Image of the Artemis telescope, the first of the SPECULOOS Northern Observatory. Artemis helped ... [+]
Here’s a sweet surprise for math and astronomy lovers alike — there’s a newly discovered planet with a serendipitous tie to the mathematical constant pi. The planet, scientifically known as K2-315b and has been affectionately dubbed “pi Earth” because it’s roughly the size of Earth and it orbits its star every 3.14 days.
But pi Earth is more than just an intriguing swirl of astronomy and math. The scientists behind it’s discovery also see it as a promising case for further study of its atmosphere to look for potential signs of life.
The discovery of pi Earth comes from the researchers of the SPECULOOS survey, which stands for The Search for habitable Planets EClipsing Ultra-cOOl Stars, a collaboration involving scientists across the globe. The survey’s goal is to build upon the success of TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) which is behind the discovery of TRAPPIST-1— a planetary system 39 light years away with seven terrestrial planets in orbit, three of which are inside the habitable zone — by observing nearby ultracool dwarf stars in the search of transiting rocky planets.
Discovering The Pi Planet
Scientists look for planets orbiting ultracool dwarf stars because cooler stars are comparatively dim. Dimmer is better in the search for an exoplanet — the term used to denote planets outside of our own solar system — because researchers look for dips in a star’s light signals. Brighter stars have glare which can make it harder to see these dips, which hint that a planet is passing by and briefly blocking light.
“Transiting planets go in front of the star, and cast a shadow,” explains Prajwal Niraula, the lead author on the paper describing the discovery.
Niraula is a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS) who works with Artemis, the first telescope in the SPECULOOS Northern Observatory. The MIT EAPS department helped to lead the installment of Artemis last year in the Canary Islands, where it now scans the sky.
He found the first sign of pi Earth earlier this year while looking through data collected by the Kepler Space Telescope in 2017 as a part of their second observing mission, the K2 Campaign. For about 90 days the telescope observed a cool white dwarf star, about a fifth the size of the Sun, labeled EPIC 249631677. The data collected over that time showed a strong periodic transit-like signal, which occurred every 3.14 days.
Members of the Artemis team developed an algorithm to predict when they could next observe pi Earth’s transit to get a better look. On the dates given by their calculation, the researchers used Artemis along with two telescopes at the SPECULOOS Southern Observatory to observe the star and were able to catch clear transits, confirming what the data suggested.
“We believe that we can find smaller and smaller planets with better algorithms,” says Niraula. “These tools were helpful, and Pi Earth was a good test bed case.”
Looking For Life
Pi Earth is too hot to be habitable — at least for life as we know it. The researchers approximate the surface temperature of the planet to be roughly 350 degrees Fahrenheit, which, while certainly too hot for humans, is the perfect temperature for baking pie — another fun twist in pi Earth’s story.
Still, the researchers believe pi Earth is a good candidate for observation by the upcoming James Webb Space Telescope (JWST), which is expected to launch in 2021. The JWST will be able to take a closer look at the atmosphere of pi Earth, and other planets like it. Though pi Earth is roughly the size of our Earth, its star is only 20 percent the size of the sun, meaning the shadow it casts is proportionately larger. “This property makes it easier to study the atmosphere of the planets as the larger shadow yields better data,” explains Niraula.
The aim of SPECULOOS is to find these Earth-like planets which make good options for further characterization and Niraula sees the discovery of pi Earth as a step toward finding even more promising candidates.
“With SPECULOOS, we are looking forward to discovering planets around even smaller and brighter stars, which would be even better for studying about their atmospheres, and looking for signatures of life,” says Niraula.
Even if pi Earth doesn’t yield a biosignature which signals the presence of life, it’s a valuable discovery in the work toward gaining a better understanding of our universe.
“Having planets like K2-315b will help us to further understand the diverse planet bodies out there.”
https://www.forbes.com/sites/allisongasparini/2020/09/23/heres-how-researchers-discovered-pi-earth-the-planet-with-a-314-day-orbit/
2020-09-23 17:29:00Z
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