Montreal: Two Super-Earths Around Star K2-18

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Montreal: Two Super-Earths Around Star K2-18

Post by bystander » Wed Dec 06, 2017 3:22 pm

Two Super-Earths Around Star K2-18
University of Montreal | 2017 Dec 05

Researchers find exciting potential for little-known exoplanet – and discover another planet in the process.
[img3="Artistic ilustration of planet K2-18b, its star K2-18 and the second planet K2-18c. Credit: Alex Boersma"] ... 8331d8.jpg[/img3][hr][/hr]
New research using data collected by the European Southern Observatory (ESO) has revealed that a little-known exoplanet called K2-18b could well be a scaled-up version of Earth.

Just as exciting, the same researchers also discovered for the first time that the planet has a neighbor. ...

In order to figure out whether K2-18b was a scaled-up version of Earth (mostly rock), or a scaled-down version of Neptune (mostly gas), researchers had to first figure out the planet’s mass, using radial velocity measurements taken with HARPS. ...

After using a machine-learning approach to figure out the mass measurement, Cloutier and his team were able to determine the planet is either a mostly rocky planet with a small gaseous atmosphere – like Earth, but bigger – or a mostly water planet with a thick layer of ice on top of it. ...

It was while looking through the data of K2-18b that Cloutier noticed something unusual. In addition to a signal occurring every 39 days from the rotation of K2-18, and one taking place every 33 days from the orbit of K2-18b, he noticed a different signal occurring every nine days. ...

While the newly described planet K2-18c is closer to its star, and probably too hot to be in the habitable zone, like K2-18b it also appears to be a Super-Earth meaning it has a mass similar to Earth. ...

Characterization of the K2-18 multi-planetary system with HARPS: A habitable zone
super-Earth and discovery of a second, warm super-Earth on a non-coplanar orbit
- R. Cloutier et al
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