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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 shape of the Milky Way as estimated from star counts by William Herschel in 1785; the Solar System was assumed to be near the center. The first project to describe the shape of the Milky Way and the position of the Sun was undertaken by William Herschel in 1785 by counting the number of stars in different regions of the sky.
Size (left) and distance (right) of a few well-known galaxies put to scale. The following is a list of notable galaxies.. There are about 51 galaxies in the Local Group (see list of nearest galaxies for a complete list), on the order of 100,000 in the Local Supercluster, and an estimated 100 billion in all of the observable universe.
A visible light image of the Andromeda Galaxy. Messier 32 is to the left of the galactic nucleus and Messier 110 is at the bottom right. The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224.
The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (163,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (c. 16 kiloparsecs (52,000 light-years) away) and the possible dwarf irregular galaxy called the Canis Major Overdensity.
The X-shape makes up 45% of the mass of the bulge in the Milky Way. The boxy/peanut bulges are in fact the bar of a galaxy seen edge-on. Other edge-on galaxies can also show a boxy/peanut bar sometimes with an X-shape. Central compact mass ESO 495-21 may host a supermassive black hole, an unusual feature for a galaxy of its size.
The Milky Way was once considered an ordinary spiral galaxy. Astronomers first began to suspect that the Milky Way is a barred spiral galaxy in the 1960s. Their suspicions were confirmed by Spitzer Space Telescope observations in 2005, which showed that the Milky Way's central bar is larger than what was previously suspected. Famous examples
Barred spiral galaxy. A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. [1] Bars are found in about two thirds of all spiral galaxies in the local universe, [2] and generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well.
Diagram of the Milky Way, with galactic features and the relative position of the Solar System labelled. 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. [259]
The Small Magellanic Cloud ( SMC) is a dwarf galaxy near the Milky Way. [5] Classified as a dwarf irregular galaxy, the SMC has a D 25 isophotal diameter of about 5.78 kiloparsecs (18,900 light-years), [1] [3] and contains several hundred million stars. [5] It has a total mass of approximately 7 billion solar masses. [6]