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When scientists first spotted Comet ATLAS last year, they hoped it would be the brightest comet of the decade. Then the frozen piece unexpectedly fell apart.
Now, astronomers believe they may have figured out two mysteries surrounding why the comet suffered such an untimely demise. The nucleus, or heart, of Comet C / 2019 Y4 (ATLAS) ruptured between April 20 and 23, 2020, when the comet was 91 million miles (146 million kilometers) from Earth, about the same distance as the sun. Stranger still, not all the pieces broke at the same rate.
Oddly enough, scientists believe that ATLAS broke away from an ancestor comet that made a relatively close passage to Earth about 5,000 years ago. This huge comet approached just 23 million miles (37 million km) from the sun, closer than the orbit of Mercury, and could have been noticed by humans at the time.
Related: New comet ATLAS is getting really bright, really fast
“The comet could have been a spectacular sight for the civilizations of Eurasia and North Africa at the end of the Stone Age,” NASA officials said. written in a press release. But coming to this conclusion – in the absence of any written or illustrated record of the Heavenly Visitor – required some science detective.
A new study suggests that ATLAS follows the same orbital path as another comet seen in 1844 that survived its journey around the sun – a likely sister of the 2020 visitor. (The link was first noted by l ‘amateur astronomer Maik Meyer and confirmed by scientists.) Comet families are not unusual in science, a famous example being the short-lived fragments of Cobbler-Levy 9 which crashed into Jupiter in 1994.
ATLAS, however, looks “bizarre” according to the study’s lead author, astronomer Quanzhi Ye of the University of Maryland at College Park. He couldn’t understand why ATLAS has disintegrated while its mother comet had stayed together while passing the sun at a much closer distance.
“If it broke so far from the sun, how did it survive the last pass around the sun 5,000 years ago? That’s the big question,” Ye said in the NASA statement. . “This is very unusual because we weren’t expecting it. This is the first time that a family member of a long-lived comet has been seen to shatter before approaching the sun.”
Observe the fragments suggest that parts of ATLAS exhibited different structures or compositions, especially because one fragment of the comet dissolved within days while another lasted for several weeks. “It tells us that one part of the core was stronger than the other,” Ye said.
The authors have a few theories as to why the fragments had different lifespans, which in turn may be linked to the unknown composition of the ancient mother comet. One theory is that “ejected matter streamers” tore the comet apart with centrifugal forces, NASA said. Or maybe volatile ice blew up the weaker room like “an exploding aerial frame,” the agency continued.
Although ATLAS is no longer, his brother should still be visible from Earth eventually, but only in the distant future. The best estimate of astronomers is that it will pass through our planet in the 50th century.
A research-based article was published on July 21 in The astronomical journal.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
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