Direct imaging of exomoons

On the Direct Imaging of Tidally Heated Exomoons
http://arxiv.org/abs/1209.4418

Tidally-heated exomoons may be good candidates for direct detection: under the right combination of parameters it could be that the moon outshines its parent planet. It may also be possible that an Earth-size exomoon tidally-heated to Earthlike temperatures in the outer regions of a planetary system is an easier target than an Earth-analogue in the habitable zone. (Whether an object experiencing such strong heating is a good candidate for habitability is another matter...)

They also suggest that Fomalhaut b might be a tidally-heated exomoon, I am not convinced of this however, not sure it fits the observations particularly well...

Agreed. The supposed "Fomalhaut b" has only been detected in visible light, not where I'd expect the moon to dominate over the planet.

They are too optimistic with moons heated by tidal force of planets

Sirius_Alpha wrote:

Agreed. The supposed "Fomalhaut b" has only been detected in visible light, not where I'd expect the moon to dominate over the planet.

Yes, IIRC the spectrum of Fom b is consistent with reflected starlight, which would not be the case with this kind of tidally-heated moon.

Latest revision of the paper updates the conclusions about Fom b.

Quote :

We note in passing that the data collected on Fomalhaut b prior to the recent detection of F435W emission (Currie et al. 2012) fits the general SED properties expected for a THEM. Specifically, aside from the F435W flux, Fomalhaut b is consistent with a THEM that is a modest fraction of the size of Io and has a surface temperature of ∼1600K if (1) an absorption feature in H-band is present and (2) surface hotspots lead to increased emission at bluer wavelengths (e.g. the F606W flux). However, the new F435W point in the object’s SED curve would require the presence of unrealistically high temperature (∼6000K) hotspots. Moreover, the optical colors of Fomalhaut b are a good match to those of its primary star, thus strongly suggesting a scattered stellar radiation explanation (Currie et al. 2012). It therefore appears quite unlikely that Fomalhaut b is a THEM. Nevertheless, it remains an interesting example of an object with some of the spectral characteristics expected for a THEM.

(THEM=Tidally Heated Exomoon)