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Transcript of stars
What is a star?
A dense sphere of hydrogen and helium gas.
With the high temperature the hydrogen atoms collide causing fusion that results in helium atoms.
The collisions release energy that opposes the force of gravity.
Layers of a star:
Radiation and Convection:
Convection- hot gas moves up, cooler denser gases move toward center.
Radiation- energy is transferred to individual atoms that absorb energy and transfer it in random directions.
Fate of a Star
A large mass of billions of stars and dust
Stars are formed in a cloud of gas and dust these are called nebula
High temperatures allow protons to collide to make hydrogen and helium, beginning the stars fusion
After 5 billion years the star will run out of hydrogen and begin to die.
The outer layer will expand and cool while the inner layer becomes dense and makes heavier atoms.
Gravity can hold large amounts of galaxies in groups called clusters. larger groups are called superclusters.
Types of Galaxies
Spiral galaxy: Huge bulge in the center an nucleus of galaxy is very dense
Star study has been in act since ancient Greece, however astronomers did not begin to learn more about stars until the invention of the optical telescope. Here's what we have learned so far about stars:
Elliptical galaxy: have no spiral arms and are either spherical or egg shaped
Stars produce wavelengths of electromagnetic radiation, from high-energy X-rays to low visible radio waves.
A stars color is related to its temperature. When the star is a dark shade of blue the star is much hotter. When it is shades of red it is a much cooler star.
Origin of the Universe
The Big Bang
Edwin Hubble discovered Red shift.
Red shift: change in wavelength of light caused by Doppler effect causing different color.
Red shift proved that stars and galaxies are moving away from each other.
If galaxies move away from each other than they would have came from one small point making the big bang theory.
The universe is about 15 billion years old.
Gravity is acting upon the universe. Three possible outcomes can happen depending on the mass of the universe.
Small mass: universe expands infinitely
Right mass: universe will slow expansion
Large mass: universe meets at one point (Big Crunch)
Astronomers think that there is matter that we cannot see (dark matter) due to the gravitational interactions between galaxies. If there is dark matter it will make up 90% of the universe and cannot be detected.
Theory of Relativity
Albert Einstein made theory into mathematical equation.
The theory was made in 1919 during total solar eclipse when a star was viewed in different location than what people expected.
Theory states that mass curves space. Larger masses can be seen easier than small masses.
Irregular galaxy: Lack regular shapes and do not have a well defined structure
Super giant stars will explode into supernovas
After a type II supernova, either a neutron star or a black hole will form
Stars with a mass less than 1.4 solar masses turn into white dwarfs.
Outer layer expands away from inner layer leaving a dense star the size of Earth that then cools slowly.