The First Earth-Size Habitable-Zone World Found By NASA’s Planet Hunter TESS

TESS – Transiting Exoplanet Survey Satellite – which is NASA’s newest planet hunter has won a major big gamechanger.

TESS has for the first time discovered a roughly Earth-size planet in the habitable zone of its host star, the zone of orbital distances where liquid water could be stable on a world’s surface. Scientists confirmed the find, called TOI 700 d, using NASA’s Spitzer Space Telescope and have modeled the planet’s potential environments to help inform future observations.

The newfound exoplanet lies just 101.5 light-years from Earth which makes it a good candidate for follow-up observations by other instruments, scientists added. This discovery was made public during the 235th meeting of the American Astronomical Society on Monday Honolulu.

The three planets of the TOI 700 system orbit a small, cool M dwarf star. TOI 700 d is the first Earth-size habitable-zone world discovered by TESS. Credit: NASA's Goddard Space Flight Center


According to Paul Hertz, who is an astrophysics division director at NASA HQ in Washington DC, the sole purpose of why TESS was designed and initiated was specifically to discover Earth-sized planets orbiting nearby stars. He further added that planets around closer stars are easiest to follow up with larger telescopes in space and on Earth. Finding TOI 700 d is a key science finding for TESS.”

The newly discovered exoplanet is part of a multi-planet system around TOI 700, a small, cool M-dwarf star in the Dorado constellation. It’s only about 40% of our sun’s mass and size, with half of the surface temperature. TOI is a short form of Tess Object of Interest.

Scientists verified their discovery using NASA’s Spitzer Space Telescope infrared capabilities with follow-up observations. They also modeled the planet’s potential environment to investigate its habitability further.

One of the other planets discovered by TESS is a red dwarf about 40% as massive, 40% as wide and 50% as hot as Earth’s sun. The innermost world, TOI 700 b, is roughly Earth-sized and completes one orbit every 10 Earth days. The center planet, TOI 700 c, is 2.6 times bigger than our planet and zips around TOI 700 every 16 days.

The most peculiar planet discovered by the team in TOI 700 d which is the outermost planet in the system. It’s just 20% larger than Earth and completes one orbit every 37 days. The alien world receives 86% of the stellar energy that Earth gets from the sun, putting TOI 700 d in the habitable zone.

Alton Spencer, a high school student, working with the TESS team, corrected a significant error that the respective star was much hotter and unable to support life which was false.

In a similar note of events Emily Gilbert a graduate student at the University of Chicago confirmed that after the initial error was corrected, they discovered that the outermost planet was about the size of the earth and in the habitable zone.

Astronomers anticipate that in the future as from 2021 using recent advanced Telescopes, it will be possible to determine if planets have atmospheres and their compositions.

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