Could the remains of a 'dead' comet still be in the solar system? Astronomers are still searching 6 years later.

The fate of a comet that was predicted to pass close to Earth remains a mystery five years after its dramatic breakup in the inner solar system — but some astronomers think a part of it might still be out there.

In early 2020, astronomers discovered the icy traveler, known as C/2019 Y4 ATLAS, and predicted it might provide a night-sky spectacle that would liven up everyone's COVID-19 pandemic lockdown: a comet visible with the unaided eye as it passed within 23 million miles (37.5 million kilometers) of the sun, or about one quarter of the distance at which Earth orbits our star. But then the comet broke into dozens of pieces, leaving would-be observers hanging — and leaving astronomers wondering whether there could still be anything substantial left of our ill-fated icy visitor.

A team of astronomers led by Salvatore A. Cordova Quijano of Boston University hoped to answer that question by scanning the autumn 2020 skies. And according to their recent paper in The Astronomical Journal, there may be a half-kilometer-wide chunk of the comet still in orbit, swinging back outward toward the cold darkness of the outer solar system.

Cordova Quijano and co-authors Quanzhi Ye and Michael S. P. Kelley scanned the skies in August and October of 2020, searching for any sign of the comet's remnants, to no avail. Observations with the Lowell Discovery Telescope (a 4.3-meter telescope in Arizona) and nightly images from the Zwicky Transient Facility (which makes a wide-view scan of the northern sky every two nights, looking for changing or short-lived objects like comets and supernovas) turned up nothing. But that doesn't mean there's nothing left of C/2019 Y4; it might just mean that what's left is smaller than the smallest fragment these telescopes would have been able to see, which comes out to about half a kilometer wide.

Besides solving an intriguing astronomical mystery, this new study of C/2019 Y4 offers some clues about what happens when comets break apart in the intense heat near the sun, as well as a chance to study the millennia-long decline of an ancient comet family (C/2019 Y4 might be a fragment of a larger comet which broke up thousands of years ago, according to a 2021 study).

In the case of C/2019 Y4, the answer to that second question may be yes: it's possible that a fragment of comet, less than half a kilometer wide, could still be tracing its larger parent's long path around the sun.

Source: www.space.com

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