First habitable-zone, Earth-sized exoplanet discovered


According to Harvard-Smithsonian Center for Astrophysics, the first habitable-zone Earth-sized exoplanet has been discovered. The planet is in the solar system TOI 700, which is over a hundred light-years away in the constellation Dorado.

NASA’s Transiting Exoplanet Survey Satellite, TESS, was launched in 2018 to discover small exoplanets around our nearest neighbors. So far, TESS has discovered seventeen small planets orbiting around eleven nearby starS. These stars fall in the category of M dwarfs, which are smaller and cooler than our Sun at less than 60% of the mass and two-thirds of the temperature. In a series of three papers, astronomers reported that one of these planets, TOI-700d, is Earth-sized and is located in the stars’ habitable zone.

The TESS detections were exciting but uncertain. To confirm the observation, scientists used the IRAC camera on the Spitzer Space Observatory. Before being turned off by NASA in February of 2020, the IRAC camera was by far the most sensitive near-infrared camera in space. IRAC acquired clear detections and gave a 61% improvement of the planet’s orbit, refined the radius of the planet to be 2.1 Earth-masses. The results suggest that this planet may be rocky and “tidally locked” like our own moon, which only ever shows us one side of itself.

If there were liquid water on the surface of TOI-700d, astronomers argue there would also be water-bearing clouds in the atmosphere. Climate system models give insight into possible properties of the planet and what more sensitive measurements might find. However, pending space missions, such as JWST, will most likely lack the sensitivity required to detect atmospheric features by a factor of ten or more. These detailed climate studies will help astronomers to speculate as to the kinds of telescopes and instruments that are required to investigate the exciting neighbor.



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