103 on Artemis I. Hera's BRM-2 burn Thursday 22 October. Skywatch Orionids peak 21–22 Oct — watch between moonset and dawn (moonset Thu morning: 03:38 Sydney, 03:22 LA, 03:12 NY, 02:49 London). Mercury 16.5° up at civil dusk from Sydney. Venus at inferior conjunction ~24 Oct. Moon ~6° from Saturn 24 Oct. Full Moon 26 Oct 04:11 UTC. UK clocks go back 25 Oct, US on 1 Nov. Always use ISO 12312-2 certified filters for any solar viewing. Sources · Watters et al. — Thrust Faulting and the Late-stage Contraction of the Moon (PSJ, 14 Oct 2026) — https://doi.org/10.3847/PSJ/ae9eae · Smithsonian NASM — New Study Reveals How Much the Moon Is Shrinking — https://airandspace.si.edu/newsroom/press-releases/new-study-reveals-how-much-moon-shrinking · University of Sydney — Sydney student creates first map of Martian soils — https://www.sydney.edu.au/news-opinion/news/2026/10/16/sydney-student-creates-first-map-of-martian-soils.html · McBratney, Irving et al. — Areths and PPACS (Catena 275) — https://doi.org/10.1016/j.catena.2026.110649 · ESA — Euclid discovers new comet — https://www.esa.int/Science_Exploration/Space_Science/Euclid/Euclid_discovers_new_comet · SwRI — New ideas about origins of Uranus, Neptune — https://www.swri.org/newsroom/press-releases/swri-staff-contribute-new-ideas-about-origins-of-uranus-neptune · Briand et al. — Contrasting C/O ratios in Uranus and Neptune (A&A 714, A364) — https://doi.org/10.1051/0004-6361/202660770 · JAXA — Launch result of MMX aboard H3 F10 — https://global.jaxa.jp/press/2026/10/20261020-1_e.html · NASA — Roman team checks out main instrument, sharpens focus — https://science.nasa.gov/missions/roman-space-telescope/ · NASA — Rigorous analysis confirms Artemis II heat shield performance — https://www.nasa.gov/missions/artemis/artemis-2/rigorous-analysis-confirms-nasas-artemis-ii-heat-shield-performance/

MMX: A Round Trip to Phobos JAXA's Martian Moons eXploration mission launched on schedule on H3 Flight No. 10 at 04:41:03 JST on 20 October 2026 (19:41 UTC 19 Oct; 06:41 AEDT Tue; 15:41 EDT / 12:41 PDT / 20:41 BST Mon). Mars orbit August 2027, Phobos quasi-satellite orbit from September 2027, Idefix rover (CNES/DLR) release early 2029, landing and sampling 2030, and at least 10 g of Phobos returned in 2031 to South Australia. Eleven science instruments including NASA's MEGANE. The aim: settle whether Phobos and Deimos are captured asteroids or debris from a giant impact on Mars. Half a Giant Mirror ESO reports that nearly 500 of the ELT's primary-mirror segments are now at Paranal — more than half of the 931 being made (798 plus 133 spares for continual recoating). Safran Reosc is finishing a segment a day and the last one is in production. The ELT is more than 75% complete, with first observations with scientific instruments planned for late 2030. The Window That Closes Carr, Cen and colleagues (Nature Astronomy, 15 Oct 2026) used Hubble/COS spectra of six matched local starbursts to show ionising light escapes most in the first few million years, before supernova-driven winds load the outflow with neutral gas and shut it down. Escape fractions fall from ~21% (mean age ~2.7 Myr) to under 0.4% (~5.4 Myr). Preprint first posted October 2025. The Treble Clef Rises Again Botteon et al. (A&A; NASA/Chandra release 14 Oct) show VLSS J0318.9+5755, behind the Milky Way's plane, is a radio phoenix in a merging cluster at z ≈ 0.117: an old black-hole outburst re-lit by a cluster collision a few hundred million years ago. Spectral index above 4 between 400 and 650 MHz; electrons ~190–200 Myr old. Preprint from July. Quick hits Hera's 93-minute BRM-1 confirmed within parameters; BRM-2 on Thursday 22 October. Sentinel-3C's first images and altimetry. Swift: no NASA re-entry