Astronomers have identified a distant exoplanet as a "super-Earth" that has the potential to harbor alien life. In addition to this, the team also discovered that this planet, K2-18b, has another similar world hiding behind it.
A super-Earth is a planet with a mass higher than Earth but smaller than larger bodies such as Uranus and Neptune.
The two new super-Earths orbit around a red dwarf star about 111 light-years away. K2-18b, scientists say, could be in an excellent location for alien life to emerge, having perfect conditions for surface water to exist, a fundamental ingredient for life.
Scientists combed the skies with the HARPS planetary hunting device of the European Southern Observatory in Chile. They found the planets circling around the red dwarf star K2-18, which is part of the constellation, Leo.
The discovery of the first planet, K2-18b, took place in 2015. Sitting inside the habitable zone of the star, astronomers have been investigating whether or not it could support life. This meant figuring out whether K2-18b was a piece of rock, like Earth, or a dense body of gas, like Jupiter.
Using HARPS fiber optic technology, astronomers observed the changing position and velocity of stars. This type of movement may indicate that a star is being dragged by the gravitational force of the orbiting planets. By collecting the "radial velocity" data in K2-18, the scientists were able to estimate the size of K2-18b.
"If you can get the mass and the radius, you can measure the apparent density of the planet and that can tell you what most of the planet is made of," lead author Ryan Cloutier said in a statement.
Using sophisticated machine learning techniques, the team discovered that the planet could well be an Earth-like planet made mostly of rocks and with a gaseous atmosphere. Alternatively, the planet could be formed by water enclosed in a thick layer of ice. Their findings have been sent to the journal Astronomy & Astrophysics.
Second discovery of the super-land
In addition to taking a giant leap to find a potentially habitable exoplanet, the team also discovered a second Earth-like planet orbiting around K2-18. This super-Earth-K2-18c-unfortunately, is a much poorer candidate for life. Sitting too close to your star, which means that the surface is probably too hot to sustain life.
The identification of two new super-Earths, however, remains a significant advance for astrophysics. According to the authors of the study, the discovery sheds an important light on the prevalence of multi-planetary systems around dwarf stars such as K2-18.
"Being able to measure the mass and density of K2-18b was tremendous, but discovering a new exoplanet was fortunate and equally exciting," Cloutier said.
Investigators will have to wait until 2019 to confirm the conditions atmospheric of K2-18b, when NASA's James Webb Space Telescope will be launched. "There is a lot of demand to use this telescope, so you must be meticulous when choosing which exoplanets to look at," said study co-author René Doyon. "K2-18b is now one of the best targets for atmospheric study, it goes to the top of the list."