The Most Earth-Like Exoplanet - What Makes LHS 1140 b so Important?

An artist's impression of a planet orbiting within the habitable zone of a red dwarf, similar to LHS 1140 b.

The exoplanet LHS 1140 b was first discovered in 2017. It was immediately a planet of note because it orbited within its star’s habitable zone—just the right distance from the star to potentially support liquid water on its surface. Nearly 10 years later, LHS 1140 b has become the center of a massive milestone in the search for life on exoplanets, thanks to a discovery announced July 16, 2026. It is the first confirmed rocky planet beyond our solar system that is in the habitable zone while also possessing an atmosphere.

What is LHS 1140 b?

LHS 1140 b is what we classify as a super-Earth, a rocky planet that’s far larger than Earth. Super-Earths aren’t necessarily more common than Earth-sized planets, but their larger size makes them easier to find, so we find them quite often. This example of a super-Earth has a radius 1.7 times larger than Earth’s and a mass equal to 5.6 Earths. It was found using the transit method, meaning we spotted the light of its star dim as the planet passed in front of it.

The planet gets its name (or rather designation number) from the star it orbits, LHS 1140. The b means that it’s the first planet discovered around the star, as the a is reserved for the star itself. There’s also a LHS 1140 c in the system as well. LHS 1140 is a red dwarf star, which is a small, dim star. Red dwarfs are the most common type of active star in the Milky Way Galaxy, if not the universe.

Not Too Hot, Not Too Cold

What made LHS 1140 b noteworthy upon its discovery was the fact that it’s in the so-called habitable zone of its solar system. We suspect that liquid water is the single most important ingredient to life. If true, for a planet to support life, it would need a large supply of liquid water. If said planet is too close to its host star, then the temperature would get too hot for water and it would boil away. If it were too far from the star it would get too cold and the water would freeze. So, for a planet to support life, it needs to be in a spot that’s not too cold and not too hot. It needs to be just right. That’s why the habitable zone is also known as the Goldilocks zone.

Each star has a unique habitable zone based on its size and temperature. Since red dwarf stars are so much smaller and cooler than stars like our Sun, the habitable zone ends up being very close to the star. LHS 1140 b orbits its star at a distance of 0.09 AU (8,366,023 miles), which is only a ninth the distance the Earth orbits the Sun. Even Mercury is 0.4 AU from the Sun, putting it nearly seven times farther from the Sun than LHS 1140 b is from LHS 1140. Being this close means that LHS 1140 b completes an orbit around its star once every 25 Earth days. Getting this up close and personal to its star is required to get the necessary heat for liquid water from a red dwarf.

Not only is it positioned right for water, but it may have a significant amount of it. Measurements of its mass and radius suggest that the planet’s density is too low to be made entirely out of rock. Instead, this may be a water world, where the entire planet is covered in a global ocean that accounts for 9 to 19% of its total mass.

A First of its Kind Discovery

But none of that is what makes LHS 1140 b truly important. What makes it special is the recent confirmation of helium gas found around the planet. In other words, an atmosphere. This makes it the first rocky planet beyond our Solar System we’ve discovered to have an atmosphere while also existing within the habitable zone. We’ve found rocky planets with atmospheres, but never in the habitable zone, and we’ve found rocky planets in habitable zones, but never with a confirmed atmosphere. That makes LHS 1140 b the single most Earth-like planet we know of beyond our Solar System.

An atmosphere is also an important feature for supporting liquid water. Without greenhouse gases in our atmosphere trapping heat, the Earth, even being right in the middle of the Sun’s Goldilocks zone, would still have a freezing cold temperature of 0°F (-18°C). This is the reason why Mercury is cooler than Venus, despite being closer to the Sun, as Mercury has no atmosphere, while Venus has one packed with greenhouse gases.

What makes this discovery of an atmosphere on LHS 1140 b important is that for the first time, it proves that a rocky planet close to a red dwarf can have an atmosphere, and therefore hold on to the heat required to support liquid water, and possibly life. Since red dwarfs are the most common type of star, this suggests there could be countless planets around these stars across the Milky Way, all with the potential to support life, significantly increasing the overall odds that we could find life beyond Earth. Perhaps even more exciting is the fact that red dwarfs can live to be extremely old—older than even the current age of the universe. A planet supporting life around one of these would have plenty of time to develop intelligence, making old red dwarfs one of the best places to look for intelligent life.

We don’t know if LHS 1140 b supports life or not, but the discovery of its atmosphere is a proof of concept that planets similar to Earth do indeed exist. And they don’t even need to exist around Sun-like stars. And in a universe as massive as ours,  where you find one, surely there are hundreds, if not thousands, or even millions of others.