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Definition
| the distance on a wave between two adjacent points having identical characteristics. the distance wave travels in one period unit: m |
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| the rate of change of an object's position with time without regard to the 'direction' of movement, units: m/s, km/h |
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| the number of times per second that a periodic process occurs |
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| electromagnetic radiation |
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| the waves of light are produced by the same things that produce electricity and magnetism. the motions of electrons and other charged particles |
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Definition
| the symbol typically used for wavelength |
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* is constant
* fast- the fastest possible speed |
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Definition
c = 3 X 10^10 cm/s
c = 3 X 10^8 m/s |
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| relation between speed, wavelength, frequency |
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Definition
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Luminosity(solar)=10^-3
Radius(Solar Radii)=0.01(=EARTH RADIUS)
Density=10^6 |
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Definition
mass (in electron massess): 1
electric charge: negative |
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Definition
Luminosity(solar)=1
Radius(Solar Radii)=1
Density (gm/cm^3)=1 |
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Definition
mass (in electron masses): 2000
electric charge: positive |
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Definition
Luminosity(solar)=10^2
Radius(Solar Radii)=50(1/4 AU)
Density (gm/cm^3)=10^-5 |
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Definition
mass (in electron masses): 2000
electric charge: none |
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Definition
Luminosity(solar)=10^6
Radius(Solar Radii)=1000(=5AU)
Density (gm/cm^3)=10^-9 |
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Definition
| _____ always surrounded by electric fields. the field extend, with rapidly decreasing strength, to infinite distance from the particle |
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Definition
| A long Clump of stars extending from the upper left corner of the HR Diagram to the lower right corner. Roughly 90% of all stars are main sequence stars. The sun is a main sequence star. |
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| charged particles exert force on each other by way of these fields |
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Definition
| the fields of oppositely charged particles interact to pull the particles together |
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| The structure of atoms: Nuclei |
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Definition
| contains protons and neutrons |
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Definition
| A long group of stars parallel to main sequence but 10,000 times fainter than main sequence stars. About 7% of stars are white dwarfs. (Some are hot and blue- white) |
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| charged particles exert force on each other by way of these fields |
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Definition
| the fields of particles with the same charge interact to push the particles apart |
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| radius of an electron orbit |
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Definition
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| Typical size of the nucleus of an atom |
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Definition
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Definition
| Stars above the main sequence, generally with temperatures near from 3000k to 5000k. About 3% of stars are redgiants. (many are cooler and orange-red.) red orange in color |
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Definition
| if a vibrating particle enters your eye and hits your retina, it makes the electrons in your retina vibrate |
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Definition
| A thin scattering of stars along the top of the HR Diagram. Very few stars are supergiants. These stars have luminosities up to 10^6 times greater than the sun. |
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Definition
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| Volume of a sphere(stars are sphere) |
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Definition
| have the same number of protons and electrons |
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Definition
| unequal number of protons and electrons, almost always too few electrons |
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Definition
Luminosity = Surface Area x Temperature^4
surface area 4piR^2 |
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| invisible (ultraviolet light) |
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Definition
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Term
| invisible (infrared light) |
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Definition
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Term
| ionization is more likely... |
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Definition
| at higher temperatures because at low temperatures most atoms are neutral |
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Definition
| all stars have roughly same mass |
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Term
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Definition
peaks/second = cycles/second
(unit of frequency) |
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Term
| a chemical element is determined by... |
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Definition
| the number of protons in the nucleus of the atom |
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Term
| White dwarfs are much smaller than main-sequence stars..... |
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Definition
| so their densities are extremely high |
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Term
| Hydrogen: # of protons and neutrons |
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Definition
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Term
| Supergiants are much larger than main-sequence stars.... |
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Definition
| so their densities are extremely low. |
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Term
| Helium: # of protons and neutrons |
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Definition
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Term
| carbon: # of protons and neutrons |
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Definition
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Term
| nitrogen: # of protons and neutrons |
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Definition
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Term
| oxygen: # of protons and neutrons |
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Definition
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Term
| nitrogen: # of protons and neutrons |
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Definition
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Term
| oxygen: # of protons and neutrons |
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Definition
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Term
| if two stars have the same temperatures but different luminosities..... |
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Definition
| their surface areas must be different. |
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Term
| iron: # of protons and neutrons |
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Definition
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Term
| uranium: # of protons and neutrons |
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Definition
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Term
| Hertzsprung-Russel (H-R) Diagram |
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Definition
The Hertzsprung-Russell Diagram is one of the most important tools for presenting information about stars.
The horizontal axis of the diagram is either the temperature of the star or something related to its temperature, such as its color. Note that the axis is plotted "backwards", with higher temperatures on the left and lower temperatures on the right.
