An exoplanet that orbits a red dwarf star about 40 light years from Earth may harbor alien life, because it is within its star's habitable zone. Now, a "super-Earth" has been found 39 light-years away, according to new research in the journal Nature.
Its star also emits less radiation than many other red dwarfs, making the planet more likely to have preserved an atmosphere.
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.
Still, he said he's confident that astronomers will find a habitable planet soon, be it LHS 1140b or another.
LHS 1140 is an elderly red dwarf, about five billion years old, and after more than two years of observations, not one flare was detected. And it may even have an atmosphere. The planet was discovered in 2014 with the MEarth-South telescope array at Cerro Tololo Inter-American Observatory in Chile, using a method that measured the faint dimming of starlight as it passed across LHS 1140's disk.
Lead scientist Dr Jason Dittmann, from the Harvard-Smithsonian Centre for Astrophysics in Cambridge, US, said: "This is the most exciting exoplanet I've seen in the past decade".
Super-Earths exist in between. That's because they're the most abundant stars in the galaxy and some of the easier stars to capture transit signals from. If a star emits this radiation often enough, the atmosphere has no time to fix itself. It all started with the observation of a dip in the light of the star. But the smaller size of the star is offset by its proximity.
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. That is proportional to the planet's mass.
When the star formed, it started out larger before condensing down to its dwarf star size.More news: Google said to be planning a built-in ad blocker for Chrome
The boundaries of the habitable zone are critical. That's what happened to Venus.
"It's just incredible what these amateurs are capable of", said Dittmann. That's where lava comes in. But Proxima b's position means astronomers can't get a good, hard look at the planet's atmosphere, if it has one.
But if it's too far, any water will freeze, as is seen on Mars. Just the right distance and equilibrium is achieved.
This habitable zone is also known as the "Goldilocks" zone, taken from the children's fairy tale. Part of what has scientists so excited about LHS 1140 is that it spends less energy sterilizing its neighborhood than Trappist-1. Depicted in blue is the atmosphere the planet may have retained. That, combined with the planet's estimated size, indicates this world is rocky.
LHS 1140b's star is comparatively larger than TRAPPIST-1 and brighter, so it could be an object of study for future ground-based telescopes in addition to the James Webb Space Telescope. "We don't have atmospheric measurements right now, but the star behaves nicely so that it's not ruling out anything", says Dittman.
"This is the first one where we actually know it's rocky", Charbonneau said.
Julien de Wit, one of the researchers that discovered the TRAPPIST-1 planets, agrees. "We plan to search for water, and ultimately molecular oxygen".
In the next several years, new telescopes should be able to use the planet's path to spy its atmosphere in what could be the best-aimed search for signs of life, said Harvard astronomer David Charbonneau, a co-author of the study. "We're essentially running down the list of the thing we want in a habitable planet and checking the boxes".