date yet. Skywatch Full Moon 26 Oct 04:11 UTC. Orionids peak 21–22 Oct: go after moonset (03:38 Sydney, 03:22 LA, 03:12 NY, 02:49 London on the 22nd). Mercury 17° up at civil dusk from Sydney (21 Oct). Venus inferior conjunction ~24 Oct. Moon ~6° from Saturn ~24 Oct. Mars–Jupiter 10.8° → 8.0° pre-dawn. Always use ISO 12312-2 certified filters for any solar viewing. Sources · JAXA — MMX launch on H3 F10 — https://mmx-news.isas.jaxa.jp/?p=2753 · ESA — Mars moon lander set to launch on 19 October — https://www.esa.int/Science_Exploration/Space_Science/Mars_moon_lander_set_to_launch_on_19_October · Australian Space Agency — MMX sample return — https://www.space.gov.au/node/950 · ESO ann26009 — More than half of the ELT's giant mirror is now in Chile — https://www.eso.org/public/announcements/ann26009/ · Carr et al. — arXiv 2510.21197 (Nature Astronomy, 15 Oct 2026) — https://arxiv.org/abs/2510.21197 · NASA — Chandra breaks down Treble Clef's galaxy cluster collision — https://science.nasa.gov/missions/chandra/nasas-chandra-breaks-down-treble-clefs-galaxy-cluster-collision/ · Botteon et al. — arXiv 2607.06659 — https://arxiv.org/abs/2607.06659 · ESA — Sentinel-3C returns its first views of Earth — https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-3/Sentinel-3C_returns_its_first_views_of_Earth · ESA Hera on X — BRM-1 confirmed — https://x.com/ESA_Hera · NASA — Lessons learned from the Swift boost mission — https://science.nasa.gov/missions/swift/nasa-highlights-lessons-learned-from-swift-boost-mission/

Show notes Time Lets Go of the Sky On 15 October 2026 the 28th General Conference on Weights and Measures in Versailles adopted Resolution 5: UTC becomes continuous on 20 May 2027, ending leap seconds, with the UTC–UT1 gap allowed to reach one hour. The driver: a growing chance (about 30% by 2035) of a first-ever negative leap second. Resolution 6 starts work on an international lunar reference time scale traceable to UTC; Resolution 4 prepares an optical-clock redefinition of the second for 2030. Earth's rotation (UT1) is still measured — by VLBI, with Australia's AuScope dishes part of the network. The Week That Was WISE 0855's changing water clouds (JWST); Hera's 93-minute braking burn; Artemis II's five lunar impact flashes; UCL questions the chemical evidence for hypernovae; the Arsia Mons cloud needs ice from nothing; the first green star. Also: ZTF J0440+2325, Meteor 2-7, Juno's crumpled magnetodisk, WASP-17 b, two planetary families, and new Magellanic Cloud pulsars from the Parkes archive. Skywatch First quarter Mon 19 Oct 03:12 AEDT (16:12 UTC Sun). Mercury 24° up at sunset from Sydney vs 10° LA, 7° NY, 3° London. Venus gone from northern evening skies; inferior conjunction ~03:00 UTC Sat 24 Oct. Saturn all evening, rings ~7° open. Orionids peak 21–22 Oct; Moon sets ~03:00–03:40 local, radiant 39–70° up at 04:30. Mars–Jupiter 11.5° apart, 1.2° on 16 Nov. AR4551 beta-gamma-delta. Solar safety: ISO 12312-2 filters only. Sources · BIPM — Resolutions adopted at the 28th CGPM: https://www.bipm.org/en/-/cgpm-2026-resolutions-adopted · BIPM — Resolution 5 (2026): https://www.bipm.org/en/cgpm-2026/resolution-5 · BIPM — Statement by the CCTF President, 15 Oct 2026: https://www.bipm.org/documents/d/guest/statement-cctf-president-cgpm-2026 · AuScope VLBI array (Lovell et al.): https://arxiv.org/abs/1304.3213 · ESA — Braking news! Hera: https://www.esa.int/Space_Safety/Hera/Braking_news!_Time_for_ESA_s_Hera_asteroid_mission_to_go_slow · JAXA — MMX launch schedule: https://global.jaxa.jp/press/2026/08/20260820-1_e.html · EarthSky — Sun news, AR4551 (16 Oct): https://earthsky.org/sun/sun-news-activity-solar-flare-cme-aurora-updates/ · Week That Was sources: see S05E202–S05E206 show notes.

