An exceptional planet, too massive for its star, has been discovered
6:56 AM EST, December 2, 2023
Researchers from Pennsylvania are investigating an extraordinary planet, LHS 3154b, which is extremely massive compared to the small and cool star it orbits. According to the scientists, this discovery challenges our current understanding of the formation of planetary systems.
LHS 3154b is a planet that is more than 13 times the mass of Earth and revolves around a small "ultracool star" named LHS 3154. The star itself is nine times less massive than our Sun, which makes the planet-star mass ratio over a hundred times larger than that of our Earth and the Sun. This finding contradicts the existing scientific knowledge about the formation of planetary systems and represents a unique case, as no such high-mass planet orbiting a low-mass star has been observed before.
"Our understanding of the universe is limited"
Suvrath Mahadevan, a professor of astronomy and astrophysics at Pennsylvania State University (also known as Penn State), said that such a mass ratio between a star and a planet has never been encountered before. Stars originate from vast clouds of dust and gas, and the residual disc of matter from this process gathers in orbit around the star, eventually forming planets.
The colossal exoplanet was detected using a spectrometer made at Penn State. The device, dubbed the Habitable Zone Planet Finder (HPF), is designed to observe intriguing stars for earth-based observation, in the pursuit of planets capable of retaining liquid water on their surfaces. This becomes significantly easier around ultracool stars, such as LHS 3154, although it implies that the potential planet is much closer to its star than the Earth's distance from the Sun. Due to the small distance and low mass of ultracool stars, detecting planet signals using HPF is relatively easier, as a planet's transit in front of its star results in a more noticeable change in the radiation spectrum received on Earth.
Existing beliefs on planetary system formation are put to the test
Our current theories of planet formation struggle to explain why LHS 3154b is so large compared to its star. As per the team's calculations, the considerable mass of the planet's core would have required a larger amount of solid material in the protoplanetary disk than what current models anticipate.
In this particular case, it suggests that at the time of the star's birth, the dust-to-gas ratio in the protostellar cloud was approximately ten times higher than those previously observed in stellar nurseries.
