3I/ATLAS Archives

This image of interstellar comet 3I/ATLAS was taken on 18 January 2026 with the FORS2 instrument on ESO’s Very Large Telescope (VLT). It is a stack of several images spanning 14 minutes. As the comet moves on the sky, the stars appear as trails in the background. Credit: ESO/O. Hainaut

Older Than The Sun: Astronomers Find New Clues To The Origin Of Interstellar Comet 3I/ATLAS

by Keith CowingJuly 7, 2026July 7, 2026

[ESO] Astronomers have used the European Southern Observatory’s Very Large Telescope (ESO’s VLT) to study the composition of 3I/ATLAS, the brightest interstellar object ever seen, in detail.

Scatter plots of potential candidate in frequency, drift rate and signal-to-noise ratio for total intensity and four polarization channels. The color and the size for each point represent the value of SNR in log space. The blue and ornage color bar are the frequency ranges of civil aviation and navigation satellites, respectively. The black dashed lines represent the expected drift rates for each observation date. -- astro-ph.IM

SETI & Technosignatures

Narrowband Radio Technosignature Search Toward 3I/ATLAS with FAST

by Keith CowingJuly 3, 2026July 3, 2026

[astro-ph.IM] 3I/ATLAS is the third confirmed interstellar object passing through the Solar System.

Continuum-subtracted emissivity of 3I/ATLAS in the 6-7 µm region in black, compared to a set of reference spectra which are described in the main text.

Comets and Asteroids

The Dust Mineralogy of Interstellar Comet 3I/ATLAS from JWST/MIRI Observations

by Keith CowingJuly 3, 2026July 3, 2026

[astro-ph.EP] We present the first spectroscopic mineralogical analysis of the dust coma of an interstellar object (ISO) from JWST mid-infrared spectroscopy of 3I/ATLAS (3I).

Interstellar Comet 3I/ATLAS (NIRSpec IFU) -- ESA (larger Image)

Comets and Asteroids

Webb Finds Clues To The Ancient Origin Of Comet 3I/ATLAS

by Keith CowingJune 23, 2026June 23, 2026

The third identified interstellar comet in human history has a surprising chemical makeup, raising questions as to how common, or unusual, conditions in our own Solar System may be.

Panels (a)–(o) show contour maps of the observed isophotes (black lines) together with the corresponding modelled isophotes (red lines) for the case 𝑟max = 1 cm. For each of these contour panels, a companion plot is displayed to the right, labelled (a′ )–(o′ ), showing a one-dimensional scan extracted along the direction indicated by the straight red line in the corresponding contour map. In these primed panels, the black and red curves represent the observed and modeled brightness profiles, respectively. The 𝑥- and 𝑦-axes in the contour plots are given in pixel units, and the innermost isophote levels as well as the physical dimensions of each image are listed in Tables 1 and 3. In panels (a)–(o), isophote levels increase outward in steps of 1 mag. In the primed panels, the 𝑥-axis is expressed in pixel units and the 𝑦-axis in surface brightness units (mag arcsec−2). -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Dust Colour, Phase Behaviour, And Monte Carlo Modelling Of Interstellar Comet 3I/ATLAS From 4 au Pre- to 4 au Post-Perihelion

by Keith CowingJune 19, 2026June 19, 2026

We report multi-band photometric imaging observations and Monte Carlo dust tail modelling of the interstellar comet 3I/ATLAS covering a wide range of heliocentric distances, from about 4 au pre-perihelion to […]

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: 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 antisunward 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: corresponding median-stacked images across the continuum wavelengths within each fluorescence region. The H2O coma map shows a significant enhancement in the emission level at large nucleocentric distances relative to the dust continuum, indicating extended H2O production within the coma. -- The Astrophysical Journal Letters

