Вадим Дудченко
Администратор портала

Comet C/2014 UN271 Bernardinelli-Bernstein, the largest comet ever discovered, was already exhibiting coma at heliocentric distances 23.8 and 21.2 AU, making it one of the most distant comets for which preperihelion activity has been directly detected, according to a new analysis of data from NASA’s Transient Exoplanet Survey Satellite (TESS).

Coadded images of comet Bernardinelli-Bernstein (C/2014 UN271) from 2018 and 2020, showing coma with a sunward asymmetry; coadded images from several Kuiper Belt objects and asteroids show examples of moving objects of similar brightness that are known to have no coma. Image credit: Farnham et al., doi: 10.3847/PSJ/ac323d.

Comet Bernardinelli-Bernstein was first observed by the Dark Energy Survey (DES) at a heliocentric distance of 29.3 AU in 2014, with additional observations through 2018.

But it was only discovered in 2021 when a focused trans-Neptunian object search of the DES data was done.

At 100 km (62 miles) across, comet Bernardinelli-Bernstein is the largest comet ever discovered by far, and it is farther from the Sun than the planet Uranus.

“Our new observations are pushing the distances for active comets dramatically farther than we have previously known,” said Dr. Tony Farnham, an astronomer in the Department of Astronomy at the University of Maryland.

In the new research, Dr. Farnham and his colleagues combined thousands of images of comet Bernardinelli-Bernstein collected by TESS from 2018 through 2020.

By stacking the images, they were able to increase the contrast and get a clearer view of the comet.

They spotted the hazy glow of dust surrounding the comet, proof that it had a coma and was active.

The size of the comet and its distance from the Sun suggests that the vaporizing ice forming the coma is dominated by carbon monoxide.

Since carbon monoxide may begin to vaporize when it is up to five times farther away from the Sun than comet Bernardinelli-Bernstein was when it was discovered, it is likely that the comet was active well before it was observed.

“We make the assumption that comet Bernardinelli-Bernstein was probably active even further out, but we just didn’t see it before this,” Dr. Farnham said.

“What we don’t know yet is if there’s some cutoff point where we can start to see these things in cold storage before they become active.”

“The ability to observe processes like the formation of a cometary coma farther than ever before opens an exciting new door for astronomers.”

“This is just the beginning. TESS is observing things that haven’t been discovered yet, and this is kind of a test case of what we will be able to find. We have the potential of doing this a lot, once a comet is seen, going back through time in the images and finding them while they are at farther distances from the Sun.”

The findings were published in the Planetary Science Journal.


Tony L. Farnham et al. 2021. Early Activity in Comet C/2014 UN271 Bernardinelli-Bernstein as Observed by TESS. Planet. Sci. J 2, 236; doi: 10.3847/PSJ/ac323d


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