Firstly astronomers found an exoplanet with a potential to harbor life. Then, they found its neighbor. Both of them lying in the habitable zone.

A team of researchers found a super-Earth planet called K2-18b using data collected by the European Southern Observatory (ESO). They say the new planet could be a scaled-up version of Earth.

So, a super-Earth is a planet with a mass higher than Earth but smaller than larger bodies like Uranus and Neptune.

Observers at the Kepler observatory discovered K2-18b while transiting its parent star K2-18. Also, the planet has an orbital period of about 33 days, putting it about 22 million kilometers from the star.

Astronomers, then, confirmed its existence using the Spitzer Space Telescope.

Later on, they find another super-Earth planet, both orbiting a red-dwarf star around 111 light years away.

“Being able to measure the mass and density of K2-18b was tremendous, but to discover a new exoplanet was lucky and equally exciting,” says Ryan Cloutier, lead author of a study published to the journal Astronomy & Astrophysics.

However, scientists think that K2-18b lies in an excellent location for surface water to exist and alien life to emerge.

About K2-18b

Astronomers observed the changing position and speed of stars using the fiber-optic High Accuracy Radial Velocity Planet Searcher (HARPS) technology. This kind of movement can tell that the gravitational force of orbiting planets are pulling the star. By collecting so-called “radial velocity” data on K2-18, the scientists were able to estimate the size of K2-18b.

The planet is about 2.3 times wider than Earth.

“If you can get the mass and radius, you can measure the bulk density of the planet and that can tell you what the bulk of the planet is made of,” lead author Ryan Cloutier said in a statement.

Cloutier and his team used a sophisticated machine-learning technique to figure out the mass measurement. Thus, determining the planet is either a mostly rocky planet with a small gaseous atmosphere or a mostly water planet with a thick layer of ice on top of it.

However, everything will be clearer with the launch of the James Webb Space Telescope (JWST).

“With the current data, we can’t distinguish between those two possibilities,” he says. “But with the James Webb Space Telescope (JWST) we can probe the atmosphere and see whether it has an extensive atmosphere or it’s a planet covered in water.”

“K2-18b is now one of the best targets for atmospheric study, it’s going to the near top of the list,” says René Doyon, a co-author.

What about its neighbor planet?

Although the existence of the second planet is not 100% certain, analyzing the HARPS data, the astronomers noticed another signal.

“When we first threw the data on the table we were trying to figure out what it was. You have to ensure the signal isn’t just noise, and you need to do careful analysis to verify it, but seeing that initial signal was a good indication there was another planet,” Cloutier says.

So, odds are that K2-18c might exist.

Scientists say that it too is a super-Earth with about 7.5 times Earth’s mass. While it doesn’t transit its own star, researchers think its orbit might be tilted a bit relative to K2-18b’s.

However, the possibility of life on this candidate planet is lower than its brother. It orbits too close to its star, so the surface is probably too hot to support life.

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Thumbnail image: Artist’s rendering of the K2-18 planetary system. Credit: Alex Boersma