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Orientation of Pluto and Charon
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Most planets have north poles that point roughly up and out of their orbit planes. The exceptions are Uranus and Pluto; these two are "rotating on their side". Like most satellites, Charon orbits above Pluto's equator. During the period from 1985 through 1990, Pluto's equator and Charon's orbit plane were aligned with the line-of-sight from the earth. Charon would pass in front and behind Pluto every 6.4 days. |
Of the nine planets in our solar system, Pluto has the least circular and most highly inclined orbit. Although Pluto's average distance from the sun is about 39.5 astronomical units (AU), itcan come as close to the sun as 29.6 AU. (An astronomical unit is approximately the distance between the sun and the earth.) From 1979 to 1999 pluto can actually be slightly closer to the sun than Neptune, which stays 30 AU from the sun throughout its entire orbit.
Pluto rotates once in 6days, 9 hours, 17minutes and 34 seconds. Charon orbits Pluto in the same amount of time, and therefore the system appears to be completely tidally locked. The rotational axis of Pluto is inclined by by 115 degree with respect to its orbital plane; in this respect, Pluto is similar to Uranus.