Milky Way

The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Galaxia Kyklos), sometimes referred to simply as "the Galaxy", is a barred spiral galaxy which forms part of the Local Group. Although the Milky Way is but one of millions of galaxies in the universe, the Galaxy has special significance to humanity as it is the home of the solar system, which is located near the Orion Arm. Democritus (460 BC - 370 BC) was the first known person to claim that Milky Way consists of distant stars.

The Sun's place in the Milky Way

The Sun (and therefore the Earth and Solar System) may be found close to the inner rim of the Orion Arm, in the Local Fluff, 8.5±0.5 kpc from the galactic center. The distance between the local arm and the next arm out, the Perseus Arm, is about 6,500 light-years (see http://www.ras.ucalgary.ca/CGPS/press/aas00/pr/pr_14012000/pr_14012000map1.html).

Related Topics:
Earth - Solar System - Local Fluff - Galactic center - 6,500 light-years

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The Apex of the Sun's Way, or the solar apex, refers to the direction that the Sun travels through space in the Milky Way. The general direction of the sun's galactic motion is towards the star Vega near the constellation of Hercules, at an angle of roughly 86 degrees to the direction of the galactic center. The sun's orbit around the galaxy is expected to be roughly elliptical with the addition of perturbations due to the galactic spiral arms and non-uniform mass distributions. We are presently about 8.5 kpc from the center of the galaxy and roughly 1/8 of an orbit before perigalacton (the sun's closest approach to the center, ~8.3 kpc).

Related Topics:
Solar apex - Hercules - Pc

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It would take the solar system about 200-250 million years to complete one orbit ("galactic year"), and so is thought to have completed about 20-25 orbits during its lifetime. The orbital speed is 217 km/s, i.e. 1 light-year in ca. 1400 years, and 1 AU in 8 days.

Related Topics:
Solar system - Orbital speed - AU

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