Planetary bodies moving around the Sun have elliptical orbits. The Sun is locate
ID: 159939 • Letter: P
Question
Planetary bodies moving around the Sun have elliptical orbits. The Sun is located at a focus (not at the center) of an ellipse representing the orbit of a planetary body. The point of the orbit that is closest to the Sun is known as the perihelion, while the point that is farthest from the Sun is the aphelion. The semi-major axis, a, represents the orbiting body’s mean distance from the Sun or the average of the perihelion distance q and the aphelion distance Q. The eccentricity, e, is a measure of the extent of the departure of an ellipse: e = 0 for a circle while e = 1 for an extremely elongated ellipse.
These quantities are related as follows.
q = a (1 – e)
Q = a (1 + e)
a. Pluto has a semi-major axis of 39.48 AU and an eccentricity of 0.249. What are Pluto’s perihelion and aphelion distances?
b. Neptune has a semi-major axis of 30.07 AU and an eccentricity of 0.009. What are Neptune’s perihelion and aphelion distances?
c. Who has more elongated orbit, Pluto or Neptune?
d. Considering your answers to parts (a) and (b), is Pluto always farther from the Sun than Neptune?
e. One of the three criteria to be a planet is that an object should have cleared the neighborhood around its orbit. According to your answer to part (d), does Pluto satisfy this criterion?
Explanation / Answer
a) perihelion of pluto is given by a(1-e)
= 39.48(1-0.249)
= 29.649
Aphelion = 39.48(1+0.249)
= 49.311
For neptune
Perihelion = a(1-e)
=30.07 (1-0.009)
=29.79
Aphelion
= 30.07(1+0.009)
=30.34
since perihelion is closest point to the sun ,pluto gets closer to the sun than neptune ever does.
Pluto has larger orbit but it comes to the sun closer than neptune.
No pluto doesnot satisfy this criteria and so it is considered as a dwarf planet . There are many objects with similar size and mass to pluto moving around the orbit and pluto crashes with them so it is not a planet because of this criteria