Comets from the deep cold of the solar system seldom survive their initial contact with the sun. One scientist believes he knows why: solar heating causes some of the cosmic snowballs to spin so quickly that they break apart.
This suggestion could help solve a decades-old mystery about what destroys many “long-period” comets, according to astronomer David Jewitt in a study on August 8. Long-period comets form in the Oort cloud, a sphere of icy objects on the outskirts of the solar system. Those who survive their first voyage around the sun only come around once every 200 years.
“These things are stable out there in the Oort cloud where nothing ever happens. When they come toward the sun, they heat up, all hell breaks loose, and they fall apart,”
David Jewitt
In 1950, Dutch astronomer Jan Oort hypothesised the Oort cloud as a cometary reservoir. He recognised that many of the comets that passed close to Earth were first-time visitors rather than repeat visitors. Something else was destroying the comets, but no one knew what it was.
One theory is that comets perish by sublimating all of their moisture as they approach the heat of the sun until they have nothing left. However, observations of comets that appeared to literally split apart into tiny chunks contradicted this. The problem was that those breakups were difficult to see in real time.
“The disintegrations are really hard to observe because they’re unpredictable, and they happen quickly,” Jewitt says.
He encountered this problem when attempting to watch Comet Leonard, a brilliant comet that put on a stunning display in winter 2021-2022. Jewitt has requested time on the Hubble Space Telescope to view the comet in April and June 2022. However, by February, the comet had shattered. “That was a wake-up call,” recalls Jewitt.
image credits: Flickr
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