The vertical axis of the diagram is the luminosity of the star. The luminosity is typically given in Solar Luminosities.
Each dot in an HR diagram represents one star. |
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Term
| electron orbits properties: correct name for the orbits |
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Definition
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Term
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Definition
temp=650,000k
radius= 12km
distance=400pc
mass 1.4solar mass
density=10^15 gm/cm^3 |
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Term
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Definition
| ___ spectrum has light at just a few wavelengths |
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Term
| electron orbits properties: the energy of an electron |
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Definition
| The energy of an electron is greater in outer orbits than inner orbits |
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Term
| electron orbits properties: innermost orbit |
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Definition
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Term
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Definition
| a hot, rarefied gas emits light at discrete wavelegth's, creating an emission line spectrum |
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Term
| electron orbits properties: The next orbit from ground state is... |
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Definition
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Term
| interpretation of Kirchhoff's second law |
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Definition
1. Suppose there is a group of atoms with many electrons in upper energy levels. This happens in a hot gas because collisions between atoms bump the electrons into upper energy levels.
The electrons in upper levels spontaneously jump to lower levels, emitting photons that carry away the difference between the energies of the levels.
The photons have wave frequencies -- and wavelengths -- corresponding to the energy differences.
Since the energy levels in the atom are discrete, the photons all have just a few common wavelengths.
Therefore the spectrum emitted by the gas has light at just a few wavelengths; it is an emission-line spectrum. |
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Definition
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| Newton's Version of Kepler's Third LAw |
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Definition
M1 + M2 =D^3/P^2
D=seperation of stars in AU
P=orbital period in years
M1 + M2= the sum of the stars in solar masses |
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Definition
| Mass: no mass Speed: 3 x 10^10 (always the same) |
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Definition
| the amount of energy a photon carries |
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Term
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Definition
| describes how velocity changes the wavelength of a wave. |
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Term
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Definition
| (photon energy)=(constant)x(wave frequency) |
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Term
doppler effect
when an object emitting a wave moves toward you |
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Definition
| the wavelength of the wave gets shorter |
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Term
doppler effect
when the object emitting a wave is moving away from you... |
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Definition
| the wavelength gets longer |
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Term
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Definition
| the wavelength emitted by the object |
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Term
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Definition
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Definition
| wavelength measured by the observer |
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Term
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Definition
| if light with a continouos spectrum passes through a cool, low-density gas, the gas removes light at discrete frequencies, producing an absorption light spectrum |
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Term
| interpretation of Kirchhoff's third law |
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Definition
Suppose there is a group of atoms with their electrons all in the lowest energy level, the ground state. This happens in cool gases.
Shine a beam of light with a continuous spectrum through the atoms.
The electrons in the atoms absorb photons whose energies correspond precisely to the difference between the energies of the ground state and any upper energy level. The electron jumps to the upper energy level.
The absorbed photons have wave frequencies -- and wavelengths -- corresponding to the energy differences.
Since the energy levels in the atom are discrete, the absorbed photons all have just a few common wavelengths.
Photons have, therefore, been removed from the continuous spectrum at just a few wavelengths, producing absorption lines and an absorption-line spectrum. |
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Term
| When is a photon emitted? |
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Definition
| When an electron in an atom jumps from a higher energy level to a lower energy level. |
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Definition
motion directly towards or away from you
only motion that affects the wavelength |
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Term
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Definition
| >30,000 Kelvin ; typical absorption lines : hydrogen, neutral and ionized helium |
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Term
| after a photon is emitted, it... |
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Definition
| carries away the difference between the 2 energy levels |
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Term
| What is the difference between two energy levels when an electron jumps from energy level 3 to energy level 2 and emits a photon: |
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Definition
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Term
| Wave frequency of emitted photon: |
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Definition
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Term
| The wavelength of the photon: |
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Definition
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Definition
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Definition
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Definition
| temp: 9000oK; strong hydrogen |
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Term
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Definition
| temp: 5,500oK; neutral and ionized metals |
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Term
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Definition
| temp: 3000oK neutral metals molecules |
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Term
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Definition
| "Oh, Be A Fine Guy, Kiss My Lips" |
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Term
| equation for the position of the peak in its continuous spectrum |
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Definition
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Term
| equation for luminosity of an object emitting black body radiation |
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Definition
