Astronomers Find ‘Pi Planet’ With 3.14-Day Orbit

by Ryan Whitwam

The longer we study the universe, the more exoplanets we find. Many of these discoveries are notable because of how Earth-like they are or because of the number of planets crammed into a single solar system. The rocky planet K2–315b, on the other hand, is notable because of its orbital period. It takes 3.14 Earth days to complete an orbit of its star. Astronomers have therefore dubbed it “pi planet.”

The planet’s name gives a hint of its origins. This is the 315th exoplanet discovered in the data from the Kepler K2 mission. That was the second phase of Kepler’s life after several of its components failed, limiting its ability to remain pointed in any one direction. That was a problem for its planet-hunting activities, but NASA managed to partially revive it by using the solar wind to stabilize Kepler along several parts of its orbit.

Kepler used the transit method to find planets, which requires scanning distant stars for long periods of time to monitor for dips in light. Those dips can signal a planet has passed in front of the star (known as EPIC 249631677). Therefore, the transmit method is best at detecting larger planets that orbit close to the star. Even though Kepler shut down some time ago, teams like the one at MIT are still poring over its data in search of new planets like K2–315b.