A group of astronomers from the University of British Columbia found that an estimate of 18% of Sun-like stars had Earth-like planets, equating about six billion Earth-like planets in our Milky Way galaxy.
This data was exported from NASA’s now-dead Kepler space telescope. NASA’s mission using the Kepler telescope helped find thousands of exoplanets. It studied 200,000 stars during its 10-year mission, which ended in 2018. The Kepler mission is the only one that was capable of finding and characterizing Earth-sized planets not only around Sun-like stars but also in year-long orbits.
The Milky Way has about 100 and 400 billion stars, 70% of them being red dwarf stars which tend to be smaller, dimmer and can flare.
In an article from Forbes they said, “to be clear, the scientists didn’t “discover” anything, but simply place an upper limit on estimating how many Earth-like planets there could be around Sun-like stars.” UBC researcher, Michelle Kunimoto, found 17 “new” exoplanets from Kepler earlier this year.
There are a few things for a planet to be considered Earth-like such as: being rocky, about Earth-sized and orbit in the habitable zones of its star. Forbes defines Habitable zone as, “being the zone in which liquid water could exist on its surface.”
Because of the size of Earth-like planets, it can be easily missed by telescopes. In order to gather accurate data, the telescope needs to be monitoring for years looking for things like a dip in brightness of a star when the planet passes in front of it which shows the orbit and existence. The Kepler telescope was out there for a decade, catching only a fraction of what could be out in space.
What’s next for space? We’ll see!