Université de Montréal physics student finds new exoplanet twice the size of Earth

Merrin Peterson's exoplanet, Wolf 503b, is about 145 light-years away from Earth, in the Virgo constellation. Peterson and her team at the Institute for Research on Exoplanets (iREx) say there's a lot to learn from these discoveries.

Merrin Peterson's exoplanet, Wolf 503b, is about 145 light-years away from Earth, in the Virgo constellation

Merrin Peterson, a master's student in physics, sometimes works out of the Mont Mégantic Observatory. (Submitted by Merrin Peterson)

When Merrin Peterson started her master's degree in physics at Université de Montréal last year, she couldn't have predicted that she'd discover a brand new exoplanet in such a short time.

"It was very thrilling," she said. "My supervisor likes to call it my planet, because I wrote the paper and I did the most work on it."

"But it was really a team discovery."

According to NASA, there are planetary objects orbiting almost every star in the sky visible to the naked eye. 

These planets orbiting stars other than our sun are called exoplanets, and they can come in many shapes and sizes.

Some are frozen. Some are boiling hot. Depending on their proximity to their star, the closest ones can make a complete orbit — marking that exoplanet's year, essentially — in only a few days.

Peterson's exoplanet is called Wolf 503b. It's twice as big as Earth, but it only takes six days to get all the way around its own star.

Wolf 503b is about 145 light-years away from Earth and is located in the Virgo constellation.

So how did Peterson and her team at the university's Institute for Research on Exoplanets (iREx) find it?

Working alongside Assistant Prof. Björn Benneke, Peterson took data from NASA's Kepler telescope and ran it through a computer program to help identify potential exoplanets.

In the search for far-away celestial bodies, it's almost about looking for something that isn't there, said Peterson. 

"When you find it right away, you've found that there's something blocking light from the star," she said.

The newly discovered exoplanet is about halfway between the size of Earth and Neptune. (NASA/Goddard/Robert Simmon)

From that information, you can find the exoplanet's radius and its mass and calculate how long it takes for the exoplanet to orbit the star.

There are many exoplanets of the same size — indeed many of those found in the Milky Way with the help of the Kepler telescope over the last few years that orbit their stars closely are about equal to Wolf503b.

Since there are no planets of this size in our solar system, astronomers aren't sure whether exoplanets like Wolf503b are rocky or gaseous.

Many researchers in the field are motivated by the goal of finding what Peterson calls "an Earth analogue," in other words, a planet that can support an atmosphere like ours and liquid water.

But for Peterson, whose interest in astrophysics was sparked as an undergraduate student at McGill, the opportunity to study these newly discovered pieces of the puzzle is reward enough.

"It's a booming field that people are getting really excited about. It's growing all the time," she said. "Most of us just want to be able to study these planets in better detail than we have now."

Details about the discovery were published in the Astronomical Journal this summer.

With files from Radio-Canada's Alain Labelle


Marilla Steuter-Martin has been a journalist with CBC Montreal since 2015.


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