Name: Vicki Martin
Status: Other
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
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)?
Replies:
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 N. (I will leave
it to you to compute how many days that is.) Note: Pluto's orbit does not
actually intersect Neptune's. Pluto's orbit has a large 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
been able to observe Pluto's motion through only about a quarter of one
orbit.
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