SPACE — Astronomers have been surprised again by the discovery of a new planet that challenges science. The enormous exoplanet orbits an ultracool dwarf star that is too small to contain it.
The existence of the planet named LHS 3154 b challenges scientists’ theories about how planets and planetary systems form. The research by the team of astronomers was published in the journal Science on November 30, 2023.
Located about 51 light years from us, the planet called LHS 3154 b is 13 times larger than Earth. This means that it has a similar mass to the ice giant Neptune in our solar system. However, it orbits a small dwarf star, LHS 3154, which is nine times smaller than the planet’s mass.
The ratio between LHS 3154 b and its parent star is 100 times greater than the mass ratio between the Earth and the Sun, something the researchers said was impossible. This is the first time a planet with such a mass has been discovered around one of its smaller stars in the universe.
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“This discovery really confirms how little we know about the universe.
“We did not expect there to be a planet of this size surrounding a low-mass star,” said study co-author and Verne M Willaman Professor of Astronomy and Astrophysics at Penn State University, Suvrath Mahadevan in a statement.
Challenging the Birth Laws of Stars and Planets
Stars form when enormous clouds of gas and dust continue to build up until they become too dense, and eventually collapse under their own gravity. This collapse causes the star to be surrounded by a disk of remaining material called a protoplanetary disk (planet-forming disk).
It is from the remaining material that scientists believe that planets will eventually emerge. The amount of material left over from star formation determines the limits of how large a planet can potentially form.
The research team determined that LHS 3154 b has a planetary core that is so heavy that the planet-forming disk must contain a lot of dense material. “In short, the model should contain much more material than current models predict,” said Penn State study co-author Megan Delamer.
Therefore, the discovery of the planet LHS 3154 b also raises questions about star formation. This is because the ratio of dust content to mass and dust content to gas in the LHS 3154 protoplanetary disk must be ten times higher than predicted in order to give birth to a planet of that size.
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The problem, Mahadevan noted, is that the planet-forming disk around the low-mass star does not have enough dense mass to form LHS 3154 b. “But (in reality) it is out there, so now we need to review our understanding of how planets and stars form,” he said.
Mahadevan and colleagues detected the exoplanet LHS 3154 b using the Habitable Zone Planet Finder (HPF). It’s an astronomical spectrograph on the Hobby-Eberly Telescope at Texa’s McDonald Observatory. HPF is designed to detect exoplanets orbiting some of the coolest stars in the Milky Way.
2023-12-01 23:02:00
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