The annual meeting of the American Astronomical Society is now in session in Austin, sure to provide us with interesting fodder for discussion in coming days. Just coming off embargo yesterday was news of further study of the interesting Kepler-16 system. This one made quite a splash last fall when the planet known as Kepler-16b was discovered to orbit two stars, with the inevitable echoes of Star Wars and the twin suns that warmed the planet Tatooine. This planet, though, was a gas giant more reminiscent of chilly Saturn than a cozily terrestrial world.
Image: An artist’s conception of the Kepler-16 system (white) from an overhead view, showing the planet Kepler-16b and the eccentric orbits of the two stars it circles (labeled A and B). For reference, the orbits of our own solar system’s planets Mercury and Earth are shown in blue. New work out of the University of Texas at Arlington explores the question of habitability in a system like this. Credit: NASA/Ames/JPL-Caltech.
You’ll recall, too, that Kepler-16b circles both a K-dwarf with about 70 percent of the Sun’s mass and a red dwarf of about a fifth of a solar mass. Although the planet’s orbit takes it within Venus-like distances of them, Kepler-16b’s central stars are small enough that temperatures would appear to be too cold for life. At the Austin meeting, however, researchers from the University of Texas at Arlington have made the case that an Earth-class planet could exist here as an exomoon orbiting the gas giant. They have no indication that such a planet actually exists, as Zdzislaw Musielak (UT-Arlington) is quick to point out, but the work is interesting nonetheless:
“This is an assessment of the possibilities,” said Musielak. We’re telling them where a planet has to be in the system to be habitable. We’re hoping they will look there.”
Making conditions on such a moon habitable would require an atmosphere with a strong warming effect that could be provided by high levels of greenhouse gases like carbon dioxide or methane. Such an atmosphere would widen what we would normally consider to be the habitable zone around the two stars. Al Jackson noted today in an email from Austin that all kinds of new ways to study Kepler candidates are coming to the fore, and remember that Kepler still has a long way to go before its primary mission is accomplished. As to exomoons, we’ve yet to identify one, but so much good work has been accomplished on how to achieve such a detection that it’s surely not going to be long before we have candidate exomoons to focus in on.
The paper on this work is not yet out, but I’ll announce it here when it’s available. Meanwhile, thoughts on how many habitable worlds are out there continue to be expansive. More on this tomorrow, as we return to news coming out of the Austin conference.