A team of astronomers has identified a comet at a distance of more than two thousand four hundred million kilometers from the Sun ; No other comet on the way to the Sun has been seen at such a great distance: beyond Saturn. And, in addition, with unique characteristics never seen in a body like this.
Called K2 , the orbit of this comet indicates that it comes from the Oort cloud , a huge, spherical region that contains billions of comets.
But the most striking thing about this comet is that it does not have a tail , at least that we can observe : it is not produced by the evaporation of water ice, since it is too far from the Sun, but it freezes like a rock.
“Because K2 is so far from the Sun and so cold, the water ice is frozen like a rock, and we know for sure that its activity is not produced by the evaporation of ice, as it happens in other comets “, according to the professor of Planetary Science and Astronomy, David Jewitt, who has led in analysis of comet observations.
Instead, substances such as nitrogen, carbon dioxide, and oxygen escape into the vacuum; even more volatile than water. That is to say: solar radiation is not strong enough to ‘throw’ these substances outside, whose molar mass is greater than that of water.
“The volatile substances on the surface of K2 are what absorb the heat from the Sun , so in a sense, the comet is shedding its outer layers ,” explains Jewitt.
But the comet is getting closer.
And in doing so, it heats up. In 2022, it will reach its closest distance from the Sun, which will be a point orbited by Mars.
“It should be more and more active when it gets closer to the Sun and, when this happens, it will form a tail,” says Jewitt.
The discovery allows scientists, for the first time, to monitor the activity of a comet at an extraordinarily far distance. These are the first signs of activity ever seen for a comment entering the planetary zone of our Solar System for the first time.
Why do we know that it is the most primitive comet we have ever seen?
Most comets are discovered much closer to the Sun, closer to Jupiter’s orbit , so the volatile gases on the surface have already been removed by the time scientists see them.
Therefore, scientists are sure that it is the oldest and most distant comet ever observed on its way into the Solar System.
Comet K2 is currently located beyond the orbit of Saturn, and has been traveling for millions of years from its home in the icy outer enclosure of the Solar System, the Oort cloud, where the temperature is approximately -262 degrees Celsius.
It was photographed by NASA’s Hubble Space Telescope and the researchers’ observations have been published in the Astrophysical Journal Letters.
It is also amazing that after finding K2 in the Hubble images, the researchers realized that the comet had already been photographed before. Specifically, in 2013, by the Hawaii Canada-France-Hawaii Telescope: Man-To Hui, a graduate student at the University of California, Los Angeles, identified K2 while searching for images in a Canadian archive. But it was so weak that no one realized it existed when the photos were analyzed.
David Jewitt. ‘A Comet Active Beyond the Crystallization Zone’ (2017). The American Astronomical Society. doi.org/10.3847/2041-8213/aa88b4
