There are hundreds of millions of planets around other stars in our Milky Way galaxy that may be habitable, argues a new research paper.
These exoplanets (planets orbiting a star other than our sun) orbit close to red dwarf stars that are smaller and cooler than the sun, and which make up over 75% of the 200 billion stars in the Milky Way.
Published today in the journal Proceedings of the National Academy of Sciences, the new research by the University of Florida looks at data collected by NASA’s Kepler spacecraft between 2009 and 2018 on 150 exoplanets. Kepler found over 2,600 exoplanets mostly in one a small region of the night sky.
It also used data from the Gaia telescope, which is measuring the distance to billions of stars in the galaxy.
Red dwarf stars may be ubiquitous in our galaxy, but the environment around them is very different to our solar system. Since they radiate less light and heat, the so-called habitable zone—where an orbiting planet can be warm rather than either frozen or furnace-like—is very close to the star.
For a planet to be warm is considered by scientists as essential in the hunt for life because only planets that are in this zone could potentially have liquid water—integral to life on Earth—on their surfaces.
Planets that orbit really close to a star are susceptible to being flayed by flares or roasted by friction caused by tidal forces, which could prevent life from forming. The researchers found this to be the case around stars where only one planet exists.
According to the paper, that rules out two-thirds of planets around red dwarf stars, leaving a third that could be promising targets to probe for signs of life outside our solar system.
Many of these candidates for life exist around stars that host multiple planets, found the researchers. They also had circular rather than eccentric orbits where the distance to the star is consistent.
“This result is really important for the next decade of exoplanet research, because eyes are shifting toward this population of stars,” said astronomy doctoral student Sheila Sagear at the University of Florida. “These stars are excellent targets to look for small planets in an orbit where it’s conceivable that water might be liquid and therefore the planet might be habitable.”
Wishing you clear skies and wide eyes.