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Among the most sought-after prizes in astronomy these days are "exomoons," or moons orbiting exoplanets. Although astronomers have detected more than a thousand exoplanets, any exomoons they might harbor have so far eluded capture. However, judging by our own Solar System, where moons greatly outnumber planets, scientists believe that hordes of exomoons are indeed out there.
To find these exomoons hiding in plain view, a new technique has just been proposed. Described in a study recently accepted in The Astrophysical Journal, the new approach relies on a particular eclipsing effect of moons when viewed against the background radiance of their host stars.
Unlike traditional exomoon hunting techniques, the new method has the advantage of being able to find natural satellites on the scale of the moons here in the Solar System. Other methods can probably only yield exomoons several times the mass of the biggest moon known, Jupiter's Ganymede — in other words, unprecedentedly monstrous moons.
"This technique is the first method that has been demonstrated to allow detection of moons akin to those in the Solar System," said study author René Heller, a postdoctoral fellow in astronomy at McMaster University, in Ontario, Canada. "Four hundred years after Galileo Galilei discovered four moons orbiting Jupiter, the first moons we knew of besides our moon, we now have the technologies and methods available to go find 'alien' moons beyond our Solar System."
Additionally, the new method can distinguish multi-moon systems, whereas standard techniques focus on solo exomoons. A third benefit is that existing data from the Kepler spacecraft should suffice for identifying exomoons. That's in contrast to some other proposed methods which would require new technologies and force exomoon hunters to await future generations of telescopes.
Intriguingly, the method could tease out the presence of exomoons orbiting planets in the so-called habitable zones of red dwarf stars and orange dwarfs. The habitable zone is the not-too-close, not-too-far-away band around a star wherein residing worlds could have liquid water.
originally posted by: swanne
a reply to: JadeStar
That's cool, especially since exomoons can, in theory, sustain life (if they're in the Goldilock region).
Consider an Earth-sized exomoon with an Earth-like density and an orbital eccentricity of just 0.005. This Earth-sized exomoon will have to orbit a Jupiter-mass gas giant planet at a distance of roughly 1.1 million kilometres in order for tidal heating to be sufficient to sustain an average surface temperature of 300 K. At this temperature, liquid water can exist on the surface of the exomoon. If the planet-moon distance were halved, tidal heating will be so effective that the surface temperature of the Earth-sized exomoon will be a blistering 1000 K, making it uninhabitable. In comparison, Jupiter’s moon Io orbits Jupiter at an average distance of 422,000 kilometres, with an orbital eccentricity of 0.004. Observing at an infrared wavelength of ~14 micrometres, a 300 K tidally heated Earth-sized exomoon will appear as bright as the Jupiter-mass gas giant planet it is orbiting.
Although their gravitational field must be much weaker than Earth,
and their sun might get eclipsed by their exoplanet as they orbit around the latter, thus leading to rather irregular solar energy reception patterns...
But still, nice find! S&F from me.
originally posted by: MarsIsRed
The trouble is, internal heating on an icy moon means that all you get is fish. Internal heating on a distant rocky moon is pretty much limited to microbes. External heating (from a star) on a rocky moon means photosynthesis, which leads to Ewoks!