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ASTRON 0089: EXAM 2
What is the Stefan-Boltzmann Law?
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Energy is proportional to (sigma*Temperature^4)
-if T doubles, L increases by a factor of 16
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What are the three forms of Universal Motion?
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Speed - d/t
Velocity - speed + a direction
Acceleration - the change in velocity
v and a are vectors (need direction)
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What is Inertia?
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the first law of motion, the tendency of a body at rest to remain at rest, or a body in motion to stay in motion
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What is mass?
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a measure of inertia, how much space an object takes up
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What is weight?
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force that presses an object to the ground, pull of gravity
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What is the first of motion?
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Inertia, a body at rest wil remain at rest, or a body in motion will remain in motion unless acted upon by an outside force
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What is the second law of motion?
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when a force acts upon a body, it will experience an acceleration of F = ma
(force = mass * acceleration)
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What is the third law of motion?
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when one body exerts a force on another, the second body exerts an equal and opposite force
(action, reaction)
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What is a Positron?
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an anti-electron, it combines with a electron to make 2 gamma rays
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What is the Law of Conservation of Energy?
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energy may change forms, but will not be created or destroyed
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What is Newton's Law of Gravity?
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all bodies are attracted to each other through gravity by the equation, acceleration of the smaller body is the largest
F = G*M*m/d^2
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What is the orbital speed of Earth and the escape speed?
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V(orb) = 8 km/s
V(esc) = 11.2 km/s
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What kind of star is the sun?
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The sun is a G2V star, fairly common and normal
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Why does the sun appear spherical?
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the photosphere is the outer most layer and emits in the visible wavelength, mostly yellow which is visible to us
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What are the 3 levels of the solar interior?
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core, radiative zone, and convective zone
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What are the 3 parts of the solar atmosphere?
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photosphere, chromosphere and corona
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What is energy?
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the ability to do work, measured in joules, 2 kinds, kinetic and potential
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What is kinetic Energy?
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energy of motion, can be measured by the equation 1/2(m)v^2
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What is potential Energy?
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energy 'stored' for later use, energy that will occur
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What is radiative energy?
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energy carried by Electromagnetic radiation, like sunlight or heat
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What is thermal energy?
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random kinetic energy of matter, vibration or rotation in solids
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What is mass energy?
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the energy that a mass could convert to measured by e = mc^2
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What is temperature?
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a measure of average kinetic energy, hotter particles move at higher speeds
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What is thermal energy dependent on?
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temperature, amount of material, type of material, and state (solid, liquid, or gas)
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What is pressure?
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a force per unit area, measured by the equation P = nkT
n = particle density
k = constant
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What is Hydrostatic Equilibrium?
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the balance of the force of gravity pulling in and the force of gas pushing out, the sun
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What 3 ways is energy transported in stars?
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Radiation, convection, and conduction
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What is radiation?
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the movement of electromagnetic radiation from one place to another, 70% of the sun is radiative
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What is convection?
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when hot matter rises and cold matter sinks, 30% of sun's interior convects
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What is Granulation?
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visible surface patterns on the sun that prove convection is occuring
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What is conduction?
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heat transfer from one atom to a colder atom, this only occurs in dense stars
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How do stars generate their energy?
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fusion
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What is fission?
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the splitting of a high number element to create energy
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What is fusion?
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the combining of two low energy elements to create energy, occurs in cores of stars, energy created is the difference in the atomic mass of the components
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What makes a gamma ray?
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a positron and an electron that collide, this produces 2 gamma rays
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What is the energy process that defines fusion in the sun
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The Proton-Proton chain
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Why can fusion occur in the cores of massive objects like the sun?
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the core has a high enough temperature and pressure that it can force two opposing forces like protons to create a new element
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What is the proton-proton chain?
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the three step process of fusion that defines a main sequence star.
1. 1H+ 1H = 2H (deterrium)+ positron and neutrino
2. 1H + 2H = 3He2 + gamma ray
3. 3He2 + 3He2 = 4He2 and 1H+ and 1H+
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How can we observe the sun's interior structure?
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Neutrino detection and Solar Seismology
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How do gamma rays escape the sun?
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radiation, they are absorbed and reemitted many times
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What is an alpha particle?
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a helium nucleus, 2 protons and 2 neutrons
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What is the photosphere?
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visible area of the sun, we can determine composition and density through absorption lines
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What is the chromosphere?
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layer above the photosphere, where solar magnetic activity occurs
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What is the corona?
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hottest part of the sun because of low density, outermost atmospherical part, emits x-rays, where it doesn't are coronal holes
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What is solar wind?
