New Technique May Find Exo-Moons Similar to Our Solar System's Moons

View from the surface of a hypothetic moon of the planet Upsilon Andromedae d - 44 lightyears away

There's been a lot of recent work done in the burgeoning field of exomoon research. Its an exciting prospect. Exomoons are moons which orbit exoplanets. The first possible detection of one came through a technique called microlensing. Other techniques look for exomoons in data from NASA's Kepler Mission.

Now enter a 3rd technique which may help us detect the equivalent of our own solar systems moons many light years away.

From Astrobiology Magazine:

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.

Continue reading here...

If I were asked to bet, I'd say this may be the year of the exomoon in Astronomy given the amount of interest in the subject and the amount of hard work going into perfecting a diverse array of techniques to detect them.

You may be absolutely right.....the thrust seems to be steadily increasing in this direction......
It will be interesting when they survey our sister star 110 lyr away....maybe it will have similar characteristics to our planetary family....
If having an exomoon is another of those sweet spots in the development and survival of life...we need to find the darn things just as bad a the planets themselves....hello out there................

a reply to: JadeStar

That's cool, especially since exomoons can, in theory, sustain life (if they're in the Goldilock region). 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.

Great post!

Planets orbiting in the habitable zone of a red dwarf are likely to be tidally locked, suffer from extreme amounts of radiation (red dwarfs are fairly unstable in that regard), and have extreme weather. This would make it hard for life to form.

However, a moon orbiting a gas giant in this region would have reasonable day/night periods (more stable weather), would be protected by the planet's magnetosphere, and, if far enough away from the planet, wouldn't be 'squashed' into a molten ball like Io. A Ganymede type moon, around a Neptune sized planet could be an ideal haven for life.

I seriously hope that discoveries are indeed possible from existing Kepler data.

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).

They don't even have to be in that region.

You see, Jupiter's moons are tidally heated and the liquid ocean under the ice of Europa is a result. There's no reason why there could not be habitable, non-icey exomoons around a planet which orbits well outside the Goldielocks/habitable zone in the cold region if they received enough tidal heating.

Here's a good article on just that possibility.

Beyond Earthly Skies: Tidally Heated Habitable Exomoons

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.

And for the technically inclined there is this paper on ArXiv from Mary Anne Peter and Edwin L Turner entitled: "On the Direct Imaging of Tidally Heated Exomoons" (Submitted on 20 Sep 2012 (v1), last revised 19 Apr 2013 (this version, v3))

Although their gravitational field must be much weaker than Earth,

Not necessarily. It depends on the size and composition of the moon. We know of exoplanets larger than Jupiter, some substantially larger. Perhaps they might have Earth sized exomoons? Jupiter and Saturn's moons are pretty big but probably not the largest moons in the galaxy.

and their sun might get eclipsed by their exoplanet as they orbit around the latter, thus leading to rather irregular solar energy reception patterns...

Atmospheric distribution of heat would make that not such a big deal. We know this because of Titan in our own Solar System.

But still, nice find! S&F from me.

Thanks

This is awesome. I hope the scientists have much luck in finding these moons. Exo-moons are indeed a key piece of the puzzle to discover exo-life.

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!

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!

Au contraire.

We do not know what types of life might be able to exist on an internally heated exomoon with a sufficiently thick atmosphere.

Think of a warm Titan for example.

While there may not be photosynthesis there may be other chemical processes used by life as happens on Earth in the deepest oceans or deep inside of cave systems.