New research has shown that the exoplanet K2-18b, which orbits around K2-18, about 111 light-years from Earth, could be a super-Earth. While they discovered it, they also found the discovery that another exoplanet also orbits around the same star.
K2-18 is a red dwarf star in the constellation of Leo and K2-18b was discovered in 2015. It was discovered that the exoplanet was in the habitable zone of the star, which means it could have liquid water on its surface , a necessary ingredient for life as we know it. But scientists were not sure if the planet was an enlarged version of Earth (a rocky or terrestrial planet) or a reduced version of Neptune (a planet of gas and ice).
"If you can get mass and radius, you can measure the apparent density of the planet and that can tell you what the bulk of the planet is made of," Ryan Cloutier, Ph.D. A student at the University of Toronto, Canada, who was the lead author of the new research, said in a statement on Tuesday.
To do so, Cloutier and his research colleagues used data from the High Precision Radial High Speed Planet Finder in the Southern Observatory 3.6-meter telescope at the La Silla Observatory, Chile. By measuring the radial velocities of the stars, which can be influenced by the presence of planets around these stars, HARPS can allow the detection of planets around stars.
The researchers surmised that K2-18b has a mass between six and 10 times more than Earth, which makes it mostly rocky with a small gaseous atmosphere or a mainly aquatic planet with a thick layer of ice on top.
"With the current data, we can not distinguish between those two possibilities," Cloutier said. "But with the James Webb Space Telescope (JWST) we can explore the atmosphere and see if it has an extensive atmosphere or if it's a water-covered planet."
JWST is the successor of the NASA Hubble Space Telescope and is currently scheduled to be launched in the spring of 2019.
The discovery of a Second planet in the star system K2-18 was a great luck. In addition to two regular signals, one every 39 days from the rotation of the star and the other every 33 days from the orbit of the planet, the researchers found a third signal that occurs every nine days.
"When we first put the data on the table we were trying to figure out what it was, you have to make sure that the signal is not just noise, and you have to do a careful analysis to verify it, but seeing that initial signal was a good indication that there was another planet, "Cloutier said in the statement.
Called K2 -18c, the newly discovered exoplanet is much closer to its host star than its already known neighbor. That means that it is very likely that there is liquid water on its surface, but it is likely that its mass is similar to that of Earth.
The research will be published in the journal Astronomy and Astrophysics and is currently available on the prepress server. arXiv.