There are hundreds of millions of habitable planets in the Milky Way

Life in the Milky Way may be less scarce than one might think: in fact, there would be hundreds of millions of planets orbiting the right distance from their star to have liquid water and thus be able to host life forms. The study indicates this published In the Journal of the American Academy of Sciences (Pnas) by Sarah Ballard, professor of astronomy at the University of Florida, and doctoral student Sheila Sager.

The two astronomers measured the eccentricity of the orbit of a sample of more than 150 planets orbiting some of the most common low-mass stars in the galaxy, M-type dwarfs, which are smaller and cooler than our sun. Thanks to data collected by NASA’s Kepler telescope and the European Space Agency’s Gaia satellite, the two researchers discovered that circular orbits around stars with multiple planets are more likely to be traversed allowing them to stay at the correct distance to keep water in a liquid state.

However, when there is only one planet, the orbit is likely to be so eccentric that it gets so close to the star that the force of gravity exerted deforms it and the resulting friction generates a great deal of heat to sterilize its surface. Given that a third of the observed planets orbit in the potentially habitable zone, it is possible that there are hundreds of millions of planets in the Milky Way that are a promising research target for life “hunters”.
According to Sager, first author of the study, this finding will be “very important for the next decade of exoplanet research.”