Planet trio could host signs of life
Scientists believe it possible that three Earth-like planets orbiting star may hold water
It seems like scientists are finding potentially habitable planets all the time these days, and they are — the Kepler Space Telescope is very, very good at its job, even though it’s technically broken. But the three exoplanets described Monday in the journal Nature manage to stand apart: According to the scientists who discovered this trio, the Earth-like worlds might represent our best-ever shot at finding signs of alien life.
The three planets were detected based on the dimming of the star they orbit, which has been named TRAPPIST-1 for the telescope it was discovered with (TRAnsiting Planets and PlanetesImals Small Telescope).
As the three planets orbit, transiting in front of TRAPPIST-1 from the telescope’s perspective, the star blinks and dims out of our view. Scientists use this dimming to calculate the size of the planets and their distance from their host star.
Because planet composition is closely tied to these metrics, scientists can say with confidence whether a world is rocky, like Earth — as opposed to a massive planet composed of gas or ice — and whether or not it could host liquid water.
The three worlds are close by, located just 40 light years away in the constellation Aquarius — the water bearer. But the fact that they’re Earth-like and promising doesn’t mean these planets actually hold water.
The researchers, led by Michael Gillon and Emmanuel Jehin of the University of Liège in Belgium, believe the worlds are tidally locked, which means they have one hot side that faces their star and one cold side plunged in eternal darkness. The planets are incredibly close to their sun, orbiting it in just a matter of days. They likely don’t receive more than a few times as much radiation as Earth does, but the first two planets are still probably a smidgen too close to have water covering their surfaces.
Still, it’s possible that certain regions of the planet are just right for water, which could allow some simple life to evolve. Other factors, such as cloud cover and geothermal activity, could tip the scales toward habitability as well. And the third, mostdistant planet’s orbit has yet to be determined, meaning it could fall into the perfect orbital range for water and life.
But it’s the star at the centre of this foreign system that makes the planets so exciting.
The three worlds orbit an ultracool dwarf star — one just one eighth the mass of our sun, and much cooler. It’s more similar to Jupiter, a planet so massive it’s almost star-like, than it is to our own sun.
Generally speaking, the Holy Grail for an Earth-like planet is one with a star just like ours. After all, the more conditions a world has in common with our own, the more likely it is that similar life could evolve there. But when it comes to detecting the kind of atmosphere that would support life as we know it, smaller stars are better. This is the first time scientists have detected rocky planets in a system like this one, making the worlds great candidates for study.
The team has already started to collect atmospheric measurements from the three planets using the Hubble, and they hope to have an approximate assessment of their atmospheres soon.