The "Habitable Zone" Problem.

It might not include frozen moons of gas-giant planets or worlds where life as we don't know it may evolve, but as long as we are aware of these limitations, it's still handy. An illustration of TOI-700 d, the first Earth-size habitable-zone planet discovered by NASA's Transiting Exoplanet Survey Satellite. ASTRONOMERS HAVE, SO far, discovered nearly 5,500 exoplanets - alien worlds orbiting alien stars - with more than 7,000 candidate planets still waiting to be confirmed. [Extracted from the article]