There could be 500 million planets capable of supporting life in our galaxy.
One of the most profound questions we can ask about our universe is whether or not life exists "out there". More popularly put, many people wonder if "they" have visited our planet? Those are good questions, but before scientists can answer those, they need to search out worlds where life might exist.
NASA's Kepler Telescope is a planet-hunting instrument specifically designed to search for worlds orbiting distant stars. During its primary mission, it uncovered thousands of possible worlds "out there" and showed astronomers that planets are quite common in our galaxy. However, does that mean that any of them are actually habitable? Or better yet, that life actually exists on the surface?
While data analysis is still underway, results from the Kepler mission have revealed thousands of planet candidates. More than three thousand have been confirmed as planets, and some of them are orbiting their host star in the so-called "habitable zone". That's a region around the star where liquid water could exist on the surface of a rocky planet
The numbers are encouraging, but they only reflect a small part of the sky. That is because Kepler did not survey the entire galaxy, but rather only one four-hundredth of the sky. And even then, its data only indicate a small fraction of the planets that could possibly exist throughout the galaxy.
As additional data is accumulated and analyzed, the number of candidates will increase. Extrapolating out to the rest of the galaxy, scientists estimate that the Milky Way could contain upwards of 50 billion planets, 500 million of which could be in their stars' habitable zones. That's a LOT of planets to discover!.