The exoplanet GJ 367b, 31 light-years away, may be made mostly of iron. Is the average density 1.85 times that of the Earth?
//Summary -Level-C2//
Researchers discovered exoplanet GJ 367b, located 31 light-years away, with an average density 1.85 times that of Earth, suggesting it may be mostly iron. Using the HARPS instrument, they found its iron core accounts for 91% of its mass. This rare finding hints at its formation in an iron-rich environment. The system also includes planets GJ 367c and GJ 367d, making it ideal for studying ultra-short-period planets.
A)
A research team led by Elisa Goffo, a doctoral student at the University of Turin, has found that the average density of the exoplanet GJ 367b (Gliese 367b), located about 31 light-years away in the constellation Sails, is about 10.2 per cubic centimetre.
This is 1.85 times the average density of the Earth (5.51 g per cubic centimetre), suggesting that GJ 367b may be composed mainly of iron. A paper summarising the research team's findings has been published in The Astrophysical Journal Letters.
B)
GJ 367b is an exoplanet whose discovery was reported in 2021 based on observations from the National Aeronautics and Space Administration's (NASA) TESS exoplanet exploration satellite. 367, its radius is about 0.458 times that of the Sun, and its mass is approximately 0.455 times).
It orbits at an average distance of roughly 0.007 astronomical units (*) with a period of about 7.7 hours, and its surface temperature is estimated to be about 1100 degrees Celsius. Planets like GJ 367b, whose orbital period is less than one day, are also called ultra-short period (UPS) planets.
* astronomical unit (au) = about 150 million km, derived from the average distance from the Sun to the Earth. 0.007 astronomical unit = about 1.05 million km, about 1/55th of the average distance from the Sun to Mercury.
The GJ 367 system was selected as a target for the 2022 International Astronomical Union (IAU) exoplanet naming campaign, and GJ 367b, discovered at the time of the campaign, was named "Tahay", and the host star GJ 367 was named "Añañuca".
C)
According to the research team, the radius of GJ 367b is about 0.699 times that of the Earth, and its mass is approximately 0.633 times that of the Earth. This gives an average density of about 10.2 g per cubic centimetre, as mentioned above.
To accurately measure GJ 367b's mass, the research team used the High Precision Radial Velocity Exoplanet Surveyor (HARPS), which is attached to the 3.6m telescope of the European Southern Observatory (ESO) at La Silla Observatory (Chile). We conducted observations using the radial velocity method.
HARPS
= High Accuracy Radial Velocity Planet Searcher
D)
The research team that analysed the internal structure of GJ 367b believes that the iron core accounts for about 91% of its total mass.
Among the more than 5,500 exoplanets discovered, one with such a high average density is rare. Goffo believes GJ 367b may have initially formed in an iron-rich environment.
They mention the possibility that the rocky mantle surrounding the iron core was later stripped away.
In addition, observations by the research team using the ESO 3.6m telescope have detected two new planets, "GJ 367c" and "GJ 367d", which were not detected by TESS observations using the transit method.
The minimum mass of GJ 367c is about 4.13 times that of Earth, and that of GJ 367d is approximately 6.03 times that of Earth, and the orbital period is about 11.5 days for GJ 367c and about 34.4 days for GJ 367d.
The research team believes that this planetary system, which includes the small and dense planet GJ 367b, is an ideal target for further studies of the formation and migration of ultra-short-period planets.
The exoplanet GJ 367b, 31 light-years away, may be made mostly of iron. Is the average density 1.85 times that of the Earth?
https://sorae.info/astronomy/20231006-gj367b.html
