A team of astronomers have presented the first polarimetric observations of interstellar comet 3I/ATLAS, finding that it has extreme negative polarization. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

On July 1, 2025, astronomers spotted an object moving through the Solar System at nearly twice the velocity of previous interstellar visitors ‘Oumuamua and Comet Borisov. The object was confirmed to be an interstellar comet with its own dusty coma, and suspected to be far larger than the previous two, with a estimated nucleus (the rocky part of the comet, excluding its coma) of around 5.6 kilometers (3.5 miles), and a possible "anomalous" mass of over 33 billion tons .

The astronomical community continued to track the object, kno

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