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A line joining a planet and the Sun sweeps out equal areas during equal intervals of time. [23] The same (blue) area is swept out in a fixed time period. The green arrow is velocity. The purple arrow directed towards the Sun is the acceleration. The other two purple arrows are acceleration components parallel and perpendicular to the velocity.
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.
The Milky Way is approximately 890 billion to 1.54 trillion times the mass of the Sun in total (8.9 × 10 11 to 1.54 × 10 12 solar masses), [7][8][9] although stars and planets make up only a small part of this. Estimates of the mass of the Milky Way vary, depending upon the method and data used.
Barnard's Star is the star with the highest proper motion. [1] In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as the internal kinematics of more distant ...
The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. [1][2] Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, [3][4][5] a compact radio source which is almost exactly at the galactic rotational center ...
Satellite galaxies that orbit from 1,000 ly (310 pc) of the edge of the disc of the Milky Way Galaxy to the edge of the dark matter halo of the Milky Way at 980,000 ly (300 kpc) from the center of the galaxy, [ a ] are generally depleted in hydrogen gas compared to those that orbit more distantly. This is because of their interactions with the ...
Dashed black lines: Uncertain calibration ladder step. The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough ...
The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from each ...