People have interpreted patterns and images in the stars since ancient times. Star is cognate (shares the same root) with the following words: asterisk, asteroid, astral, constellation, Esther. Some scholars believe the word is a borrowing from Akkadian "istar" (venus), however some doubt that suggestion. Compare Latin stella, Greek aster, German Stern. The word "star" ultimately derives from the Proto-Indo-European root "h₂stḗr" also meaning star, but further analyzable as h₂eh₁s- ("to burn", also the source of the word "ash") + -tēr (agentive suffix). Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy. When two such stars have a relatively close orbit, their gravitational interaction can significantly impact their evolution. Stars can form orbital systems with other astronomical objects, as in the case of planetary systems and star systems with two or more stars. Astronomers can determine stellar properties-including mass, age, metallicity (chemical composition), variability, distance, and motion through space-by carrying out observations of a star's apparent brightness, spectrum, and changes in its position in the sky over time. These elements are then recycled into new stars. Stellar mass loss or supernova explosions return chemically enriched material to the interstellar medium.
Stellar nucleosynthesis in stars or their remnants creates almost all naturally occurring chemical elements heavier than lithium. At the end of a star's lifetime, its core becomes a stellar remnant: a white dwarf, a neutron star, or-if it is sufficiently massive-a black hole. This process releases energy that traverses the star's interior and radiates into outer space. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core. Its total mass is the main factor determining its evolution and eventual fate. Still, most are invisible to the naked eye from Earth, including all individual stars outside our galaxy, the Milky Way.Ī star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. The observable universe contains an estimated 10 22 to 10 24 stars. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Many other stars are visible to the naked eye at night, but their immense distances from Earth make them appear as fixed points of light. A star-forming region in the Large Magellanic CloudĪ star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity.
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