What is LHS 3154 b? What we know about the exoplanet which can change the way we look at the solar system

Researchers discovered an exoplanet, LHS 3154 b, that is seemingly too massive for its star. Astronomers at the University of California, Irvine, said the discovery muddled the solar system models. The research team detected the planet by connecting the Habitable Zone Planet Finder instrument with the Hobby-Eberly Telescope at the University of Texas McDonald Observatory.

The planet is found to be 13 times bigger than Earth, and it is orbiting LHS 3154, the ‘ultracool’ star, which is nine times less colossal than our sun. This finding is included in a paper that was published on December 1 on Science.org. Paul Robertson, the co-author of the paper and an associate professor of physics and astronomy at UCI, said:

“The HPF instrument was designed to study exoplanets orbiting dwarf stars, so in that regard, this was a perfectly normal project, but the results were anything but ordinary. This is the first time such a high-mass planet has been found orbiting close to a lower-mass star, and it calls into question our previous assumptions about interactions between stars and planets.”

Another co-author, Suvrath Mahadevan, explained how stars are believed to be formulated with large clouds of dust and gas. The remaining substance eventually accretes to create planets. Mahadevan continued that the planet-forming disk around LHS 3154, which is a low-mass star, is not deemed to have sufficient solid mass required to create the planet LHS 3154 b. He added:

“But it’s out there, so now we need to reexamine our understanding of how planets and stars form.”

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LHS 3154 b orbits its star in 3.7 days

Guðmundur Stefánsson, the first author of the paper and an astrophysicist at New Jersey’s Princeton University said about the discovery:

“Previously, it was just thought that, ‘Oh, no, there’s no way the lowest-mass stars can actually form this type of planet. Now at least there is a proof of concept that they can form it.”

Stefánsson and his team began observing the low-mass star LHS 3154 which was classified as M dwarf. They soon noticed hints of a periodic shift in the star’s spectrum every 3.7 days. It was a significant sign that the wobble in the star’s position was caused by a planet’s gravitation pull — a planet that was likely orbiting it.

The stat LHS 3154 is relatively close to Earth, about 50 light years away, and is about a thousand times less luminous than our sun. Stefánsson said it can barely be called a star, adding:

“It has a mass just above the cutoff of supporting hydrogen fusion to be considered a star.”

LHS 3154 b, the planet orbits its star at about 2.3% of the orbital distance between Earth and the sun. This exoplanet circles its star every in 3.7 days and is much closer to LHS 3154 than Mercury is to the sun in our solar system.

Guðmundur Stefánsson revealed LHS 3154 b raises questions about how planets are formed around stars with the lowest mass as such stars were previously believed to only be able to produce small terrestrial planets that had similar mass to Earth.