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28 New Planets Found Outside Solar System
elkcsr writes "The San Jose Mercury news reports on the phenomenal discovery of 28 new extra-solar planets out there in our galaxy. All of them are outside of the band scientists consider necessary for supporting life as we know it, but the solar systems analyzed should still be quite familiar to those of us in this neck of the woods. System layouts feature small rocky planets towards the star and gas giants further out. The biggest difference seen is a preference for elliptical orbits, instead of generally circular orbit we enjoy. ' For example, the team also described new details about one specific exoplanet, discovered two years ago. This planet, which circles the star Gliese 436, is thought to be half rock, half water. Its rocky core is surrounded by an amount of water compressed into a solid form at high pressures and low temperatures. It makes a short, 2.6-day orbit around Gliese 436. Based on its radius and density, scientists calculate that it has the mass of 22 Earths, making it slightly larger than Neptune. "The profound conclusion is, here we've found yet another type of planet that is already represented in our solar system," Marcy said.'"
Umm it's been ages since I took any astronomy course, but I thought Kepler figured out that *our* orbit was elliptical?
I assume the article meant "elliptical" in the qualitative sense, that their orbits "looked" like ellipses while our orbit "looks" like a circle.
A circular (or near-circular) orbit should be extremely rare. It is the special case of an elliptical orbit where the speed is very very close to the theoretical speed required to orbit at that distance from the sun and the direction of motion is very close to being at right-angles to the sun.
The Earth is an intriguing case - the original third planet collided with a planet the size of Mars, resulting in part of the crust being blasted off into space forming a mass that is now our moon and a debris ring. A collision on that scale - two almost equally massive objects slamming at an angle - must have resulted in a change in velocity. Since Earth is now on a near-circular orbit, it would seem not unreasonable to assume it started off on a much more elliptical path.
Virtually all of the known objects in the Kepler Belt follow extreme orbits - some varying by 300+ AU in distance from the sun. However, these are all very old objects. They have not been subject to many collisions and are almost in their original state.
On the basis of our extrasolar observations to date, plus the Kepler Belt observations, plus the Earth enigma, I would conclude that elliptical orbits are the norm for younger solar systems and that more circular orbits become slightly more common in older systems where there is a chance that collisions will have averaged things out better.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Actually, so far, 241 extrasolar planets have been discovered.
Ben Hocking
Need a professional organizer?
Mass of the star can be calculated from its spectrum and brightness. We have models for star formation, based on studies of the nuclear reactions that happen at the core. These stars are all relatively near, so the distance to several of them can be measured directly from the parallax. Knowing the type of the star and the distance, the mass can be calculated from the brightness.
This book shows in an introductory way how it's done, with examples of all the calculations in BASIC. It's a very interesting book, highly recommended.