Difference between revisions of "Stars"
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==Etymology== | ==Etymology== | ||
[https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] sterre, from [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] steorra; akin to Old High German sterno star, Latin stella, [[Greek]] astēr, astron | [https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] sterre, from [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] steorra; akin to Old High German sterno star, Latin stella, [[Greek]] astēr, astron | ||
| − | *Date: before [ | + | *Date: before [https://www.wikipedia.org/wiki/11th_Century 12th century] |
==Definitions== | ==Definitions== | ||
*1 a : a [[natural]] [[luminous]] [[body]] visible in the sky especially at night | *1 a : a [[natural]] [[luminous]] [[body]] visible in the sky especially at night | ||
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:d : a person who is preeminent in a particular field | :d : a person who is preeminent in a particular field | ||
==Description== | ==Description== | ||
| − | A '''star''' is a massive, luminous ball of [ | + | A '''star''' is a massive, luminous ball of [https://en.wikipedia.org/wiki/Plasma_(physics) plasma] that is held together by [[gravity]]. The nearest star to [[Earth]] is the [[Sun]], which is the [[source]] of most of the [[energy]] on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun. Historically, the most prominent stars on the [[celestial]] [[sphere]] were grouped together into [https://en.wikipedia.org/wiki/Constellation constellations], and the brightest stars gained proper [[names]]. Extensive [[Astrometry|catalogues]] of stars have been assembled by astronomers, which provide [[standardized]] star designations. |
| − | For most of its life, a star shines due to [ | + | For most of its life, a star shines due to [https://en.wikipedia.org/wiki/Thermonuclear_fusion thermonuclear fusion] in its core releasing [[energy]] that traverses the star's interior and then radiates into outer [[space]]. Almost all elements heavier than [https://en.wikipedia.org/wiki/Hydrogen hydrogen] and [https://en.wikipedia.org/wiki/Helium helium] were [[created]] by [[fusion]] processes in stars. [[Astronomers]] can determine the [[mass]], age, [[Chemistry|chemical]] composition and many other properties of a star by observing its [[spectrum]], [[luminosity]] and [[motion]] through [[space]]. The [[total]] [[mass]] of a star is the principal determinant in its [[evolution]] and [[eventual]] [[Destiny|fate]]. Other characteristics of a star are determined by its [[evolutionary]] [[history]], including the diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a [https://en.wikipedia.org/wiki/Hertzsprung-Russell_diagram Hertzsprung-Russell diagram] (H–R diagram), allows the age and evolutionary state of a star to be determined. |
| − | A star begins as a collapsing cloud of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily [[converted]] into helium through the [[process]] of nuclear [[fusion]]. The remainder of the star's interior carries [[energy]] away from the core through a combination of [ | + | A star begins as a collapsing cloud of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily [[converted]] into helium through the [[process]] of nuclear [[fusion]]. The remainder of the star's interior carries [[energy]] away from the core through a combination of [https://en.wikipedia.org/wiki/Radiation radiative] and [https://en.wikipedia.org/wiki/Convection convective] processes. The star's internal pressure prevents it from collapsing further under its own [[gravity]]. Once the hydrogen fuel at the core is exhausted, those stars having at least 0.4 times the mass of the Sun[2] expand to become a [https://en.wikipedia.org/wiki/Red_giant red giant], in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of the [[matter]] into the interstellar environment, where it will form a new [[generation]] of stars with a higher proportion of heavy elements. |
| − | [ | + | [https://en.wikipedia.org/wiki/Binary_star Binary] and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable [[orbits]]. When two such stars have a [[relatively]] close orbit, their gravitational [[interaction]] can have a significant impact on their [[evolution]]. Stars can form part of a much larger gravitationally bound [[structure]], such as a cluster or a [[galaxy]].[https://en.wikipedia.org/wiki/Star] |
[[Category: Astronomy]] | [[Category: Astronomy]] | ||
Latest revision as of 01:56, 13 December 2020
Etymology
Middle English sterre, from Old English steorra; akin to Old High German sterno star, Latin stella, Greek astēr, astron
- Date: before 12th century
Definitions
- b : a self-luminous gaseous spheroidal celestial body of great mass which produces energy by means of nuclear fusion reactions
- 2 a (1) : a planet or a configuration of the planets that is held in astrology to influence one's destiny or fortune —usually used in plural (2) : a waxing or waning fortune or fame <her star was rising>
- b obsolete : destiny
- 3 a : a conventional figure with five or more points that represents a star; especially : asterisk
- b : an often star-shaped ornament or medal worn as a badge of honor, authority, or rank or as the insignia of an order
- c : one of a group of conventional stars used to place something in a scale of value
- 4 : something resembling a star <was hit on the head and saw stars>
- 5 a : the principal member of a theatrical or operatic company who usually plays the chief roles
- b : a highly publicized theatrical or motion-picture performer c : an outstandingly talented performer <a track star>
- d : a person who is preeminent in a particular field
Description
A star is a massive, luminous ball of plasma that is held together by gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun. Historically, the most prominent stars on the celestial sphere were grouped together into constellations, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations.
For most of its life, a star shines due to thermonuclear fusion in its core releasing energy that traverses the star's interior and then radiates into outer space. Almost all elements heavier than hydrogen and helium were created by fusion processes in stars. Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star are determined by its evolutionary history, including the diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung-Russell diagram (H–R diagram), allows the age and evolutionary state of a star to be determined.
A star begins as a collapsing cloud of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily converted into helium through the process of nuclear fusion. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. The star's internal pressure prevents it from collapsing further under its own gravity. Once the hydrogen fuel at the core is exhausted, those stars having at least 0.4 times the mass of the Sun[2] expand to become a red giant, in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of the matter into the interstellar environment, where it will form a new generation of stars with a higher proportion of heavy elements.
Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a cluster or a galaxy.[1]