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Term
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Definition
| the fundamental way to measure the distances to stars by noting the motion of a foreground star against a background of stars so far away they appear fixed |
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Term
| The Doppler shift applies to any wave...... |
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Definition
| including the light emitted be stars (or galaxies, or anything else). If a star is approaching, the observed wavelength of its light is shorter than the emitted wavelength. We say the light is blueshifted. If the star is traveling away, the observed wavelength is longer and we say the light is redshifted. |
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Definition
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Definition
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Term
| Annual Parallax: The basic principle is called... |
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Definition
| triangulation. Consider a long, skinny triangle. The length of the triangle can be calculated if the length of the base and the angle at the narrow apex are known. |
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Term
| The Doppler shift equation |
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Definition
v / c = (λ - λ R) / λ R
where
v = the radial velocity (has the same units as c)
c = the speed of light
λ = the observed wavelength
λR = the emitted (rest) wavelength |
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Term
| A positive radial velocity means |
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Definition
| the object is moving away |
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Term
| A negative radial velocity mean |
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Definition
| the object is approaching |
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Term
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Definition
| The positions of the Earth in its orbit around the sun at two times 1/2 year apart.(The length of the base is 2 AU.) |
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Term
| base of the triangle: star to be measured position |
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Definition
| The star to be measured is at the apex of the triangle. |
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Term
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Definition
| measures how fast atoms and molecules are moving; particles moving at higher speed have higher __________ |
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Term
| The symbol for the parallax angle is... |
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Definition
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Term
| equation used to convert parallax to distance: |
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Definition
| D(parsecs) = 1 / P(arcseconds) |
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Term
| How do we know the rest wavelengths for stars? |
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Definition
| We use absorption lines in the star's spectrum |
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Term
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Definition
| defined as the distance to a star whose parallax is 1 arcsecond. |
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Definition
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| The parallax of a centauri equation |
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Definition
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Definition
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Definition
| Crucial concept: A spectrum is a plot of the amount of light emitted at each wavelength. The vertical axis (the amount of light) is sometimes given as "Intensity" and sometimes as "Flux". The horizontal axis (wavelength) is often given in Ångstroms |
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Term
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Definition
| Distance:1.3pc triple star |
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Definition
| A hot solid, liquid, or opaque gas emits light at all wavelengths, forming a continuous spectrum. |
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Definition
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Definition
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| a parsec away and are faint and red |
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Term
| how can temperatures be measured? |
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Definition
| temperatures can be measured, from their spectral type, their color, and from the wavelength |
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Term
| More than half of stars are in |
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Definition
| double or triple star systems |
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Term
| black body radiation and temp |
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Definition
| in ideal conditions the continuous spectrum emitted bu a hot, solid or liquid or opaque gas |
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Term
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Definition
Hot objects emit more energy than cool objects.
The continuous spectrum has a single, broad maximum.
The wavelength of the maximum depends on the temperature of the object that emitted the light.
The relation between the wavelength of the maximum and the temperature of the emitting object is: |
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Term
| Because of the Doppler shift, the spectrum of an approaching star |
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Definition
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Term
| Because of the Doppler shift, the spectrum of a receding star |
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Definition
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Term
| as two stars in a binary system travel around their orbits |
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Definition
| their spectra oscillate back and forth between redshift and blue shift. |
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Term
| The radial velocities of the stars can be calculated from the shift of their spectra using the Doppler shift formula |
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Definition
| A graph of the radial velocities against time is called a radial velocity curve. |
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Term
| two stars orbiting each other in a binary star system. one star is approaching us and the other is receding. Half an orbital period later..... |
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Definition
| the stars have reversed themselves. The first star is now receding and the second is approaching |
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Term
| The information needed to apply Kepler's Third Law can be extracted from the radial velocity curve: |
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Definition
The orbital period P is the length of time it takes the radial velocity curve to repeat itself.
If the orbit is edge-on, the true velocities of the stars in their orbits are given by the maximum and minimum radial velocities in the radial velocity curve. (If the orbit is not edge on, things get much more complicated.)
The radius of each orbit is given by R = (v P) / (2 π), where v is the velocity of the star in its orbit and P is the orbital period (you do not need to remember this equation). The separation of the stars D is equal to the sum of the orbital radii of the two stars.
