Forget exomoons. Let’s talk exorings

November 25, 2011 By Jon Voisey, Universe Today
An artist impression of an exomoon orbiting an exoplanet, could the exoplanet's wobble help astronomers? (Andy McLatchie)

In an article earlier this month, I discussed the potential for discovering moons orbiting extrasolar planets. I’d used an image of an exoplant system with rings, prompting one reader to ask if those would be possible to detect. Apparently he wasn’t the only person wondering. A new paper looks more at exomoons and explores exoring systems.

The idea of detecting rings around distant planets dates back to at least 2004. Then, Barnes & Fortney suggested that rings would be potentially detectable from the eclipse they would cause if the photometric precision were as one part in ten-thousand. This is a big challenge, but one that’s more than met by telescopes like Kepler today. But for this to be possible, the rings needed to block the most possible, meaning that they would have to be viewed face on, instead of edge on.

Fortunately, a study this year by Schlichting & Chang demonstrated that, even if the planet’s spin is aligned with the plane of orbit, it’s quite possible that the rings will be significantly warped due to gravitational interactions with the star.

So it should be possible, but what do astronomers need to look for?

The new paper attempts to answer this question by simulating light curves for a hypothetical ringed exoplanet. The first result is that the extra area of the star’s surface covered by the rings reduces the light detected. However, this is difficult to disentangle from the effects of simply having a larger planet that blocks the light.

Simulated light curve for exoplanet system with rings vs model lacking rings. Credit: Tusnski & Valio

A second effect is based on the shape of the light curve (a graph of the brightness as a function of time) as the planet begins and ends the transit. In short, the semi-transparent nature of the rings makes the drop in brightness softer, rounding off the edges of the light curve. When modeled against a planet that lacked rings, this would be readily detectable for an instrument like Kepler.

With such precision, the team suggests that Kepler should be more than capable of detecting a ring system similar in size and nature to those of Saturn. However, other transit finding telescopes, such as CoRoT, would mistake the rings for a slightly larger planet.

In the future, the team plans to take their model and reexamine data from Kepler and CoRoT to search for both rings and moons.

Explore further: Cassini Returns Never-Before-Seen Views of the Ringed Planet

Related Stories

Will Kepler find habitable moons?

September 3, 2009

( -- Since the launch of the NASA Kepler Mission earlier this year, astronomers have been keenly awaiting the first detection of an Earth-like planet around another star. Now, in an echo of science fiction movies ...

Rings on the horizon

January 26, 2011

The Cassini spacecraft has taken a some recent images of two of Saturn’s most notorious moons, where in both images the planet’s rings serve as a backdrop. Above, Enceladus stands out with its cratered surface, ...

Forget exoplanets. Let's talk exomoons

November 7, 2011

It wasn’t that long ago that astronomers began discovering the first planets around other stars. But as the field of exoplanetary astronomy explodes, astronomers have begun looking to the future and considering the possibility ...

Recommended for you

Saturn and Enceladus produce the same amount of plasma

February 12, 2016

The first evidence that Saturn's upper atmosphere may, when buffeted by the solar wind, emit the same total amount of mass per second into its magnetosphere as its moon, Enceladus, has been found by UCL scientists working ...

Gravitational waves found, black-hole models led the way

February 11, 2016

Gravitational waves were predicted by Einstein's theory of general relativity in 1916, and now, almost exactly 100 years later, the faint ripples across space-time have been found. The advanced Laser Interferometric Gravitational-wave ...

The 'glitching' of the Vela pulsar

February 9, 2016

(—A team of Australian astronomers has conducted an intensive observation of a curious young pulsar to investigate changes in its rotation frequency known as 'glitching'. Located about 910 light years from the ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.