Show notes Episode 206 opens with the first results from ALMA's COMPASS survey: the first detection anywhere in interstellar space of fully deuterated methanol, and methanol masers turning up around more than half of a sample of young Sun-like stars. Then the first star that would look green, Magellanic Cloud pulsars recovered from decades-old Parkes data, a supernova caught days old when the universe was 1.2 billion years old, quick hits on Hera, CRS-35 and MMX, and a both-hemispheres skywatch built around the Orionids. Heavy methanol around a newborn star ALMA's COMPASS programme (11 protostars, 100+ hours, seven A&A papers) reports the first interstellar CD3OD around IRAS 4A2 in Perseus (Belloche, MPIfR) and methanol masers in more than half of its low-mass protostars (Jeong, SNU). Deuterium fraction as a formation clock; current models can't reproduce the pattern. The first green star Warwick's Hollands et al. (RASTI) compute white dwarf colours from spectra: WD J1330+6435 comes out chartreuse thanks to accreted sodium; WD J1011+2845 may be the reddest star known. Of 151 white dwarfs within 20 pc, about 1 in 30 is oddly coloured, and the median is white. Pulsars hiding in the Parkes archive Reprocessing Murriyang's Magellanic Cloud surveys finds six pulsars, five in the LMC including a 3.8 s spinner (Sengar et al., preprint); a separate search finds PSR J0103−72, the slowest radio pulsar in the SMC (Wang & Sengar, preprint). A supernova caught days old JWST's NEXUS survey caught AT 2026abck at z = 5.017 roughly 4–10 rest-frame days after explosion — the first robust z ≳ 5 transient in an unlensed field (preprint; no spectrum yet). Quick hits Hera's BRM-1 braking burn (result pending at recording), CRS-35 docks with the last iROSAs, and MMX launches Tuesday morning Japan time. Skywatch First quarter 18 Oct, Orionids peak 21–22 Oct with the Moon down before dawn everywhere, evening Mercury for the south, Venus heading into conjunction, Saturn after dark, Mars and Jupiter closing before dawn. Sources · ALMA — Cosmic Cocktail: ALMA Reveals Exotic Methanol Around Young Stars (7 Oct 2026) — https://www.almaobservatory.org/en/press-releases/cosmic-cocktail-alma-reveals-exotic-methanol-around-young-stars/ · Belloche et al., COMPASS VII, arXiv 2610.07279 — https://arxiv.org/abs/2610.07279 · University of Warwick — true colours of white dwarf stars — https://warwick.ac.uk/news/pressreleases/astronomers-reveal-true-colours-of-white-dwarf-stars/ · Hollands et al., RASTI DOI 10.1093/rasti/rzag069 — https://academic.oup.com/rasti/article/doi/10.1093/rasti/rzag069 · Sengar et al., arXiv 2610.12450 — https://arxiv.org/abs/2610.12450 · Wang & Sengar, arXiv 2610.12143 — https://arxiv.org/abs/2610.12143 · Zhuang, Shen et al., arXiv 2609.38373 — https://arxiv.org/abs/2609.38373 · ESA — Brake! Time for ESA's Hera asteroid mission to go slow — https://www.esa.int/Space_Safety/Hera/Brake!_Time_for_ESA_s_Hera_asteroid_mission_to_go_slow · NASA Space Station blog — CRS-35 docking — https://www.nasa.gov/blogs/spacestation/ · JAXA — MMX launch schedule — https://global.jaxa.jp/press/2026/08/20260820-1_e.html