Astronomers discover exoplanet where a year lasts four-and-a-half hours

The Earth-sized exoplanet is in a high-speed orbit around its star.

Known as EPIC 228813918 b, the exoplanet orbits the m-dwarf star in less than four and a half hours, making one day the equivalent of more than five years.

"We report the discovery from K2 of a transiting terrestrial planet in an ultra-short-period orbit around an M3-dwarf," reads the paper in which the findings were presented. "EPIC 228813918 b completes an orbit in only 4.3 hours, the second-shortest orbital period of any known planet, just 4 minutes longer than that of KOI 1843.03, which also orbits an M-dwarf."


The findings were submitted to the Monthly Notices of the Royal Astronomical Society from a group of scientists using NASA's Kepler Space Telescope.

The average human life span is 79 years on Earth, which would make the average lifespan on EPIC 228813918 b about 150,000 years. 

EPIC 228813918 b is about the size of Earth (the paper puts it at 0.89 +/- 0.09 radii) and has an iron mass of greater than 45 percent iron. By comparison, the Earth's crust is made up of several elements, including 47 percent oxygen, 27 percent silicon, 8 percent aluminum and 5 percent iron. 

Finding exoplanets with short revolution patterns around a star is not uncommon.

In 2013, scientists found an Earth-sized "lava planet" that had an 8.5 hour year, known as Kepler-78b.