2023-12-04 11:45:31
The discovery of a Neptune-mass planet orbiting a red dwarf star challenges theoretical models of planet formation.
The star around which this exoplanet (a planet outside our solar system) rotates is called LHS 3154, it is of spectral type M and has very little mass.
The planet, called LHS 3154b, has a mass at least 13 times that of Earth. The star is 9 times smaller than the Sun. This shows that small stars can sometimes host larger planets than previously thought.
Planets form in the dense circumstellar disks of gas and dust that surround newborn stars. The amount of material in these structures determines the mass level up to which the planets that form inside them can grow.
Because the mass of dust contained in protoplanetary disks is largely determined by the mass of the host star, theories of planet formation predict that red dwarf stars (M dwarfs, the smallest type of star) should not host exoplanets in close orbit with masses greater than that of Neptune (17 Earth masses).
Although candidates for massive planets have been detected around a few very low-mass dwarfs, until now they all had very long orbital periods.
Artist’s rendering of the planet LHS 3154b in the foreground, with its star behind. (Illustration: Penn State. CC BY-NC-ND)
Using precise near-infrared radial velocity observations from the Habitable-zone Planet Finder (HPF) spectrograph, Guomundur Stefánsson’s team from Princeton University in the United States detected the aforementioned huge exoplanet in a close orbit around LHS 3154. .
Observations of LHS 3154 revealed Doppler shifts indicating the presence of an exoplanet of nearly Neptune’s mass with an orbital period of 3.7 days.
The currently most accepted theories of planet formation, including core accretion and gravitational instability mechanisms, have difficulty explaining how such a large planet formed around LHS 3154.
Stefánsson and his colleagues also ran simulations of planet formation to show that the amount of dust in the protoplanetary disk that formed the planet would have to be at least 10 times greater than what is typically observed in the protoplanetary disks surrounding stars. low mass.
The study is titled “A Neptune-mass exoplanet in close orbit around a very low mass star challenges formation models.” And it has been published in the academic journal Science. (Source: AAAS)
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