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Blacker than coal astronomers saw the nucleus of a huge ancient comet
(ORDO NEWS) — Thanks to the latest Hubble images, astronomers have been able to determine the size of the nucleus of the giant comet Bernardinelli-Bernstein.
Comet C/2014 UN271 was first discovered in archival data from the Dark Energy Survey by cosmologists Gary Bernstein and Pedro Bernardinelli. Despite the huge distance, the object was very bright, so scientists immediately had suspicions about its colossal size.
Image of Comet Bernardinelli-Bernstein from the Dark Energy Survey, October 2017
By comparing the new Hubble images with a computer model and ALMA radio observations , a team of Japanese and American astronomers was able to confirm the comet's record-breaking size of 119 ± 15 kilometers.
Comets are one of the oldest objects in the solar system. These are lumps of ice, dust, and rocks that were ejected from the center of the system during the turbulent period of planetary formation. They did not leave our system forever, but began to fly in highly elongated orbits far from the center.
When comets fly into the region of the planets and get closer to the Sun, volatile substances begin to sublimate from their surface.
From this dust and gas, a coma and a tail are formed – the main visual difference between comets and asteroids. The main thing is that behind the luminous coma it is difficult to see the nucleus of the comet and determine the true size of the object. Therefore, scientists used computer simulations.
The team took five pictures of the comet taken by Hubble on January 8, 2022. If the comet were closer, the space telescope could see the nucleus. Instead of clear boundaries, the device recorded a "flash" of brightness in the region of the core.
Based on these data, scientists built a computer model of the comet's coma and "subtracted" its brightness from the telescope images. Only a core with a diameter of 119 ± 15 kilometers remained.
The images illustrate how scientists got rid of a bright coma. On the left is a Hubble image taken on January 8, 2022. In the middle is a computer model of a coma. On the right – the core, "cleared" from the coma
The team then compared the result with observations from the ALMA radio telescope in Chile. Size calculations from Hubble images matched ALMA data (137 ± 17 kilometers), but the surface of the core turned out to be much darker than scientists thought.
"It is huge and blacker than coal," commented one of the authors, David Jewitt , a professor of planetary science and astronomy at the University of California, Los Angeles.
The orbital period of C/2014 UN271 is about three million years. According to scientists, its aphelion, located at a distance of 40-55 thousand astronomical units from the Sun, the comet passed more than a million years ago and since then has been "falling" into the center of the system at a speed of about 35,405 kilometers per hour.
With a diameter of about 120 kilometers, Comet Bernardinelli-Bernstein is about 50 times larger than most comets known to us. Its mass reaches 500 trillion tons. These data will allow scientists to refine the size distribution of objects in the Oort cloud and its total mass.
The Oort Cloud is a hypothetical cluster of comets far beyond the Kuiper belt. Judging by the fact that comets come from all directions, the cloud forms a complete sphere around the solar system.
To understand its size: Voyagers will need about 300 more years to get to the inner edge of the cloud, and another 30,000 years to fly through it. Unfortunately, cloud objects are too faint to observe directly, so astronomers speculate by studying "guests" like comet Bernardinelli-Bernstein.
The giant comet will approach the Sun at a distance of about 1.6 billion kilometers, before reaching the orbit of Saturn. The closest approach will occur in 2031, so scientists have many years to observe.