Comet Archives

This artist’s concept depicts a near-Earth asteroid with an elongated orbit. A few objects such as these can exhibit significant perturbations in their motion around the Sun and, like the asteroid 1998 SH2, could turn out to be regular comets with a weak tail and coma (the gas and dust around a comet’s nucleus). Credit: NASA/JPL-Caltech

NASA Study Finds Near-Earth Asteroid Is Actually Comet

by Keith CowingJuly 19, 2026July 19, 2026

[NASA] The object looks like an asteroid but moves like a comet, so astronomers used some of the most powerful observatories on the planet to confirm its identity.

Candidate component r55 with period of P0 = 18.87 s in 1050–1140 MHz (a) and r952 with period of P0 = 16.58 s 1300–1450 MHz (b) in our search. The layout of the two panels are the same as Figure 1. -- [astro-ph.IM]

SETI & Technosignatures

Periodic Radio Technosignature Search Toward 3I/ATLAS With FAST

by Keith CowingJuly 13, 2026July 13, 2026

[astro-ph.IM] 3I/ATLAS, the third confirmed interstellar object discovered in the Solar System, provides a unique opportunity for targeted technosignature searches.

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

Comets and Asteroids

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.

[TOP] Example observations of (2060) Chiron for survey/telescopes (left) ATLAS, (middle) ZTF, and (right) LCO/LOOK. [BOTTOM] Example observations of 103P/Hartley 2 for survey/telescopes (left) ATLAS, (middle) ZTF, and (right) LCO/LOOK. -- astro-ph.EP

Comets and Asteroids

Multi-year Ground-Based Survey Photometry of Active Comet 103P/Hartley 2 and Centaur (2060) Chiron: A Tale of Two Comets in the Pre-LSST Era

by Keith CowingJuly 5, 2026July 5, 2026

[astro-ph.EP] Comets and Centaurs trace the evolution of trans-Neptunian objects (TNOs) into the inner solar system.

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).

Images of comet 7P/Pons–Winnecke taken during a period of quiescence (left, taken at 2021 July 28 10:25:23 UTC) and the 2021 July 10 outburst (right, taken at 2021 July 10 02:29:58 UTC). The outburst ejecta is apparent as distortions in the observed surface brightness as compared to the ambient coma image. The bottom row shows the logarithmically scaled data with contours spaced every 0.5 mag/arcsec2 . A color bar provides the surface brightness scale. Images are oriented with north up, and east to the left. -⊙ represents the anti-solar direction and V is the heliocentric velocity direction, and a linear scale bar is shown. The blue arrows highlight two linear features as a result of the ejecta distribution that are meeting at a near-right angle in front of the nucleus. -- astro-ph.EP

Uncategorized

A Look At Eight Outbursts Of Comet 7P/Pons-Winnecke

by Keith CowingJune 26, 2026June 26, 2026

Cometary outbursts may be used as a means to infer the physical processes occurring on cometary nuclei. To that end, we studied eight outbursts of comet 7P/Pons-Winnecke identified between 2021 […]

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 […]