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bigsednafan
2004-Mar-24, 11:30 PM
During all the Planet X nonsense, I read about the physical impossibilities of the proposed orbits, specifically involving escape velocities that would send a planet hurling out of the solar system. With Sedna having an orbit stretching an estimated 1,000 au, with known science, what is the maximum distance an object can be from the sun and still have an orbit? What would be the ramifications of a larger or smaller object having the same orbit as Sedna? Would the larger object be more likely to escape given the distance or the smaller object? Finally, if a planet the size of say Neptune was 1,000 au, (Sedna's most distant point), would we be able to spot it with current technology?

Just a few questions from a non-scientific perspective. Thanks.

2004-Mar-25, 12:19 AM
With Sedna having an orbit stretching an estimated 1,000 au, with known science, what is the maximum distance an object can be from the sun and still have an orbit?
The maximum distance is probably close to 100,000 A.U. which is the maximum distance of an Oort Cloud comet. 100,000 A.U is about 1.5 ly.

What would be the ramifications of a larger or smaller object having the same orbit as Sedna?
A sufficiently large object would cause sizeable gravitational tug, I guess. Smaller? It wouldn't be as significant.

Would the larger object be more likely to escape given the distance or the smaller object?
I don't think it would matter, but I'm not sure.

Finally, if a planet the size of say Neptune was 1,000 au, (Sedna's most distant point), would we be able to spot it with current technology?
Um let me do some calculations on this. 1,000 au is 30 times Neptune's current distance of 30 au, so it would receive 1,000 times less sunlight, according to the inverse-square law. And because Neptune doesn't emit its own light, the reflected light would be further dimmed by a factor of 1,000. This means that Neptune would appear 1,000,000 (1,000)(1,000) times dimmer. This is a magnitude difference of 15. Neptune's current magnitude is 9, so it would be magnitude 24. Extremely difficult to detect-We could see it if we knew it was there, but it would be almost impossible to find.

JohnOwens
2004-Mar-25, 07:52 AM
With Sedna having an orbit stretching an estimated 1,000 au, with known science, what is the maximum distance an object can be from the sun and still have an orbit?
The maximum distance is probably close to 100,000 A.U. which is the maximum distance of an Oort Cloud comet. 100,000 A.U is about 1.5 ly.
Well, the Sun's L1 point with respect to the galaxy ought to be at most around 6,600 AU out, so I would think just about anything as close as or further than that would eventually be lost. This might apply less as an object orbits further from the galactic plane, though.