New Largest Comet Ever Observed “Wings its way” Toward the Interior Solar System

Astronomers officially hailed Bernardinelli-Bernstein as the biggest comet ever observed, hitting a new record after it was identified in 2021.

According to recent observations, the 85-mile-wide comet is winging its way toward the interior of the solar system, but will remain outside Saturn's orbit.

At the time the comet was first discovered by University of Pennsylvania cosmologist Gary Bernstein and University of Washington postdoctoral scholar Pedro Bernardinelli, it was too distant that the researchers missed to "get a good gauge" at its size. The new record bumps the Hale-Bopp comet to the pedestal, Space.com reported.

Hale-Bopp was first discovered in 1995 and was about 46 miles (74 kilometers) across. Comet Bernardinelli-Bernstein, also known as comet 2014 UN271, has now been calculated to be about 85 miles (137 km) across, according to the astronomy news website.

Largest detected Oort-cloud object

The recently announced comet moving rapidly through the Oort cloud - a vast scrapyard of icy rocks, billions of miles from Earth, is "remarkable in at least three respects", as per the preprint website arXiv.

"First, it was discovered inbound as far as ~29 au from the Sun (with prediscovery images up to ~34 au); Second, it showed cometary activity already at almost 24 au; and third, its nuclear magnitude (Hr ~ 8.0) indicates an exceptionally large object," authors wrote.

The comet is expected to get closest to Earth in 2031, though not too close for comfort, LiveScience reported.

"The object appeared to be headed our way, and it even had a glowing tail, or "coma", behind it - a clear indication of an icy comet approaching the relatively warm inner solar system," the website adds.

"We owe our current view of the large, distant comet to the Dark Energy Survey (DES) - a project to study the expansion of the universe, which ran between August 2013 and January 2019."

Invisible in the naked eye

Astrononer Emmanuel Lellouch at the Observatoire de Paris used data from the Atacama Large Millimeter Array in South America, taken in August 2021 when the comet was 19.6 AUs away.

The team was able to infer the comet's size throught the reflected light wavelengths coming off the comet's bulk. "This is the longest distance at which this type of measurement has been done before," the researchers wrote in their new paper.

"It's exciting to get a measurement while the comet is still so distant," the researchers added, "because Bernardinelli-Bernstein will likely shrink significantly by the time it gets closer to Earth."

Moreover, as it gets closer to the sun, its tail of dust and gas will expand, while its main body will melt and shrink.

The comet is expected to be invisible to the naked eye, as Hale-Bopp was at its closest approach. However, researchers hope to gain more understanding about the Oort cloud objects through it.

"Large telescopes like the Atacama Array will allow scientists to learn more about the chemical composition of the comet as it passes," Lellouch and his colleagues wrote, noting that they should also know more soon about the comet's temperature, spin and shape.