Transit Method Reveals Many Extrasolar Planets 174
eldavojohn writes "You might recall not too long ago the first photo of an extra solar planet or, more recently, the mapping & speculation on these planets that lie outside our own solar system. Long since those first few spotted in the 90s, we're now starting to find them in droves due to the popularity of a method that relies on the planet passing directly between the viewer on earth and the star that it orbits. Be sure to check out Space.com's list of the most interesting extra-solar planets. Will we ever find Earth 2.0 candidates?"
Ummm....It's The Wobble Method That's Tops (Score:5, Informative)
Re:Pegs that variable in the Fermi equation... (Score:3, Informative)
Re:perhaps not so lucky (Score:5, Informative)
"Finally I note that we are not really interested in planets that don't rotate in their orbital plane since otherwise they'd be roastingly hot on one side and freezing on the other."
The rotation of the planet has nothing to do with the detection of planets in this method, only the orbit determines the ability to detect it. So while some planets may or may not be rotating on the correct axis to support multiple seasons, it isn't accounted for in this type of study because they can't detect this with the transient method.
Also, there are actually a large variation of planes that can be detected with this method. Imagine our solar system as a disk. Then imaging looking at it from the top view. This view does not allow the planet detection using the transient method. However, angle your view down until you can see just one of the planets cross over the sun. From this angle on, and twisted up to 360 degrees, is where this transient method works. So actually, there are many planes of orbit which can be used to detect planets with this method. And assuming that a percentage of these planets are within the habitable distance from their star, and that a percentage of these rotate on a reasonable axis, then they could contain life. But nothing in these studies is determining that any of this is the case. Right now they are just looking for ANY planets. so we can detect extrasolar planets even if their orbital planes are perpendicular to the galactic disk, so long as they are close to parallel to our viewing line of site. With this in mind, you can imagine that if you can view stars in our galaxy from 360 degrees around our planet, that we would be able to detect every orbital plane angle available in the galaxy, depending on which direction we are looking from the earth. So while we can't see all of them, we can see a very large subset of them with this method.
Also, the reason that all the planets in the solar system follow close to same typical plane of orbit is because of the way solar systems form. They start as a gaseous body collapsing. As the rotation of the gas nears closer and closer to the center of the nebula, the rotational inertia causes the forming of a disk due to inertia. The same thing happens to drag car tires when they spin fast (they turn more disk-like). From this disk-like nebula the planets form. The center typically ends up with something larger than a gas giant (the sun, or a couple of suns) and the other planets turn into gas giants (Jupiter) or solid planets (i forgot the name, but they gain gravitational pull and pull in particles from the nebular disk)
So this is why the planets are all in one plane of orbit. If all star systems are formed in this general method (something that is assumed) then it is fairly easy to say that they should all be in a single plane. But each system does not necessarily have to be in the same plane relative to each other just because they are in the same galaxy. Each nebula forms independently and collapses typically from an outside force, but not necessarily on the same rotational plane.
Also, the planets have their own disks associated with them. The moons and rings of Uranus and Saturn and Jupiter follow different planes. They don't necessarily need to follow the same plane as the solar system. This is because each of those planets also formed independently of each other. The spin of those depends on the angular momentum of the local mass as it formed, which would be different than the parent nebular disk especially when you take into account collisions of forming bodies. The same could be said to happen on the galaxy level, if you compare the galaxy formation to solar system formation.
These are just my points of view of what I have studied. Many people will have different points of view formed from the same observations.
Re:Earth 2.0? (Score:2, Informative)
Re:There are NO extrasolar planets. (Score:3, Informative)
More precisely, the new definition [iau.org] does not attempt to classify extra-solar bodies as either planets or not-planets. It starts out like this (emphasis mine):
The IAU's working group on extra-solar planets [ciw.edu] does offer a working definition, subject to change. [ciw.edu] See Wikipedia [wikipedia.org] for more details. See also rogue planets. [wikipedia.org]