Term
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Definition
-the process by which nuclei merge to form a single nucleus.
--If the right nuclei combine, energy is PRODUCED (E=mc2).
--If the wrong nuclei combine, energy is USED. |
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Term
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Definition
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Term
| Stars are made up of primarily ________ (75%) and some ______ (25%) witha little bit of other elements. |
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Definition
| primarily HYDROGEN, some HELIUM |
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Term
| The nucleus of ________ is a single proton (no neutrons) |
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Definition
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Term
| Protons have what kind of charge? |
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Definition
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Term
| Electrons have a negative charge in exactly the same amount as a ______ |
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Definition
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Term
| Opposite charges _______, like charges ______ |
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Definition
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Term
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Definition
Z=Proton (Atomic number.
N= Nucleon (proton + Neutron)number
Z tells us which Element it is (hydrogen has Z=1, Helium has Z=2, etc.) |
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Term
| Stable Hydrogen has ___ proton and __ neutrons |
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Definition
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Term
| Stable Hydrogen has ___ proton and __ neutrons |
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Definition
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Term
| Stable Helium has ___ protons and ___ neutrons. |
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Definition
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Term
| Isotopes have the same number of ________ but different numbers of ________ |
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Definition
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Term
| Most isotopes are stable/unstable. |
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Definition
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Term
| Describe the Proton-proton chain: |
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Definition
-4 Hydrogen nucleii combine to produce a Helium-4 nucleus and some energy
-The energy comes about because the Helium nucleus is lighter than the total of the four hydrogen nuclei. |
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Term
| If you can get protons close enough together, the strong force will overcome the _____________ _____ |
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Definition
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Term
| How do you get protons close? |
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Definition
| By making them hot and squshing them with pressure |
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Term
| What stops gravity squashing the Sun down to a point? |
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Definition
| Gravitational Equilibrium |
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Term
| Why doesn't the sun keep shrinking and evetually reach the size of the Earth annd smaller? |
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Definition
| Because the star is producing heat |
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Term
| As gravity pulls gas in, what happens to the gas at the center of the star? |
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Definition
| The gas at the center of the star gets more sqashed (i.e. reaches a higher density) |
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Term
| What happens if Hydrogen nuclei are squshed closer together? |
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Definition
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Term
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Definition
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Term
| What happens as a result of hotter gas wanting to expand in a star? |
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Definition
| The hotter gas wants to push outwards on the rest of the gas |
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Term
| what makes the core less dense? |
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Definition
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Term
| less fusion in a star takes place when... |
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Definition
| gas pushes out, making the core less dense |
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Term
| What terms define the structure of the sun? |
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Definition
Ball of Plasma
Core
Radiation and Convection Zones
Photosphere
Chromosphere
Corona
Sunspots and Solar Wind |
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Term
| What are three energy transfer mechanisms? |
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Definition
| Conduction, convection, and radiation |
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Term
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Definition
| Heat transter by atom collisions |
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Term
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Definition
| Heat transfter by mass movement of groups of atoms |
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Term
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Definition
| Heat transfer through electromagnetic radiation |
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Term
| What is an example of conduction in the kitchen? |
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Definition
you put a frying pan on the stove burner
the burner gets hot and is in contact with the pan
the heat then travels through the metal of the frying pan by atom collisions, heating all of the frying pan |
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Term
| What is an example of convection in the kitchen? |
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Definition
you heat some water in a saucepan
the water in contact with the metal of the saucepan heats through conduction
hot water is less dense than cold water and so rises. Cold water falls
the hot and cold water mix, spreading the heat between ataoms by mass motion. |
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Term
| What is an example of radiation in the kitchen? |
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Definition
you turn on a burnter
to test if the burner is hot you place your hand above the burner (not touching it)
your hand gets hot
Your hand is absorbing infra-red radiation being emitted by the burner |
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Term
| where does fusion take place? |
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Definition
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Term
| what is the temperature of the core? |
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Definition
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Term
| what is the powersource of the Sun and most other stars? |
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Definition
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Term
| in the core, hydrogen nuclei form _______ nuclei and release lots of energy. |
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Definition
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Term
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Definition
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Term
| Heat gets from the core to the surface of the Sun by two of the three heat transfer mmechanisms: |
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Definition
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Term
| Where does the radiation zone occur? |
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Definition
| between the core and one-third of the way to the surface |
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Term
| What is the Temperature of the radiation zone? |
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Definition
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Term
| how is energy carried from the core? |
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Definition
| by photons/ electromagnetic radiation |
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Term
| The temperature of the radiation zone means there are a lot of _______, a trilion times more intense than visible light. |
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Definition
