Scientists Discover Three Earth-Like Planets Orbiting an Ultracool Star

Monday, 02 May 2016 - 11:01AM
Alien Life
Monday, 02 May 2016 - 11:01AM
We may have just found the three most promising candidates in the search for alien life. Researchers have just found three potentially habitable planet in a nearby star system, only 12 parsecs (approximately 40 light years, or the same distance as the Kessel Run) away from Earth.

The star, called TRAPPIST, is an "ultracool dwarf," which refers to any star with lower temperatures (less than 2700 K). According to the core-accretion model of planet formation, given the small masses of these stars, we would expect to find many terrestrial planets surrounding them. In a new study, published in Nature, astronomers revealed their discovery of three exoplanets surrounding TRAPPIST, the first planets ever found orbiting this type of star. 

Two of the planets are in tight, close orbits around the star; a year on either planet passes in only three Earth days. But still, since the star is relatively dim, they only get as much sunlight as Venus (four times and two times the amount of starlight as Earth, respectively). They are technically too close to their star for liquid oceans to develop, but since they are tidally locked--meaning one side is permanently faced towards the star--their "night" side might be cool enough to support life.

The third planet is further away, and receives significantly less sunlight than Earth. It might even be colder than Mars, which would mean it's likely covered by a sheet of ice. But similar to near-Earth objects like Europa, there's still a possibility that it could host alien life, especially if there's a possibility of a subsurface ocean. 

We can't know for sure the composition of the planets, since we don't know their exact masses. However, the researchers claim that, judging from their Earth-like sizes and orbits, they are most likely rocky. And between their composition and positioning in relation to their star, they're perfect contenders in the search for alien life.

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"This is basically a paradigm shift," co-author Julien de Wit told Gizmodo. "If these planets have atmospheres, they really are the best places to look for life."
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And TRAPPIST has one other significant advantage: since the star system is so close to us, it will be much easier than usual to study these planets' atmospheres. We generally focus on brighter stars in the search for potentially habitable exoplanets, but the light tends to wash out the signal from the orbiting planets. Between the short distance and the dimness of the ultracool dwarf, we should be able to discover whether these planets have atmospheres fairly easily.

We don't have the technology to travel to the TRAPPIST star system (yet), but if we are able to detect the planets' atmospheres, then the next step will be to look for biosignatures. We don't quite have the capability to do this yet, but by all accounts, the state-of-the-art James Webb Space Telescope will be able to hunt for chemicals surrounding the planets, such as carbon dioxide, water vapor, and oxygen, that indicate the presence of life.

Image credit: M. Kornmesser / ESO

Alien Life

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