Dubbed TOI 700 d by NASA, the exoplanet orbits its sun at distances where conditions could allow liquid water to exist on the surface. NASA’s exoplanet-hunter the Transiting Exoplanet Survey Satellite (TESS) made the discovery and the Spitzer Space Telescope confirmed the find.
Scientists have already started to model the exoplanet’s potential environments to help inform future observations.
TOI 700 d is one of the very first Earth-size planets spotted in the so-called “Goldilocks Zone”.
The Goldilocks Zone is a region of space from a host star where surface temperatures are not too hot or too cold, but just right for liquid water exist.
Other potentially promising exoplanets include several rocky worlds in the TRAPPIST-1 system.
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“Confirming the planet’s size and habitable zone status with Spitzer is another win for Spitzer as it approaches the end of science operations this January.”
TOI 700 is a small, cool M dwarf star found a little more than 100 light-years away in the southern constellation Dorado.
The star is approximately 40 percent of the Sun’s mass and size and about half its surface temperature.
TOI 700 appears in 11 of the 13 sectors TESS monitors during the NASA mission’s first year, and scientists spied several occasions of the orbiting planet crossing in front of its star from our perspective – an event known as a transit.
The star was initially misclassified as being more similar to the Sun in our Solar System, with the planets orbiting it consequently appearing larger and hotter than in reality.
Researchers including Alton Spencer, a high school student working with members of the TESS team, identified the error.
Emily Gilbert, a graduate student at the University of Chicago, said: “When we corrected the star’s parameters, the sizes of its planets dropped, and we realised the outermost one was about the size of Earth and in the habitable zone.
“Additionally, 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.”
The most innermost planet TOI 700 b is roughly Earth-size, likely rocky and completes an orbit every 10 days.
Middle planet TOI 700 c is 2.6 times larger than Earth – between the sizes of Earth and Neptune – orbits the sun every 16 days and is thought to be a gas-dominated world.
The outermost known planet TOI 700 d is the only one in the habitable zone, is 20 percent larger than Earth, orbits every 37 days and receives from its star an estimated 86 percent of the energy the Sun provides Earth.
All of the planets are believed to be tidally locked to TOI 700, meaning they rotate once per orbit so that one side is constantly bathed in daylight.