NASA has reported the discovery of an Earth-size planet, named TOI 700 d, orbiting its star in the “habitable zone”.

Goldilocks Zone

• A habitable zone, also called the “Goldilocks zone”, is the area around a star where it is not too hot and not too cold for liquid water to exist on the surface of surrounding planets.
• Our Earth is in the Sun’s Goldilocks zone. If Earth were where the dwarf planet Pluto is, all its water would freeze; on the other hand, if Earth were where Mercury is, all its water would boil off.
• Life on Earth started in water, and water is a necessary ingredient for life as we know it.
• So, when scientists search for the possibility of alien life, any rocky exoplanet in the habitable zone of its star is an exciting find.

TOI 700 d

• The newest such planet was found by NASA’s Transiting Exoplanet Survey Satellite (TESS) mission, which it launched in 2018.
• The star, TOI 700, is an “M dwarf” located just over 100 light-years away in the southern constellation Dorado, is roughly 40% of our Sun’s mass and size, and has about half its surface temperature.
• The find was confirmed by the Spitzer Space Telescope, which sharpened the measurements that TESS had made, such as orbital period and size.
• TOI 700 d measures 20% larger than Earth. It orbits its star once every 37 days and receives an amount of energy that is equivalent to 86% of the energy that the Sun provides to Earth.

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