Exoplanet could be 'super-Earth,' Canadian astronomers say

Canadian astronomers have not only discovered that a world orbiting a star 111 light years away could be a"super-Earth," they've also discovered a new exoplanet in the same solar system.

The newly discovered world was found when a team of researchers, led by Ryan Cloutier, a PhD student at theUniversity of Toronto's department of astronomy and astrophysics, was analyzing data collected from the European Southern Observatory (ESO) on the K2-18 star system which was found to have a planet K2-18borbitingin 2015.

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The new datasuggestsK2-18biseither alarge, rocky planet, like Earth,orone with mostly ice and water on its surface.It's what astronomers call a "super-Earth" a new but vaguely defined class of exoplanetswhose sizeand mass are between those of Earth andNeptune, which is about four times larger than our planet.

"These are actually the most common typeof planetin the universe," Cloutier told CBCNews. "Things that are between the size of Earth and Neptune are more common than Earths and more common than Neptunes."

If these super-Earthsorbit in the habitable zone an area where liquid water can exist on the surface they could be rocky worlds with oceans, and possibly life.

K2-18b'sorbittakes it around its red M-dwarfstar (one of the most common types of stars) every 33 days, meaning it'sabout 15 per cent the distance from its star aswe are from the sun. It's about 2.5 times bigger than Earth, but eight times more massive.

K2-18c the newly discovered planet has roughly the same size and mass. However, itorbitscloser to its host star, about60 per cent the distance ofK2-18b. For that reason, it's unlikely to be a potentially habitable world.

Uncovering the new world

One of the more common methods of finding exoplanets is by theirtransit. A space telescope, like Kepler, measures a star's brightness. If it dims by a tiny fraction, that indicates that a planet has most likely crossed or transited between the star and the observer.

In the case of the ESO, the data was collected using the High Accuracy Radial Velocity Planet Searcher (HARPS) on a telescope in Chile. While studying a transit can reveal the existence and size of an exoplanet,studying the radial velocity the tiny wobbles of the star can shed light on its mass and, in turn, density.

It was while studying those tiny movements of the starthat something interesting was discovered: the star wasn't wobbling as it should if there was just one planet. There was a indicationin the data that arose every nine days.

"So you go, what the heck's that thing at nine days?" Cloutier said.

After eliminating other possibilities, such as activity on the star itself, it was clearthere was another planet orbiting the star. Kepler was unable to spot it as it was on an inclined plane and didn't pass in front of the star.

It was an exciting discovery for Cloutier who said he had always hoped to discover an exoplanet.

"The most thrillingpart was that first hint that there might be something there,"saidCloutier."That was more exciting than when it got confirmed."

Unravelling the mysteries

RenDoyon,Cloutier'sco-supervisor and a co-author of the paper published Tuesday in the journalAstronomy and Astrophysicssaid the next step will be to determine the atmosphere of K2-18b, since it's the most promising candidate for sustaining life. And thatwill rely on the next generation of space telescope, the James Webb, set to launch in 2019.

The planet "is one of our prime targets for observation with the future James Webb Space Telescope," Doyontold CBCNews. "It's in the habitable zone, so it's very unique."

Aspart of the agreement for Canada's contribution to the telescope, the instrument team is guaranteed 450 hours of observation time.

The Canadian-made Near-InfraRedImager and Slitless Spectograph (NIRISS) is specifically designed to probe the atmospheres of exoplanets, and Doyon said that K2-18 is at the top of the list.

"I can't wait," he said.

With the continual discovery of so many exoplanets, in particular those in habitable zones, Doyon said that he's anticipating future discoveries of worlds that could one day be habitable.

And another instrument that will be contributingto the search will be theSpectroPolarimtre Infra-Rouge (SPIRou) instrument that will be installed at the Canada-France-Hawaii Telescope later this year.

"It's exciting times," he said."The next decade will be the golden age of exoplanets."