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Term
| What is the Temperature range of the Convecton zone? |
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Definition
| 10 Million K at the bottom and 6000 K at the top |
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Term
| The plasma near to the radiation zone _____ and the plasma near the photoshere _____ |
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Definition
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Term
| What are three methods scientists use to know what is inside the sun? |
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Definition
Mathematical Models
Sun Quakes
Solar Neutrinos |
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Term
| What are sun quakes cause by? |
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Definition
| the movement of the gas in the Sun causes vibrations |
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Term
| _______ _____ of light from the surface tells us about the vibrations. |
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Definition
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Term
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Definition
May have no mass
travel at or near to the speed of light
don't interact well with anything |
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Term
| about how much of the total energy of fusion is carried off by neutrinos? |
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Definition
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Term
| What do solar neutrinos do? |
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Definition
| give us a way of probing the core of the sun |
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Term
| plasma is at ______ in a sunspot |
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Definition
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Term
| Why is there no convection with sunspots? |
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Definition
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Term
| what does the closeness of magnetic field lines tell us? |
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Definition
| thhow strong the field is |
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Term
| where do sunspots appear? |
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Definition
| where closely packed magnetic field lines poke through the surface of the sun. |
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Term
| Solar flares occur when... |
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Definition
| magnetic fields through sunspots can undergo rapid change, which produce these thtense storms |
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Term
| What are the Chromoshere and Corona? |
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Definition
| atmosphere around the Sun |
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Term
| What is hotter than the surface of the Sun? |
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Definition
| The surrounding Chromosphere and Corona |
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Term
| The magnetic field carries energy from within the star in which direction? |
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Definition
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Term
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Definition
| throw a huge amount of gas into space |
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Term
| What in ejections can affect the Earth's magnetic field? |
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Definition
| Magnetic fields in ejections |
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Term
| What are the causes of sunspot cycles? |
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Definition
Magnetic poles on the sun seem to flip with the cycles, every 11 years
Sun rotates faster at the equator than at the poles |
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Term
| What is Luminosity and how is it measuered?? |
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Definition
| The Amount of power the star emits in all directions. It is measured in units of Watts (W) = Energy/second |
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Term
| What is apparent brightness? |
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Definition
The brightness that a star appears to have (Usually used as the brighness as viewed from the earth.
Measured in Units of Watts/meter2) |
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Term
| What is the Inverse square law of light? |
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Definition
relates luminosity and apparent brightness
Brightness= Luminosity/ 4(3.14)(Distance)2 |
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Term
| How many light-years is equal to 1 pc (parsec)? |
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Definition
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Term
| Any star that has a parallax less than __ arcsecond, is further than 1 parsec away. |
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Definition
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Term
1 degree = __ arcminutes
1 arcminute = __ arcseconds |
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Definition
1 degree = 60 arcminutues
1 arcminute = 60 arcseconds |
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Term
| How can we obtain the luminosity of individual stars? |
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Definition
| By combining a distance measurement with apparent brightness |
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Term
| Color is directly related to what? |
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Definition
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Term
| What color is the sun, Betelgeuse, and Sirius as related to their temperature? |
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Definition
Sun- 5800K (White-orange)
Betelgeuse - 3400K (red)
Sirius- 9400K (blue) |
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Term
| What will the temperature of a star affect? |
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Definition
| The absorption spectrum that is seen coming from it. |
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Term
Stars with ionized element spectra are____ ____
Stars with molecular spectra are _____ ___ |
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Definition
Ionized elemet spectra = Very hot star
Molecular spectra = cool star |
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Term
| What can orbital motions tell? |
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Definition
| The mass of the object being orbited |
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Term
| What is a Binary star system? |
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Definition
| Two stars that orbit eachother |
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Term
| What are visual binaries? |
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Definition
| A pair of stars that can be seen to orbit each other |
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Term
| What are Eclipsing Binaries? |
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Definition
| A pair of stars that orbit each other but cannot be seen as distinct due to the plane of the orbit being edge on. |
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Term
| What is the Hertzsprung-Russell Diagram? |
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Definition
Plot of luminosity vs. spectral type/temperature
all stars sit on this graph |
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Term
| What are the 4 regions on the Hertzsprung-Russell Diagram? |
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Definition
-Main sequence stars
-Giants
-Supergiants
-White Dwarfs |
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Term
| Describe all four regions, main sequence stars, Giants, supergiants, and white dwarfs. |
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Definition
Main sequence stars: most stars are MS stars, including the sun
GIants: More luminous but cooler than equivalent MS stars
Supergiants: Even more luminous than giants, but roughly the same temperature
White dwarfs: Lower luminosity but higher temperature than the equivalent MS star |
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Term
| Name the main characteristics of Main Sequence Stars |
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Definition
-Hydrogen Burning
-Core of the star fuses Hydrogen to form Helium
-Direct relationship between luminosity and temperature
---- Hot stars are bright, cool stars are dim. |
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Term
| What determines every property of an MS star? (temperature, size, lifetime, luminosity) |
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Definition
MASS!
