1I/`Oumuamua 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.

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, […]

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 […]

Position on the Gaia CMD diagram of the stars that experienced a close encounter with 3I/ATLAS, with spectral types indicated in the legend that comes from O. L. Creevey et al. (2023). The background shows all the sources from our Gaia DR3 500 pc sample with available RVs, after applying the same magnitude and parallax error cuts as for the encounter stars. The dashed line marks the MS-locus defined in (M. J. Pecaut & E. E. Mamajek 2013, PM13 in the legend). -- astro-ph.EP

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

3I/ATLAS: In Search Of The Witnesses To Its Voyage

by Keith CowingSeptember 10, 2025September 10, 2025

3I/ATLAS is the third interstellar object discovered to date, following 1I/’Oumuamua and 2I/Borisov.

Astrochemistry, Astrogeology, Comets and Asteroids, Icy Worlds, Interstellar, Missions & Hardware, Press Release

SwRI-proposed Mission Could Encounter And Explore A Future Interstellar Comet Like3I/ATLAS Up Close

by Keith CowingSeptember 3, 2025September 18, 2025

Southwest Research Institute (SwRI) has completed a mission study detailing how a proposed spacecraft could fly by an interstellar comet, providing remarkable insights into the properties of bodies originating beyond […]

Near-UV to visible reflectance spectrum of 3I/ATLAS obtained with OSIRIS/GTC and normalized to unity at 5500 Å. Normalized reflectance of 1I/’Oumuamua (in brown) from Fitzsimmons et al. (2018) and 2I/Borisov (in green) from de León et al. (2020) are also shown for comparison, together with D-type spectral taxon from DeMeo et al. (2009). -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Assessing Interstellar Comet 3I/ATLAS With The 10.4 m Gran Telescopio Canarias And The Two-meter Twin Telescope

by Keith CowingJuly 25, 2025July 25, 2025

Context. Theories of the formation and evolution of small bodies in planetary systems predict that they may escape into interstellar space at any time.

ESO’s Very Large Telescope (VLT) has obtained new images of 3I/ATLAS, an interstellar object discovered last week.

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

VLT Timelapse Of 3I/ATLAS, A New Interstellar Object

by Keith CowingJuly 13, 2025

ESO’s Very Large Telescope (VLT) has obtained new images of 3I/ATLAS, an interstellar object discovered last week. Identified as a comet, 3I/ATLAS is only the third visitor from outside the […]

Top view of the Milky Way galaxy showing the estimated orbits of both our Sun and the 3I/ATLAS comet. 3I/ATLAS is shown in red dashed lines, and the Sun is shown in yellow dotted lines. The large extent of 3I’s orbit into the outer thick disk is clear, while the Sun stays nearer the core of the galaxy. Credit M. Hopkins/Ōtautahi-Oxford team. Base map: ESA/Gaia/DPAC, Stefan Payne-Wardenaar, CC-BY-SA 4.0 Licence type Attribution (CC BY 4.0)

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release

Interstellar Object 3I/ATLAS May Be The Oldest Comet Ever Seen

by Keith CowingJuly 12, 2025July 12, 2025

A mystery interstellar object discovered last week is likely to be the oldest comet ever seen – possibly predating our solar system by more than three billion years, researchers say.