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The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools. The cooling causes the internal pressure to drop, and the star or planet shrinks as a result. This compression, in turn, heats the core of the star/planet.
where G is the gravitational constant, M is the mass of the star, R is the radius of the star, and L is the star's luminosity. As an example, the Sun 's thermal time scale is approximately 15.7 million years.
The sun loses mass due to the solar wind at a very small rate, (2–3) × 10 −14 solar masses per year. [2] The solar wind carries trace amounts of the nuclei of heavy elements fused in the core of the sun, revealing the inner workings of the sun while also carrying information about the solar magnetic field. [3]
Astronomers have discovered a phenomenon that causes the sun to form enormous objects similar to meteors or "shooting stars" in its corona, the outer layer of its atmosphere, that then fall back ...
The internal structure of a main sequence star depends upon the mass of the star. In stars with masses of 0.3–1.5 solar masses (M ☉), including the Sun, hydrogen-to-helium fusion occurs primarily via proton–proton chains, which do not establish a steep temperature gradient. Thus, radiation dominates in the inner portion of solar mass stars.
Neutron stars are formed by the gravitational collapse of the cores of larger stars. They are the remnant of supernova types Ib , Ic , and II . Neutron stars are expected to have a skin or "atmosphere" of normal matter on the order of a millimeter thick, underneath which they are composed almost entirely of closely packed neutrons called ...
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.
The free-fall time is the characteristic time that would take a body to collapse under its own gravitational attraction, if no other forces existed to oppose the collapse.. As such, it plays a fundamental role in setting the timescale for a wide variety of astrophysical processes—from star formation to helioseismology to supernovae—in which gravity plays a dominant ro