The Virgo Supercluster itself is thought to be a component of an even larger structure called the Laniakea Supercluster. At the center of this supercluster sits the Virgo Cluster, a massive collection of 1,000 to 2,000 galaxies about 54 million light-years away. The Local Group is one member of a larger structure called the Virgo Supercluster, which is surrounded by several great intergalactic voids, according to Durham University. Together with Andromeda and about 80 smaller galaxies, the Milky Way is a part of the Local Group, which is a group of galaxies, about 10 million light-years across, bound together by their common gravity, according to Swinburne University. Our nearest neighbor is the Andromeda galaxy, located about 2.5 million light-years away. The Milky Way has two major satellite galaxies - the Large and Small Magellanic Clouds - and dozens of smaller satellites. (Image credit: Ron Miller/Stocktrek Images via Getty Images) The Milky Way and the other members of our Local Group of galaxies. The dark matter extends even farther, up to 400,000 light-years from the center, according to a study published in 2019 in the journal Astronomy & Astrophysics. The halo contains old stars and globular clusters, all orbiting the galactic center in random directions. Our solar system sits in the disk, about 27,000 light-years from the galactic center, near the inner rim of the Orion Arm.īeyond the disk of the Milky Way is its halo, which is a spherical region with a radius of about 100,000 light-years.
Within the disk sit several major spiral arms, according to NASA, where the density of stars and gas is higher than average and star formation occurs at a higher rate, making these arms stand out in visual observations. The stellar disk of the Milky Way has a radius of 75,000 to 100,000 light-years, but it is only about 1,000 light-years thick. At the very center of the galaxy sits Sagittarius A*, a supermassive black hole with a mass that's 4.1 million times that of the sun, according to the UCLA Galactic Center Group. Up to a quarter of all the stars in the Milky Way reside in the core the density of stars there is up to a million times greater than it is in the neighborhood of the sun, according to the Space Telescope Science Institute. The core isn't spherical it's elongated into the shape of a bar anywhere from 5,000 to 20,000 light-years long. The Milky Way has three main parts: the core, the disk and the halo. When we look in a direction away from the disk, we see only the stars close to our solar system. When we are looking in the direction of the disk, Earthlings see the combined light of all the stars in the galaxy. This explains why it appears as a band in our sky. The Milky Way is a relatively thin, flattened disk. The sun is in a finger called the Orion Spur. The Milky Way Galaxy is organized into spiral arms of giant stars that illuminate interstellar gas and dust. However, in the early 1920's, astronomer Edwin Hubble made detailed observations of the Andromeda Nebula, revealing that it was its own "island" of stars - a galaxy in its own right - located millions of light-years away from us, according to Britannica. Up until the early 1900's, astronomers assumed that the Milky Way contained all the stars in the universe (either the Milky Way extended to fill the entire cosmos, or it was a finite size and surrounded by an infinite void). The stars themselves are too far away to see all of them individually, but their combined light gives the familiar band. Astronomers and philosophers debated the nature of the Milky Way until Galileo Galilei first observed it with a telescope and found that the light of the Milky Way comes from innumerable distant stars. This is where the English name comes from: The Romans called it Via Lactea and envisioned it as a band of spilled milk. From our vantage point on Earth, the Milky Way looks like a band of diffuse light that arcs across the nighttime sky.