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New Object Found at Edge of Solar System
Rei writes to tell us NewScientist is reporting that a new object has been found beyond Pluto. The new object, nicknamed "Buffy", has an almost circular orbit which is tilted some 47 degrees off of most other bodies in our solar system. From the article: "Neptune has been blamed for scattering many other [Kuiper Belt Objects] into tilted paths. But these tend to show other signs of a past interaction with the giant planet, such as moving in elliptical paths and having one part of their orbit pass near Neptune's at 30 astronomical units from the Sun. [Buffy], however, follows a nearly circular path. And it is too distant to have come into direct contact with Neptune, traveling between 52 and 62 AU from the Sun. Its orbit is also too circular - and too small - to have been tilted by a passing star."
Then I hate to break this to you, but the oort cloud, which is part of our solar system, is between 50,000 and 100,000 Astronomical Units away:
http://en.wikipedia.org/wiki/Oort_cloud
I don't get it.
A brown dwarf companion of the sun would probably have been discovered by now. The closest known brown dwarves are Epsilon Indi Ba and Epsilon Indi Bb, located 11.8 light years (3.63 parsecs) away. While they have very low visual luminosities (I haven't seen any published figures), they are relatively bright in the infrared (11.9 in the J band). Now, let's say a conjectured companion of the sun is 10,000 AU away. That's 0.05 parsecs, or 72.6 times closer than the Epsilon Indi brown dwarves. Since brightness is proportional to the square of the distance, that makes it 5271 times brighter or about 9.3 magnitudes brighter, giving a magnitude of 2.6 in the J band. There just aren't that many stars that bright in the infrared. It would have been noticed by now by the 2 Micron All-Sky Survey.
Similarly, nearby stars are usually discovered by proper motion surveys since nearby stars will appear to move faster against the background than far stars. Any companions of the sun would have been noticed. So there, in a nutshell, is a nail in the coffin of the Nemesis theory.
Actually, they've discovered several hundred objects beyond the orbit of Neptune. They're called Kuiper Belt objects. The ones that get the press are big ones, oddly shaped ones, or in this case, ones with weird orbits.
http://en.wikipedia.org/wiki/Kuiper_belt
If the orbits are correct then you can hide the companion from our view. Very unlikily but stranger things are seen in the galaxy.
No, you really can't. You see, everything in the universe that's made of matter has its own gravity, and this gravity tends to affect things in its vicinity. In fact, it could be said that everything in the universe affects everything else; luckily, most of these interactions are so tiny that they can be safely thrown out of the equations and the margin of error is on an order of magnitude so small that even an angel would have to pick up his robes and tread carefully to dance on it.
In a closer vicinity, such as the solar system, things affect each other with real-world measureable results. Distant suns wobble distinctly when they have planets orbiting them. The Earth's orbit is changed slightly by the presence of the other planets, and the planets' motions are changed slightly by the presence of ours, all in ways that people can predict, if they put enough variables in their equations (for the mathematically inclined: the orbit is no longer a single conic section at that point-- it becomes a very complex set of joined conic sections). If another sun, or even a planet, existed in our same orbit on the other side of the sun (actually in the L3 libration point, which is the only place it could orbit the sun and not allow us to see it, ever) we might not be able to directly observe it from Earth, but we would certainly be able to notice the effect it has on the other planets in the solar system. Jupiter would wobble just the wrong way, and Mars would not be quite where we thought it would be after factoring in the gravity of every known object in the solar system.
Come to think of it, perhaps the Mars Polar Lander was expecting the ground to be a few kilometers farther away than it really was...
But I digress. My point is that a mathematically closed two-body orbital system is a pipe dream. There is no such thing as a closed system in the universe when it comes to orbits, and we have become quite good at predicting the presence of objects just by watching how they affect the orbits of known objects.
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