With the discovery of a planet orbiting Proxima Cenuri, our nearest neighbor in the Universe, questions arose again regarding the possibility of life on another world. Several things helped bring this about. The planet is close to the size of Earth, just slightly larger which means it is not a gas giant. And, it appears to be in the Goldilocks Zone of its star, the region where water can exist in the liquid state. But, is that enough?
Yes, planets orbiting other stars have been discovered on a regular basis since the early 90s. The early finds were gas giants, which can cause a noticeable wobble of a planet’s star. Smaller planets require more elaborate technology, such as monitoring stars for a slight, and I do mean slight, dimming as the planet transits the face of the star. Or, use of Doppler shifts to determine when a star is moving towards, then away, from Earth as a planet orbits it. Direct observation is not practical.