Researchers say the discovery of a planet too large for its nearest star is challenging existing theories about the dynamics of planetary formation, according to recent findings.
The discovery, reported by researchers at Penn State University, involves a massive planet orbiting LHS 3154, a star that is around nine times smaller than our Sun, and thereby also much cooler.
By comparison, the newly named planet, LHS 3154b, which orbits it is more than 13 times the size of Earth, which planetary scientists say should not be possible.
Put into context, the mass ratio of the planet to its host star is greater than 100 times that of Earth and the Sun, making LHS 3154b the largest planet ever discovered orbiting an ultracool dwarf star and, more fundamentally, a planet too large to easily fit within current models about how such celestial objects form.
Suvrath Mahadevan, the Verne M. Willaman Professor of Astronomy and Astrophysics at Penn State, said he and his colleagues were surprised by the discovery.
“We wouldn’t expect a planet this heavy around such a low-mass star to exist,” Mahadevan said in a press release describing the new findings.
Generally, once a star is formed, gas and dust surrounding it will form a protoplanetary disk, which will eventually form planets over long periods. However, the disk around LHS 3154 does not have enough solid mass to facilitate planetary formation in the case of an object like LHS 3154b, Mahadevan says.
“But it’s out there,” he adds, “so now we need to reexamine our understanding of how planets and stars form.”
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