Comet ATLAS could be a remnant of a mysterious ancient fireball

Comet ATLAS could be the remnant of a “mysterious fireball” that swept less than 37 million kilometers from the sun 5,000 years ago, according to a new study.

During its most recent appearance in the Inner Solar System in early 2020, Comet ATLAS met untimely death when it disintegrated into a cascade of chunks of ice, according to the University of Maryland team. at College Park.

In this new study, using data from the Hubble Space Telescope, they discovered that it had broken away from an ancient giant comet that last arrived in the inner solar system 5,000 years ago.

This same comet gave birth to at least two smaller comets, ATLAS which visited in 2020, and its sister, the Large Comet which was last seen from Earth in 1844.

When the mother comet visited the inner solar system, it approached the sun as Mercury, about 23 million kilometers away, and reportedly presented a “spectacular sight” to the Stone Age civilizations in Eurasia and North Africa, according to the team.

There is no historical record of the fireball crossing the sky as the comet passed Earth around 3000 BC.

However, the Maryland team speculated on what our ancestors may have seen as they explored the path their child, ATLAS, took around the sun in 2020.

They also compared it to the path taken by the Great Comet of 1844 – a bright comet with the naked eye seen by astronomers in the Victorian era.

ATLAS (C / 2019 Y4) was first detected by the Land Asteroid Impact Alert System (ATLAS), operated by the University of Hawaii in 2019.

Early predictions, based on how quickly it got brighter, suggested it could reach magnitude zero, making it easily visible to the naked eye.

However, this was not to be the case, as on March 22, 2020, the comet began to disintegrate under the heat of the sun, shattering into small fragments in May 2020.

Now, in a new study exploring its origins, University of Maryland astronomer Quanzhi Ye has found it to be a shattered piece of a much larger ancient comet.

Ye and his colleagues confirmed that ATLAS originated from this larger, unnamed comet that last entered the inner solar system 5,000 years ago, due to the orbital path.

Essentially, ATLAS follows the same orbital “train tracks” as that of a comet seen in 1844, meaning the two are likely siblings of the same parent comet that broke away centuries earlier, according to l team behind the study.

The “Great Comet” of 1844 was almost as bright as the brightest star with the naked eye, Sirius, but will not be seen in the inner solar system until the 50th century.

The link between the two comets, ATLAS and the Great Comet of 1844, was first noted by German astronomer and comet hunter Maik Meyer.

Such families of comets are common, according to Ye, and the most dramatic visual example was in 1994 when doomed comet Shoemaker-Levy 9 (SL9) was dragged into a chain of pieces by Jupiter’s gravitational pull.

This “train of comets” was short-lived, he explained, because it fell piece by piece on Jupiter in July 1994, without any evidence of its existence remaining after its fall.

But Comet ATLAS is just “weird,” says Ye, who observed it with Hubble at the time of the snap in May 2020.

Unlike its supposed parent comet, ATLAS disintegrated when it was further from the sun than Earth, at a distance of over 100 million miles.

It was much farther than the distance her parent passed the sun, which “underscores her oddity even more,” Ye said.

“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, ”said the study’s author.

“It’s very unusual because we wouldn’t expect it. This is the first time that a member of the long-period comet family has been seen to shatter before approaching the sun.

Being able to observe the comet’s breaking up fragments with a telescope like Hubble gave clues to how the mother comet was first put together, Ye said.

The conventional wisdom is that comets are fragile agglomerations of dust and ice, and that they can be “lumpy, like grape pudding.”

After a year of analysis, Ye and his colleagues discovered that one piece of ATLAS disintegrated within days, while another piece lasted for weeks.

“This tells us that one part of the core was stronger than the other part,” he said.

One possibility is that streamers of ejected matter spun the comet so quickly that centrifugal forces tore it apart.

An alternate explanation is that it has so-called super-volatile ice cream that just blew up the room like an exploding aerial firework display.

“It’s complicated because we’re starting to see these hierarchies and the evolution of comet fragmentation. The behavior of comet ATLAS is interesting but difficult to explain. ‘

The results were published in the Astronomical Journal.