Comet Bernardinelli-Bernstein confirmed as largest ever observed

(ORDO NEWS) — Comet Bernardinelli-Bernstein, discovered in 2021, is officially the largest comet ever observed.

The new record, published on the preprint site arXiv and now accepted for publication in the journal Astronomy and Astrophysics Letters, swept Comet Hale-Bopp out of first place.

Hale-Bopp was discovered in 1995 and became visible to the naked eye in 1996; its size was about 46 miles (74 kilometers) across. Bernardinelli-Bernstein, also known as comet 2014 UN271, is estimated to be about 85 miles (137 km) across.

Comet Bernardinelli-Bernstein is named after its discoverers, University of Pennsylvania cosmologist Gary Bernstein and University of Washington graduate student Pedro Bernardinelli, who first spotted the comet in the Dark Energy Survey dataset.

Images of the comet refer to 2014, which is why this year is indicated in the official scientific designation of the comet. Bernardinelli and Bershtein noticed the movement of the tiny dot when they studied photographs from subsequent years.

At that time, the comet was too far away for the researchers to accurately determine its size, although they could say that it was most likely quite large. The comet hails from the Oort cloud, a cloud of chunks of ice and rock that hangs at the edge of the solar system. Its orbit passes at a distance of a light year from the Sun, and it takes 5.5 million years.

The comet is currently heading deep into the solar system. It will come closest to Earth in 2031, but not too close: the Comet will remain outside the orbit of Saturn, reports Live Science.

The new study, led by Emmanuel Lellouche, an astronomer at the Paris Observatory, used data from the Atacama Large Millimeter Array in South America taken in August 2021 when the comet was at a distance of 19.6 AUs.

(AU is the distance between the Earth and the Sun, which is approximately 93 million miles or 150 million kilometers). The researchers studied microwave radiation emanating from the main mass of the comet.

From these reflected wavelengths of light, the team was able to determine the size of the comet. This is the largest distance at which such measurements have previously been made, the researchers write in their new work.

It’s very interesting to get the measurements while the comet is still so far away, the researchers added, because comet Bernardinelli-Bernstein is likely to be much smaller by the time it approaches Earth. As a comet approaches the Sun, its tail of dust and gas will expand, while its main body will melt and shrink.

The comet won’t be visible to the naked eye like Hale-Bopp did during its closest approach, but scientists expect to learn a lot about Oort cloud objects.

Large telescopes, such as the Atacama Array, will allow scientists to learn more about the comet’s chemical makeup during its flyby, write Lellouche and colleagues. In addition, they will soon be able to learn more about the temperature, rotation and shape of the comet.

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