An absolutely bizarre new exoplanet has been observed orbiting a star just 31 light-years away. The planet, dubbed GJ 367b, orbits a small, dim red dwarf star approximately 31 light-years from the sun, according to its discoverers.

GJ 367b is one of the tiniest exoplanets ever discovered, only slightly larger than Mars; however, it is also one of the most compact, with a density nearly equal to that of pure iron. It's also incredibly close to its host star, completing one full orbit every eight hours, making it an "ultra-short period" (USP) planet - a mysterious and understudied class of world.

"We already know a few of these, but their origins are currently unknown," study co-lead author Kristine W. F. Lam, of the Institute of Planetary Research at the German Aerospace Center (DLR), said in a statement.

"By measuring the precise fundamental properties of the USP planet, we can get a glimpse of the system's formation and evolution history," Lam added.

GJ 367b was discovered using data gathered by NASA's Transiting Exoplanet Survey Satellite (TESS), which launched to Earth orbit in April 2018. Lam, co-lead author Szilárd Csizmadia, also of the DLR's Institute of Planetary Research, and their colleagues discovered GJ 367b using data gathered by NASA's Transiting Exoplanet Survey Satellite (TESS), which launched to Earth orbit in April 2018.

TESS uses the "transit method" to look for planets, detecting the small brightness dips that occur when a planet crosses its star's face from the spacecraft's perspective. The TESS scans of the red dwarf GJ 367, which is about half the size of our sun, showed such a dip, and the discovery team confirmed that the signal was created by a transiting planet.

GJ 367b's super-short orbital period, as well as its size in relation to its host star, were uncovered by TESS measurements. The High Accuracy Radial Velocity Planet Searcher (HARPS), an instrument installed on the European Southern Observatory's 3.6-meter telescope in Chile, was used to further characterize the planet.

The HARPS observations revealed how much GJ 367b was dragging on its host star, allowing the researchers to compute the exoplanet's mass. The researchers were able to establish GJ 367b's density, which is higher than that of Earth, by combining the multiple measurements.

"The high density indicates the planet is dominated by an iron core," Csizmadia said in the DLR statement. "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 discovery of GJ 367b may lead to the discovery of other worlds that are more habitable.

"Since this star is so close by, and so bright, we have a good chance of seeing other planets in this system. It's like there's a sign saying, 'Look here for extra planets!'," astronomer George Ricker of MIT's Kavli Institute for Astrophysics and Space Research said.

The team's research has been published in Science.