Earth-size 'pi planet' rocks a 3.14-day orbit

It's Pi Day every day on exoplanet K2-315b.

Amanda Kooser
Freelance writer Amanda C. Kooser covers gadgets and tech news with a twist for CNET. When not wallowing in weird gear and iPad apps for cats, she can be found tinkering with her 1956 DeSoto.
Amanda Kooser
2 min read

Researchers found a "pi Earth" that orbits its star every 3.14 days as this illustration suggests.

NASA Ames/JPL-Caltech/T. Pyle, Christine Daniloff, MIT

Everyone's favorite mathematical constant has received an inadvertent tribute from the universe. A team led by MIT researchers discovered a distant planet that orbits its star every 3.14 days, mirroring the famous first three digits of pi. 

MIT described the rocky Earth-sized planet K2-315b as "baking hot" and "likely not habitable" in a statement on Monday. "The planet moves like clockwork," said MIT graduate student Prajwal Niraula, lead author of a paper on the planet published in the Astronomical Journal this week. 

The team found the exoplanet (a planet located outside our solar system) in data gathered in 2017 by NASA's Kepler Space Telescope K2 mission. The planet-finding telescope was put into a permanent sleep mode in 2018.

The researchers confirmed the planet's existence by taking another look with the ground-based Speculoos telescope network. "Speculoos" stands for "Search for habitable Planets EClipsing ULtra-cOOl Stars." It's also a fun reference to a type of spiced cookie.

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K2-315b has to move fast to keep up its pi orbit around its cool and dim host star. The exoplanet travels at 181,000 mph (291,000 kph). The close relationship to its star means the planet's surface reaches about 350 degrees Fahrenheit (177 degrees Celsius). MIT noted this would be perfect for baking actual pie.

The research team said the planet could be an excellent candidate for future observations by NASA's long-delayed James Webb Space Telescope, which could give us a better idea of its atmosphere.

MIT called K2-315b's fortuitous orbit "a delightful alignment of astronomy and mathematics." 

We love to celebrate Pi Day and its magical first three digits here on Earth on March 14 every year. We can now extend that celebration farther out into the universe.