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It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is a typical star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere. Astronomers classify it as a G-type main ...
Whether the presence of the isotopes iron-60 and aluminium-26 can be interpreted as a sign of a birth cluster containing massive stars is still under debate. If the Sun was part of a star cluster, it might have been influenced by close flybys of other stars, the strong radiation of nearby massive stars and ejecta from supernovae occurring close by.
Star density maps of the Gaia Catalogue of Nearby Stars.The Sun is located at the centre of both maps. The regions with higher density of stars are shown; these correspond with known star clusters (Hyades and Coma Berenices) and moving groups. This is a list of nearby stellar associations and moving groups.
The nebula nearest to the Sun where massive stars are being formed is the Orion Nebula, 1,300 light-years (1.2 × 10 16 km) away. [11] However, lower mass star formation is occurring about 400–450 light-years distant in the ρ Ophiuchi cloud complex .
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution
The Sun is a G-type main-sequence star (G2V), informally called a yellow dwarf, though its light is actually white. It formed approximately 4.6 billion [a] years ago from the gravitational collapse of matter within a region of a large molecular cloud.
The main sequence is sometimes divided into upper and lower parts, based on the dominant process that a star uses to generate energy. The Sun, along with main sequence stars below about 1.5 times the mass of the Sun (1.5 M ☉), primarily fuse hydrogen atoms together in a series of stages to form helium, a sequence called the proton–proton chain.
Of the main-sequence star types, stars more massive than 1.5 times that of the Sun (spectral types O, B, and A) age too quickly for advanced life to develop (using Earth as a guideline). On the other extreme, dwarfs of less than half the mass of the Sun (spectral type M) are likely to tidally lock planets within their habitable zone, along with ...