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← Astronomy and space this week · 26 October 2026 · 5 min read

Astronomy and space this week

From pristine asteroid samples to a galaxy leaking early starlight, six new preprints explore what the universe preserves, produces and lets escape.

How to check the findings and keep reading? Illustrated guide

An interstellar comet’s changing face #

A long observing campaign with the Keck and Gemini telescopes followed interstellar comet 3I/ATLAS from July 2025 to May 2026, recording its dust, gas and colors as it passed through the Solar System. Its optical colors showed no significant change across its closest approach to the Sun, even as its compact sunward feature and surrounding dust cloud broadened. Meanwhile, the relative abundances of several carbon-bearing molecules changed, and its dust activity declined more steeply with distance on the outbound journey than it had increased inbound.

The researchers estimate that the comet shed several billion to ten billion kilograms of dust, depending on the dust-speed method and adopted assumptions. They found no water-ice absorption that remained convincing across their different calibration and continuum choices—a limit on what these spectra reveal, not proof that the comet lacks ice. Together, the observations provide a detailed reference for comparing future visitors from other planetary systems.

Bennu gives the Solar System’s chemical recipe a check #

Material returned from asteroid Bennu offers something meteorites cannot: a carbon-rich asteroid sample protected from terrestrial weathering before its arrival. Four laboratories measured 63 elements in roughly eight grams of aggregate material and found no statistically significant compositional differences among the tested portions, even across sample sizes ranging from tens of milligrams to several grams. Their combined elemental inventory is called Best Bulk Bennu, or B3.

B3 closely matches CI chondrites, the rare meteorites long used as benchmarks for the Solar System’s bulk chemical composition. The agreement suggests that terrestrial alteration has not substantially changed those meteorites’ overall abundances of elements other than the most volatile ones, even if it altered their minerals or moved elements around internally. Rather than replacing the old benchmark, Bennu strengthens it with an independently collected sample.

A neutron-star pair with an extraordinary close encounter #

A newly reported double neutron star system spends most of its 79-day orbit far from its closest encounter, then rushes through that encounter at remarkable speed. Its orbital eccentricity is about 0.992, making the path extremely elongated. Near closest approach, the stars reach a relative speed of about 1,140 kilometers per second. The radio pulsar also disappears in an 85-second eclipse, indicating that we see the orbit nearly edge-on.

The preprint’s authors argue that producing such an extreme orbit requires a strong kick from the supernova that formed the second neutron star. Their models put the probability of detecting a system like this below roughly half a percent, making the discovery a challenge for current accounts of binary evolution. The pair should also emit recurring bursts of gravitational waves, with peak energy flux at frequencies relevant to the proposed LISAmax mission—not a claim that those waves have already been detected.

A very blue galaxy may let most of its ionizing light escape #

Deep James Webb Space Telescope spectroscopy has sharpened the picture of EBG-1, a gravitationally lensed galaxy at redshift 9.244, seen during the universe’s first several hundred million years. Its exceptionally blue ultraviolet light and measured emission lines point to low oxygen abundance—about three percent of the Sun’s—and relatively little carbon compared with oxygen.

Comparisons with synthetic spectra favor a scenario in which at least about three-quarters of the galaxy’s hydrogen-ionizing photons escape, with roughly 85 percent giving the best overall match. That fraction is model-inferred, not directly measured. If the interpretation holds, it shows how a relatively ultraviolet-bright galaxy could contribute strongly to reionization, the era when radiation stripped electrons from the hydrogen filling intergalactic space.

Looking for stars that vanish without exploding #

Some massive stars may end their lives by collapsing directly into black holes rather than producing conspicuous supernovae. A search through the Zwicky Transient Facility’s optical catalog identified 125 sources with fading patterns worth examining, but no definitive failed supernova. Some remain suggestive; the preprint does not establish any as a direct-collapse event.

The absence of a confirmed detection is consistent with the team’s simulations, which predict that ZTF would observe only about 0.234 such events per century. Treating the search as a null result gives a much looser upper limit on the actual Milky Way rate: 147 per century at 99 percent credibility. The distinction matters—an event can occur without being detectable by a particular survey. The authors predict that monitoring with the Rubin Observatory’s Legacy Survey of Space and Time and the Roman Space Telescope could eventually turn these elusive disappearances into a population that can be studied statistically.

A harsh cloud with a rich molecular inventory #

Near the center of the Milky Way, shocks and intense cosmic-ray activity help make the molecular cloud G+0.693-0.027 a productive chemical laboratory. A new review brings together results from sensitive, broad-frequency spectral surveys and laboratory spectroscopy: more than 140 molecules have been identified there, including 28 first detected in interstellar space in this cloud.

The inventory includes precursors relevant to prebiotic chemistry, molecules containing elements such as phosphorus and magnesium, charged molecules, and alternative molecular arrangements that are relatively high in energy. These findings do not amount to evidence for life. They show how extensive chemistry can become in a demanding interstellar environment, and how laboratory measurements make it possible to recognize its products across space.

These six preprints, drawn from 542 papers announced in astronomy and space this week, share a concern with reading incomplete traces: dust from a passing comet, elements preserved in an asteroid, pulses from an extreme binary, light escaping an early galaxy, disappearing stars and molecular fingerprints. None of these reports is yet peer reviewed. Their value lies both in the patterns they reveal and in the limits they make explicit—what an observation establishes, what a model suggests and what remains beyond reach.

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Written by AI from the 542 papers of the week in this field. Most are preprints, not yet peer reviewed: the text says what their authors report.

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