Nasa’s planet-seeking satellite has spotted a second Earth-size exoplanet that may have once harboured life.
The planet, named TOI 700 e, is located around 100 light years away from our world in the habitable zone of the red dwarf star that it orbits. Its proximity to the star would allow liquid water to exist on its surface, indicating that it could be (or may have once been) suitable for life.
The latest discovery was announced at the 241st meeting of the American Astronomical Society in Seattle on Tuesday, CNN reported. A paper about the exoplanet has been accepted for publication by The Astrophysical Journal Letters.
Nasa believes it to be a rocky planet that is 95 per cent the size of Earth. It is the fourth exoplanet to be spotted orbiting the red dwarf star TOI 700 by the Transiting Exoplanet Survey Satellite, or TESS, which Nasa launched in April 2018.
A neighbouring planet with similar life-bearing characteristics was identified by TESS in 2020. In all, the satellite has unearthed 285 confirmed exoplanets and more than 6,000 candidates. TESS finds planets by looking at changes in the brightness of large stars for about a month at a time. These fluctuations indicate that a planet has passed between its telescope and the stars, called transits.
The remaining two exoplanets in the TOI 700 system orbit too close to the star to resemble Earth.
One of the planets, TOI 700 b, is 90 per cent the size of Earth and completes an orbit of the star every 10 Earth days. TOI 700 c is 2.5 times bigger than our planet and concludes its orbit every 16 days.
Nasa says the planets are likely to be tidally locked, which means they spin only once per orbit so that one side always faces the star, just as one side of the Moon is always turned towards Earth.
By comparison, the two possibly habitable planets, TOI d and e, have longer orbits of 37 days and 28 days each.
“This is one of only a few systems with multiple, small, habitable-zone planets that we know of,” said Emily Gilbert, a postdoctoral fellow at Nasa’s Jet Propulsion Laboratory in Southern California who led the work. “That makes the TOI 700 system an exciting prospect for additional follow-up. Planet e is about 10 per cent smaller than planet d, so the system also shows how additional TESS observations help us find smaller and smaller worlds.”