Hunting for alien life: Super-Earth LHS 1140b could be the best exoplanet to search signs of life

A new Earth-like planet that orbits a red dwarf star located about 40 light-years away has been discovered and scientists believe it could be the best place yet to hunt for alien life beyond our solar system.

An international team of astronomers used the European Southern Observatory (ESO)’s HARPS instrument at La Silla and other telescopes around the world for the discovery. They found the exoplanet orbiting in the habitable zone around the faint star LHS 1140.

The newly discovered planet is larger and more massive than our Earth and it is likely to have retained most of its atmosphere.

What makes the exoplanet one of the most exciting future targets for atmospheric studies is the fact that it passes in front of its parent star as it orbits.

Red dwarfs are much smaller and cooler compared to the Sun. The super-Earth LHS 1140b is ten times closer to its star than the Earth is to the Sun, but still it only receives about half as much sunlight from its star as the Earth. It lies in the middle of the habitable zone.

From the Earth, the orbit is seen almost edge-on. As the exoplanet makes a transit of the star once per orbit it blocks a little of its light every 25 days.

“This is the most exciting exoplanet I’ve seen in the past decade,” said Jason Dittmann of the Harvard-Smithsonian Centre for Astrophysics in the US.

“We could hardly hope for a better target to perform one of the biggest quests in science - searching for evidence of life beyond Earth,” said Dittman.

“The present conditions of the red dwarf are particularly favourable - LHS 1140 spins more slowly and emits less high-energy radiation than other similar low-mass stars,” said Nicola Astudillo-Defru from Geneva Observatory in Switzerland.

A planet must have liquid surface water and retain an atmosphere in order to sustain life. Dwarf stars during the young phase emit radiation that could damage the atmospheres of the planets that orbit them. The large size of the planet in that case suggests that a magma ocean could have occurred on its surface for millions of years.

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. According to astronomers estimate, the age of the planet to be at least five billion years.

They also deduced that it has a diameter 1.4 times larger than the Earth - almost 18 000 kilometres. However, with a mass around seven times greater than the Earth, and hence a much higher density, it implies that the exoplanet is probably made of rock with a dense iron core.

This super-Earth may be the best candidate yet for future observations to study and characterise its atmosphere, if one exists, researchers said.

“The LHS 1140 system might prove to be an even more important target for the future characterisation of planets in the habitable zone than Proxima b or TRAPPIST-1,” according to Xavier Delfosse and Xavier Bonfils both at the CNRS and IPAG.

Observations coming up soon with the NASA/ESA Hubble Space Telescope will be able to assess exactly how much high-energy radiation is showered upon LHS 1140b, so that its capacity to support life can be further constrained. 

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(With inputs from PTI)