An artist impression of an exomoon orbiting an exoplanet, could the exoplanet's wobble help astronomers? (Andy McLatchie)

Astronomers Now Looking For Exomoons Around Exoplanets

14 Dec , 2008 by

[/caption]It looks like astronomers have already grown tired of taking direct observations of exoplanets, been there, done that. So they are now pushing for the next great discovery: the detection of exomoons orbiting exoplanets. In a new study, a British astronomer wants to use a technique more commonly associated with the indirect observation of exoplanets. This technique watches a candidate star to see if it wobbles. The wobble is caused by the gravitational pull of the orbiting exoplanet, revealing its presence.

Now, according to David Kipping, the presence of exomoons can also be detected via the “wobble method”. Track an exoplanet during its orbit around a star to see its own wobble due to the gravitational interaction between the exoplanet/exomoon system. As if we needed any more convincing that this is not already an ‘all kinds of awesome’ project, Kipping has another motivation behind watching exoplanets wobble. He wants to find Earth-like exomoons with the potential for extraterrestrial life…

If you sat me in a room and asked me for ten years over and over again: “If you were an astronomer, and you had infinite funds, what would you want to discover?“, I don’t think I would ever arrive at the answer: the natural satellites orbiting exoplanets.” However, now I have read an article about it and studied the abstracts of a few papers, it doesn’t seem like such a strange proposition.

David Kipping, an astronomer working at the University College London (UCL), has acquired funding to investigate his method of measuring the wobble of exoplanets to reveal the presence of exomoons, and to measure their mass and distance from the exoplanet.

Until now astronomers have only looked at the changes in the position of a planet as it orbits its star. This has made it difficult to confirm the presence of a moon as these changes can be caused by other phenomena, such as a smaller planet,” said Kipping. “By adopting this new method and looking at variations in a planet’s position and velocity each time it passes in front of its star, we gain far more reliable information and have the ability to detect an Earth-mass moon around a Neptune-mass gas planet.”

Kipping’s work appeared in the December 11th Monthly Notices of the Royal Astronomical Society and could help the search for exomoons that lie within the habitable zone. Of the 300+ exoplanets observed so far, 30 are within the habitable zones of their host stars, but the planets themselves are large gas giants, several times the size of Jupiter. These gas giants are therefore assumed to be hostile for the formation for life (life as we know it in any case) and so have been discounted as habitable exoplanets.

But what if these exoplanets in the habitable zone have Earth-like exomoons orbiting them? Could they be detected? It would appear so.

Prof. Keith Mason, Chief Executive of the Science and Technology Facilities Council (STFC), added, “It’s very exciting that we can now gather so much information about distant moons as well as distant planets. If some of these gas giants found outside our Solar System have moons, like Jupiter and Saturn, there’s a real possibility that some of them could be Earth-like.”

Watch this space for an announcement of the first Earth-like exomoon to be discovered, at the rate of current technological advancement in astronomy, we could be looking at our first Earth-like exoplanet exomoon sooner than we anticipated…

Source: New Scientist, STFC


Sort by:   newest | oldest | most voted
Thunder Pig
Guest
December 14, 2008 3:12 AM

Wouldn’t the radiation fields around a “Jupiter-class” exo planet fry the surface of a potentially habitable exo-moon?

Or is a standard magnetic field good enough to protect our aliens with a killer view featured in so many SciFi stories?

Oh, and not even bringing up the whole tidal-lock thing that would kill a the development of a magnetic field.

Still, this is very exciting. Imagine what we will be able to detect if we can get swarms of instruments into interplanetary space.

Squee!!!

leafguy
Member
December 14, 2008 4:30 AM
Thunder Pig, First off, being tidally locked to a planet would not hinder a bodies ability to develop a magnetic field. Take a look at europa and ganymede. Also, if the moon is far enough away from the exo planet, it may be far enough away from the radiation belt of the planet. Example, again ganymede. I would say that the odds of finding a moon that fits this criteria to be close to nil, but it is entirely plausible. However, Im interested to see if we are capable of detecting wobbles in the orbit of an object even as small as a hot jupiter around certain stars. I suppose its possible, but I d have my doubts.
Dutch Delight
Guest
Dutch Delight
December 14, 2008 4:51 AM

But is there any possibility for us to detect the composition of atmospheres of these moons?

Grinspoon
Guest
Grinspoon
December 14, 2008 7:26 AM

Bring on the discover of the endor moon!

Is it actually possible for a gas giant to have a moon that is an earth like planet?
Or will it always be a moon that can at most support basic life? What implications are there to moons roations, sizes, and how often they face the sun?

Jorge
Guest
December 14, 2008 7:46 AM

Hm… I’m confused by this.

Wouldn’t the gravitational effects of the planet AND the moon on the star combine as if it were a single gravitation source, centered on the planet-moon system’s center of mass?

