4 billion year old relics from the early solar system on their way to us

This sequence shows how the core of Comet C / 2014 UN271 (Bernardinelli-Bernstein) was isolated from a huge shell of dust and gas surrounding the solid ice-cold core. To the left is a photo of the comet taken by NASA’s Hubble Space Telescope’s Wide Field Camera 3 on January 8, 2022. A model of the coma (center panel) was obtained by adjusting the surface brightness profile collected from the observed image on the left. This allowed the coma to be subtracted, revealing the point-like glow from the nucleus. Combined with radio telescope data, astronomers arrived at an accurate measurement of the core size. It’s not a small farm from something about 2 billion miles away. Although the core is estimated to be as large as 85 miles across, it is so far away that it cannot be solved by Hubble. Its size is derived from its reflectivity as measured by Hubble. The core is estimated to be as black as charcoal. The core area is taken from radio observations. Credit: NASA, ESA, Man-To Hui (Macau University of Science and Technology), David Jewitt (UCLA) Image Processing: Alyssa Pagan (STScI)

A huge comet – about 80 miles across, more than twice as wide as Rhode Island – is on its way to us at 22,000 miles per hour from the edge of the solar system. Fortunately, it will never get closer than 1 billion miles from the Sun, which is slightly further from Earth than Saturn; it will be in 2031.

Comets, among the oldest objects in the solar system, are icy bodies that were thrown out of the solar system without ceremonies in a game of gravity between the massive outer planets, David Jewitt said. The UCLA professor of planetary science and astronomy co-authored a new study of the comet in Astrophysical Journal Letters. The displaced comets took up residence in the Oort cloud, a large reservoir of distant comets that orbit the solar system out to many billions of miles into deep space, he said.

A typical comet’s spectacular multimillion-mile long tail, which makes it look like a sky rocket, contradicts the fact that the source at the heart of the fireworks is a solid ice core mixed with dust – essentially a dirty snowball. This huge, called Comet C / 2014 UN271 and discovered by astronomers Pedro Bernardinelli and Gary Bernstein, could be as large as 85 miles across.

“This comet is literally the tip of the iceberg for many thousands of comets that are too faint to see in the more distant parts of the solar system,” Jewitt said. “We’ve always suspected that this comet was going to be big because it’s so bright at such a great distance. Now we’re confirming that it is.”

This comet has the largest nucleus ever seen in a comet by astronomers. Jewitt and his colleagues determined the size of its core using NASA’s Hubble Space Telescope. Its core is about 50 times the size of most known comets. Its mass is estimated to be 500 trillion tons, one hundred thousand times larger than the mass of a typical comet found much closer to the sun.

“This is an amazing object considering how active it is when it’s still so far from the sun,” said lead author Man-To Hui, who took his doctorate from UCLA in 2019 and is now at Macau University of Science and Technology in Taipa, Macau. “We guessed the comet could be quite large, but we needed the best data to confirm this.”

So the scientists used Hubble to take five images of the comet on January 8, 2022, and incorporated radio observations of the comet into their analysis.

4 billion year old relics from the early solar system on their way to us

Diagram comparing the size of the icy, solid core of comet C / 2014 UN271 (Bernardinelli-Bernstein) with several other comets. Credit: NASA, ESA, Zena Levy (STScI)

The comet is now less than 2 billion miles from the sun and will return to its nesting site in the Oort cloud in a few million years, Jewitt said.

Comet C / 2014 UN271 was first observed serendipitally in 2010, when it was 3 billion miles from the sun. Since then, it has been intensively studied by terrestrial and space-based telescopes.

The challenge of measuring this comet was how to determine the solid core from the huge dusty coma – the cloud of dust and gas – that encloses it. The comet is currently too far away for its core to be visually dissolved by Hubble. Instead, the Hubble data shows a sharp bright spot at the location of the core. Hui and his colleagues then made a computer model of the surrounding coma and adjusted it to fit the Hubble images. Then they deducted the embers from the coma, leaving the core.

Hui and his team compared the brightness of the core with previous radio observations from the Atacama Large Millimeter / submillimeter Array, or ALMA, in Chile. The new Hubble measurements are close to the previous size estimates from ALMA, but convincingly suggest a darker core surface than previously assumed.

“It’s big and it’s more black than coal,” Jewitt said.

The comet has been falling towards the sun for well over 1 million years. The Oort cloud is thought to be the nesting site of trillions of comets. Jewitt believes that the Oort cloud extends from a few hundred times the distance between the sun and the Earth to at least a quarter of the way out to the distance of the nearest stars to our sun, in the Alpha Centauri system.

The comets of the Oort cloud were thrown out of the solar system billions of years ago by gravity from the massive outer planets, according to Jewitt. The distant comets only travel back toward the sun and the planets if their orbits are disturbed by the gravity of a passing star, the professor said.

The Dutch astronomer Jan Oort, first assumed in 1950, the Oort cloud is still a theory because the comets that make it up are too faint and distant to be observed directly. This means that the largest structure of the solar system is almost invisible, Jewitt said.


Comet 2014 UN271 the largest ever observed


More information:
Man-To Hui et al., Hubble Space Telescope Detection of Comet Core C / 2014 UN271 (Bernardinelli – Bernstein), The Astrophysical Journal Letters (2022). DOI: 10.3847 / 2041-8213 / ac626a

Provided by the University of California, Los Angeles

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