2I/Borisov Archives

Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in Northern California -- SETI Institute

Astrochemistry, Astronomy & Telescopes, Biosignatures & Paleobiology, Comets and Asteroids, Imaging & Spectroscopy, Intelligence & Language, Interstellar, Press Release, SETI & Technosignatures

SETI Institute Looks for Signs of Technology in Interstellar Visitor 3I/ATLAS

by Keith CowingJune 4, 2026June 4, 2026

Scientists at the SETI Institute searched for technological signals from 3I/ATLAS, the third interstellar object observed in our Solar System.

Top row: coma maps of H2O, CO2, and CH4, computed as the molecular column density from a pixel-by-pixel retrieval analysis for Observations 6, 15, and 6, respectively. The sunward and target velocity directions are denoted by the white arrows. The target centroids, computed as the photocenter in the median-stacked images (Figure 1), are marked with the black points. For H2O and CO2, the white contours correspond to emission levels of 50% and 20% relative to the maximum value and illustrate the slight anti-sunward extension of the respective comae. The contours are omitted in the CH4 panel due to the poorer signal-to-noise ratio of the data. Bottom row: corresponding median-stacked images across the continuum wavelengths within each fluorescence region. The H2O coma map shows significant enhancement in emission level at large nucleocentric distances relative to the dust continuum, indicating extended H2O production within the coma. -- arxiv.org

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Intelligence & Language, Interstellar, Press Release

Interstellar Comet Reveals Methane On Its Journey Through Our Solar System

by Keith CowingApril 18, 2026April 18, 2026

Interstellar comet 3I/ATLAS is now on its way out of our solar system, never to return.

The green-to-red intensity ratio of [O I] (G/R) in 3I (filled circle), compared with measurements for a sample of Solar System comets: Jupiter-family comets (JFCs; open triangles), Oort Cloud comets (OCCs; open squares), and Halley-type comets (HTCs; crosses) from A. Decock et al. (2013); A. McKay et al. (2015); Y. Shinnaka & H. Kawakita (2016); Y. Shinnaka et al. (2020), as well as C/2016 R2 from C. Opitom et al. (2019) and 2I/Borisov from C. Opitom et al. (2021). -- astro-ph.GA

A Post-perihelion Constraint On The CO2/H2O Ratio Of Interstellar Comet 3I/ATLAS From [O I] Forbidden Lines

by Keith CowingMarch 31, 2026March 31, 2026

We present high-resolution optical spectroscopy of interstellar comet 3I/ATLAS (C/2025 N1) obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope on UT 2026 January 7, when the comet […]

Averaged 18 cm OH lines (scaled to 1667 MHz) of 3I obtained in four observations with both a Gaussian and a trapezoid fit: September 8 and 9 (top), September 18 and 23 (bottom). The Astrophysical Journal

Astrochemistry, Astronomy & Telescopes, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Unique Water Release Mechanism Uncovered In Interstellar Comet 3I/ATLAS

by Keith CowingMarch 23, 2026June 11, 2026

A research team from the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences (CAS) has conducted high-sensitivity radio observations of the interstellar comet 3I/ATLAS using the Tianma Telescope, […]

Stacked images of 3I/ATLAS acquired by HiRIC CMOS camera onboard Tianwen-1 spacecraft (upper row) and the corresponding 1/ρ divided images (lower row) from the three epochs. All images are displayed north up and east to the left. The stacked images are displayed with logarithmic brightness stretch, and the enhanced images are displayed with a linear brightness stretch. The arrows in the upper panels mark the projected directions of the Sun and the heliocentric velocity vector. The scalebars are 10,000 km. The bright star trails are visible in each stack due to the apparent movement of 3I in the sky background during each 30-second observation epoch. -- astro-ph.EP

Interstellar Object 3I/ATLAS Observed from Mars by China’s Tianwen-1 Spacecraft

by Keith CowingMarch 14, 2026March 14, 2026

China’s Tianwen-1 Mars orbiter successfully imaged the third interstellar object, 3I/ATLAS, during its close encounter with Mars using the onboard HiRIC CMOS camera. This is China’s first deep-space observation of […]

An artist's impression of 3I/ATLAS is shown as it passes near the Sun, illuminating one side of the comet. On the side of the comet closer to the sun, the methanol gas is shown in blue, with icy dust grains still present in the gas. On the dark side of the comet, the hydrogen cyanide is shown in orange. Credit: NSF/AUI/NSF NRAO/M.Weiss

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release

ALMA Detects Extremely Abundant Alcohol in Interstellar Comet 3I/ATLAS

by Keith CowingMarch 6, 2026March 6, 2026

Comet 3I/ATLAS continues to make astonishing headlines, thanks to new findings from astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), of which the U.S. National Science Foundation National Radio Astronomy […]

Distribution of hits (circles) and events (stars) over frequency and drift rate. The marker size gives the S/N. The gray-shaded regions show ranges not sampled, including narrow notch filter regions in the L and S bands. The color-shaded regions give the range of drift rates expected from Earth’s orbital motion and rotational motion and 3I/ATLAS’s rotation at each of the four observing bands. These regions do not perfectly align between bands due to 3I/ATLAS’s radial acceleration changing during overhead time between observations. No events lie in the expected drift rate regions. -- astro-ph.IM

Astronomy & Telescopes, Comets and Asteroids, Imaging & Spectroscopy, Intelligence & Language, Interstellar, SETI & Technosignatures, Status Report

Breakthrough Listen Observations Of 3I/ATLAS With The Green Bank Telescope at 1-12 GHz

by Keith CowingDecember 31, 2025December 31, 2025

3I/ATLAS (also designated C/2025 N1 (ATLAS) and, formerly, A11pl3Z) is the third interstellar object (ISO), following 1I/‘Oumuamua and 2I/Borisov, to be discovered during a passage through the Solar System. The […]

Sample images showing the morphological development of 3I/ATLAS. The image dates and heliocentric distances of the comet are shown in each panel, as is a 10′′ scale bar. Sunward is West. The location of the brightest pixel is marked with a red dot, showing that the dust is extended asymmetrically towards the West in the early data, reversing to the East as the radiation pressure swept tail develops in the later data. -- astro-ph.EP

Astronomy & Telescopes, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Pre-perihelion Development of Interstellar Comet 3I/ATLAS

by Keith CowingOctober 22, 2025October 22, 2025

We describe pre-perihelion optical observations of interstellar comet 3I/ATLAS taken during July – September 2025 using the Nordic Optical Telescope.

ExoMars TGO image of comet 3I/ATLAS -- ESA

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release

ExoMars And Mars Express Observe Interstellar Comet 3I/ATLAS

by Keith CowingOctober 7, 2025October 7, 2025

Between 1 and 7 October, ESA’s ExoMars Trace Gas Orbiter (TGO) and Mars Express spacecraft turned their eyes towards interstellar comet 3I/ATLAS, as it passed close to Mars.