Mega comet inbound from Oort Cloud

Curved lines showing solar system plus arc of new mega comet by Saturn's orbit.
View full-sized image. | The newly discovered mega comet, 2014 UN271, is currently diving from the outer solar system. At its closest to our sun, it’ll come close to the orbit of the outer planet Saturn in 2031. Image via NASA.

Don’t worry, but a huge comet is headed toward our sun. Scientists found it while studying old images from 2014 to 2018 taken for the Dark Energy Survey. Two University of Pennsylvania astronomers, Pedro Bernardinelli and Gary Bernstein, spotted the object heading inward from the Oort Cloud, possibly from as far as half a light-year away. Many have been calling it a mega comet.

The object was originally designed 2014 UN271. It’s now been officially named Comet Bernardinelli-Bernstein, for its discoverers.

It’s thought to be the largest comet yet discovered, possibly as big as a dwarf planet. It’s still far away and hard to see, but the current estimate suggests its nucleus, or core, is between 62 to 230 miles (100 to 370 km) in diameter. Whoa! That’s big for a comet.

The mega comet is not coming very close to us. It’ll make its closest approach in 2031, when it’ll sail just outside of the orbit of our sun’s 6th planet, Saturn. Saturn’s orbit is some nine and a half times farther from the sun than Earth’s orbit. So there’s no danger to us here.

Pedro Bernardinelli announced the discovery on Twitter on June 19, 2021.

Mega comet will near Saturn by 2031

The scientists scoured the survey images and discovered 2014 UN271 moving from 29 astronomical units, or AU (1 AU is the distance between Earth and the sun), to 23 AU. At its closest approach, 2014 UN271 will come within about 10 AU to the sun, which is in the realm of Saturn. Scientists didn’t find just this mega comet, though. The full search of the six years of survey data for trans-Neptunian objects turned up more than 800 objects.

Pixelated large white dot in gray background, labeled Signal.
The signal within the noise. This is the mega comet or dwarf planet-sized object labeled as a signal. The scientists examined old images to find 2014 UN271 as it lumbers inward toward the sun. Image via Pedro Bernardinelli.

Is 2014 UN271 the largest comet yet?

So the current estimate is that 2014 UN271 is between 62 to 230 miles (100 to 370 km) in diameter. If it turns out to be at the larger end of that range, it would be the largest Oort Cloud object yet discovered. (Comet Sarabat of 1729 is potentially the largest comet ever seen, with size estimates of 100 km, about 60 miles, in diameter. Comet Sarabat came much closer, within 3 AU of Earth, during its closest pass.) Whether 2014 UN271 takes on a traditional comet appearance and will grow a coma or a tail is yet to be seen. Scientists will have their eyes trained on the mega comet as it nears Saturn in 2031.

2014 UN271’s unusual orbit, which takes it from deep in the Oort Cloud straight in toward the sun, is hundreds of thousands of years long, the exact number yet to be determined. Despite its large size for a comet and nearness to us in 2031, astronomers do not expect the mega comet to brighten enough for us on Earth to see without powerful telescopes.

Scientists are working on a paper about the new object, which should be published in the new few months.

Bottom line: Scientists discovered a new object headed toward the inner regions of the solar system. 2014 UN271 may be the largest Oort Cloud object currently known.

Via Pedro Bernardinelli


June 24, 2021

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