An international team of scientists has announced the discovery of a new "super-Earth" exoplanet (a planet with more mass than Earth, but not quite as big as our gas giants) that could represent our best chance of finding life outside of our solar system. The planet is in orbit around a dim red dwarf called LHS 1140, which is located a mere 40 light-years from Earth in the direction of the constellation Cetus - in astronomical terms, that's pretty close.
The exoplanet, which has been (rather unimaginatively) named LHS 1140b, orbits right in the middle of the red dwarf's habitable zone (HZ) – the region of space around a star in which a planet could potentially sustain liquid water on its surface.
As LHS 1140 is much smaller and cooler than our own star, it doesn't throw out anything close to the levels of radiation that our Sun is capable of emitting. Accordingly, the HZ of the red dwarf occupies a range of space roughly ten times closer to its central ball of fire than the HZ in our own solar system.
The initial discovery was made using the MEarth facility, which detected the tell-tale dip in light from LHS 1140 as LHS 1140b passed between the surface of the star and the observatory.
Follow-up observations carried out by a range of telescopes, including the European Southern Observatory's HARPS instrument then went on to characterize the planet's mass, density, and orbital period.
Scientists believe that one of the major factors that governed the emergence of life on Earth was the presence of liquid water, and so telescopes target distant worlds capable of harboring this precious resource when searching for the hallmarks of life beyond our planet.
LHS 1140b orbits in the HZ of its parent star, which is an important tick in the "can-host-liquid-water" column, but there are a myriad of other factors that could prevent the world from maintaining the vital asset. One of these factors is the red dwarf around which the distant world orbits.
It is estimated that the roughly five billion year old exoplanet orbits its star once every 25 Earth days (Credit: M. Weiss/CfA)
Red dwarfs have been observed to be extremely volatile soon after their creation. During this period, it is possible that radiation from a red dwarf could strip away significant amounts of the water content of a planet's atmosphere, which could induce the kind of conditions we see on Venus today. Whilst Venus may sometimes be described as Earth's twin, it's pretty far from it, and with a surface temperature exceeding 880 degrees Fahrenheit (470 degrees Celsius), it's probably not the best environment in which to search for life.
However, it is possible that LHS 1140b could have escaped this fate, thanks to its size. The newly discovered exoplanet is believed to have a density of around seven times that of Earth, and a diameter of 18,000 km (11,184 miles), making it 1.4 times the size of our blue marble.
These measurements hint that the planet is most likely comprised of rocky material, and that it harbors a dense iron core. It is possible that the size of the planet allowed a magma ocean to exist on its surface for millions of years. This ocean may have infused the atmosphere with steam for a prolonged period, which would have effectively replenished the planet's water supply.
Furthermore, scientists believe that the red dwarf, as we see it today, is emitting less high-energy radiation and spinning slower than other stars of its type, both of which are factors conducive to life.
It is currently believed that LHS 1140b receives only half as much radiation from its parent star as the Earth does from the Sun. Further observations are set to be carried out by the venerated Hubble Space Telescope, which will study in greater detail just how much radiation is being lavished upon the planet by its star. These observations will in turn inform the likelihood that the planet is capable of sustaining life.
We live in an exciting time of exoplanet discovery and the interconnected search for life. It is possible that LHS 1140b could represent a better prospect for atmospheric analysis than the TRAPPIST-1 worlds and even Proxima-b, which was discovered last year orbiting in the HZ of Proxima Centauri, only four light years from our Sun.
Scroll down to embark on an animated journey to LHS 1140b.