It has been claimed that the exoplanet ‘GJ 367b’, located about 31 light years away from Earth, is composed mostly of iron. ‘GJ 367b’, first observed in 2021, is an ultra-short-period planet that orbits the main star in about 7.7 hours.
In a recently released observation report, a research team from the University of Turin, Italy, reported that the average density of the exoplanet ‘GJ 367b’ in the constellation Mast is about 10.2 g per 1 cm3. This is 1.85 times that of the Earth, which is 5.51g per 1㎤, suggesting that its constituent material may be mainly iron.
The identity of ‘GJ 367b’ was revealed in the process of analyzing observation information from NASA’s exoplanet exploration telescope ‘TESS’. It orbits about 0.007 astronomical units (about 1.05 million km) away from the main star, the red dwarf ‘GJ 367’, with a period of about 7.7 hours. Because it is close to the main star, its surface temperature is estimated to reach 1,100 degrees Celsius.
GJ 367b orbits the red dwarf GJ 367 in about 7.7 hours. <사진=NASA 공식 홈페이지>
The research team closely observed ‘GJ 367b’, which is attracting attention for its extremely short orbital period, for nearly two years. In this process, it was found that the radius of ‘GJ 367b’ is about 0.699 times that of the Earth, and the mass is about 0.633 times that of the Earth.
An investigation official said, “We observed ‘GJ 367b’ using the 3.6m telescope of the La Silla Observatory in Chile operated by the European Southern Astronomical Observatory (ESO),” and added, “HARPS (High Accuracy), a high-precision radial velocity exoplanet exploration device mounted on the telescope. “We found the mass of ‘GJ 367b’ using ‘Radial Velocity Planet Searcher’,” he said.
The radial velocity method indirectly observes exoplanets through the movement of the main star, which slightly shakes in a circle according to the exoplanet’s orbit. As the main star fluctuates according to the planet’s revolution, the color of the light periodically changes from blue when the main star approaches the Earth to red when it moves away. In order to capture the color change of this star, a spectroscopic observation device is needed.
NASA’s TES exoplanet exploration telescope. An exoplanet, LP 791-18d, 90 light years away was discovered. <사진=NASA 공식 홈페이지>
An investigation official said, “As a result of analyzing the internal structure of ‘GJ 367b’, it is reasonable to assume that about 91% of the total mass is a core made of iron.” “It’s rare,” he emphasized.
The research team considered the possibility that ‘GJ 367b’ was originally born in an iron-rich environment, or that the rocky mantle surrounding the iron core was peeled off after the planet was created. The research team’s position is that high-precision observations using additional equipment, such as the James Webb Space Telescope, are needed to know exactly which is correct.
Reporter Jeong Ian [email protected]
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