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Stars brighter and hotter than the Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs, make up about 75% of the fusor stars in the Milky Way. [80] The Sun is a population I star, having formed in the spiral arms of the Milky Way galaxy.
This core convection occurs in stars where the CNO cycle contributes more than 20% of the total energy. As the star ages and the core temperature increases, the region occupied by the convection zone slowly shrinks from 20% of the mass down to the inner 8% of the mass. [25] The Sun produces on the order of 1% of its energy from the CNO cycle.
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. A stellar association is a very loose star cluster, looser than an open cluster. A moving group is the remnant of such a stellar association ...
The Sun formed about 4.6 billion years ago from the collapse of part of a giant molecular cloud that consisted mostly of hydrogen and helium and that probably gave birth to many other stars. [125] This age is estimated using computer models of stellar evolution and through nucleocosmochronology. [13]
As those population II stars died, they returned metal-enriched material to the interstellar medium via planetary nebulae and supernovae, enriching further the nebulae, out of which the newer stars formed. These youngest stars, including the Sun, therefore have the highest metal content, and are known as population I stars.
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
Since about half of all known stars form systems of multiple stars and because Jupiter is made of the same elements as the Sun (hydrogen and helium), it has been suggested that the Solar System might have been early in its formation a protostar system with Jupiter being the second but failed protostar, but Jupiter has far too little mass to ...
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. [12]