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OUT OF THIS WORLD | What's Up In Space - a weekly look at the biggest news coming down to Earth from space

Newfound inbound comet is farthest active comet ever spotted

Scott Sutherland
Meteorologist/Science Writer

Thursday, September 28, 2017, 17:52 - A brand new comet has been spotted by the Hubble Space Telescope, and remarkably, even though it is still far enough away from the Sun that its water ice would be as hard as rock, it is already showing signs of activity.

That makes this new comet, called C/2017 K2 (PANSTARRS), or just K2 for short, the farthest active comet astronomers have ever seen - at a distance of 1.5 billion miles from the Sun, which is beyond the orbit of Saturn.

Discovered in May in 2017, using Hawaii's Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), astronomers used the Hubble Space Telescope to get a better look at "K2".

Hubble revealed that the comet's coma - the gassy, dusty "atmosphere" that surrounds the comet's solid nucleus - was already around 80,000 miles across. That's roughly the diameter of the planet Saturn!

Comet "K2" and its Saturn-sized coma. Credit: NASA, ESA, and D. Jewitt (UCLA)

In contrast, the solid nucleus of K2 is probably more like 12 miles wide.

"K2 is so far from the Sun and so cold, we know for sure that the activity - all the fuzzy stuff making it look like a comet - is not produced, as in other comets, by the evaporation of water ice," David Jewitt, an astronomer at UCLA. said in a Hubble news release.

"Instead, we think the activity is due to the sublimation [a solid changing directly into a gas] of super-volatiles as K2 makes its maiden entry into the solar system's planetary zone. That's why it's special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock."

Related Video: Three comets swinging by Earth in 2017 and 2018.

According to Jewitt, this activity is likely the comet "shedding its outer skin" of volatile gases, such as oxygen, nitrogen, carbon dioxide and carbon monoxide, as those gases are heated by light from the distant Sun.

This schematic of the solar system shows the position and orbit of Comet C/2017 K2 (PANSTARRS). Credit: NASA, ESA, and A. Feild (STScI)

"Most comets are discovered much closer to the Sun, near Jupiter's orbit, so by the time we see them, these surface volatiles have already been baked off," he said. "That's why I think K2 is the most primitive comet we've seen."

In fact, based on the observations that Jewitt and his team gathered, they believe that K2 is a pristine remnant of the primordial solar system, which has already been traveling for several million years, and that this is its first and only trip through the solar system. Also, after looking back in the image archives from the Canada France Hawaii Telescope, they estimated that K2 has already had its dusty coma for at least 4 years - since it was over 2 billion miles away, which would put it between the orbits of Uranus and Neptune.

It will take K2 another 5 years to reach its closest point to the Sun, which will bring it to just beyond the orbit of Mars in the year 2022. Since its activity will increase during its approach, and it will likely sprout a tail as it gets closer to the Sun, this represents a great opportunity for astronomers to study a new comet in detail.

"We will be able to monitor for the first time the developing activity of a comet falling in from the Oort Cloud over an extraordinary range of distances," Jewitt said.

Sources: Hubble | NASA

Watch Below: Simulating life on Mars: NASA mission comes to end

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