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Westerhout 51 nebula in Aquila - one of the largest star factories in the Milky Way (August 25, 2020). Star formation is the process by which dense regions within molecular clouds in interstellar space—sometimes referred to as "stellar nurseries" or "star-forming regions"—collapse and form stars. [1]
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
IMF not only describes the formation and evolution of individual stars, it also serves as an important link that describes the formation and evolution of galaxies. [1] The IMF is often given as a probability density function (PDF) that describes the probability of a star that has a certain mass during its formation. [2]
Typical boundary conditions set the values of the observable parameters appropriately at the surface (=) and center (=) of the star: () =, meaning the pressure at the surface of the star is zero; () =, there is no mass inside the center of the star, as required if the mass density remains finite; () =, the total mass of the star is the star's ...
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.
Most stars form in groups of dozens to hundreds of thousands of stars. [57] Massive stars in these groups may powerfully illuminate those clouds, ionizing the hydrogen, and creating H II regions. Such feedback effects, from star formation, may ultimately disrupt the cloud and prevent further star formation. [58]
During the merger, if there is enough gas, the increased gravity will force the gas to the centre of the forming elliptical galaxy. This may lead to a short period of intensive star formation called a starburst. [137] In addition, the infalling gas will feed the newly formed black hole, transforming it into an active galactic nucleus. The force ...
The visible-light (left) and infrared (right) views of the Trifid Nebula, a giant star-forming cloud of gas and dust located 5,400 light-years (1,700 pc) away in the constellation Sagittarius. Stars are thought to form inside giant clouds of cold molecular hydrogen—giant molecular clouds of roughly 300,000 M ☉ and 65 light-years (20 pc) in ...