The Hubble Space Telescope, which has remained our eyes and ears, into the mysteries of deep space, is in no mood to disappoint even after three decades of its record service. The flying observatory has now revealed the largest icy comet nucleus ever seen by astronomers.

Dubbed C/2014 UN271 (Bernardinelli-Bernstein), the massive comet is nearly 128 kilometers wide and weighs a staggering 500 trillion tons. The nucleus of this mega-comet is 50 times larger than found at the heart of most known comets and its mass is a hundred thousand times greater than the mass of a typical comet found much closer to the Sun.

The previous record was held by C/2002 VQ94, which had a 96-meter-wide nucleus discovered in 2002 by the Lincoln Near-Earth Asteroid Research (LINEAR) project. The findings by Hubble have been published in the new study in The Astrophysical Journal Letters.


The comet was discovered by astronomers Pedro Bernardinelli and Gary Bernstein from the archival images of the Dark Energy Survey at the Cerro Tololo Inter-American Observatory in Chile and was first observed in November 2010. At the time, the comet was nearly 4.8 billion kilometers away from the Sun.

“This comet is literally the tip of the iceberg for many thousands of comets that are too faint to see in the more distant parts of the solar system. We’ve always suspected this comet had to be big because it is so bright at such a large distance. Now we confirm it is,” David Jewitt, a professor of planetary science and astronomy at the University of California said.

Nasa said that the comet at the moment is too far away for Hubble to clearly analyse it, so the astronomers made a computer model of the surrounding coma and adjusted it to fit the Hubble images. It is worth mentioning that the Hubble data show a bright spike of light at the nucleus’ location. Hui and his team compared the brightness of the nucleus to earlier radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. This combined data constrains the diameter and the reflectivity of the nucleus.


Astronomers said that the comet has been falling toward the Sun for well over 1 million years and is coming from the Oort Cloud outside our Solar System, which is the nesting ground of trillions of comets. The comet has an elliptical orbit around the Sun, but given its staggering distance, it takes it 3 million years to go around the Sun.

Nasa said that the comet is now less than 3.2 billion kilometers from the Sun, falling nearly perpendicular to the plane of our solar system. In spite of the massive distance, the comet is experiencing a temperature of 175 degrees Celsius, enough to vapourise it and give it its glowing tail.

The Oort Cloud still remains a theory because the innumerable comets that make it up are too faint and distant to be directly observed. The comets in this region didn’t actually form so far from the Sun; instead, they were tossed out of the solar system billions of years ago by a gravitational “pinball game” among the massive outer planets, when the orbits of Jupiter and Saturn were still evolving.

“Comet Bernardinelli-Bernstein provides an invaluable clue to the size and distribution of comets in the Oort Cloud and hence its total mass. Estimates for the Oort Cloud’s mass vary widely, reaching as high as 20 times Earth’s mass,” Nasa said.


India today