# Astronomy help

If a comet has a perihelion distance of 1.AU and an orbital period of 125 Earth years.. What is the comet's aphelion? Cannot seem to find the correct calculation

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asked by Liz
1. If a comet has a perihelion distance of 1.AU and an orbital period of 125 Earth years.. What is the comet's aphelion? Cannot seem to find the correct calculation

1 AU = ~92,960,242 miles = 4.908300778x10^11 feet

The period of the comet about the Sun derives from

T = 2Pisqrt(a^3/µ) where T = the period in seconds, a = the semi-major axis of the orbit in feet and µ = the gravitational constant of the Sun, 4.68772x10^21

For T = 125 earth years T = 125(365.25(24(3600) = 3,994,700,000 seconds

The perihelion radius from the Sun's cen
ter 1AU = ~92,960,242 miles = 4.908300778x10^11 feet

Therefore
3,994,700,000 = 2(3.14)sqrt[a^3/4.68772x10^21)] from which a^3 = 1,847,693,311 or a = 1,227,090,599x 10^13 feet

The aphelion radius is therefore, 2a - r(per).

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posted by Liz

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