Astronomers have recently spotted an extrasolar planet that is a lightweight as well as fast-mover. Dubbed as GJ 367 b, this ultra-light and superfast planet has half the mass of Earth. Moreover, it is one of the lightest among the nearly 5000 exoplanets known today.
The planet has an orbital period of only one-third of Earth’s day. In simple words, it orbits its star, which is a red dwarf called GJ 367, in eight hours. The planetary system, where the planet lies, is located just under 31 light-years from Earth.
This ultra-light and superfast planet- GJ 367 b- has a diameter of just over 9000 kilometers. It is slightly larger than Mars. The discovery of this planet indicates the possibility of determining the properties of even the smallest, least massive exoplanets.
W. F. Lam and Szilárd Csizmadia from the Institute of Planetary Research at DLR (German Aerospace Center) said, “From the precise determination of its radius and mass, GJ 367b is classified as a rocky planet. It seems to have similarities to Mercury. This places it among the sub-Earth-sized terrestrial planets and brings research one step forward in the search for a ‘second Earth.'”
Because of its short orbital period, the GJ 367 b belongs to the ‘ultra-short period’ (USP) group of exoplanets.
Kristine Lam said, “We already know a few of these, but their origins are currently unknown. By measuring the precise fundamental properties of the USP planet, we can get a glimpse of the system’s formation and evolution history.”
Scientists discovered this planet using TESS and the transit method. They then studied its spectrum from the ground using the radial velocity method. Using the HARPS instrument on the European Southern Observatory’s 3.6m telescope, they determined the mass of this ultra-light and superfast planet.
The meticulous study and combination of different evaluation methods allowed scientists to determine the planet’s radius: 72 percent of Earth’s radius and its mass 55 percent of Earth’s mass.
Based on its mass and radius, the team could conclude the exoplanet’s inner structure. It is a low-mass rocky planet but has a higher density than the Earth.
Szilárd Csizmadia said, “The high density indicates an iron core dominates the planet. These properties are similar to those of Mercury, with its disproportionately large iron and nickel core that differentiates it from other terrestrial bodies in the Solar System.”
“The planet’s proximity to its star means it is exposed to an extremely high level of radiation, more than 500 times stronger than what the Earth experiences. The surface temperature could reach up to 1500 degrees Celsius – a temperature at which all rocks and metals would be melted. GJ 367 b, therefore, cannot be considered a ‘second Earth.'”
- Kristine W. F. Lam, Szilard Csizmadia, Nicola Astudillo-Defru, et al. GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star. DOI: 10.1126/science.aay3253