Finding Pandora and Endor
Sub-Earth-Mass Moon Orbiting a Gas Giant Primary or a High Velocity Planetary System in the Galactic Bulge
“We present the first microlensing candidate for a free-floating exoplanet-exomoon system, MOA-2011-BLG-262, with a primary lens mass of M_host ~ 4 Jupiter masses hosting a sub-Earth mass moon. The data are well fit by this exomoon model, but an alternate star+planet model fits the data almost as well. Nevertheless, these results indicate the potential of microlensing to detect exomoons, albeit ones that are different from the giant planet moons in our solar system. The argument for an exomoon hinges on the system being relatively close to the Sun. The data constrain the product M pi_rel, where M is the lens system mass and pi_rel is the lens-source relative parallax.”
Pretty cool if they can somehow confirm it. It seems like it would be difficult – you’d not only have to find the planet-moon system against the star, but then you’d have to find the moon against the big planet it’s orbiting around.
I’m not sure how habitable they’d be, though. Wouldn’t the giant planet draw in a ton more potential impactors? Most of them would hit the gas giant, but a lot of them would hit its satellites – including the big moon.
Under the planet+moon scenario, the two are free-floating away from any star. So they would not be habitable at all, unfortunately.
I haven’t had time to read the paper, but I also assume that like ~all microlensing detections this will be impossible to confirm. Which makes the uncertainty in the interpretation all the more frustrating.