Major semi-axis of the earth
The major semi-axis of the earth is a term that cannot be deduced from the meaning of the word itself. It denotes a certain distance to the sun.
The semi-major axis is 1 AU and corresponds to 149.6 million. km. Understood? A little bit of theory beforehand.
The earth orbits the sun on an ellipse
- Our solar system, whose central star is the sun, consists of 9 large planets. These planets move on planetary orbits around the sun. All planetary orbits are almost circular ellipses, with the sun as the central star of the system at the center. The time required by a planet for a complete orbit around the sun on its planetary orbit is the planetary year.
- The earth also moves in an elliptical orbit around the sun. The sun can be found in one of the focal points of this ellipse. The distance between the earth and the sun changes over the course of a year due to the slightly elliptical shape of the earth's orbit around the sun.
The ellipse endpoints are called aphelion and perihelion
- At 3. January each year reaches the earth in orbit with approx. 147,000,000 km its closest point to the sun (perihelion). At 4. July reaches it with approx. 152,000,000 km its furthest point from the sun (aphelion). In January the earth orbits the sun on its planetary orbit with the highest and in July with the lowest orbital speed.
- Aphelion (point closest to the sun) and perihelion (point closest to the sun) are the two endpoints in the main axis of the ellipse.
How do I compute an orbit?
How and why do you actually calculate an orbit? The question is easily explained. …
The major semi-axis is approx. 149,600,000 km
- The mean value of the distance between aphelion and perihelion is the major semi-axis of the ellipse or the earth. It is around 149,600,000 km on average. This distance was used to define the astronomical unit (AU). So the term refers to the distance between the earth and the sun. So you shouldn't speak of the semi-axis of the earth, but rather of the semi-major axis of the elliptical orbit.
- The AU is an astronomical unit of length used to indicate distances within the solar system. This AE is now defined with a length of 149,597,870,700 meters.
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