Eccentric Worlds: Strange Orbits Puzzle Astronomers

Eccentric Worlds: Strange Orbits Puzzle Astronomers

By Michael Schirber
Staff Writer
posted: 10 May 2005
06:25 am ET


BALTIMORE - Of the more than 130 planets found around distant stars, a large number have highly elliptical orbits, crazy oblong shapes that have surprised theorists who try to explain the configurations with near collisions or perturbing disks of gas.

An elliptic orbit is characterized by the eccentricity, which is how much a planet's distance from its star varies as it carves out a year. Most of the planets in our solar system have relatively low eccentricities, less than about 5 percent (tiny Pluto being a notable exception and considered not really a planet by some astronomers).

By contrast, the average eccentricity of extrasolar planets is about 25 percent. And these are not Plutos. They are typically more massive than Jupiter.

"The eccentricities are the most remarkable thing about these planets," said Geoff Marcy of the University of California, Berkeley, during a meeting here last week at the Space Telescope Science Institute (STScI). The conference was set up to celebrate 10 years of successful exoplanet hunting.

Some have eccentricities of 80 percent, which is as high as the crazy orbits of some comets in our solar system....cont'd

http://www.space.com/scienceastronomy/050510_eccentric_orbits.html

considering that that is one of the ways we find the planets. We look for extrasolar planets by looking for wobbles they cause in the star they orbit. Its only natural that the ones with the wildest orbits cause the most noticible wobbles, and get found first.

:shrug:

of course we can only sense extraordinary planets at the moment. We're well aware of that; after all, most of the planets we've seen so far are bigger than Jupiter.

The problem is: how did such odd star systems come to be in the first place?

It is a theoretical problem. We think we have a pretty good handle on how a star system like our own would form. But to have a massive planet with a tight, eccentric orbit is, as you say, "wild." It doesn't seem like a stable configuration, and we don't yet understand how one might form on its own.

EDIT: spelling. :)