NASA’s TESS mission continues to find the strange and different when it comes to exoplanets. A new paper was published in Science this week that details the discovery of a planet about the size of Mars, called GJ 367b, that orbits its star in a blistering eight hours. So mark another one in your sub-Earth column and in your ultra-short-period column, just in case you’re counting.

But wait! There’s more. This relatively small world is close enough to its star that scientists could actually calculate its mass, and now we get to the even more interesting part: GJ 367b is a rocky world with a similar composition to Mercury and a solid core of iron and nickel, possibly making up as much as 86 percent of the interior.

TESS observed the parent star’s patch of the sky back in 2019, with the planet showing up as a dip in the star’s light. Astronomers confirmed the planet using the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument at the ESO’s telescope in Chile. From there, the team analyzed all of the data to calculate the various characteristics of GJ 367b.

Mind you this is not a habitable planet in the slightest. While the star is a red dwarf, the planet is still getting blasted by 500 times more radiation than the Earth gets from our Sun. And with that close orbit, daytime temperatures are up around 1,500 degrees Celsius.

However, it is very possible that this small world has a family since red dwarf stars typically tend to have multi-planet systems. And some of those family members could be more habitable to life. And with the parent star being only 31 light-years away from our solar system, this system is one to keep an eye, or rather a spacecraft’s eye, on.

More Information

DLR Institute of Planetary Research press release

MIT press release

“GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star,” Kristine W. F. Lam et al., 2021 December 2, Science