New exoplanet orbiting binary stars is likely too big for liquid water

It’s really hard to see something 3,700 light-years away, especially if it’s not emitting any light of its own. Instead, you have to look for the gravitational or visual shadow of that object as it either perturbs the path of the star it orbits, or temporarily eclipses it. Both detection methods are significantly complicated when there are two stars, not one, at core of a solar system, since a potential planet is likely to eclipse one star, but not both, at a time, wiping out any detectable silhouette. Despite their probable abundance, these confounding factors make the discovery of circumbinary planets much more unusual than the thousands of other planets we’ve seen in in the universe.

Even number of planets may not be odd

A circumbinary planet is one that orbits two stars at once. From our perspective, this would seem like a very exotic concept, but calculations find that such solar systems are likely to be common across the universe. They haven’t been as aggressively identified partially because we have lowered expectations that they can support Earth-like life. If the gravity from the two stars force planets into a highly elliptical orbit, temperatures will vary too much to maintain liquid water. It’s thought that our best shot for finding Earth-like exoplanets in the so-called “habitable zone” will be in binary solar systems where the stars are either under one-tenth of one astronomical unit (AU) apart, or over seven AU. With such a limited set of options, it’s easy to see why a planet like Kepler-1647b isn’t found every day.

While first spotted in 2011, Kepler-1647b has finally been confirmed as the largest circumbinary planet we’ve seen yet. Adding to the excitement is that it appears to be in a water-friendly orbit, which would be great if it weren’t so big. Kepler-1647b’s size means that it’s likely a gas giant like Jupiter, and so nobody is expecting that it will harbor life directly. There’s a chance that it may have rocky moons enjoying the tepid temperatures, and that they may be home to life, but at these distances, and with how hard it was to even catch a glimpse of Kepler-1647b itself, we don’t have any way to look for smaller objects. Still, it can serve as reference data for what will likely be a larger and larger group of hard-to-spot planets as we keep looking at binary solar systems.

Source: New planet is largest discovered that orbits 2 suns, Scienmag