Scientists find planets with potential for harbor life

An exoplanet in the Goldilocks habitable zone of its star is now suspected to have a liquid water ocean and an atmosphere.

The planet, named LHS 1140 b, is about 1.7 times the size of Earth and is located about 48 light-years away.

This distant world, first discovered in 2017, has now been found to be a rocky world like ours, but with 10 to 20 percent of its mass made up of water, according to a new study that will be published in The Astrophysical Journal Letters this week (currently available on the arXiv preprint server).

“Of all the currently known exoplanets, LHS 1140 b may be our best bet to one day indirectly confirm liquid water on the surface of an alien world beyond our solar system,” paper co-author Charles Cadieux, a PhD student at the Université de. Montreal, it said in a statement. “This would be a major milestone in the search for potentially habitable exoplanets.”

LHS 1140 b orbits a red dwarf about 20 percent the size of our sun and is at a certain distance from its sun that places it in the “Goldilocks” or habitable zone. This refers to the range of distances from a star where conditions are suitable for liquid water to exist on the surface of a planet. If a planet is too close to its star, it will be too hot, causing water to evaporate, while if it is too far from its star, it will be too cold, causing water to freeze.

The size and type of star significantly affect the location of the habitable zone. For example, the habitable zone is closer to a smaller, cooler star (like a red dwarf) and further away from a larger, hotter star.

Previously, astronomers weren’t sure whether LHS 1140 b was a rocky planet like Earth or a gas giant more like Neptune, but eventually, they determined that the exoplanet was something called a super-Earth.

Using data collected by the James Webb Space Telescope (JWST), they found that LHS 1140 b was less dense than expected for a completely rocky world, and that between 10 and 20 percent of its mass may consist of water, meaning the planet could be an ice world with a liquid ocean beneath the ice, like Jupiter’s moon Europa.

They also discovered that the planet has an atmosphere, possibly containing a similar amount of nitrogen to our planet. The presence of this atmosphere would enable the planet to hold liquid water on the surface.

“This is the first time we’ve ever seen a hint of an atmosphere in a rocky or ice-rich exoplanet habitable zone. Detecting atmospheres on small rocky worlds is a primary goal for JWST, but these signals are much more harder to see than the planet’s giant atmospheres,” co-author Ryan MacDonald, also a University of Montreal researcher, said in the statement.

“LHS 1140 b is one of the best small exoplanets in the habitable zone capable of supporting a thick atmosphere, and we may just have found evidence of air on this world.”

Using models, astronomers predicted that if LHS 1140 b has an atmosphere like Earth’s, it could consist of a planet-wide sheet of ice, with a single ring of ocean surface about 2,500 miles across, roughly half the the size of the Atlantic Ocean. According to the paper, this ocean can have a surface temperature as warm as 68 degrees F.

This discovery therefore makes LHS 1140 ba a prime candidate for life beyond our world, as its possible atmosphere and liquid water could harbor Earth-like life.

“This is our first tantalizing view of an atmosphere on a super-Earth in the habitable zone. Compared to other known habitable-zone exoplanets, such as those in the TRAPPIST-1 system, the star LHS 1140 appears to be quieter and less active, making it significantly less challenging to disentangle the atmosphere of LHS 1140 b from the stellar signals caused by starpoints,” MacDonald said.

“Our initial detection of LHS 1140 b with JWST has revealed that this is possibly the best known habitable-zone exoplanet currently known for atmospheric characterization. While we need more JWST observations to confirm the nitrogen-rich atmosphere and to look for other gases, this is a very promising start”.

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