The close ties between math and astronomy are brought even closer by a recently discovered Earth-sized exoplanet.

Astronomers have discovered an alien planet that orbits its host star every 3.14 Earth days, a close approximation of the popular mathematical constant pi, the ratio between the circumference of a circle and its diameter. (Pi is an irrational number; it goes on indefinitely with the digits to the right of its decimal point.)

A new study reports that the exoplanet, named K2-315b, orbits a dwarf star which lies 186 light-years from Earth. During the extended K2 mission of NASA's Kepler space telescope, K2-315b was observed in data obtained in 2017 and was confirmed by a ground-based telescope network called SPECULOOS (a fun acronym for Search for Habitable Planets Eclipsing Ultra-cool Stars) in 2020 observations.

"The planet moves like clockwork," study lead author Prajwal Niraula of Massachusetts Institute of Technology (MIT) in Cambridge, said in a statement.

K2-315b is the 315th alien world discovered using K2 data, as its name indicates, which implies that the discovery team was only one exoplanet away from even more serendipitous symmetry.

Niraula and his colleagues predict that about 95% of K2-315b is as wide as Earth. This size implies that the alien world is rocky, but at the moment, this is not confirmed since the mass of K2-315b is unspecified.

The host star of K2-315b is only one-fifth of our sun's size and not nearly as hot. But the extreme orbital proximity of the newfound exoplanet nevertheless makes its atmosphere very toasty, measured by the research team at around 350 degrees Fahrenheit or 177 degrees Celsius.

"This would be too hot to be habitable in the common understanding of the phrase," Niraula noted.

But, as the MIT statement mentions, this temperature is ideal "for baking real pie." (With this analysis, it should be noted that there is another baking tie-in: Speculoos are also a form of spiced shortbread cookie common in Belgium and other parts of Europe.)

Using the transit method, Kepler looked for alien planets, observing the small brightness dips they produced when passing the faces of their host stars from the viewpoint of the spacecraft. Kepler's replacement, NASA's Transiting Exoplanet Survey Mission, implements this same technique.

In November 2018, after 5 1/2 years of revolutionary research, NASA decommissioned Kepler. Approximately 4,300 confirmed exoplanets have been found by astronomers to date, and Kepler is responsible for around two-thirds of these discoveries via its main and K2 missions. The Kepler dataset continues delivering, as the latest study reveals, even though the spacecraft itself has been dead for almost two years.

The new paper, which was published online on Sept. 21 in The Astronomical Journal is called "Pi Earth: a 3.14-day Earth-sized Planet from K2's Kitchen Served Warm by the SPECULOOS Team."