Exam 3 Astronomy Notes Created by Gregory Galmin The Sun cont Once you get above the photosphere around 5000K the temperature sky rockets to a million degrees This is the corona We can produce magnetic field about a thousand times more than sun spots at the magnet lab Those huge flairs are called prominences Their lifetime is about a few minutes The magnetic field of the sun goes out passed the edges of the solar system The galactic center is about 30000 light years away from us The center may be a supermassive black hole The sun does its own motion around the galactic center The sun moves around the galactic center at 200km s 200 000 000 years to go around the galactic center How many times has the solar system gone around the galactic center since the beginning of the universe 30 or 40 times A star farther out goes around the center at the same speed As you move away from the center of gravity you expect things to slow down The sun spot cycle is 11 years The next peak is in 2023 The little ice age was when the earth was very cold the sun s activity was dramatically lower Trees grow like crazy every 11 years Global warming may not be human caused The Butterfly diagram shows periodicity of solar activity Can we explain the 11 year cycle The magnetic field starts out straight but the equator of the sun is moving faster than the poles of the sun It stretches the magnetic field The stretches keep going and knots form Then sun spots form and the magnetic field goes back to its original state The sun has differential rotation the equator and poles rotate around the sun s center at different speeds Stellar Evolution Molecular cloud some stars form here Nebula are where stars are born These cloud s densities are extremely low like 1 molecular per cubic inch Nebula are light years across and made of hydrogen and helium atoms The coloring is because of some makeup from a supernova Nebula is an embryo How do stars form There are density fluctuations and things that are denser can attract more Stars are born over billions of years matter and become even more massive Ice skater effect when it contracts it rotates faster When matter falls together it spins faster Gravity contracts you The disk flattens so it goes faster The density of the center gets higher and higher a protostar forms Protostar has light because the energy of the infalling material becomes heat At about 20000 K a protostar is formed When the core of the protostar gets to 1000000 degrees you get nuclear fusion and you get a main sequence star Light from the protostar is blocked by the disk Main sequence star gets its energy from converting Hydrogen into helium The solar wind then blows away the disk Things are still falling in Equilibrium between these two processes are formed We don t have time to see a star be born We get snapshots of different places in the universe of stars How do we form planets Rings form from condensation When it cools off protoplanets form We don t like Pluto because it doesn t fit our theory As a function of the distance from the sun the temperature of the planets go down Different boiling points of elements The solar system was in a vapor state in the beginning Then you can go to higher and higher elements As heavier elements form the hydrogen concentration becomes less and less First thing that happens hydrogen fuses into helium at the core Then you start to burn helium If the star is big enough you can burn helium into heavier nuclei carbon nitrogen oxygen Stars spend billions of years in the main sequence stage When you exhaust your fuel in the core you become more luminous and become a red giant Then you become a planetary nebula Then you become a white dwarf This kind of path is one for a main sequence star with about the mass of the The skinnier the nebula the slower the process of star formation Red main sequence stars are small yellow are bigger bluish white are even sun bigger and hotter Our sun from inside to out is nuclear reacting core radiative region and convective region Little stars only have nuclear core and convective region Large stars have their radiative region outside of the convective region Bigger stars tend to live shorter Our sun lives for 10 billion years The way you die is more characteristic of your size Bigger stars tend to die in a supernova Our sun will end up a white dwarf At 100000000 degrees you can burn helium At 600 million you can burn carbon The most stable are formed the most You can think of Carbon being three helium nuclei Red giants go through unstable phases There is an equilibrium between pressure forces and gravity forces The limit of the white dwarf is1 4 times the mass of the sun Little bit of radiation is good for you Just gonna get a lil bit of cancer Stan White Dwarfs A white dwarf is a very massive high density star An alpha particle is a helium nucleus two protons and two neutrons In the white dwarf you have a soup of alpha particles and the electrons are unbound The electron gas keeps the star from contracting further The electron gas is a fermion system Particles that have spin one half are fermions Electrons and neutrons are fermions You can pile up bosons forever Pauli exclusion principle Integer spin particles are bosons Fermions hate each other
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