NASA's Kepler Space telescope, which launched in 2009, discovered more than 2,000 exoplanets (planets outside our solar system) by the time it was retired in 2018. Another 2,400 exoplanet candidates are waiting for NASA confirmation.
More than 50 of those exoplanets were deemed potentially habitable, meaning they fall within the "Goldilocks zone" of their respective star — where conditions might enable liquid water to pool on the surface. (Earth and Mars fall within our sun's "just right" zone.)
In 2013 astronomers reported that, based on Kepler data, there could be as up to 40 billion planets comparable in size to Earth that existed within these favorable "Goldilocks zones."
Even if just .001% of those Earth-like planets hosted life, that would still mean 40 million planets out there have life on them.
Another orbiting telescope, the Transiting Exoplanet Survey Satellite (TESS) is now scouting the sky for alien worlds. TESS recently found a planet circling a nearby star in the Hydra constellation; the world could support liquid water if it turns out to have a thick atmosphere and be made of rock.