(ORDO NEWS) — Astronomers using NASA‘s Hubble Space Telescope have confirmed the existence of the largest comet ever discovered to pass our Sun in the next decade.
Comets differ from asteroids in that asteroids are rocky objects while a comet is a ball of ice and dust. Comets are also known for the “tail” they leave behind and the glowing head, or nucleus, that appears as the comet approaches the Sun.
Astronomers have now determined the size of “the largest icy comet core ever observed.” Comet C/2014 UN271, also known as Comet Bernardinelli-Bernstein, is about 130 km wide. The mass of its nucleus is estimated at 500 trillion tons, which is about 100,000 times that of most comets.
In addition, the comet is moving at a speed of 35,500 km per hour and is approaching the Earth. When it approaches the Earth in 2031, it will not pose any danger, as it will be at a distance of about 1.5 billion km from the Sun, which is slightly more than the distance between Earth and Saturn. The results of the comet study were published Tuesday in The Astrophysical Journal Letters.
“This comet is literally the tip of the iceberg for the many thousands of comets that are too dim to observe in the more distant parts of the solar system,” David Jewitt, professor of planetary science and astronomy at the University of California and co-author of the study, said in a statement.
“We always suspected that this comet must be large because it is so bright at such a great distance. We now confirm that it is.”
First discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images in 2014, the comet was seen when it was more than 5 billion km from the Sun, an indication of its size.
“We assumed the comet might be quite large, but we needed the best data to confirm it,” said Man-To Hui of the Macau University of Science and Technology in Taipa, Macau, and lead author of the study.
To confirm the comet’s size, astronomers took pictures of it with the Hubble Space Telescope on January 8. But the difficulty in deciphering the images was to distinguish the nucleus of a comet from the surrounding cloud and tail, or coma. As the comet approaches the Sun, it heats up and the coma expands.
The comet is at a distance of about 3 billion km from the Sun, where the temperature is about minus 211 degrees Celsius, but this is enough for gas to sublimate from the surface of the comet and form a coma.
Hui and his colleagues then created a computer model of the comet and fitted it to the telescope images. They were then able to remove the coma, leaving only the core.
The team then took photographs of the core and compared its brightness with radio observations taken with the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile. The combined data allowed astronomers to determine its diameter, as well as what the core actually looks like.
“It’s big and it’s blacker than coal,” Jewitt said.
The comet takes 3 million years to orbit the solar system, and it reaches a distance of half a light year from the Sun.
Astronomers hope the comet will provide answers to questions about what comets from the Oort cloud are like. The Oort Cloud is thought to be a huge nest for trillions of comets; it has yet to be observed directly.
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