Astrochemistry, Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release

Webb Detects Methane on Interstellar Comet 3I/ATLAS

by Keith CowingJune 2, 2026June 2, 2026

NASA’s James Webb Space Telescope has collected its first mid-infrared chemical fingerprint of an interstellar object during a recent revisit to comet 3I/ATLAS. The team’s results published recently in The […]

Juice-UVS saw gas and dust elements stretching up to more than 5 million km from 3I/ATLAS’s nucleus on November 25, 2025, when the comet had dimmed considerably relative to November 2 observations. Black spots are where stars appeared in the scanned image, removed here for clarity. Credit: NASA/ESA/Southwest Research Institute

Astrochemistry, Astrogeology, Comets and Asteroids, Europa, Icy Worlds, Imaging & Spectroscopy, Missions & Hardware, Press Release

Two Spacecraft Observed Both Hemispheres Of Interstellar Comet 3I/ATLAS Simultaneously

by Keith CowingMay 14, 2026May 14, 2026

The Southwest Research Institute-led Ultraviolet Spectrograph (UVS) instruments aboard ESA’s Jupiter Icy Moons Explorer (Juice) spacecraft and NASA’s Europa Clipper made unique observations of interstellar comet 3I/ATLAS in late 2025. […]

A new study of the interstellar comet 3I/ATLAS led by the University of Michigan shows that its water has a remarkably high content of deuterium. This form of hydrogen is comparatively less abundant in our solar system, enabling researchers to glean new insights about other planetary processes at work in our galaxy. Image credit: U-M News/Hans Anderson

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

The Interstellar Comet 3I/ATLAS Was Born Somewhere Much Different From Our Solar System

by Keith CowingApril 28, 2026April 28, 2026

Less than a year ago, astronomers discovered a comet soaring through our sky that was not from our solar system.

This artist’s impression compares the semi-heavy water content of the interstellar comet 3I/ATLAS (left) and Earth (right). Insets illustrate the relative abundance of deuterated water (HDO) molecules, showing that 3I/ATLAS contains over 30 times more HDO than is found in Earth’s oceans. This elevated ratio suggests the comet formed in an extremely cold environment, very different from the conditions that shaped our Solar System. Credit: NSF/AUI/NSF NRAO/M.Weiss

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

ALMA Reveals Interstellar Comet 3I/ATLAS Formed in a Far Colder World Than Our Own

by Keith CowingApril 23, 2026April 23, 2026

New observations from the Atacama Large Millimeter/submillimeter Array (ALMA) have yielded the first-ever measurement of deuterated water — also known as semi-heavy water — in an interstellar object. The discovery […]

3I/ATLAS

Older Than The Sun: Astronomers Find New Clues To The Origin Of Interstellar Comet 3I/ATLAS

Narrowband Radio Technosignature Search Toward 3I/ATLAS with FAST

The Dust Mineralogy of Interstellar Comet 3I/ATLAS from JWST/MIRI Observations

Webb Finds Clues To The Ancient Origin Of Comet 3I/ATLAS

Dust Colour, Phase Behaviour, And Monte Carlo Modelling Of Interstellar Comet 3I/ATLAS From 4 au Pre- to 4 au Post-Perihelion

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

Webb Detects Methane on Interstellar Comet 3I/ATLAS

Two Spacecraft Observed Both Hemispheres Of Interstellar Comet 3I/ATLAS Simultaneously

The Interstellar Comet 3I/ATLAS Was Born Somewhere Much Different From Our Solar System

ALMA Reveals Interstellar Comet 3I/ATLAS Formed in a Far Colder World Than Our Own

A Search For Narrowband Technosignatures From LTT 3780 With The Allen Telescope Array And The Karl G. Jansky Very Large Array

Tricorder Tech: Identifying Proteins, Molecule By Molecule

First Completed Rocky Worlds Program Observations Open New Era in Exoplanet Studies

Pioneer 10/11 Telemetry Explanatory Almanac

Diverse Organic Molecules Discovered Surrounding A Newly Formed Star