An artists illustration of a distant exoplanet. Shutterstock.

Meet “Earth Pi” an Exoplanet That Orbits its Star Every 3.14 days

This exoplanet orbits its star, a ultracool dwarf, every 3.14 days, hence its name Earth Pi.


The universe is an amazing place. Each day, we learn just how little we know about the cosmos. Each new discovery offers an unprecedented insight into the wonders of our universe. Scientists have discovered a planet they’ve dubbed “Earth Pi.” It’s a planet the size of the Earth that rotates around its star every 3.14 days, in orbit reminiscent of the universal mathematical constant.

Earth Pi discovered in old data

Researchers at MIT (Massachusetts Institute of Technology) and other institutions discovered signals from the planet in data taken in 2017 by NASA’s Kepler Space Telescope K2 mission. By focusing on the system earlier this year with SPECULOOS (not the Belgian cookies, no), a network of ground-based telescopes, the team confirmed that the signals were from a planet orbiting its star. And in fact, the planet still appears to be circling its star today, with a period similar to pi, every 3.14 days. Furthermore, astronomers say that the planet moved around its star like clockwork.


SPECULOOS is an acronym for Search for Habitable Planets EClipsing ULtra-cOOl Stars. SPECULOOS is a network of observational telescopes composed of four one-meter observatory positions in Chile’s Atacama Desert. SPECULOOS can scan the sky across the southern hemisphere in an unprecedented way.

SPECULOOS is expanding. Scientists recently installed a fifth observatory, which became the first telescope of the program located in the northern hemisphere. Specifically, SPECULOOS is designed to look for Earth-like planets orbiting ultracool dwarfs, stars that lack the glare of much brighter and larger stars, the astronomers revealed. The exoplanet’s official designation is K2 315b, the 315th planetary system uncovered using K2 data.


Earth Pi has a radius of around 0.95, that of Earth

Astronomical observations suggest that Earth Pi has a radius of around 0.95 that of Earth, which makes it an Earth-sized planet. The exoplanet revolves around a cool, low-mass star believed to be no more than one-fifth the size of our star. The planet travels around the star every 3,14 days, zooming through space at 81 kilometers per second, or about 181,000 miles per hour.

Although the exoplanet’s mass has not been determined, astronomers believe the planet is a rocky world, similar to our planet. Nonetheless, the world is unlikely to be habitable, given its extremely close orbit to its star. Astronomers say that a surface temperature of 450 kelvins or around 176 degrees Celsius would make life as we know it impossible on the planet.

Earth PI is really hot

“This would be too hot to be habitable in the common understanding of the phrase,” explained Prajwal Niraula, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS).

Astronomers look for stars with signs of tanists, and periodic dips in the star’s brightness, which hint at the possibility of a star crossing the path between the star and our observational point. Months ago, researchers potted a cool dwarf that appeared warmer than the commonly accepted threshold for ultracool dwarfs within the Kepler Space Telescope’s second observing mission. Three years ago, the Kepler Space Telescope turned towards a part of the sky where the cool dwarf–dubbed in the K2 data as EPIC 249631677–was located.

20 signals for Earth Pi

Eventually, Niraula decided to comb through the period’s data painstakingly and came across a signal. He came across 20 signals in the data showing as many as 20 dips in the star’s brightness. Curiously, these were found to repeat every 3.14 days. After spotting the exoplanet in the data, the next step was to look at the star with SPECULOOS but to do that; they first had to find the time to make the observations to see the planet transit its star. Scientists developed an algorithm that allowed them to forecast the transit. This helped the researchers to narrow the transits to several nights in February 2020.


Observing it transit its star

They pointed SPECULOOS’ telescopes toward the star and observed as many as three crystal clear transits, proving the planet orbited its sun every 3.14 days. The three transits were observed with the network’s Southern Hemisphere telescopes and one with SPECULOOS’ Artemis telescope in the Northern Hemisphere. With the help of data obtained by the Kepler Space Telescope and follow-up observations by SPECULOOS, astronomers have found a planet they’ve dubbed Earth Pi.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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