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The Question

(Submitted August 05, 1997)

I am having trouble finding information regarding Planet X. Could you please advise of an Internet site or an e-mail address that I could inquire regarding this fascinating subject.

The Answer

I can understand why you had troubles finding Internet sites about Planet X ! It seems to be a popular name for a number of non-astronomy topics (comic books among them !).

I did eventually find, however, a very interesting article at

by Paul Schlyter. The section entitled "Planet X" discusses at some length the search for a trans-Neptunian planet, the discovery of Pluto, and the subsequent continued search for a tenth planet. It discusses the use of Halley's Comet, Voyager 2, Pioneer 10 and Pioneer 11 to search for any deflections from unknown gravity sources. The article concludes that although a trans-Plutonian planet has never been found (and likely doesn't exist), the search has instead yielded a new class of asteroids at the outer reaches of the solar system.

I hope this helps.

Jim Lochner
for Ask an Astrophysicist

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