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TOI 700 d – First Earth-size planet in its star’s habitable zone

In the 235th annual American Astronomical Society meeting in Honolulu, Hawaii Nasa’s scientists have announced the planet named TOI 700 d the first Earth-size planet in its star’s habitable zone. This was done with the help of NASA’s Transiting Exoplanet Survey Satellite (TESS) and also the discovery was later confirmed by the Spitzer Space Telescope.

TESS monitors the large area of sky for 27 days at a time and checks for the stellar brightness caused by an orbiting planet crossing in front of its star. This kind of event is named as transit.

TOI 700 appears to be small star in the southern constellation and also it is categorised in M dwarf star which has 40% of the Sun’s mass and half its surface temperature. It appears in the 11th sector.

The outermost size of the star was about the size of earth and it is in the habitable zone. According to Emily Gilbert, a graduate student at the University of Chicago it is easy to model its atmospheric and surface conditions as TOI 700 d is habitable.

TOI 700 d the outermost planet is 20% larger than the earth which orbits every 37 days and receives 86% of the energy from the star that the sun provides to earth. In this system the innermost planet is known as TOI 700 b which is almost Earth’s size and the middle planet is known as TOI 700 c which is 2.6 times larger than the earth. The innermost planet completes its orbit every 10 days and the middle planet completes its orbit every 16 days.

Joseph Rodriguez, an astronomer at the Centre for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts, said that they really wanted to observe the planet by understanding its system as much as possible. We saw the TOI 700 d transit exactly when we wanted to see it, Rodriguez said. It also helped to the mission that confirmed two of the TRAPPIST-1 planets and also identified five more.

Rodriguez used 1 meter ground based telescope to improve the confidence in the scientists in the orbits. With the help of these ground based telescope scientist’s estimates that inner and outer planets are made of rock and the middle planet is made of gas. Their future missions are to check whether the planets have atmospheres or not.

To make the predictions and generate the computer models researchers at NASA have made 20 potential versions of TOI 700 d based on the current information such as size of the planet and the type of star it orbits to determine if any of the version determines the surface temperature and pressure. They have also developed a 3D model with different types of surface and atmospheric compositions. The cloud formation and wind patterns of the planet may be different from Earth’s because TOI 700 d is locked to its star.

They made a simulator of TOI 700 d with an atmosphere with dense carbon dioxide similar to mars when it was young. Two models were made one with too many layers of clouds facing the star and another no clouds, only land version of modern Earth where wind flows one from one side of the planet and meets directly at the point facing the star.

Gabrielle Engelmann-Suissa, modelling team expert at Universities Space Research Association said that “It’s exciting because no matter what we find out about the planet, it’s going to look completely different from what we have here on Earth.”