The ratio of the masses is given by the ratio of the orbital radii. |
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Term
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Definition
has the fastest proper motion(motion across the sky)
180 years to move a distance equal to the diameter of the moon in our sky. |
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Term
| Normal stars have masses between |
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Definition
| 0.08 and 100 solar masses. Most have masses between 0.1 and 5 solar masses. |
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Term
| White dwarfs have masses between |
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Definition
| 0.3 and 1.4 solar masses. Most have masses very close to 0.6 solar masses. |
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Term
| Neutron stars all seem to have masses close to |
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Definition
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Term
| If a star is on the main sequence, its position on there is determined almost entirely by |
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Definition
| its mass. (Its chemical composition and age also have a small effects.) This means that a main-sequence star's temperature, luminosity, and radius are determined almost entirely by its mass. |
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Term
| older differ from younger |
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Definition
| more helium and hydrogen but not completely helium and hydrogen |
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Term
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Definition
| the amount of energy the star emits |
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Term
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Definition
| Hydrogen 75%, helium 25%, all others 2% (carbon, oxygen, nitrogen etc.) |
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Term
| brightness of a star depends on: |
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Definition
1)the luminosity
2)star's distance |
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Term
| composition of extremely old stars |
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Definition
Older stars have a lower abundance of heavy elements (heavy elements are all elements except hydrogen and helium).
The older the star the lower the abundance of heavy elements.
The oldest stars found so far are almost (but not entirely) entirely hydrogen (75%) and helium (25%). |
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Term
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Definition
| Temperature (K) >30,000Typical Absorption Lines= hydrogen, neutral and ionized helium |
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Term
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Definition
| Temperature (K) =15,000 Typical Absorption Lines=hydrogen natural helium |
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Term
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Definition
| Temperature (K) =9,000 Typical Absorption Lines=Strong Hydrogen |
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Term
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Definition
| Temperature (K) = 6,500 Typical Absorption Lines=hydrogen ionized metals |
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Term
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Definition
| Temperature (K) = 5,500 Typical Absorption Lines=neutral and ionized metals |
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Term
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Definition
| The amount (or abundance) of each chemical element in stars |
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Term
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Definition
| Temperature (K) = 4,000 Typical Absorption Lines=neutral metals |
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Term
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Definition
| Temperature (K) = 3,000 Typical Absorption Lines= neutral metals molecules |
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Term
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Definition
| Temperature (K) = <2,500 Typical Absorption Lines=molecules, dust |
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Definition
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Term
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Definition
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Term
| Spectral types G, K, and M |
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Definition
| These stars are cool and their hydrogen atoms are both neutral and unexcited. The only photons the hydrogen atoms can absorb have ultraviolet wavelengths, such as 1216 Å, so these stars do not show hydrogen lines in the visible region of their spectra. |
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Term
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Definition
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Term
| Spectral types F, A, and B |
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Definition
| These stars are hot enough to excite their hydrogen atoms but not hot enough to ionize the hydrogen. Many electrons are in the n = 2 energy level and can absorb photons at wavelengths like 6563 Å. These lines are at visible wavelengths, so these spectral types show strong lines of hydrogen in the visible region of their spectra. |
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Term
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Definition
| These stars are very hot, so most of the hydrogen atoms are ionized. Ionized hydrogen has no electrons, and therefore cannot produce absorption lines. |
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Term
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Definition
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Term
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Definition
1)measure brightness
2)distance of the star
3)energy received decrease as the square of the distance |
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Term
| inverse square law for the propagation of light |
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Definition
| brightness= luminosity/d^2 |
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Term
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Definition
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Term
| Why is the sequence of spectral types a temperature sequence? |
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Definition
| Temperature affects the appearance of stellar spectra because of ionization and excitation. |
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Term
| Ionization: Why is the sequence of spectral types a temperature sequence? |
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Definition
The spectra of ionized and neutral atoms of the same element are different.
The atoms in a high-temperature gas move at high speeds, so collisions between atoms are more violent at high temperatures. If the temperatures are high enough and the collisions hard enough, an electron can be knocked out of one of the atoms.
Thus, Atoms are more likely to be ionized at high temperatures. For example, the helium in hot stars (30,000 K) is ionized, while the helium in cooler stars (15,000 K) is neutral. |
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Term
| Hot stars are more likely to show lines of ionized elements than cool stars |
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Definition
| Note that O stars have lines of ionized helium, while B stars have lines of neutral helium; and the sequence from F stars to K stars shows decreasing amounts of ionized metals. |
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Term
| The effects of excitation on stellar spectra |
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Definition
If an electron is in a higher energy level than normal, both the electron and the atom are called "excited."
Atoms do not generally stay excited very long because an excited electron will spontaneously jump to a lower energy level.
The spectral lines from excited atoms have different wavelengths than the lines of unexcited atoms. For example:
If the electron in a hydrogen atom is in the n = 1 energy level (unexcited), it can only absorb photons whose energies correspond to jumps from energy level 1 to higher levels. It can only absorb photons with wavelengths such as 1216 Å and 1026 Å.
If the electron is excited to the n = 2 energy level, it can only absorb photons whose energies correspond to jumps from level 2 to yet higher levels. It can only absorb photons with wavelengths such as 6563 Å and 4861 Å. |
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