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The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
The Solar System is located in the Milky Way, a barred spiral galaxy with a diameter of about 100,000 light-years containing more than 100 billion stars. The Sun is part of one of the Milky Way's outer spiral arms, known as the Orion–Cygnus Arm or Local Spur.
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. [1] [2] The word is derived from the Greek galaxias ( γαλαξίας ), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System.
The Milky Way started out small and grew in size as it merged with other galaxies, gaining stars as well as hydrogen to form more stars. Each galaxy has hydrogen gas that aids in the birth of stars.
The universe is all of space and time [a] and their contents. [10] It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of energy and matter, and the structures they form, from sub-atomic particles to entire galactic filaments. Space and time, according to the prevailing ...
The Milky Way is about 100 000 light-years across. 1.65 × 10 5 ly R136a1 , in the Large Magellanic Cloud , the most luminous star known at 8.7 million times the luminosity of the Sun, has an apparent magnitude 12.77, just brighter than 3C 273 .
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles ). [a] The parsec unit is obtained by the use of parallax and trigonometry, and is ...
The Andromeda Galaxy is approaching the Milky Way at about 110 kilometres (68 miles) per second. [128] It has been measured approaching relative to the Sun at around 300 km/s (190 mi/s) [1] as the Sun orbits around the center of the galaxy at a speed of approximately 225 km/s (140 mi/s).
It is now known that the Milky Way is only one of as many as an estimated 200 billion (2 × 10 11) to 2 trillion (2 × 10 12) or more galaxies in the observable universe. [8] [9] Also, astronomers generally accept that the nova Shapley referred to in his arguments was in fact a supernova , which does indeed temporarily outshine the combined ...
The Milky Way contains billions of stars, arranged in two strikingly different structures: halo and disc. On clear dark nights in unpolluted areas, when the Moon appears thin or below the horizon, the Milky Way, a band of what looks like white dust, can be seen.