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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.
The inner Solar System is the region comprising the terrestrial planets and the asteroids. [ 89 ] Composed mainly of silicates and metals, [ 90 ] the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn.
Kepler's laws of planetary motion. Illustration of Kepler's laws with two planetary orbits. The orbits are ellipses, with foci F1 and F2 for Planet 1, and F1 and F3 for Planet 2. The Sun is at F1. The shaded areas A1 and A2 are equal, and are swept out in equal times by Planet 1's orbit. The ratio of Planet 1's orbit time to Planet 2's is.
Group of at least 80 galaxies of which the Milky Way is a part. Dominated by Andromeda (the largest), the Milky Way and Triangulum; the remainder are dwarf galaxies. [39] Local Sheet: 7 Mpc 2.16×10 20: 20.33: Group of galaxies including the Local Group moving at the same relative velocity towards the Virgo Cluster and away from the Local Void ...
Coordinate systems in astronomy can specify an object's relative position in three-dimensional space or plot merely by its direction on a celestial sphere, if the object's distance is unknown or trivial. Spherical coordinates, projected on the celestial sphere, are analogous to the geographic coordinate system used on the surface of Earth.
The following outline is provided as an overview of and topical guide to the Solar System: Solar System – gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets (including Earth), with the remainder being ...
The Oort cloud (/ ɔːrt, ʊərt /), [ 1 ] sometimes called the Öpik–Oort cloud, [ 2 ] is theorized to be a vast cloud of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). [ 3 ][ note 1 ][ 4 ] The concept of such a cloud was proposed in 1950 by the Dutch astronomer Jan Oort, in ...
The path-line is the combined motion of the planet's orbit (deferent) around Earth and within the orbit itself (epicycle). Around 210 BCE, Apollonius of Perga shows the equivalence of two descriptions of the apparent retrograde planet motions (assuming the geocentric model), one using eccentrics and another deferent and epicycles . [ 43 ]