Scientists discover second-nearest Earth-like exoplanet

Rocky world may be best known location to search for extra-terrestrial life.
By Laurel Kornfeld | Nov 17, 2017
Scientists studying a red dwarf star 11 light years from Earth using the High Accuracy radial velocity Planet Searcher (HARPS) instrument in Chile discovered an orbitingEarth-like planet that could potentially be habitable.

Like Proxima Centauri, the closest star to host an Earth-like planet, the star Ross 128 is a faint red dwarf, but it is far less active, meaning it does not regularly blast harmful, high-energy radiation.

The planet, designated Ross 128 b, has approximately 1.35 Earth masses, orbits 20 times closer to its star than Earth does to the Sun, and circles the star every 10 Earth days.

It is a low-mass world, meaning it likely is rocky rather than gaseous.

However, the star is about 280 times less luminous than the Sun. While the planet receives about 40 percent more light from Ross 128 than Earth does from the Sun, it could still be in the star's habitable zone, where temperatures allow liquid water to exist on the surface.

The habitable zones of cool red dwarf stars are closer than those of yellow stars such as the Sun. Most of the Earth-like exoplanets discovered to date orbit red dwarf stars.

Unlike many red dwarfs, Ross 128 is a quiet star, the least active red dwarf in our stellar neighborhood known to host a rocky planet.

Temperatures on the planet's surface are estimated to range between minus 60 to 20 degrees Celsius, making it a temperate world although the researchers cannot be certain it actually is in the star's habitable zone.

While the planet has several factors that make it an ideal location to search for extra-terrestrial life, its climate and the composition of its atmosphere remain unknown.

Xavier Bonfils of the Institute of Planetology and Astrophysics in Grenoble, France, who is also lead author of a study on the discovery published in the journal Astronomy and Astrophysics, noted the planet, which may be tidally locked and always show the same face to the star, could have clouds on the star-facing side that reflect heat into space, causing a cooling effect.

On the other hand, the planet could have an atmosphere that absorbs so much heat and light that like Venus, it experiences a runaway greenhouse effect.

As a next step, the researchers want to search for atmospheric gases associated with biological processes, such as water vapor, oxygen, and methane.

None of today's telescopes are capable of directly observing Ross 128 b directly, but the Extremely Large Telescope, which is being constructed in Chile and expected to be operative around 2025, may be capable of doing this and of identifying the gases in its atmosphere.

NASA's James Webb Space Telescope (JWST), which will launch in 2019, may also be capable of studying exoplanets' atmospheres.




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