The largest known comet has a black nucleus of 135 kilometers

Comet 2014 UN271 is 50 times larger than most of these known stars. Fortunately, it will not pass close to our planet in its orbit.


An analysis with the Hubble telescope of comet  2014 UN271 , which enters the Solar System from the Oort cloud, reveals that its nucleus spans about 135 kilometers and is blacker than carbon.

Research by David Jewitt, professor of planetary science and astronomy at UCLA, and published in the Astrophysical Journal Letters , further determines that the nucleus of this comet is about 50 times larger than that of most known comets . Its mass is estimated at 500 billion tons, one hundred thousand times greater than the mass of a typical comet that is much closer to the sun.

There is no danger

Fortunately, this object first discovered by astronomers Pedro Bernardinelli and Gary Bernstein in 2014 will never come closer than 1.5 billion kilometers from the Sun, which is slightly farther from Earth than Saturn; that will be in 2031.

“This comet is literally the tip of the iceberg of many thousands of comets that are too faint to see in more distant parts of the solar system,” Jewitt said. “We have always suspected that this comet had to be big because it is so bright at such a great distance. Now we confirm that it is.”

“This is an amazing object, given how active it is when it’s still so far from the Sun,” lead author Man-To Hui, who earned his Ph.D. from UCLA in 2019 and now works at the University of Science, said in a statement. and Macau Technology in Taipa, Macau. “We assumed that the comet could be quite large, but we needed the best data to confirm it.”

So the researchers used Hubble to take five photos of the comet on January 8, 2022, and incorporated radio observations of the comet into their analysis.

The comet is now less than 3 billion kilometers from the Sun and in a few million years it will return to its nesting place in the Oort cloud, Jewitt said.

The challenge in measuring this comet was how to determine the solid core of the huge dusty coma, the cloud of dust and gas, that enveloped it. The comet is currently too far away for Hubble to visually resolve its nucleus. Instead, the Hubble data shows a spike of bright light at the core’s location. Hui and his colleagues then made a computer model of the surrounding coma and adjusted it to fit the Hubble images . Then, they subtracted the glow from the coma, leaving the nucleus behind.

Hui and his team compared the brightness of the core with previous radio observations from the Atacama Large Millimeter/submillimeter Array, or ALMA, in Chile. The new Hubble measurements are close to previous ALMA size estimates, but convincingly suggest a darker core surface than previously thought. “It’s big and blacker than coal,” Jewitt said. (EuropePress)