Newly discovered KOI-4777 b is the smallest known ultra-short period exoplanet

560 light years away lies small red dwarf star KOI-4777. On a tight orbit around this star there is a small rocky exoplanet KOI-4777 b (KOI-4777.01). According to a new scientific study it has a radius only about half of Earth, which makes it the smallest known exoplanet with a year shorter than 24 hours.

Star KOI-4777 (also TIC 158427808 or 2MASS J19090291+4201563) is a red dwarf with only about 10 % mass of the Sun. KOI-4777 b is the only known exoplanet around this star.

The exoplanet has about one third mass of Earth and half of its radius. In size it is comparable to Mars, but it is 3 times heavier than the red planet.