As many have already guessed throughout the ages, planet Earth is not the only habitable planet in the galaxy. There might be up to 300 million habitable planets in the Milky Way galaxy. This information is derived from the data from Kepler Space Telescope and the Gaia mission analysed by scientists from the SETI Institute, NASA, and other international organizations. This study not only holds a clue to how many other life-bearing planets might potentially exist, but also correlates to the Drake equation – an estimation of extra-terrestrial civilizations might exist.
Dr Frank Drake came up with the Drake equation in 1961. It is by far the most famous formula for searching for extra-terrestrial technological civilizations that may potentially communicate with Earth using radio signals. Factors for this equation include things like the rate of star formation, how many of the stars have planets, then how many habitable planets surround a star, which of them support life, which of them produce intelligent life, the number that produce a technological civilization and the life span of that civilization.
There is only one problem with this equation – none of these factors can be known for certain. The exercise ranges from logical estimates to guess. Anyhow, the Drake equation postulates that there are anywhere between one and 100 million technological civilizations in our galaxy. As one can imagine, it isn’t a very helpful estimate.
To have clearer and more condensed and reliable range, data from Kepler exoplanet-hunting mission was used to estimate how many habitable planets are there in the galaxy. They looked for factors like exoplanets that were the same size as Earth, that revolve around a star (like our Sun), have similar age and temperature, are in the habitable zone i.e. where liquid water could exist.
Studies like this have been conducted before. But SETI claims the new research is more refined as it looks at an additional factor – how much light the planet receives from its star. The Gaia mission has data about the amount of energy the host star emits, and it was combined with Kepler data.
The result – there may be around 300 million potentially habitable planets in our galaxy. Some may be as close as being 30 light-years away from Earth. Other factors can be studied to refine this data even more (like atmosphere, liquid water etc). One of the authors, Michelle Kunimoto, says by aiming surveys at small, potentially habitable planets around Sun-like stars will require these results to maximize their chance of success and truly finding life on other planets.