The largest comet ever observed is on its way to Earth

Discovered the largest comet ever observed with modern telescopes: it will light up the skies for decades.

It's called Bernardinelli-Bernstein, and it was first seen back in 2014 by a telescope in the Atacama Desert, Chile. Confirmation of the discovery by the Minor Planet Center in Cambridge did not come until June 2021: the search for celestial bodies beyond Neptune by Dr. Pedro Bernardinelli, of the University of Washington, gave the world a new comet.

And it's not just any comet: it's so large that it's believed its size may be comparable to that of the immense light trail that crossed the Solar System in 1729, to date the largest comet ever seen by the human eye.

Comet Bernardinelli-Bernstein

The comet is billions of kilometers from the Sun, nearly twice the distance between our star and Neptune, beyond the darkness of deep space. Scientists estimate that the comet's nucleus measures 150 kilometers, making it the largest comet ever studied with modern telescopes.

Comet Bernardinelli-Bernstein comes from the Oort cloud, the spherical cloud of comets beyond the boundary of the Solar System from which so-called "long-period" comets, such as Hale-Bopp, the great comet of 1997, are believed to come.

According to Bernardinelli, whose observations were published in The Astrophysical Journal Letters, this is a primordial comet, presumably one of the oldest celestial objects that can happen to be seen from Earth, and almost certainly a long-period comet, which will be visible in our skies for years to come.

In the next ten years, Comet Bernardinelli-Bernstein will approach our planet: it will be visible until 2040 and probably beyond.

On its way to the Solar System

The comet is approaching. From the Oort Cloud, comet Bernardinelli-Bernstein will arrive very close to the Sun, just farther than Saturn is from its star.

On January 21, 2031, the comet will reach the closest point to our planet, about 1 billion and a half kilometers from the Sun: then, depending on the amount of gas released, it could be visible even with amateur instruments. It will be at its closest point to the Sun in more than three million years.

According to numerous observations following Bernardinelli's discovery, the comet was releasing enough gas to form the typical comet tail already when it was more than 3 billion kilometers from the Sun.

It would appear that the Bernardinelli-Bernstein comet contains enough volatile materials to be able to create a tail even at deep space temperatures: generally, comets begin to form their tails, with the sublimation of icy compounds into gas, near the Sun. The large comet that will illuminate the sky in the coming decades, however, has already begun to form its tail: this not only confirms the epic size of the newly discovered celestial body, but also gives an important clue about its origin.

The comet must be, in the words of Bernardinelli, an object "extraordinarily pristine", able to speak of the deepest secrets that lie at the edge of the Solar System. On the other hand, as Ben Montet, co-author of the paper with Bernardinelli, reminds us, "It's amazing what you can get from a relatively small number of photons".

The scientific community is in turmoil: some scientists are already thinking about how to reach it, when it will be close, with a spacecraft.