Orbit interpretation

Planets move in ellipses with the Sun at one focus (Kepler's first law). The closest point is perihelion a(1 − e) and the farthest is aphelion a(1 + e).

☀ ellipseOrbit interpretation

📐 Formula

perihelion = a(1 − e); aphelion = a(1 + e)

✏️ Worked example

Earth: a = 1 AU, e = 0.017: perihelion 0.983 AU (early January), aphelion 1.017 AU.

🌍 Where it is used

Space missions, satellite orbits, comets.

❓ Quick check

Where is the Sun in a planet's elliptical orbit?

🏋️ Practice

EasyHalley's comet: a = 17.8 AU, e = 0.967. Perihelion?

Answer: ≈ 0.59 AU

MediumAphelion of Mars (a = 1.52, e = 0.093)?

Answer: ≈ 1.66 AU

ChallengeAn orbit with e = 0 is a…?

Answer: Circle