A recent survey by astronomers from the University of Florida (USA) revealed that in the Milky Way there would be hundreds of millions of planets orbiting at the appropriate distance from their star to have liquid water and therefore able to harbor life forms.
Research has found that a third of the planets orbiting red dwarf stars (M dwarfs) may be located in a habitable zone (in the area known as “golden loop orbit”), making them ideal candidates for housing life.
Illustration showing habitable zones for different types of stars showing too hot (red), too cold (blue) and just enough (green) for liquid water to exist on a planetary surface. Since red dwarfs are cooler than our Sun, their habitable zone is closer to the star. Credit: NASA/Kepler Mission/Dana Berry.
How was the investigation
The study published by Sarah Ballardprofessor of astronomy at the University of Florida, and by doctoral student Sheila Sagarused the data collected by the NASA’s Kepler and European Space Agency’s Gaia telescopes (ESA), which capture information about exoplanets as they move past their host stars.
astronomers analyzed the orbital eccentricities of 163 exoplanets, which are roughly the size of Jupiter and orbit red dwarf stars in 101 systems. The larger the oval shape of an orbit, the greater its eccentricity.
When a planet orbits very close to its star, similar to the distance between Mercury and the Sun, an eccentric orbit can lead to a phenomenon called tidal warming. Due to the different gravitational forces that act on the planet due to its irregular orbit, it undergoes stretching and deformation, which generates friction and subsequently increases its temperature. In the most extreme cases, this heating process can result in a complete “cooking” of the planet, eliminating any possibility of liquid water.
Artist’s impression of a young red dwarf star surrounded by three planets.
To measure the orbits of the planets, Ballard and Sagear they particularly focused on the time it took for the planets to move across the “face” of the stars. Additionally, they were also based on new data from the Gaia Telescope which measured the distance to billions of stars in our galaxy.
“Distance is really the key piece of information that we were missing before that allows us to do this analysis now,” Sagear said.
Results
The investigation revealed that the stars with several planets they were most likely to have the kind of circular eye sockets that allowed them to hold liquid water. In contrast, stars with a single planet have more frequently experienced extreme tides that have “sterilized” the surface of the planet.
Given that a third of the planets in this small sample had orbits smooth enough to potentially support liquid water, our galaxy could contain hundreds of millions of planets where life could thrive.
According to Sagear, this result will be “very important for the next decade of exoplanet research”.
The study was published in the journal Proceedings of the National Academy of Sciences.
References: Live Phys/Sciences.
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