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Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms direct and prograde are equivalent in this context, the former is the ...
In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. the true horizon and north to an observer on Earth's surface). [1]
Efficiency measures. Propulsive maneuvers. v. t. e. Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics (classical mechanics) to astronomical objects, such as stars and planets, to produce ephemeris data.
In astronomy and celestial navigation, an ephemeris (/ ɪ ˈ f ɛ m ə r ə s /; pl. ephemerides / ˌ ɛ f ə ˈ m ɛ r ə d iː z /; from Latin ephemeris 'diary' and Greek ἐφημερίς (ephemeris) 'diary, journal') [1] [2] [3] is a book with tables that gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and ...
Astronomical transit. Phobos transits the Sun, as viewed by the Perseverance rover on 2 April 2022. In astronomy, a transit (or astronomical transit) is the passage of a celestial body directly between a larger body and the observer. As viewed from a particular vantage point, the transiting body appears to move across the face of the larger ...
Total solar eclipse. 2027 August 7. Asteroid (137108) 1999 AN 10 will pass within 388,960 km (0.0026 AU) of Earth. 2028 January 12. Partial lunar eclipse. 2028 January 26. Small annular solar eclipse. 2028 July 22. A total solar eclipse will be visible across Australia, including Sydney, and New Zealand.
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way.
Ecliptic coordinates are convenient for specifying positions of Solar System objects, as most of the planets' orbits have small inclinations to the ecliptic, and therefore always appear relatively close to it on the sky. Because Earth's orbit, and hence the ecliptic, moves very little, it is a relatively fixed reference with respect to the stars.