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Material from the corona, accelerated out into space, flow of high speed electrons and protons from the loss of solar mass
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What are kinds of solar activity?
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sunspots, plages, flares, filaments, and prominences
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What is a sunspot?
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A dark, cooler region on the surface of the sun, resulting from magnetic activity, darkest part called an umbra, surrounded by penumbra
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What is plage?
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bright regions that compensate for dark sunspots
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What is a solar flare?
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A sudden eruption of intense, high-energy radiation, usually near a sunspot, causes Northern Lights and affects radio reception
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What is a prominence?
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a solar flare that shoots off the edge of the sun
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What is a filament?
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a long string-like protrusion of the surface of the sun
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What is the length of a solar cycle?
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22 years
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What is the Maunder minimum?
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the period of the least sunspot activity, or magnetic activity
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What is the solar maximum?
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the highest period of solar activity, many sunspots
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What is a parallax?
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the effect that describes the shift of an object when viewed from another location
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What is a parsec?
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an astronomical measure
2.06*10^5 AU
3.26 light years
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What is the formula for the trigonometric parallax of a star?
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d = (1 arcsec(1parsec))
p
NMI
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What is luminosity?
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the intrinsic brightness of an object, total energy emitted per second, measured in watts
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What is apparent brightness?
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how bright an object appears to our naked eye, dependent on distance and luminosity
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What is the formula for luminosity
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L = 4piR^2(sigma)T^4
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What is the inverse square law?
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apparent brightness is inversely proportional to the distance of the object squared
if an object is twice as far away
1/2^2 = 1/4 as bright
twice as close
2^2 = 4 times as bright
b=L/4pi(d^2)
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What is the magnitude scale?
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a scale used to measure brightness, logarithmic, 0 = highest brightness, and -1 = 2.512 times the brightness
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What is absolute magnitude?
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the unbiased measurement of the luminosity of a star at 10 parsecs
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What is an HR diagram?
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Hertzsprung-Russell diagram, it measure the life, luminosity and temperature of a star
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What is the main sequence?
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a diagonal line on the HR diagram that represents the period of a star's life where Hydrogen fusion occurs
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Given the sun, if it is the same temperature but larger in size?
or smaller in size?
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greater luminosity = bigger star
lesser luminosity = smaller star
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What is color?
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a measure of energy at different wavebands
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what can we determine from the color of a star?
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surface temperature and composition, or properties of the spectrum
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What is photometry?
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the measure of apparent brightness
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What is the order of classification of stars?
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OBAFGKM
o is hottest
o is largest
o is most luminous
o is shortest lifespan
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Why do the ionizations of absorbing atoms change?
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Higher temperatures allows greater energy, which strips electrons from atoms and molecules
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What is the mass-luminosity relation?
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the relationship between m and l, measured by the equation
(L/Ls) = (M/Ms)^3.5
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What is a center of mass?
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the orbital point of a binary star system
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What drives the stellar evolution process?
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gravity, forces high pressures and temperatures, and therefore fusion
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After a massive star has completed its main sequence what happens?
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it becomes a black hole
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How is the evolution of a star determined?
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by its mass, a greater mass will result in a shorter lifetime, and the opposite
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How are stars formed?
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interstellar dust clouds collapse from gravity, until fusion occurs
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What is electron degeneracy pressure?
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the idea that two electrons cannot occupy the same space, stops white dwarfs from shrinking, seen in incredibly dense objects like WD's
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What are Population II stars?
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first generation of stars, formed from heavy element deficient material
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What are Population I stars?
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formed later, aided by heavy elements formed in pop. II fast evolving, massive stars
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What is the start of a star (its collapse) governed by?
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Mass, temperature, strength of magnetic fields, and rotation rate
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What is the Pauli Exclusion Principle?
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no two electrons can have the same position, momentum, and spin
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What happens to the pressure of a gas when it is degenerate?
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it is not dependent on temperature
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What is a star cluster?
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a large concentration of related stars (same age) 2 kinds of clusters- open and globular
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What can you assume if two stars have similar spectrums?
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they will have the same composition
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Why do helium flashes occur?
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the core is degenerate, not temperature dependent
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What happens to a star after it is finished with its main sequence?
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it will become a red giant when helium fusion begins, then it will fall onto the horizontal branch, then, it will begin a supergiant and fuse heavier elements until it cannot fuse anymore,where it will become a white dwarf
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What are the 2 effects of the red giant phase?
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-energy generation increases because of Helium fusion which increases the luminosity
-the outer layers expand and the surface temperature will decrease
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What is the triple alpha process?