Bigger MS stars are more luminous, hotter, and live a shorter time |
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Term
| What are some of the main characteristics of Giants/ Supergiants? |
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Definition
| -Cooler but more luminous than MS stars. Therefore, they must have a much bigger surface area- which means a bigger radius |
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Term
| What are some of the main characteristics of white dwarfs? |
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Definition
-Hotter but less luminous than MS stars. Therefore they must have a much smaller surface area-- which means smaller radius
-WD have no fusion at all taking place in their core because all their fuel is gone. |
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Term
| Name the Luminosity class and relative sizes of stars in order from largest to smallest. |
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Definition
I- Supergiants
II- Bright Giants
III- Giants
IV- Subgiants
V- Main sequence stars
WD- White Dwarfs |
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Term
| What are the 2 properties of star clusters? |
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Definition
1) all stars lie the same distance from the Earth
2) All stars formed roughly the same time from the same cloud. |
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Term
| What are the two types of star clusters? |
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Definition
1) open clusters
2) Globular clusters |
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Term
| Which contains more stars, open or globular cluster? |
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Definition
| Globular clusters- contain more than a million stars whereas, open clusters contain only several thousand stars |
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Term
| The Pleaides cluster shows no O stars, what does this mean? |
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Definition
the cluster is old enough that O stars are already extinct
Clusters are dated by the Sequence Turn- off point |
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Term
| What are the age of stars in open clusters compared to the age of stars in globular cluster? |
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Definition
Open clusters generally contain young stars, ages of less than 5 billion years
Globular clusters contain stars less massave than the Sun, making them older than 10 billion years. |
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Term
| What do stars need to form? |
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Definition
COLD, DENSE GAS!
( clouds of this type are called Molecular Clouds) |
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Term
| Cold temperatures mean molecules of __ and __ and particles of dust can form. |
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Definition
| -- H2 and CO can form in cold temperatures |
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Term
| As the cloud collapses, what happens? |
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Definition
it starts to heat up
(early on, the large cloud radiates most of this new heat away and stays below 100K.) |
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Term
| How is a Protostar formed? |
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Definition
-As cloud collapses it starts to heat up
-As the density of the gas increases, radiating heat away gets harder.
-The central region of the cloud starts to hea, and the pressure starts to increase
-Heat and pressure start to resist gravity, and slow the collapse- PROTOSTAR IS FORMED |
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Term
| After a protostar is formed, describe the process that takes place next. |
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Definition
-The gravity of the protostar keeps pulling gas from the surrounding cloud.
