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

About TOI 700 d: 

  • It is 20% larger than Earth and 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.
  • It 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.
  • Two other planets orbit the star TOI 700 b, which is almost exactly Earth-size, probably rocky, and TOI 700 c, the middle planet, which is 2.6 times larger than Earth, is probably gas-dominated.
  • The find was confirmed by the Spitzer Space Telescope, which sharpened the measurements that TESS had made, such as orbital period and size.

About Goldilocks zone 

  • It is a habitable zone in 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.  


About the Spitzer Space Telescope

  • It is the final mission in NASA's Great Observatories Program.
  • Spitzer is designed to detect infrared radiation, which is primarily heat radiation. Due to which it was able to see and reveal features of the universe including objects that were too cold to emit visible light.

NASA’s Great Observatories Program

It aims to collect and analyze radiation emitted throughout the entire electromagnetic (EM) spectrum in space.

This program consists of a family of four space-based observatories each observing the universe in a different kind of light. 

  1. Visible-light Hubble Space Telescope (HST)
  2. Compton Gamma-Ray Observatory (CGRO)
  3. Chandra X-Ray Observatory (CXO)
  4. The Spitzer Space Telescope

Very few such Earth-size planets have been found so far, including some by NASA’s Kepler mission, and this one is the first such discovery by TESS.