January 7, 2020
NASA Satellite Finds New, Earth-Sized Planet In Nearby Star's 'Inhabitable Zone'

A NASA satellite has found evidence of a planet in another solar system -- referred to as an "exoplanet" -- that is roughly similar in size to Earth. The exoplanet is reportedly far enough away from its sun that it could potentially support life, Space reports.

The Transiting Exoplanet Survey Satellite, or TESS, has been scouring the skies for evidence of exoplanets for a couple of years now. The organization's latest find, TOI 700 d, holds quite a bit of promise.

Finding exoplanets is one thing, but finding potentially inhabitable exoplanets is another. In order for an exoplanet to potentially support life -- or at least, life as it's currently understood -- several conditions must be met.

In order to retain life, the planet can't be too big. Similarly, it can't be too small or the gravitational pull will be too weak to support life. The planet also can't be too close to its sun since that would result in too much light, heat, and radiation to support life. Moreover, the planet can't be too far from its sun for similar reasons.

In other words, astronomers are looking for planets in the so-called "Goldilocks Zone."

TOI 700 d checks all of those boxes. The planet is believed to be roughly equivalent to the size of the Earth, and it sits comfortably within its star's Goldilocks Zone.

Emily Gilbert, a graduate student at the University of Chicago, says that the exoplanet's sun is -- not unlike ours -- mostly consistent in its energy output, making it easier for scientists to model. As a result of its energy output, the planet is potentially able to support life.

"In 11 months of data, we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions," said Gilbert.

This marks the first time that TESS has found such an exoplanet. Moreover, at a comparatively-close 101.5 light-years away, the planet invites further study.

Joseph Rodriguez, an astronomer at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said that his team was keen to confirm the existence of the planet with another dataset. In order to do so, they turned toward a telescope on the ground: NASA's Spritzer Space Telescope. According to Rodriguez, the device confirmed the existence of the planet.

"Spitzer saw TOI 700 d transit exactly when we expected it to," said Rodriguez.

TESS also discovered two other planets orbiting TOI 700 d's star -- neither of which is likely to be inhabitable.

The first evidence for the existence of exoplanets was found over a century ago in 1917. Since that time, more than 4,000 exoplanets have been found, but most of them are likely uninhabitable.