Comet Bernardinelli-Bernstein as Big as 15 Mount Everests, Experts Say; Will It Pass By Earth By 2031?

Scientists have verified the finding of the biggest comet ever seen and revised its measurements to around 85 miles in diameter. It is nearly double the size of the notorious comet Hale-Bopp, which held the previous record.

The ice monster is C/2014 UN271 (Bernardinelli-Bernstein), or BB, which is currently speeding toward the Sun and will make its closest approach on January 21, 2031. The comet, which is also almost 15 times the size of Mount Everest, provides an unparalleled glimpse of a massive comet from the furthest regions of our solar system.

Researchers uploaded the study, "Size and Albedo of the Largest Detected Oort-Cloud Object: Comet C/2014 Un 271 (Bernardinelli-Bernstein)," on the preprint server arXiv and has been accepted for publication in the journal Astronomy and Astrophysics Letters.

Bernardinelli-Bernstein (C/2014 UN271) Is the Biggest Comet Ever Found

Comet Bernardinelli-Bernstein is the biggest Oort Cloud object yet discovered, measuring nearly twice as huge as comet Hale-Bopp. C/2014 UN271 is also bigger than Comet Sarabat, found in 1729 and had a nucleus diameter of about 62 miles (100 kilometers).

The biggest comet experts have previously measured relatively precisely is Hale-Bopp, which measures 464 miles (746 kilometers), IFL Science said. Despite the estimate being on the lower end of the initial range, C/2014 UN271 is still larger than all but one of the active Centaurs, which orbit between Jupiter and Neptune and occasionally emit comet-like outbursts.

KENNEDY SPACE CENTER, FL - MARCH 10: The comet Hale-Bopp appears in the sky over Merrit Island, Florida, early 10 March, south of the Kennedy Space Center. The comet can be seen from late March to the beginning of April, before disappearing for the next 2,400 years. The comet is an occasional visitor from the outer solar system. GEORGE SHELTON/AFP via Getty Images

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Lellouch and co-authors used the Atacama Large Millimeter Array to study C/2014 UN271 at four wavelengths between 1 and 2 millimeters, avoiding the ones where dust is brightest. As a result, they may conclude that the contribution from comet dust was very definitely small - practically everything was coming from the nucleus itself.

The brightness of the different wavelength bands shows a characteristic composition of comets that reflect 5% of the light they receive. Lellouch and co-authors calculated that Bernardinelli-Bernstein would have to be 8510 miles (13717 kilometers) broad to produce this much radiation. The ambiguity stems from a lack of knowledge about the comet's sphericality and residual uncertainty regarding its reflectance.

Latest Data to Be Used For BB's Close Approach to Sun

The researchers quantified BB's surface brightness from a distance of 20 astronomical units, roughly twice as far as Saturn-the most distant measurement of a comet's albedo ever undertaken. Vice News said all of these data will aid scientists in preparing for BB's closest approach to the Sun in 2031.

While this is unlikely to be visible to the human eye from Earth, scientists will undoubtedly direct advanced observatories, such as the recently launched James Webb Space Telescope, towards this massive object as it rushes through the sky, where it might lose half of its mass in the Sun's brightness. Given that BB's orbit is predicted to be completed only every three million years or more, this is a once-in-a-lifetime opportunity to observe it up close.