Comet ATLAS (also known as C/2019 Y4) made headlines last year when it was predicted to make its closest approach to the sun on May 31, 2020 at a distance of 23.5 million miles (37.8 million kilometers). Since it was increasing in brightness, it would have been about as bright as the moon and visible to us on Earth by using a small telescope or a pair of decent binoculars. However, just weeks before the highly anticipated sky show, astronomers announced that the comet had broken apart.
Astronomers did get the chance to study the comet while it passed through space and they have revealed new information regarding its origins. It is believed that the comet was a fragment of a much larger body that people living on Earth about 5,000 years ago might have witnessed traveling through space – specifically those living in Eurasia and North Africa.
Astronomer Quanzhi Ye from the University of Maryland in College Park analyzed data collected by NASA’s Hubble Space Telescope and found that Comet ATLAS was a piece that broke off a larger comet that came within 23 million miles from the sun at the end of the Stone Age. Furthermore, it followed the same “railroad track” as a comet that was witnessed back in 1844 which indicates that the two of them were probably fragments that came from the same parent comet. Scientists won’t be able to study ATLAS’ sibling for quite a while as it won’t make another approach until the 50th century.
Ye described Comet ATLAS as being “weird” based on the fact that it broke apart more than 100 million miles from the sun. “If it broke up this far from the Sun, how did it survive the last passage around the Sun 5,000 years ago? This is the big question.” “It’s very unusual because we wouldn’t expect it. This is the first time a long-period comet family member was seen breaking up before passing closer to the Sun.” “This emphasizes its strangeness.”
By observing the comet breaking apart – one piece disintegrated in just days while another part lasted for several weeks – the researchers were able to determine that “…part of the nucleus was stronger than the other part.” (Pictures of Comet ATLAS breaking apart can be seen here.)
They went on to explain that the ejected materials could have caused the comet to spin so fast that it ended up breaking apart. Another theory was that it contained super-volatile ices that exploded, causing the comet to tear apart. “It is complicated because we start to see these hierarchies and evolution of comet fragmentation. Comet ATLAS’ behavior is interesting but hard to explain.”
Their research was published in the Astronomical Journal where it can be read in full.
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