Perihelion | Definition, Origin and Key Differences

*Definition:*
*Perihelion:* The point in the orbit of a planet closest to the Sun.

*Origin:*
"Perihelion" derives from the Greek roots *peri-* (meaning "near") and *helios* (meaning "Sun").

*Significance:*
Understanding perihelion is vital for studying planetary orbits and solar energy distribution. It ties directly to Johannes Kepler's laws of planetary motion, which describe how celestial bodies move in elliptical orbits, with perihelion marking the nearest approach to the Sun.

*Key Differences:*
Perihelion contrasts with **aphelion**, the farthest point in a planet's orbit from the Sun. These points are critical for understanding variations in solar radiation and the seasonal climate differences across hemispheres. For instance, Earth reaches perihelion in early January, yet it experiences winter in the Northern Hemisphere due to the planet's axial tilt, not its distance from the Sun.

*Key Facts:*
- Perihelion is a feature of elliptical orbits, as explained by Kepler's laws.
- Earth's perihelion occurs in early January each year.
- The opposite of perihelion is aphelion, which occurs in early July for Earth.

*Source:*

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