Image Compliments of Astronomy Today
The NASA Kepler Space Telescope was launched in 2009 to peer at an area of space as big as a hand extended at arms length. It's mission was to detect possible planets orbiting their host star by a detecting minute drop in light intensity as the planet passed in front of the star. The mission was a resounding success resulting in the discovery of over 4,000 exoplanets, some of which are present within the habitable zones around their stars and therefore can possibly contain life.
The newest NASA telescope placed in orbit is called TESS (Transiting Exoplanet Survey Satellite). It is designed to discover planets that pass in front of their host stars blocking small portion of the light normally emitted. TESS was put in orbit April 18, 2018 and is intended to replace the Kepler Telescope that is now out of service. TESS watches the stars in an area 400 times larger than the Kepler Telescope and when a planet passes in front of a star, the overall light emitted is dimmed.