A galaxy is a large, gravitationally bound method that consists of stars & stellar remnants, an interstellar medium of gas dust, & an important but poorly understood part tentatively dubbed dark matter.[1][2] The name is from the ancient Greek word galaxias , literally meaning "milky", a reference to the Milky Way galaxy. Typical galaxies range from dwarfs with as few as0 million (107) stars,[3] up to giants with a hundred trillion (1014) stars,[4] all orbiting the galaxy's middle of mass. Galaxies may contain lots of star systems, star clusters, & various interstellar clouds. The Sun is of the stars in the Milky Way galaxy; the Solar Method includes the Earth & all the other objects that orbit the Sun.
Historically, galaxies have been categorized according to their apparent shape (usually known as their visual morphology). A common form is the elliptical galaxy,[5] which has an ellipse-shaped light profile. Spiral galaxies are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as irregular galaxies, and usually result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately lead to galaxies merging, may induce episodes of significantly increased star formation, producing what is called a starburst galaxy. Small galaxies that lack a coherent structure could even be known as irregular galaxies.
Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational information suggests that supermassive black holes may exist at the middle of lots of, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least such object within its nucleus.
There are probably over 170 billion [one.7 � 1011] galaxies in the observable universe.7,8 Most galaxies are one,000 to 100,000(9) parsecs in diameter & are usually separated by distances on the order of millions of parsecs (or megaparsecs).10 Intergalactic space [the space between galaxies] is filled with a tenuous gas of an average density less than atom per cubic meter. all of galaxies are organized in to a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are usually arranged in to sheets & filaments, which surround immense voids in the universe.11
Historically, galaxies have been categorized according to their apparent shape (usually known as their visual morphology). A common form is the elliptical galaxy,[5] which has an ellipse-shaped light profile. Spiral galaxies are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as irregular galaxies, and usually result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately lead to galaxies merging, may induce episodes of significantly increased star formation, producing what is called a starburst galaxy. Small galaxies that lack a coherent structure could even be known as irregular galaxies.
Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational information suggests that supermassive black holes may exist at the middle of lots of, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least such object within its nucleus.
There are probably over 170 billion [one.7 � 1011] galaxies in the observable universe.7,8 Most galaxies are one,000 to 100,000(9) parsecs in diameter & are usually separated by distances on the order of millions of parsecs (or megaparsecs).10 Intergalactic space [the space between galaxies] is filled with a tenuous gas of an average density less than atom per cubic meter. all of galaxies are organized in to a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are usually arranged in to sheets & filaments, which surround immense voids in the universe.11