An artist's concept of Gliese 876 in Aquarius and its super-Jupiter, with two hypothetical moons. [G. Bacon / STScI / NASA]
Posted on 01/14/2009 8:37:24 PM PST by SunkenCiv
The tally of known exoplanets currently stands at 334. The list includes nearly three dozen systems that have two or more known planets... The elliptical orbits of most exoplanets discovered so far do hint at possible past chaos... in a groundbreaking study announced Wednesday at the American Astronomical Society meeting in Long Beach, California, Jacob Bean (Institute for Astrophysics Goettingen, Germany) presented an analysis that reveals the inclinations of the two outer planets in the three-planet system around the red-dwarf star Gliese 876, a 10th-magnitude speck 15 light-years away in Aquarius. The study shows that the two planets orbit in nearly the same plane, just like those in our solar system...
The two Gliese 876 worlds are locked in a 2-to-1 resonance, orbiting the star every 30.3 days and 60.9 days (presumably with a slight back-and-forth drift, or "libration," around this perfect ratio). You can watch a movie of how it works. The resonance means that the planets gravitationally interact with each other repeatedly each time their positions line up; that's how they stay in resonance. And this planet-planet interaction affects the star's radial velocity (its gravitational wobble toward and away from Earth) in a measurable way, as has been tracked by Geoff Marcy (University of California, Berkeley) and his colleagues at the Keck Observatory in Hawaii...
The study also reveals that the planets' orbits are inclined a good 50° to the plane of the sky. This allowed Bean to convert the measured minimum masses that are given by the star's radial-velocity wobbles to the planets' actual masses. The middle planet has about 0.8 times the mass of Jupiter, and the outer planet weighs 2.6 Jupiters.
(Excerpt) Read more at skyandtelescope.com ...
An artist's concept of Gliese 876 in Aquarius and its super-Jupiter, with two hypothetical moons. [G. Bacon / STScI / NASA]
How Long Until We Find a Second Earth?
Discover Magazine | 10/10/08 | Robert Kunzig
Posted on 10/11/2008 12:59:49 AM PDT by LibWhacker
http://www.freerepublic.com/focus/f-chat/2102983/posts
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