Astronomers Now Looking For Exomoons Around Exoplanets

by Ian O'Neill on December 14, 2008

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

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

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


[Follow me on Twitter (@astroengine)]

[Check out my space blog:]

[Check out my radio show: Astroengine Live!]

Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog:, be sure to check it out!

Comments on this entry are closed.

Previous post:

Next post: