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The Milky Way is approximately 890 billion to 1.54 trillion times the mass of the Sun in total (8.9 × 10 11 to 1.54 × 10 12 solar masses), [7][8][9] although stars and planets make up only a small part of this. Estimates of the mass of the Milky Way vary, depending upon the method and data used.
There is evidence that the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. [ 1 ] Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and ...
The most widely accepted model of planetary formation is known as the nebular hypothesis. This model posits that, 4.6 billion years ago, the Solar System was formed by the gravitational collapse of a giant molecular cloud spanning several light-years. Many stars, including the Sun, were formed within this collapsing cloud.
Historical models of the Solar System. Approximate sizes of the planets relative to each other. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Jupiter's diameter is about 11 times that of the Earth's and the Sun's diameter is about 10 times Jupiter's.
The Solar System's location in the Milky Way is a factor in the evolutionary history of life on Earth. Spiral arms are home to a far larger concentration of supernovae , gravitational instabilities, and radiation that could disrupt the Solar System, but since Earth stays in the Local Spur and therefore does not pass frequently through spiral ...
With the development of the heliocentric model by Nicolaus Copernicus in the 16th century, the Sun was believed to be the center of the Universe, with the planets (including Earth) and stars orbiting it. In the early-20th century, the discovery of other galaxies and the development of the Big Bang theory, led to the development of cosmological ...
Galactocentrism. In astronomy, galactocentrism is the theory that the Milky Way Galaxy, home of Earth ' s Solar System, is at or near the center of the Universe. [1][2] Thomas Wright and Immanuel Kant first speculated that fuzzy patches of light called nebulae were actually distant "island universes" consisting of many stellar systems. [3]
The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. [1][2] Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, [3][4][5] a compact radio source which is almost exactly at the galactic rotational center ...