To address your second question… Yes, astronomers have discovered some giant planets that spend much or some of their time in the “habitable zone”. Unfortunately, none of those have been observed to transit.

As you point out, transit searches have a good chance of some day finding a large transiting planet in the “habitable zone” of an M dwarf. Then we could search for a rocky habitable Trojan with this technique.

BTW, in my paper we state,
“In principle, our technique could be applied to search for terrestrial-mass
Trojans of giant planets orbiting in the habitable zone of their stars
(Schwarz et al. 2005). While present search techniques are strongly
biased towards finding transiting planets at short orbital periods,
future space missions (e.g., Corot, Kepler) offer the prospect of
finding transiting planets in the habitable zone of their stars,
particularly for low mass stars where the habitable zone can be
~0.015AU away from the star.”

Regards,
Eric

Good question. I think that because of the essentially threshold nature of Jovian planet formation, you’re much more likely to have L4 or L5 companions winding up much smaller than the primary.

Among the fourteen known transiting planets, there are clearly no Jovian-mass trojan companions, so it’s at least clear that near-equal mass trojan ratios are not the usual mode of formation for hot Jupiters.

Using Ford’s timing approach, we will soon have good limits on Earth-mass trojan companions to transiting giant planets.

best,
Greg

Is it reasonable to expect that if something forms at L4 or L5 in the same orbit as a Jovian, that the Trojan planet(s) are likely to be smaller — rocky?

I thought of that question after remembering your argument about M stars as places to look for habitable planets. Are any of the Jovians found thus far in these systems in a habitable orbit — habitable in the liquid water sense for their hypothetical smalller Trojan companions?

wb.