The orbits of exoplanets

October 25, 2011
An image of the dusty disk around Fomalhaut, with its planet, Fomalhaut-b, seen in the insert (at two different epochs). The orbit of the planet is less circular than the Earth's orbit. A new paper analyzes the probable orbital character of transiting exoplanets. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley)

( -- An exoplanet is a planet orbiting a star other than our sun.

As of this week, the exoplanet encyclopedia website lists 694 confirmed planets around other stars. Most of them have numerous physical parameters reasonably well determined, such as planetary mass and size of the orbit. One important parameter is the of an orbit, a measure of how non-circular it is; a circular orbit has an eccentricity of zero, while the maximum eccentricity is one.

In our , for example, the Earth's eccentricity is 0.017 (almost a perfect circle), and the largest planetary eccentricity is Mercury's, 0.206. Since the eccentricity in part determines how the of a planet varies over its year, it is a critical parameter for inferring whether possible on an exoplanet surface (non has yet been discovered) could stay liquid over its whole year.

In striking contrast to solar system planets, studies of have found that most have large eccentricities, many greater than 0.3. The Kepler satellite has detected over a thousand exoplanets (or candidate exoplanets) so far using the transit technique (i.e., seeing the starlight dim as the planet passes across the face of the star). Obtaining the orbital parameters of transiting exoplanets, however, is not as easy as with other techniques. Nevertheless, models can analyze the statistical behavior of the transits and infer general characteristics.

CfA astronomers Matt Holman, Samuel Quinn, Darin Ragozzine, and Guillermo Torres joined with colleagues on the Kepler science team to estimate the eccentricities of exoplanets around stars slightly cooler than the sun. With some fairly general assumptions, they find an average eccentricity is probably somewhat larger than Mercury's in our solar system, and with extreme values on either end (close to zero or to one) unlikely. The new results, which will refined as more data are collected and analyzed, are important not only for their implications about habitable planets, but because they will help astronomers better how planets form and settle into their stable orbits.

Explore further: Kepler and the Search for Life in Our Galaxy

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1 / 5 (8) Oct 25, 2011
It is important to remember that the first exoplanets discovered were rocky, Earth-like planets orbiting a pulsar [1,2].

Meteorites and planets also formed here from supernova debris orbiting a pulsar [3-5]

1. "A planetary system around the millisecond pulsar PSR1257 + 12", Nature 355, 145147 (1992)

2. "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR B1257+12". Science 264, 538542 (1994)

3. Origin of the Solar System

4. "Strange xenon, extinct super-heavy elements, and the solar neutrino puzzle", Science 195, 208-209 (1977)

5. "Isotopes tell Suns origin and operation", AIP Conference Proceedings 822, 206-225 (2006)


With kind regards,
Oliver K. Manuel
1 / 5 (1) Oct 27, 2011
Oliver Manuel's recent efforts to plaster and other public news sites with his theories and personal URLs are a bit puzzling, as scientists have a variety of publications available to communicate directly to each other in. My best guess is that he is desperately trying to prop up his legacy in light of his arrest in his university office on 7 charges of rape and sodomy based on allegations by 4 of his own children. The charges have been reduced to one count of felony attempted sodomy, not necessarily because of his innocence, but because of the statute of limitations. One can only guess how the recent charges and decades of family strife have affected his ability to reason rationally and to remain objective while defending his unpopular theories.


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