Maxwell
Member
Maxwell
December 14, 2008 9:16 AM

Capable of supporting life and capable of developing life are probably two different things.
I’m positive that among the various forms of earth life, we could find some that would survive in pockets of the moons we know about. The question would be if a moon could exist around a giant planet, in some kind of stable condition, long enough for life to develop from scratch.

maudyfish
Guest
maudyfish
December 14, 2008 9:23 AM
Not to change the subject but I wish this web site would do a special on spelling. There are so many new scientific words out there and. For some it may trivial but I think it would be worth it to comment. For example: exo-planet or exoplanet super nova or supernova exo-earths or exoearths jobian or Jovian mass less or massless redshift or red shift kiloparsec or kilo parsec Thanks
Ilya
Guest
Ilya
December 14, 2008 9:24 AM

Wouldn’t the gravitational effects of the planet AND the moon on the star combine as if it were a single gravitation source, centered on the planet-moon system’s center of mass?

Yes, but that center of mass will not move in complete accordance with Kepler’s Laws. It will periodically speed up and slow down. Which is Kipping’s whole point.

tacitus
Member
December 14, 2008 10:02 AM
But is there any possibility for us to detect the composition of atmospheres of these moons? Sure, some day. We expect to be able to directly resolve Earth-sized exoplanets and smaller one day, so observing large moons should not be much more difficult than that, and given it’s the large moons that have atmospheres, we will probably get to see them one day. Sooner than that, I suspect we’ll be able to observe transiting moons of transiting planets. We can already subtract the light spectrum of a star from that of a planet in transit, so in theory if there is a large moon in just the right place (in front of the star but not in front… Read more »
Jason
Guest
Jason
December 14, 2008 10:41 AM

It would seem that if we could detect the very slight speeding up and slowing down of a planet moon system, that we could just a easly detect an earth sized planet going around a star. Which is thus far beyond our capibilities.

Also ther are most likley mutiple moons for each planet, like Jupiter and saturn, which will muddy every thing up as well.

Keep looking though, we called it impossible to find planests not so long ago.

It seems more likley, that now we have imaged exoplanets that we could simply observe the planet itsself for wobles caused by exomoons.

Kevin F.
Member
December 14, 2008 10:59 AM

I’ve been expecting the possibility. We already are thinking there might be life of some odd manner on two of our gas giants – Titan and Europa. It would be perfectly reasonable to have a gas giant in the habitable zone having a life-bearing moon.

mang
Member
mang
December 14, 2008 11:37 AM

I continue to be amazed at the precision of measurement and analysis that can be produced. Just when you get used to the idea of exoplanets, we are on the verge of finding exoasteroids[1] and exomoons!

[1] http://mangsbatpage.433rd.com/2008/08/hot-jupiter-trojans-most-finds.html

Ilya
Guest
Ilya
December 14, 2008 11:50 AM

It would seem that if we could detect the very slight speeding up and slowing down of a planet moon system, that we could just a easly detect an earth sized planet going around a star. Which is thus far beyond our capibilities.

Sorry, but your intuition is wrong. An earth sized planet going around a star can not be detected (yet) because the wobble it induces is too small. If a gas giant planet induces a readily detectable wobble, the speed with which it rises and falls is much easier to measure. I have no links handy, but in several known multi-planet systems, planets’ gravitational influence on each other has already been found.

Jason
Guest
Jason
December 14, 2008 12:42 PM

@ Ilya

Yea, I would guess that the much shorter frequency of wobble induced by an earth sized moon would be easier to detect than that of a earth sized planet.

The concept of a Titan or Europa like moon in the habitable zone of a star is exciting.

Jorge
Guest
December 14, 2008 2:28 PM

Yes, but that center of mass will not move in complete accordance with Kepler’s Laws. It will periodically speed up and slow down. Which is Kipping’s whole point.

Hm… still trying to wrap my head around this. So. I can think of only one way for this to happen: if the motion is such that we have to throw in relativity. Right?

If so, surely the variations would be minute?…

Silver Thread
Member
Silver Thread
December 14, 2008 3:32 PM

That’s no moon…..

Some Guy
Guest
Some Guy
December 14, 2008 4:13 PM

ok, no ones brought this up, so i will
any habitable moon that orbits a jupiter like planet beyond its radiation belt will likely have a pretty wide orbit. SO! that being said, this wide orbit could vary the moon’s distance from the host star by hundreds of thousands of kilometers within a very short period of time, would that not cause violent tidal swings on the surface, leading to aggressive weather, and putting any life there up against some tough odds?

Dark Gnat
Guest
Dark Gnat
December 14, 2008 5:56 PM

Even if it does change, it probably wouldn’t be too gret of a change.

Perhaps something like a global winter and summer. Titan might be a good model.

I think this would be very possible, and a worthy effort!

Ilya
Guest
Ilya
December 14, 2008 6:08 PM

Now that I thought of it, I have to take back what I wrote about center of mass not moving in a simple Keplerian orbit. In short, I have no answer to Jorge’s question. All I can guess is that David Kipping is NOT expecting the star’s wobble to follow planet-moon center of mass, but to follow just the planet. Why, I do not know. And will try to find out.

trux
Guest
December 14, 2008 6:49 PM

2 Ilya: I may be wrong, but perhaps the method relies on both measuring the gravitational wobble, and spectrographic analysis of planet transitions. In that case, although the travel of the center of the moon-planet system would be regular, there would be disaccords with the spectral transition measurements, which would then prove the moon presence. It surprises me though that the technology is already so sensitive that it could be detected. In any way, I’d love to read much more details about the methods used.

wpDiscuz