The first subtle signs of the planet's presence were recorded in 2014, but no one noticed until Jason Dittmann, then at the Harvard-Smithsonian Center for Astrophysics, re-analyzed the data. The planet weighs about 6.6 times the mass of Earth and is shown passing in front of LHS 1140.
In our Solar System, such a planet would be so scorched that any atmosphere and surface water would be stripped away.
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The fact that LHS 1140b is a super-Earth is a bit concerning to any hopes that - if humans ever manage to master interstellar travel - we could one day settle the planet and establish a colony.
"This planet's orbit places it within the habitable zone, where conditions may be right for liquid water - neither too hot that the water boils off nor too cold that it is always frozen solid".
In February NASA announced the discovery of TRAPPIST-1, a system of seven Earth-like planets orbiting a Jupiter-sized dwarf star 235 trillion miles away from Earth.
"What I truly find exciting is that we have a potentially habitable, rocky planet orbiting a nearby star that is now very calm and stable and doesn't flare", Dittman said. That means in the next several years, new telescopes can spy its atmosphere in a targeted search for signs of life.
The exoplanet takes 25 days to orbit its star and despite being 10 times closer to LHS 1140 than Earth is to the Sun, it only receives about half the "sunlight" that Earth does.
The planet LHS 1140 b, described in the journal Nature, provides a tempting target for astronomers looking to probe an exoplanet's thin but essential shell of air, which could offer clues about whether such a world could host life. The host star is also relatively close to Earth, which means its light is just bright enough to be used as a tool to peer into the planet's atmosphere.
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The star that LHS 1140b orbits is both small and faint.
The exoplanet therefore lies in the middle of the habitable zone of the star, meaning it has numerous conditions needed to grow alien life. One of these factors is the red dwarf around which the distant world orbits.
"But for Proxima Centauri b, we only know the minimum mass and for the Trappist-1 planets, we know their size and their mass is not very well known - except for one, which we know isn't rocky", fellow author Xafier Bonfils from the University of Grenoble told WIRED.
The seven known planets in the TRAPPIST-1 system make transits, which fortunately allows for further study. The signal for star LHS 1140 looked like the telltale dip in light that signifies an exoplanet in orbit. This affects the planet's ability to maintain an atmosphere, water and stable compounds.
The Webb telescope is expected to launch next year, but the Giant Magellan telescope won't be online until 2025, and the EELT won't be working until 2024.
Because red dwarfs are dimmer and cooler than Sun-type stars, however, their planetary habitable zone is much closer in.
In the next few years, telescopes should be able to use the planet's path to examine its atmosphere, Charbonneau said.
Exoplanet discoveries in the past decade have made it clear there are plenty of other solar systems, but in the previous year we've increasingly spotted new worlds that indicate there may be plenty of other Earths out there too.
"But the key part is for the first time in human history, we're going to have the ability to probe the atmospheres to see molecules in the atmospheres of temperate, rocky worlds orbiting nearby stars", he said. "We'll basically be taking a look at this planet right out of the starting gate", says Dittmann. "We plan to search for water, and ultimately molecular oxygen".