NASA has spotted a record-breaking large comet heading closer to Earth.
Its icy cores are larger than ever – about 80 miles in diameter, and 50 times larger than the cores of most known comets. It is also believed to have a mass of about 500 trillion tons – a hundred thousand times greater than the mass of a typical comet found near the Sun.
And the thing, known as C/2014 UN271 (Bernardinelli-Bernstein), is fast heading in that direction. It travels at 22,000 miles per hour, moving from the edge of the solar system toward its center.
However, we must be completely safe. The comet won’t get closer than a billion miles from the sun — even farther than Saturn — and it won’t happen until 2031.
This object has been known since November 2010, at which point it was 3 billion miles from the Sun or the distance to Neptune. Since then, researchers have been looking to understand more about it, using telescopes in space and on Earth.
As part of this research, scientists used NASA’s Hubble Space Telescope to estimate the comet’s size, revealing its massive size.
The researchers thought the comet should be at least reasonably large, given how active it is even at a long distance from the sun. But the new data came from five images taken earlier this year by Hubble.
However, measuring the size is not as simple as taking those pictures. Scientists must distinguish the hard core in the middle from the large dusty coma that wraps around it, too far for the images to be clear enough to tell the difference.
Instead, the scientists looked at the bright spot of light that characterizes the nucleus at the comet’s core. Then they made a computer model of the coma surrounding it and adjusting it in line with the images.
Taken together, these images allowed for an understanding of scale. Researchers can put out the coma’s glow and leave only the hard core behind.
The data also reveals more about the comet, when combined with other radio observations taken from the ALMA telescope in Chile. The sizes were similar, but the data suggests that the comet’s surface is darker than previously thought – one researcher described the object as “large and blacker than coal.”
The comet is billions of years old, and as such is a relic from the early days of our solar system. It came from the Oort cloud at the edge of our planet’s neighborhood, and has been receding toward our sun for at least a million years.
The comets of the Oort cloud are believed to have begun their lives near our star. But in its early days, they were thrown to the fringes of the solar system during the solar system’s first, chaotic days, when massive exoplanets were still finding their orbits.
The new record-breaking object could help us better characterize the Oort cloud, which is 5,000 times as far from our sun as we are, and so hard to see directly that it remains a theory. By studying Comet Bernardinelli-Bernstein, researchers can understand how and how large objects in that distant cloud, for example, increase in size.
The results are reported in a new paper, “The Hubble Space Telescope Discovery of the Nucleus of Comet C/2014 UN271 (Bernardinelli-Bernstein)”, published in Astrophysical Journal Letters.