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Most centaurs have a prograde orbit around the Sun. The first centaur with a retrograde orbit to be discovered was 20461 Dioretsa. [25] Other known centaurs with retrograde orbits include 2004 NN 8, 2012 TL 139, (434620) 2005 VD, 2006 BZ 8, and 2006 RJ 2. All of these orbits are highly inclined, with inclinations in the range of 160 to 180º.
An inclination of 0° means the orbiting body has a prograde orbit in the planet's equatorial plane. An inclination greater than 0° and less than 90° also describes a prograde orbit. An inclination of 63.4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. [3]
Retrograde (backward) and prograde (forward) are observed as though the stars revolve around the Earth. Ancient Greek astronomer Ptolemy in 150 AD believed that the Earth was the center of the Solar System and therefore used the terms retrograde and prograde to describe the movement of the planets in relation to the stars. Although it is known ...
Apart from those in Sun-synchronous orbit, few satellites are launched into retrograde orbit on Earth because the quantity of fuel required to launch them is greater than for a prograde orbit. This is because when the rocket starts out on the ground, it already has an eastward component of velocity equal to the rotational velocity of the planet ...
The point towards which the Earth in its solar orbit is directed at any given instant is known as the "apex of the Earth's way". [4] [5] From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same vantage point, both the Earth and the Sun would ...
471325 Taowu (provisional designation 2011 KT 19, formerly nicknamed Niku (/ n iː k uː /)) is a trans-Neptunian object whose orbit is tilted 110° with respect to the planets' orbital plane. Thus, it has a nearly polar retrograde orbit around the Sun. [5]
where is the semimajor axis of the planet's orbit relative to the Sun; and are the masses of the planet and Sun, respectively. This simplification is sufficient to compute rough estimates of fuel requirements, and rough time-of-flight estimates, but it is not generally accurate enough to guide a spacecraft to its destination.
The apparent motion of the sun is approximately +1° per day (360° per year / 365.2422 days per tropical year ≈ 0.9856473° per day), so apparent motion of the sun relative to the orbit plane is about 2.8° per day, resulting in a complete cycle in about 127 days. For retrograde orbits ω is negative, so the precession becomes positive.