Aphelion facts for kids
.svg)
The aphelion is a special point in an object's orbit around the Sun. It's the moment when the object is farthest away from the Sun. Think of it as the longest distance between a planet and our star.
The opposite of aphelion is called the perihelion. This is when an object in orbit is closest to the Sun.
The word "aphelion" comes from ancient Greek words. "Apo" means "away from" or "far off," and "Helios" is the Greek word for the Sun. So, "aphelion" literally means "away from the Sun."
Earth's Aphelion
Our own planet, Earth, travels around the Sun in an oval-shaped path. This means its distance from the Sun changes throughout the year.
- Earth reaches its aphelion around July 5th each year.
- At this time, Earth is about 152.1 million kilometers (or 94.5 million miles) away from the Sun.
- Even though Earth is farthest from the Sun in July, it's summer in the Northern Hemisphere. This is because the seasons are caused by Earth's tilt, not its distance from the Sun.
Why Orbits Are Not Perfect Circles
Planets and other objects don't orbit the Sun in perfect circles. Instead, they follow an ellipse, which looks like a stretched-out circle.
- This elliptical shape means there will always be a point where the object is closest to the Sun (perihelion) and a point where it is farthest (aphelion).
- The Sun is not exactly in the center of this ellipse. It's at one of the two "focus points" of the ellipse. This is why the distance changes.
Other Orbits
The terms aphelion and perihelion are used specifically for objects orbiting the Sun. For objects orbiting other stars or planets, different terms are used:
- Apoapsis is the general term for the farthest point in any orbit.
- Periapsis is the general term for the closest point in any orbit.
- For objects orbiting Earth, the farthest point is called apogee, and the closest is perigee.
- For objects orbiting Jupiter, the farthest point is apojove, and the closest is perijove.
Understanding aphelion helps us learn more about how planets move and how our solar system works!
Images for kids
-
The two-body system of interacting elliptic orbits: The smaller, satellite body (blue) orbits the primary body (yellow); both are in elliptic orbits around their common center of mass (red +). Periapsis and apoapsis are the smallest and largest distances between the orbiter and its host body.
-
Keplerian orbital elements: point F, the nearest point of approach of an orbiting body, is the pericenter (also periapsis) of an orbit; point H, the farthest point of the orbiting body, is the apocenter (also apoapsis) of the orbit; and the red line between them is the line of apsides.
See also
In Spanish: Afelio para niños
