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To take into account such movement, celestial pole definitions come with an epoch to specify the date of the rotation axis; J2000.0 is the current standard. An analogous concept applies to other planets: a planet's celestial poles are the points in the sky where the projection of the planet's axis of rotation intersects the celestial sphere.
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 ...
The rotation curve of the Milky Way agrees with the universal rotation curve of spiral galaxies, the best evidence for the existence of dark matter in galaxies. Alternatively, a minority of astronomers propose that a modification of the law of gravity may explain the observed rotation curve. [247]
The motion of nearly 1.3 billion stars has been recorded as well as the location and brightness of 1.7 billion. ... visualizations of what the Milky Way looks like. The image you see above ( full ...
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.
Milky Way with galactic plane, ecliptic and celestial equator. The galactic plane is the plane on which the majority of a disk-shaped galaxy 's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms galactic plane and galactic poles usually refer specifically to the plane and poles ...
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 ...
The Oort constants (discovered by Jan Oort) and are empirically derived parameters that characterize the local rotational properties of our galaxy, the Milky Way, in the following manner: where and are the rotational velocity and distance to the Galactic Center, respectively, measured at the position of the Sun, and v and r are the velocities ...