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the fusion of helium (alpha particles) into carbon, byproduct of gamma rays
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What is the planetary nebula phase?
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an ejection of a planetary nebula (gaseous material) around the star after the star is a supergiant
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Why are planetary nebulas visible to us?
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The gas in the planetary nebula is excited by UV radiation from the star
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What characterizes a white dwarf?
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a 'burned out' star supported only by electron degeneracy pressure, incredibly dense, not hot enough to fuse carbon
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What is the Chandrasekhar Limit?
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1.4 solar masses - more mass than this can no longer be supported by electron degeneracy pressure and will collapse (to a neutron star or supernova)
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What is the relationship between the main sequence and stellar lifetime?
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a long main sequence results in a short lifetime (OBA stars) and a short main sequence results in a long lifetime
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How do massive stars evolve?
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they first become a yellow giant before the red giant phase
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what is Nucleosynthesis?
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the process of creating heavy elements, ends with iron
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Where do elements heavier than iron originate from?
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supernovas
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After an iron core is inside of a star, gravity rapidly accelerates, yielding what 3 results?
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-iron is split into neutrons and protons
-protons and electrons become neutrons
-neutrinos are created from the neutron production
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what makes a neutrino?
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a byproduct of the first step in the proton proton chain
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What is a terrestrial planet?
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inner planet, rocky composition, earthlike planets
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what is a jovian planet?
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an outer gaseous planet
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what is eccentricity?
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the ellipticalness of an ellipse
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what is density?
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the measure of a thickness
D= m/v
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How did the sun form?
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nebulae collapsed and rotated from its own gravity
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What is a rotating nebula called?
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protoplanetary disk or proplyd
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what is the process of chemical differentiation
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the sinking of heavy material to the center of a planet or other object and the rising of lighter material toward the surface. contributes to planet formation
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what is helioseismology
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study of vibrations in the sun's interior
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What is differential rotation?
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the phenomena that the suns polar regions do not rotate as rapidly as the equatorial regions
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What is a coronal mass ejection (CME) and how is the Earth protected from them?
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large violent gas eruption, billions of charged particles are ejected into space. Earth is protected by its magnetic field
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What are the brown dwarf stars?
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stars with very low mass which cannot support fusion, lower than 'M' stars
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What is the law of conservation of momentum?
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linear momentum is conserved unless acted upon by an outside force
angular momentum is conserved unless acted upon by a torque (twisting force)
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What is escape speed?
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the speed which it takes to break an orbit
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What defines a planet?
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1. it is in orbit about the sun
2. it has enough mass to support hydrostatic equilibrium
3. it has a clear orbital path
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How do we measure color?
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energy in blue band/ energy in red band
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What do stellar spectra reveal?
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composition temperature and mass of a star
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what is a spicule?
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a jet of gas that arises from the photosphere
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Why do we see “split” spectral lines in the spectra of sunspots?
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the magnetic field alters the quantization of atoms and ions
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What does helioseismology allow us to discover?
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size of convective zone and rotation rate below the surface
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What is a proton?
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a positively charged subatomic particle, a hydrogen nucleus
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What is a positron?
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a form of antimatter, opposite of electron, can create gamma rays when combined with electrons
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What is a star doing above the main sequence?
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It is a protostar forming or it is fusing helium or a heavier element as a giant
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What is a star doing below the main sequence?
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it is essentially dead, they are finished burning and radiate their stored energy
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What is a protostar?
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a star that is still in the process of forming, low temperature, still collapsing
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Why are protostar so luminous?
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they are stil collapsing so they are massive, and gravitational contraction fuels luminosity
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What do stars in a cluster have in common?
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they are similar distances and similar ages
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What is an open cluster?
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a randomly shaped cluster that contain massive stars, found in galactic disks
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what is a globular cluster?
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a star cluster formed around a central point, have old (smaller) stars
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How is energy transferred in massive star cores?
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convection
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How do massive stars differ in fusion from smaller stars?
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they fuse using the CNO cycle which uses the heavier elements as a catalyst for fusion
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what are the two results of the beginning of the red giant phase?
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-the core shrinks and the outer layers expand and surface t decreases
-rate of fuel consumption increases and luminosity increases
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When does the helium flash occur?
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in the red giant phase, when te star is massive enough to begin helium fusion
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what is the triple alpha process?
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fusion after the red giant phase, 3He -------> 1C
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what characterizes the supergiant phase?
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the star is hot enough to burn the outer core of helium and inner core of carbon
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what is the planetary nebula phase?
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a star in the giant phase will become unstable and shed its outer layers in a stellar wind
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