Astronomers discover ‘pi Earth’ planet that orbits its star every 3.14 days

Astronomers have discovered a charming coincidence of mathematics in the heavens: An exoplanet that orbits its star every 3.14 days. The Earth-sized planet has been dubbed the “pi Earth” due to its orbiting period being close to the mathematical constant of pi (π).

Technically known as K2-315b, the planet has a radius 95% that of Earth’s and orbits a cool star that is much smaller than our sun, at about one-fifth of the size. A year there lasts only a few days as it orbits very close to its star, moving at a wild speed of 181,000 miles per hour.

“The planet moves like clockwork,” said lead author Prajwal Niraula, a graduate student at the Massachusetts Institute of Technology, in a statement.

 Caption: Scientists at MIT and elsewhere have discovered an Earth-sized planet that zips around its star every 3.14 days.
Scientists at MIT and elsewhere have discovered an Earth-sized planet that zips around its star every 3.14 days. NASA Ames/JPL-Caltech/T. Pyle, Christine Daniloff, MIT

The planet was first discovered by the Kepler telescope in 2017 as part of its K2 mission, and recently its orbit was confirmed as part of the SPECULOOS project (Search for habitable Planets EClipsing ULtra-cOOl Stars), which is a network of telescopes used to search out Earth-like planets.

Don’t start planning a future on pi Earth yet though, as it’s far too hot for us to live on. It has a surface temperature of around 350 degrees Fahrenheit — which, MIT points out, is perfect for baking a pie.

The astronomers themselves are having fun with the discovery too, having titled their Astronomical Journal paper about the finding “π Earth: A 3.14-day Earth-sized Planet from K2’s Kitchen Served Warm by the SPECULOOS Team.”

“Everyone needs a bit of fun these days,” said co-author Julien de Wit.

As well as being an entertaining oddity, this planet could be a good candidate for study with future telescopes. The upcoming James Webb Space Telescope (JWST) will be able to tell if distant exoplanets like pi Earth have an atmosphere, which will help determine their habitability.

This finding is an indication of the many fascinating exoplanet discoveries yet to come, according to the researchers. “There will be more interesting planets in the future, just in time for JWST, a telescope designed to probe the atmosphere of these alien worlds,” Niraula said.

“With better algorithms, hopefully one day, we can look for smaller planets, even as small as Mars,” he added.

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