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Name: vicki maiden
Status: N/A
Age: N/A
Location: N/A
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Date: 1993 - 1999

We are 5th graders at Munhall School in St. Charles. We are studying Astronomy and want to know how long is Pluto inside Neptune's orbit (in days?

According to the book "The Planet Pluto" by A. J. Whyte (1980) Neptune and Pluto were equidistant from the Sun on January 23, 1979; from that date until March 15, 1999, Pluto will be closer to the Sun than Neptune. (I'll leave it to you to compute how many days that is.) Note: Pluto's eccentricity compared with the other planets (that is, most of the planets have orbits that are nearly circular; Pluto's orbit is notably elliptic), and the plane of its orbit is significantly tilted with respect to the plane of Neptune' s orbit.

A number of books I have consulted give 1999 or 1998 for the year that Pluto again becomes the ninth planet (in terms of distance from the Sun). Why the discrepancy? I suspect that this might be because of uncertainty about Pluto's orbit. Remember, Pluto was discovered only a little over 60 years ago; since its "year" is about 248 Earth years, we have b een able to observe Pluto's motion through only about a quarter of one orbit.

RC Winther

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