Stellar Evolution. ‘The life-cycle of stars’. Star Energy. Nuclear Fusion – a nuclear reaction in which to atoms are fused together… New elements are created and energy is released. This process is responsible for creating ALL elements found in the universe…
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Stellar Evolution ‘The life-cycle of stars’
Star Energy • Nuclear Fusion – a nuclear reaction in which to atoms are fused together… • New elements are created and energy is released. • This process is responsible for creating ALL elements found in the universe… in other words, we are all made from star dust.
Star Energy (con’t) • Hydrogen fusion H + H He + • Helium fusion He + He Be + • As the mass of elements increases, energy production increases Energy More Energy
1. Nebula • A cloud of gas and dust • Gravity causes the cloud to collapse and condense • Temperatures begin to increase = Glows • Fusion begins at VERY high temps. (Some of the extra gas and dust may form planets)
Main Sequence Stars • Core reaches a temp of ~15 million K. • Hydrogen begins to fuse into Helium in the core. • ~90% of stars lifetime is spent in the main sequence stage. • Classified based on temperature and luminosity
Giant Stars • Core decreases in size as • All (or most) H is consumed • He fusion is occurring – producing more energy • Diameter increases x10 • Surface temp decreases as star expands
Super Giants • Form from massive stars • A chain of reactions take place in the core producing He, C, O, Ne, Mg, Si, S, Ar, Ca, Ti, Cr, Fe • Highest temperature = Blue Super Giants • Usually explode in a tremendous event called a supernova
Nova/Super Nova • The core of a giant star produces too much energy in it’s core and causes the outside of the star to expand. • The outer layer of gasses are blown out to space (nova, or supernova), leaving behind a small, hot core…
White Dwarf • Stars decrease in size ~ same diameter as earth, mass stays the same • Mass of sun, size of Earth • DENSITY INCREASES TREMENDOUSLY D = 1,000,000 g/cm3 1 sugar cube > 1 car • Solid, but still hot, so it is glowing • Luminosity decreases
Neutron stars • Form from the remains of extremely massive stars after a supernova. • Very small ~ 30 km across • D = 2 x 1014 • 1 sugar cube = mass of humanity