-and as it shrinks it starts to spin faster (conservation of anglular momentum)
-spinning causes a disk of gas to form (calle a protoplanetary disk)
- as the star nears fusion, they can throw out jets. |
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Term
| Can fusion take place in a protostar? |
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Definition
| no, protostars are hot, but fusion has not started. The temperature is only 1 million K, 10 Million K is needed to start fusion. |
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Term
| When fusion stars, __________ stops. |
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Definition
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Term
| What happence as soon as the core stabilizes in a protostar? |
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Definition
| it becomes a Hydrogen- burning Main Sequence Star |
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Term
| What determines the speed of development and lifetime of the protostar? |
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Definition
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Term
| O and B (bright blue) MS stars form faster or slower than M or N (dim red) MS- stars? |
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Definition
| O and B MS stars for FASTER than M or N MS stars |
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Term
| Models suggest stars cannot exceed 100 solar masses, why is this so? |
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Definition
The gravity of more massive stars is not strong enough to hold on to the outer layers of gas
as the star heats up, these outer layers get blown in to space, decreasing the star mass. |
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Term
| Why can't stars with masses below 0.08 solar masses start fusion? |
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Definition
| Gravity collapses the gas cloud, but heat is never strong enough to resist it, eventually DEGENERACY PRESSURE steps in to stop the collapse |
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Term
| Is degeneracy pressure temperature dependent? |
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Definition
| NO, unlike thermal pressure in most stars, degeneracy pressure is NOT temperature dependent |
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Term
| What is Degeneracy Pressure |
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Definition
When atoms cannot be squashed down anymore.
In an atom, electrons can only occupy certain orbits.
As you squash electrons together, a similar thing happens
The Pauli Exclusion Principle states that no two electrons can occupy the same state/position |
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Term
| What are the main characteristics of Brown Dwarfs? |
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Definition
-Mass is less than 0.08 solar masses
-Not quite a star, too big for a planet
-Heat caused by contraction is the only heat
-Slowly cool as degenerate pressure keeps it from collapsing further
-Glows in the infra-red. |
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Term
| What happens after hydrogen starts to run out of low mass stars? |
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Definition
| Low Mass MS star -> Red Giant -> White Dwarf + Nebula |
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Term
| How does a star become a Red Giant? |
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Definition
Hydrogen in the core begins to run out
-When fusion slows, the heat emitted from the core drops
-Gravity starts to overcome the pressure and the core starts shrinking again.
-When the core collapses it starts to heat
-The helium in the core cannot fuse yet
-But, the hydrogen in the shel around the shrinking core can
-Hydrogen shell burning
-The very hot shell causes hot layers to expand outward |
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Term
| When the core is bigger, what happens to the size of the star? |
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Definition
gets smaller
when the core shrinks, it makes it get hotter, which makes the shell hotter, allowing hydrogen to burn faster, which makes helium faster, which makes the core more massive... on and on. |
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Term
| What happens when the core reaches 100 million K? |
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Definition
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Term
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Definition
-Thermal pressure isnot holding up the core, degenerate pressure is-- degenerate pressure does not depend on temperature.
-So helium burning does not make the core expand. The core jst heats up causing more fusion, which makes it hotter, causing more fusion, etc.. (helium flash)
-Within seconds of helium fusion starting, thermal pressure takes over again.
-The core starts pushing outwards
-The hydrogen shell is pushed out, slowing its reactions.
-The surface of the star starts to shrink. |
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Term
| As helium starts to run low in a star, what happens? |
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Definition
-The core has become predominantly carbon
-core starts to shrink again
-Rising heat causes burning of a Helium shell around the core, AND a hydrogen shell around the Helium shell.
-Shells and core contract, star surface expands |
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Term
| Describe a low mass star death |
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Definition
-at the end of fusion, the star is huge
- the gas around the edge of the star is only held weakly by gravity
-this leads to a strong solar wind
-this gas eventually gets blown in to space
-the exposed hot core heats the cloud, ionizing the gas with intense UV radiation
-PLANETARY NEBULAE |
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Term
| What are the 3 kinds of Nebulae? |
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Definition
| Ring, Eskimo, and Hourglass Nebula |
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Term
| What are the main characteristics of white dwarfs? |
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Definition
-THe hot core that remains is made primarily of carbon
-Degeneracy holds it up against its own gravity
-Core slowly cools, getting dimmer and cooler with time. |
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Term
| Low mass stars don't produce elements heavier than what? |
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Definition
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Term
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Definition
Stronger Gravity
Stronger gravity requires that the core be hotter to produce the balancing thermal pressure
hotter cores allow protons in Hydrogen to get close to larger nuclei, like Carbon, Oxygen, and Nitrogen
The CNO Cycle |
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