Helium burning in the core stabilizes the star and it shrinks to a yellow giant

Helium burning in the core stabilizes the star and it

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The core contracts and heats up until helium burning begins in the core. Helium burning in the core stabilizes the star, and it shrinks to a yellow giant on the horizontal branch. Helium runs out in the core and starts burning in a shell, and the star balloons again to another red giant phase. How stars die Low mass star Since low mass stars take so long to burn their hydrogen, none of these stars has ever left the main sequence. When they eventually do, they will just cool down. Sun-like star A Sun-like star will blow off its outer layers when helium is burning in a shell. These outer layers form a planetary nebula, which has nothing to do with planets. The remaining core of the star will become a white dwarf, a very small, very hot star about the size of the Earth. Even though it is very hot, a white dwarf is a dead star, no reaction are occur- ring in it. How stars evolve throughout their lives Massive star A massive star goes through the same phases as a Sun-like star, it just goes through more of them. After helium stops burning in the core, carbon burning starts. After carbon, neon starts burning. Then oxygen, and finally silicon. Each phase occurs faster and faster. Silicon burns into iron, and iron fusion does not pro - duce energy. Therefore, iron marks the end of the line for the star. How stars die Massive star After the core burns to iron, pressure can no longer provide support against gravity. Grav - ity wins, and the core of the star collapses. The core rebounds and helps to blow the star apart in a massive explosion called a supernova. All the elements heavier than iron (gold, silver, lead, etc.) were created in supernova. Star clusters Stars form in clusters Remember that the mass of a main sequence star is related to its lifetime We can determine the age of a star cluster by looking at the highest mass stars that are just about to leave the main sequence The age of the cluster is the main sequence lifetimes of those stars What are the two types of star clusters? Open clusters are loosely packed and contain up to a few thousand stars Globular clusters are densely packed and contains hundreds of thousands of stars What is a white dwarf? A white dwarf is the inert core of a dead Sun-like star Electron degeneracy pressure balances the inward pull of gravity What is a neutron star? A ball of neu - trons left over from a massive star supernova and supported by neutron degeneracy pressure How were neutron stars discovered? Beams of radiation from a rotating neutron star sweep through space like lighthouse beams, making them appear to pulse Observations of these pulses were the first evidence for neutron stars What is a black hole? A black hole is a massive object whose radius is so small that the escape velocity exceeds the speed of light What happens to space and time near a black hole? Near the event horizon time slows down Light emitted by an object falling into a black hole is redshifted What would it be like to fall into a black hole? You would suffer spaghettification be - fore crossing the event horizon
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