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A “yellow dwarf” is the common name for a G-type main-sequence star. The Sun is the best-known example, classified as G2 V: “G2” describes its spectral type, while “V” identifies its main-sequence stage.
What makes a star a yellow dwarf?
The name combines two different parts of stellar classification. The letter G is the star’s spectral class, based on properties such as its spectrum and temperature. The number 2 is a subtype within that class. The Roman numeral V is its luminosity class: it identifies a main-sequence star.
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“Dwarf” is a technical classification, not a claim that the star is tiny by everyday standards. It distinguishes this luminosity class from giant stars; it does not mean every star that is not a giant is a yellow dwarf.
Why is the Sun called a yellow dwarf?
NASA classifies the Sun as G2 V, making it a G-type main-sequence star. It is about 4.6 billion years old. “Yellow” is a useful shorthand for the G spectral class, but it should not be taken as a precise description of how the Sun looks in every context: ESA/Hubble describes its apparent color as yellowish white.
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How hot is a yellow dwarf?
The Sun’s temperature varies greatly by region. Its visible surface, the photosphere, is about 5,500 °C; its core is about 15 million °C. These figures refer to different parts of the Sun, not competing estimates of one overall temperature.
G is one place in a sequence of spectral classes that broadly runs from hotter to cooler: O (blue), B (blue-white), A (white), F (yellow-white), G (yellow), K (orange), and M (red). In this simplified color scheme, F stars are hotter than G stars, while K stars are cooler.
How does a yellow dwarf produce energy?
Main-sequence stars steadily fuse hydrogen into helium. That fusion supplies the energy associated with this stage of a star’s life. The Sun is currently in its main-sequence phase.
What will happen to the Sun?
The Sun will eventually leave the main sequence and expand into a red giant. Later, it will shed its outer layers, leaving its core exposed. This is the broad path of its evolution; the stages are not a precise dated schedule for an individual star.
Stars with less mass generally spend longer on the main sequence. That relationship does not establish one universal lifetime for every G-type star.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does a yellow dwarf have habitable planets?
A G-type classification describes a star; it does not establish whether planets orbit it, whether any are habitable, or whether life exists there. Those questions require information about the planets and their environments, not just the star’s spectral class.
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