Astronomy Daily S05E148 — "Far Side" Thursday 23 July 2026 Starship gets a second shot at Flight 13 — with a schedule caveat worth knowing about. The first far-side lunar samples reveal that Earth has been quietly shielding the side of the Moon that faces us. Astronomers debate whether the lunar far side should be closed to industry. The Milky Way's only helium nova finally steps out from behind twenty-five years of dust. And the case that our entire galaxy once turned over. Plus a skywatch closer with a straightforward piece of advice about the Delta Aquariids: do not wait for the peak.

In this episode Starship Flight 13 ● Window opens 6:45pm EDT / 2245 GMT Thursday 23 July — 8:45am AEST and 10:45am NZST Friday 24 July. ● Schedule is not locked: Starbase road and beach closure notices point to further Pad 2 testing. ● The 16 July attempt aborted at T-0 when four of 33 Raptors missed start parameters; the limit is three. ● Two Raptors were removed and replaced before this attempt. ● First-ever Starship deployment of V3 Starlink satellites — 20 of them. ● Super Heavy splashes down in the Gulf at ~7 minutes; Ship targets the Indian Ocean off Western Australia at ~65 minutes. No catch attempts. Chang'e-6 and the solar wind ● Published in Nature Geoscience by a team at the Chinese Academy of Sciences' Institute of Geology and Geophysics. ● Based on 1,935 grams of regolith returned from the South Pole–Aitken basin on the lunar far side. ● First direct laboratory comparison of solar wind implantation between the near and far sides. ● Far-side soil records faster, deeper-penetrating particles; the neon isotope ratio sits below every near-side sample measured. ● About a quarter of the solar wind exposure at the Chang'e-5 near-side site involved wind decelerated by Earth's magnetosphere. The far-side site shows none. ● Opens the possibility of using lunar noble gases as a fossil record of Earth's magnetic field over deep time. The far side debate — NAM 2026 ● Held Tuesday 21 July at the RAS National Astronomy Meeting, University of Birmingham. Convened by Prof Martin Ward. ● For the motion: Prof Joe Silk (Johns Hopkins) and Dr Jonathan McDowell (Durham Space Research Centre). ● Against: Dr Nikita Chiu (Durham) and Dr Manuel Salvoldi (aerospace engineer and educator). ● For: the far side is the only radio-quiet site near Earth — critical for detecting the cosmic dark ages, and an exceptional platform for gravitational wave detection. ● Against: commercial investment is what makes lunar exploration sustainable, and governance can let science and industry coexist. ● Audience support for the motion rose from 68% to 76% across the debate. V445 Puppis ● Presented at NAM 2026 by John Mills, University of Warwick. ● The only confirmed helium nova in the Milky Way. Erupted in late 2000, then vanished behind its own dust for over twenty years. ● Now confirmed as a white dwarf accreting from a rare stripped helium star — only a few thousand such stars are thought to exist in the entire galaxy. ● Orbital period of 3.7 days, roughly double previous estimates. Mass transfer has resumed. ● Unexplained high-speed "bullets" of possibly oxygen-rich gas travelling up to 20 million mph (~9,000 km/s) — never seen in any other nova. ● Data from ESO's Very Large Telescope, Hubble, the Southern African Large Telescope and TESS. ● Helium novae may be one pathway to Type Ia supernovae, the standard candles used to measure cosmic expansion. The Milky Way disc flip ● Presented at NAM 2026 by Kirill Batrakov, Durham University. ● Based on 25 Milky Way-like galaxies in the Auriga simulation suite, followed across roughly 11 billion years. ● Galaxies with the most slowly rotating stellar haloes shared a major head-on merger and a disc reorientation greater than 90 degrees. ● Our stellar halo rotates at only 10–20 km/s; the disc moves at around 220 km/s. ● The Gaia-Sausage-Enceladus collision roughly 10 billion years ago is the candidate trigger. ● Batrakov describes a disc flip as likely rather than confirmed, and is looking for independent signatures. ● Separate 2026 work led by Ling Zhu, using 600,000+ giant stars from Gaia and LAMOST, found the outer dark matter halo oriented almost vertically to the stellar disc — consistent with the disc having tilted. Skywatch ● Southern Delta Aquariids are active now, running into late August, with maximum around 30 July. ● Full Moon on 29 July means peak night is close to 98% illuminated — the worst conditions of the run. ● Best window: the pre-dawn mornings from now until roughly 27 July, after moonset. ● Radiant near Skat in Aquarius. Use Fomalhaut and the Great Square of Pegasus to locate it. ● Australia and New Zealand: radiant climbs near overhead. Best from around 2am to first light. ● North America: radiant sits low in the south — fewer meteors, but a better chance of long-trailed earthgrazers. Same 2am-to-dawn window, local time. ● Sunspot region AR4493 has grown rapidly to beta-gamma-delta complexity — the highest classification — and has already fired three M-class flares in a day. Worth watching aurora alerts. Sources ● SpaceX / Space.com — Starship Flight 13 mission details and timing ● Nature Geoscience — noble gas analysis of Chang'e-6 regolith (Chinese Academy of Sciences, Institute of Geology and Geophysics) ● Royal Astronomical Society — NAM 2026 far side governance debate ● Royal Astronomical Society — NAM 2026, V445 Puppis (John Mills, University of Warwick) ● Royal Astronomical Society — NAM 2026, Milky Way disc flip (Kirill Batrakov, Durham University) ● EarthSky and the American Meteor Society — Delta Aquariid observing guidance ● NOAA Space Weather Prediction Center / EarthSky Sun News — AR4493 activity

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