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".
The planet may be 5 billion years old, which is just slightly older than Earth.
In a paper detailing the discovery, the researchers also say they believe the planet has an atmosphere, adding that both star LHS 1140 and planet LHS 1140b are so close to Earth that "telescopes now under construction might be able to search for specific atmospheric gases in the future". This same instrument also helped figure out the planet's orbital period and mass. The TRAPPIST-1 star and other similar red dwarfs are usually pretty active, meaning they send out high intensity solar flares quite frequently.
It's about 40 percent bigger than our home planet, hence the moniker super-Earth, and it's much more dense, weighing about 6.6 times as much as Earth, giving it three times the gravitational pull.
Since this planet transits its star, unlike the closest world Proxima b, it can be examined for the presence of air.
Other planets are less cooperative with scientists than 1140b.
In a rare find, a rocky "super-Earth" planet has been located orbiting around a cool dwarf star - and it's just a mere 39 light years away. That would have put the exoplanet right in the thick of the star's volatile energy blasts. Depicted in blue is the atmosphere the planet may have retained. If that did happen, it would have caused a runaway greenhouse effect like we see on Venus.
There might be another Earth out there, and its name is LHS 1140b.
"The present conditions of the red dwarf are particularly favorable - LHS 1140 spins more slowly and emits less high-energy radiation than other similar low-mass stars", explains Nicola Astudillo-Defru, one of the astronomers behind the discovery. And that means there's a better chance that this planet may be holding onto some valuable chemicals, like organic molecules and water. This seething ocean of lava could feed steam into the atmosphere long after the star has calmed to its current, steady glow, replenishing the planet with water. That space-based observatory is meant to study the earliest galaxies and stars of the Universe, but it will also have enough precision to peer into LHS 1140b's atmosphere. The James Webb Space Telescope, which NASA plans to launch into space in 2018, could also search 1140b for ozone, which is made of oxygen.
Xavier Delfosse and Xavier Bonfils, both members of the team, talked more about the discovery.
The planet is 1.4 times the size of Earth, and its mass is seven times greater, suggesting it is made of made of rock with an iron core. "This has been a remarkable year for exoplanet discoveries!" "Now we can say rocky Earth-size planets are probably fairly common", Bruce Macintosh, an exoplanet expert at Stanford who was not involved in this study, tells The Verge.