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  2. Local standard of rest - Wikipedia

    en.wikipedia.org/wiki/Local_standard_of_rest

    The Sun follows the solar circle (eccentricity e < 0.1) at a speed of about 255 km/s in a clockwise direction when viewed from the galactic north pole at a radius of ≈ 8.34 kpc [4] about the center of the galaxy near Sgr A*, and has only a slight motion, towards the solar apex, relative to the LSR.

  3. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    A galaxy's recessional velocity is typically determined by measuring its redshift, a shift in the frequency of light emitted by the galaxy. The discovery of Hubble's law is attributed to work published by Edwin Hubble in 1929, [ 2 ] [ 3 ] [ 4 ] but the notion of the universe expanding at a calculable rate was first derived from general ...

  4. Proper motion - Wikipedia

    en.wikipedia.org/wiki/Proper_motion

    This motion is caused by the movement of the stars relative to the Sun and Solar System. The Sun travels in a nearly circular orbit (the solar circle ) about the center of the galaxy at a speed of about 220 km/s at a radius of 8,000 parsecs (26,000 ly) from Sagittarius A* [ 5 ] [ 6 ] which can be taken as the rate of rotation of the Milky Way ...

  5. Oort constants - Wikipedia

    en.wikipedia.org/wiki/Oort_constants

    Figure 1: Geometry of the Oort constants derivation, with a field star close to the Sun in the midplane of the Galaxy. Consider a star in the midplane of the Galactic disk with Galactic longitude at a distance from the Sun. Assume that both the star and the Sun have circular orbits around the center of the Galaxy at radii of and from the Galactic Center and rotational velocities of and ...

  6. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...

  7. Speed - Wikipedia

    en.wikipedia.org/wiki/Speed

    The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; [2] the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Speed is the magnitude of velocity (a vector), which indicates additionally the direction of ...

  8. Solar apex - Wikipedia

    en.wikipedia.org/wiki/Solar_apex

    The solar apex is in the constellation of Hercules near the star Vega. [1]For more than 30 years before 1986 the speed of the Sun towards the solar apex was taken to be about 20 km/s [2] but all later studies give a smaller component in the vector toward galactic longitude 90°, reducing overall speed to about 13.4 km/s. [3]

  9. Introduction to the mathematics of general relativity - Wikipedia

    en.wikipedia.org/wiki/Introduction_to_the...

    That is, the Sun's mass causes the regular grid coordinate system (in blue) to distort and have curvature. The radio wave then follows this curvature and moves toward the Sun. Curvilinear coordinates are coordinates in which the angles between axes can change from point to point. This means that rather than having a grid of straight lines, the ...