G-type main-sequence star

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A main G-type-sequence-star (Spectral type: GV), often (and incorrectly) is called yellow dwarf , or Dwarf star , is the main sequence star (luminosity class V) of the G-type spectrum. Such a star has about 0.84 to 1.15 solar masses and a surface temperature of between 5,300 and 6,000 K. ^{, Table VII, VIII.} Like other main sequence stars, G-type main sequence stars convert the hydrogen element to helium in essence by using nuclear fusion. The sun, the star in which the Earth is gravitationally bound in the Solar System and the object with the largest apparent magnitude, is an example of a G-type main type (G2V type). Every second, the Sun brings about 600 million tons of hydrogen to helium, turning about 4 million tons of matter into energy. In addition to the Sun, other notable examples of the main G-type stars include Alpha Centauri A, Tau Ceti, and 51 Pegasi.

The term is a misnomer, since G-type stars actually range in color from white, for more luminous species such as the Sun, only very little yellow for the less massive and glowing G-type - the next star. The sun is actually white, and its spectrum culminates in blue and green light, but often looks yellow, orange or red through the earth's atmosphere due to atmospheric Rayleigh scattering, especially at sunrise and sunset. In addition, although the term "dwarf" is used to distinguish the main yellow-star stars from the giant stars, the yellow dwarfs like the Sun exceed 90% of the stars in the Milky Way (most of which are much fainter orange, red dwarf, and white dwarfs, the latter being the rest of the stars).

The G-type main sequence star will combine hydrogen for about 10 billion years, until it runs out in the star center. When this happens, the star extends to many times its previous size and becomes a red giant, like Aldebaran (or Alpha Tauri). Eventually the red giant releases its outer gas layer, which becomes the planetary nebula, while its core rapidly cools and contracts into dense solid white dwarfs.

Video G-type main-sequence star

Spectral star standard

The revised Yerkes Atlas system (Johnson & Morgan 1953) lists 11 standard G-type dwarf-spectrum stars; However, not all of these survive to this day as a standard.

The "anchor point" of the MK spectral classification system among G-type main dwarf-type stars, the standard stars that have remained unchanged for years, are the CVn (G0V), Sun (G2V), Kappa1 Ceti (G5V)), 61 Ursae Majoris (G8V). Other major MK standard stars include HD 115043 (G1V) and 16 Cygni B (G3V). The standard choices of dwarf G4 and G6 have changed little over the years among expert classifiers, but frequently used examples include 70 Virginis (G4V) and 82 Eridani (G8V). Until now there has not been a generally approved G7V and G9V standard.

Maps G-type main-sequence star

Planet

Some of the nearest G-type stars known to have planets include the Sun, 61 Virginis, HD 102365, HD 147513, 47 Ursae Majoris, Mu Arae, Tau Ceti and Alpha Centauri.

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See also

• Brown dwarf
• Hertzsprung-Russell diagram
• K-type main-sequence star
• Red dwarf
• Solar twin
• Number of stars, stellar survey
• Star classification, class G

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Note

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References

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External links

Media related to Yellow dwarfs on Wikimedia Commons Also known as G2V

Source of the article : Wikipedia