Re: Abstand Erde-Sonne = ca. 150 Millionen km (=1 AU)
Geschrieben von XI am 01. Juli 2002 09:55:51:
Als Antwort auf: Geschwindigkeit von Asteroiden geschrieben von Georg am 29. Juni 2002 22:44:08:
1 AU = 149,597,870.691 kilometers
Definition: An Astronomical Unit is the mean distance between the Earth and the Sun. It is a derived constant and used to indicate distances within a solar system. The Earth orbits at a distance of 1 AU from the Sun.
Technical Definition: AU is short for Astronomical Unit and defined as: the radius of a Keplerian circular orbit of a point-mass having an orbital period of 2*(pi)/k days (k is the Gaussian gravitational constant). Since an AU is based on radius of a circular orbit, one AU is actually slightly less than the average distance between the Earth and the Sun (approximately 150 million km or 93 million miles).
Historical Background: Tycho Brahe estimated the distance between the Sun and the Earth at 8 million kilometers (5 million miles). Later, Johannes Kepler estimated the AU was at 24 million kilometers (15 million miles). In 1672, Giovanni Cassini made a much better estimate by using Mars. By observing Mars from Paris and having a colleague, Jean Richer, also observe Mars at the same time in French Guiana in South America, Cassini determined the parallax of Mars. From that Cassini was able to calculate the distance from Earth to Mars, and then the distance from Earth to the Sun. Cassini calculated the AU to be at 140 million kilometers (87 million miles), which is lower, but very close to the modern day number.