Astronomers earlier this week announced the existence of 1,284 newly discovered planets, of which nine are potentially habitable, The Wall Street Journal reports.The discovery was made using NASA's Kepler Space Telescope."This is the most exoplanets that have ever been announced at one time," Princeton University astrophysicist Timothy Morton told The Wall Street Journal. "This more than doubles the number of known Kepler exoplanets."An exoplanet is defined as a planet that orbits a star other than the Sun.Water that can pool is the essential factor for the nine exoplanets considered habitable. Further, more than 100 of the discoveries are about the same size as Earth, and nearly 550 could be rocky planets like Earth, The Journal reports.NASA launched the Kepler mission in 2009 to make discoveries like this. However, these new planets have yet been confirmed by independent sightings from telescopes here on Earth.Over the past few years, astronomers have detected thousands of planets, leading some to believe that each star in the Milky Way is likely to have at least one planet in orbit around it, The Journal reports."You quickly realize that there are 10 billion such potentially habitable planets in our galaxy," Kepler mission scientist Natalie Batalha told The Journal.