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What is currently the closest known heavenly body, brown dwarf, rogue planet or other to our solar system? At one time it was Alpha Centauri.

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    $\begingroup$ What size does an object need to be to be a rogue planet as opposed to a rogue dwarf planet or rogue large asteroid? Odds are pretty good that the nearest non solar-system body, planet size or larger is an undiscovered rogue planet. $\endgroup$ – userLTK Aug 23 '17 at 22:56
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    $\begingroup$ How do you define the limits of our solar system? In other words, how do you differentiate "close to our solar system" to "inside our solar system"? $\endgroup$ – barrycarter Aug 24 '17 at 2:34
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    $\begingroup$ I hear Russell's Coffeepot is just a bit outside the Oort Cloud :-) $\endgroup$ – Carl Witthoft Aug 24 '17 at 13:25
  • $\begingroup$ @barrycarter I think it's unfair to ask the OP to come up with an original definition of the limits of the solar system. The whole class of "What is your definition of X" comments where X is a well recognized term with existing definitions tend to just derail conversations. If there is a convention, why not assume the OP would naturally defer to it. If there is no working convention for it, then you should point that out in a helpful way rather than posing this in the form of a counter-question to the OP. $\endgroup$ – uhoh Aug 26 '17 at 6:26
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The closest body we currently know to exist is Proxima Centauri which is part of the Alpha Centauri system at about 4.25 light years away.

There may be rogue planets that are closer but we haven't been able to detect any. Objects down to brown dwarf size that are closer than Alpha Centauri have not been found by extensive surveys.

Here is a list of close objects to the solar system: https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs

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  • $\begingroup$ We know that astronomy is always changing, faster now than ever. In my lifetime we have discovered exoplanets brown dwarfs and rogue planets or at least hypothesized about them. It is possible there are black dwarfs which might be the same as rogue planets and can only be detected by gravitational waves. Additionally some of the planets in our solar system may have originated outside the typical proto star development. The existence of the rocky planets and all the moons seem to suggest that they may have been captured from the outside. We also don't have a clear idea of what dark matter is $\endgroup$ – P Pitch Aug 28 '17 at 15:44

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