(ORDO NEWS) — Comet Bernardinelli-Bernstein, identified in 2021, is officially the largest comet ever observed.
A new paper published on arXiv and now accepted for publication in Astronomy and Astrophysics Letters knocks Hale-Bopp out of first place. Comet Hale-Bopp was discovered in 1995 and became visible to the naked eye in 1996, and its diameter was about 74 kilometers.
Comet Bernardinelli-Bernstein, also known as comet 2014 UN271, is currently estimated to be about 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 discovered the comet in the Dark Energy Research dataset.
The images showing the comet are from 2014, so that year is the comet’s official scientific designation. Bernardinelli and Bershtein noticed that the tiny dot was moving as they studied images from subsequent years.
At the time, the comet was too far away for the researchers to accurately estimate its size, although they could say it was probably quite large. The comet originates from the Oort Cloud, a cloud of chunks of ice and rock hovering at the edge of the solar system. Its orbit is a light year away from the Sun – and the orbit takes 5.5 million years to complete.
The comet is currently moving towards the inner part of the solar system. It will approach Earth in 2031, although not too close for comfort: the comet will remain outside the orbit of Saturn, reports Live Science.
The new study was led by Emmanuel Lellouche, an astronomer at the Paris Observatory, and 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 AU. (AE is the distance between the Earth and the Sun, which is about 150 million kilometers).
The researchers studied the microwave radiation emanating from the comet. From these wavelengths of reflected light, the team could determine the comet’s size. This is the largest distance at which this type of measurement has been made before, the researchers write in their new paper.
The researchers added that it’s very interesting to take measurements while the comet is still so far away because the Bernardinelli-Bernstein will likely be much smaller by the time it approaches Earth. As a comet approaches the Sun, its tail of dust and gas will expand and its main body will melt and contract.
The comet will not be visible to the naked eye, but scientists expect to learn a lot about Oort Cloud objects from this visitor.
Large telescopes such as the Atacama Array will allow scientists to learn more about the comet’s chemical composition as it approaches, Lellouche and colleagues wrote. They should also learn more about the comet’s temperature, rotation and shape soon.
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