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The Milky Way [c] 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.
The Milky Way galaxy is a member of an association named the Local Group, a relatively small group of galaxies that has a diameter of approximately one megaparsec. The Milky Way and the Andromeda Galaxy are the two brightest galaxies within the group; many of the other member galaxies are dwarf companions of these two.
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 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 ...
Galactic Center. 17 45 40.04, −29° 00′ 28.1″. The Galactic Center, as seen by one of the 2MASS infrared telescopes, is located in the bright upper left portion of the image. Marked location of the Galactic Center. The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy.
Outer space (or simply space) is the expanse beyond celestial bodies and their atmospheres. It contains ultra-low levels of particle densities, constituting a near-perfect vacuum [1] of predominantly hydrogen and helium plasma, permeated by electromagnetic radiation, cosmic rays, neutrinos, magnetic fields and dust.
The centre of the Milky Way is about 26 000 light-years away. 1 × 10 5 ly: 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. 10 6: 2.5 × 10 6 ly
Image of Sirius A and Sirius B taken by the Hubble Space Telescope. Sirius B, which is a white dwarf, can be seen as a faint point of light to the lower left of the much brighter Sirius A. A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun 's ...
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 whose ...