Researchers with the University of British Columbia have provided a new estimate for the potential number of habitable Earth-like planets (called exoplanets) located in our galaxy: up to six billion. The estimate is based on the number of G-type stars in our galaxy, which are similar to Earth’s own Sun. For a planet to be habitable, it must be in the ‘goldilocks’ zone of its star where it neither too hot nor too cold.
The study comes from co-authors and UBC researchers Michelle Kunimoto and Jaymie Matthews; it was recently published in The Astronomical Journal. The team focused specifically on the Milky Way, which is estimated to have up to a massive 400 billion stars, though only around 7-percent of them are Sun-like ‘G-Type’ stars.
Many of these stars have planets, but many of them will not be habitable due to excessively hot or cold temperatures. When a planet is in its star’s goldilocks zone, however, it is likely to have liquid water and a climate that could potentially support life — these are called exoplanets.
According to Kunimoto, there may be up to 0.18 exoplanets for each G-type star, which works out to up to six billion of these Earth-like celestial bodies. The results are based on a method called forward modeling, with Kunimoto explaining:
I started by simulating the full population of exoplanets around the stars Kepler searched. I marked each planet as ‘detected’ or ‘missed’ depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalog of planets. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars.
The study joins a different one from the University of Nottingham that estimates there may be more than 30 intelligent civilizations in the Milky Way.