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  2. Stellar kinematics - Wikipedia

    en.wikipedia.org/wiki/Stellar_kinematics

    Typical examples are the halo stars passing through the disk of the Milky Way at steep angles. One of the nearest 45 stars, called Kapteyn's Star, is an example of the high-velocity stars that lie near the Sun: Its observed radial velocity is −245 km/s, and the components of its space velocity are u = +19 km/s, v = −288 km/s, and w = −52 ...

  3. Newton's theorem of revolving orbits - Wikipedia

    en.wikipedia.org/wiki/Newton's_theorem_of...

    Newton illustrates his formula with three examples. In the first two, the central force is a power law, F(r) = r n−3, so C(r) is proportional to r n. The formula above indicates that the angular motion is multiplied by a factor k = 1/ √ n, so that the apsidal angle α equals 180°/ √ n.

  4. Zenith - Wikipedia

    en.wikipedia.org/wiki/Zenith

    In Islamic astronomy, the passing of the Sun over the zenith of Mecca becomes the basis of the qibla observation by shadows twice a year on 27/28 May and 15/16 July. [ 5 ] [ 6 ] At a given location during the course of a day, the Sun reaches not only its zenith but also its nadir , at the antipode of that location 12 hours from solar noon .

  5. List of unsolved problems in astronomy - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    A sample of 229 nearby "thick" disk stars has been used to investigate the existence of an age-metallicity relation in the Galactic thick disk and indicates that there is an age-metallicity relation present in the thick disk. [13] [14] Stellar ages from asteroseismology confirm the lack of any strong age-metallicity relation in the Galactic ...

  6. Parabolic trajectory - Wikipedia

    en.wikipedia.org/wiki/Parabolic_trajectory

    At any time the average speed from = is 1.5 times the current speed, i.e. 1.5 times the local escape velocity. To have t = 0 {\displaystyle t=0\!\,} at the surface, apply a time shift; for the Earth (and any other spherically symmetric body with the same average density) as central body this time shift is 6 minutes and 20 seconds; seven of ...

  7. Shapiro time delay - Wikipedia

    en.wikipedia.org/wiki/Shapiro_time_delay

    The Shapiro time delay effect, or gravitational time delay effect, is one of the four classic Solar System tests of general relativity. Radar signals passing near a massive object take slightly longer to travel to a target and longer to return than they would if the mass of the object were not present.

  8. Binet equation - Wikipedia

    en.wikipedia.org/wiki/Binet_equation

    The Binet equation, derived by Jacques Philippe Marie Binet, provides the form of a central force given the shape of the orbital motion in plane polar coordinates.The equation can also be used to derive the shape of the orbit for a given force law, but this usually involves the solution to a second order nonlinear, ordinary differential equation.

  9. Thermal time scale - Wikipedia

    en.wikipedia.org/wiki/Thermal_time_scale

    In astrophysics, the thermal time scale or Kelvin–Helmholtz time scale is the approximate time it takes for a star to radiate away its total kinetic energy content at its current luminosity rate. [1]