Kepler-34, Kepler-35, Kepler-38, Kepler-64 and Kepler-413 — multiple star systems located between 2,764 and 5,933 light-years away in the constellations of Lyra and Cygnus — support a permanent habitable zone, a region around stars in which liquid water could persist on the surface of any as yet undiscovered Earth-like planets, according to a paper published in the journal Frontiers in Astronomy and Space Sciences. Of these systems, Kepler-64 is known to have at least four stars orbiting one another at its center, while the others have two stars; all are known to have at least one giant planet the size of Neptune or greater.
This artist’s concept shows a hypothetical aquaplanet around the binary star system of Kepler-35. Image credit: NASA / JPL-Caltech.
“Life is far most likely to evolve on planets located within their system’s habitable zone, just like Earth,” said Dr. Nikolaos Georgakarakos, an astronomer in the Division of Science at New York University Abu Dhabi.
“Here we investigate whether a habitable zone exists within nine known systems with two or more stars orbited by giant planets.”
“We’ve known for a while that binary star systems without giant planets have the potential to harbor habitable worlds,” added Professor Ian Dobbs-Dixon, also from New York University Abu Dhabi.
“What we have shown here is that in a large fraction of those systems Earth-like planets can remain habitable even in the presence of giant planets.”
In the work, the astronomers investigated the effects of stellar binarity and circumbinary giant planets on the habitable zones of nine systems: Kepler-16, Kepler-34, Kepler-35, Kepler-38, Kepler-64, Kepler-413, Kepler-453, Kepler-1647, and Kepler-1661.
They confirmed earlier studies that suggested Kepler-16 and Kepler-1647 are not suitable for hosting a terrestrial planet within their classical habitable zone.
In contrast, Kepler-34, Kepler-35, Kepler-38, Kepler-64, and Kepler-413 seemed more promising with Kepler-38 being the best candidate. Their habitable zones are between 0.4-1.5 AU (astronomical units) wide beginning at distances between 0.6-2 AU from the center of mass of the binary stars.
Kepler-453 and Kepler-1661 stand between the previous two categories of systems.
“Our best candidate for hosting a world that is potentially habitable is the binary system Kepler-38, approximately 3,970 light years from Earth, and known to contain a Neptune-sized planet,” Dr. Georgakarakos said.
“Our study confirms that even binary star systems with giant planets are hot targets in the search for Earth 2.0. Watch out Tatooine, we are coming!”
Nikolaos Georgakarakos et al. Circumbinary Habitable Zones in the Presence of a Giant Planet. Front. Astron. Space Sci, published online April 15, 2021; doi: 10.3389/fspas.2021.640830