A new study has attempted to pin down the properties of interstellar comet 3I/Atlas, finding it is "anomalously massive" at around 33 billion tons. 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, which was confirmed to be an interstellar comet with its own dusty coma, and suspected to be far larger than the previous two, with a then-estimated nucleus (the rocky part of the comet, excluding its coma) of around 5.6 kilometers (3.5 miles).

Sizing comets is a tricky business, primarily because to do so, you need to distinguish the comet from its coma. As

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