Habitable exoplanets

Why in news?

• Data from the Kepler space telescope revealed that there could be at least 300 million potentially habitable planets within the Milky Way galaxy, but outside of our Solar System.

About habitable exoplanets:

• A potentially habitable exoplanet is a hypothetical type of planet that could be habitable for humans.
• The main feature of potentially habitable exoplanets is that they have to be located in the habitable zone of their stellar systems.
• Mass (between 0.1 and 10 Earth masses) , Radius (between 0.5 and 2.5 Earth radii), Temperature etc are major characteristics.
• The Earth Similarity Index (ESI) is a proposed characterization of how similar a planetary-mass object or natural satellite is to Earth and is designed from scale from zero to one, with Earth having a value of one.
• The most potentially habitable exoplanet discovered so far is Teegarden b, with an Earth Similarity Index of 0.93.

About the Kepler space telescope:

• The Kepler space telescope is a retired space telescope launched by NASA to discover Earth-size planets orbiting other stars.
•  Named after astronomer Johannes Kepler, the spacecraft was launched on March 7, 2009, into an Earth-trailing heliocentric orbit.
• The principal investigator was William J. Borucki.
• After nine years of operation, the telescope's reaction control system fuel was depleted, and NASA announced its retirement on October 30, 2018

PRELIMS QUESTION

Transiting Exoplanet Survey Satellite (TESS), a  space telescope designed to search for exoplanets, was launched by:
(a)European Space Agency
(b)Japan Aerospace Exploration Agency
(c)National Aeronautics and Space Administration 
(d)China National Space Administration 

Answer to prelims question