Term
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Definition
| 1 AU/ 8 light minutes/1.5 x 10^8 km/ 93 million miles |
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Definition
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| 4 light minutes at its closest/ 20 light minutes at its farthest |
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Definition
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Definition
| 4.3 light years away/ nearest star to us |
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Term
| Distance to Horsehead Nebula |
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Definition
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Term
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Definition
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Definition
| big cloud of dust and gas --> glows near hot stars when dust absorbs light |
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Definition
| example of the death of a star like the sun/ 1000 light years away |
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Definition
- our galaxy
- 200 billion stars and 100,000 light years across
- Sun is 28,000 light years from center of bulge |
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Definition
- Discovered by Hubble
- Distance of 2 million light years
- Closest galaxy to Milky Way
- Only thing outside our galaxy the naked eye can see |
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Term
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Definition
| Milky Way, M-33, Andromeda |
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Term
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Definition
- nearest cluster of galaxies
- 60 million light years away |
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Definition
-10,000 galaxies in area 1/10 diameter of moon
- farther away galaxies look really different --> everything evolving |
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Term
| Cosmic Microwave Background Radiation |
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Definition
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Term
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Definition
- High energy charged particles (electrons, protons, nuclei, etc.)
- Can lead to mutations and cancer |
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Term
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Definition
- Elusive, very fast, low mass particles produced in nuclear reactions that don't really react with matter
- Trillions pass through the body every second from the sun
- Helps us learn about reactions on Sun
- Takes neutrinos 8 light minutes to get to earth |
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Definition
- AKA electromagnetic radiation
- properties of wave and particle |
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Term
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Definition
- 1 Angstrom = 10^-8 cm
- used to express optical wavelengths |
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Definition
- describe frequency
- units/sec |
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Term
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Definition
| Shortest- Guy Experiments Upon Only Limited Microwave Resources- Longest |
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Definition
| Studying light at different wavelengths coming from object to understand that object (can tell us about temperature, composition, and velocity) |
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Term
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Definition
| # of photons you detect (y axis) compared to wavelength (x axis) |
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Definition
- Stars can be approximated by these
- Object that absorbs all light incident upon it |
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Definition
1) Spectrum of hotter blackbody radiator is bluer and peaks at shorter wavelengths
2) The hotter blackbody radiates more light at all wavelengths |
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Definition
| Emitted by a radiating solid, liquid, or highly pressurized gas |
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Term
| Absorption- Line Spectrum |
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Definition
| Can be seen when source of continues spectrum is observed through a cool gas cloud (light removed at certain discrete wavelengths) |
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Term
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Definition
| Seen when gas cloud is observed against a cold, dark background (light only appears at certain discrete wavelengths) |
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Definition
- electron jumps to higher energy level
- certain atoms only "eat" certain ohotons depending on wavelengths and move, thus creating an absorption line |
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Term
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Definition
| Electron moves to lower energy level |
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Term
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Definition
The measured wavelength of light emanating from a source depends on the relative motion of the source and the observer
- Towards you: Blue shift
- Away from you: Red shift |
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Term
| Things to remember about Doppler Effect |
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Definition
1) velocities measured from Doppler Effect are relative velocities
2) Doppler effect only measures component of an object's velocity along our line of sight |
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Term
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Definition
-Uses lenses
- Yerkes Observatory is the largest one
- Dearborn Observatory is one |
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Term
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Definition
- Use mirrors
- Palomar was the largest one until the 80s |
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Term
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Definition
| Amateur grade reflective telescope model with an objective mirror and a secondary mirror |
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Term
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Definition
| Common type of reflective telescope for professionals (hole punched in objective mirror) |
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Definition
- Hasn't been affected by light pollution
- Located in Fort Davis, Texas
- Reflective Telescope
- Shot 3 times and still functions |
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Term
| Why build bigger telescopes? |
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Definition
1) Collect more light
2) Get sharper images |
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Term
| How much light a telescope gathers (this is a rule) |
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Definition
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Term
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Definition
- How tiny an angle we can see on the sky
- Think about angles, not distances
- 60 arc minutes in 1 degree
- 60 arc seconds in 1 arc minute
- Moon and Sun are 1/2 degree |
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Term
| Best resolving power we can see on earth |
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Definition
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Term
| Charged- Coupled Device Detectors (CCD) |
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Definition
- Detect nearly every photon that hits them
- Record digitally
- Cooling CCD detectors lessens background noise from heat |
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Term
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Definition
- Gives us the sharpest images we can get because
- Above atmosphere so:
1) Able to get really sharp images (1/20 of arc second resolution)
2) Space is dark- no light pollution!
3) Can look at certain wavelengths of light that can't make it through atmosphere to ground (UV and some infrared)
- When first launched there was a defect in mirror so resolution was just as good as that of telescopes on earth
- First servicing mission: Replaced solar panels and fixed telescopes |
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Term
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Definition
- 23.5 degrees
- Main reason why seasons occur |
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Term
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Definition
- entire sky appears to rotate around it (very close to N. celestial pole)
- angle that the North Star subtends above the northern horizon is the same as your latitude on earth |
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Term
| The sky you see is a function of where you are on Earth... |
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Definition
1) At N. Pole, you don't see stars rise or set, you just see stars in N. Celestial Pole rotating around Polaris
2) If you're at equator, you'll see every star in sky rise and set
3) No south star |
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Term
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Definition
| Circular path around celestial sphere that describes apparent path of sun as earth revolves around sun |
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Term
| Sun directly above you at equator on... |
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Definition
| March 21st or September 21st |
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Term
| Sun directly above you at 23 1/2 degrees North on... |
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Definition
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Term
| Sun directly above you at 23 1/2 degrees south on... |
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Definition
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Term
| Sun can only be directly overhead between... |
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Definition
| 23 1/2 degrees N and 23 1/1 degrees S |
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Definition
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Definition
1) travel across the ecliptic (stars don't)
2) Move with respect to background stars
3) Don't twinkle because it comes through atmosphere as a disc |
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Definition
| Other part of Moon not being hit by Sunlight has a faint glow |
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Definition
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Definition
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Definition
Moon and Sun have same angular size in sky (1/2 degree)- because even though sun is bigger, it's much farther away
- We would have a solar eclipse every month if orbit of moon around earth was same as orbit of earth around sun (it's inclined by 5 degrees0
- Occur when everything aligned on the line of nodes |
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Definition
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Term
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Definition
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Term
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Definition
- Moon passes into earth's shadow
- During a full Moon
- Whole dark side of Moon can see eclipse
- Sunlight refracted through earth's atmosphere- only reddest light makes it through... moon faintly lit |
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Term
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Definition
140 AD
- Earth at center of universe BUT planets also move in their own circle (circles on top of circles) |
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Term
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Definition
300 BC
- Said sun was at center of universe
- argument against him was that stars would change if everything was moving |
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Term
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Definition
| What you see is dependent on point of view |
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Term
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Definition
1500s
- Heliocentric theory |
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Term
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Definition
- Spent 30 years meticulously observing the heavens
- Searched for parallaxes but they were too small to see |
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Term
| Kepler's Three Laws of planetary motion |
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Definition
1) Planets move in elliptical orbits around the Sun with the Sun at one focus
2) A line joining a planet and the Sun sweeps out equal areas of the planet's orbit in equal time (aka planets move slower in orbits the farther they are from the sun)
3) P^2 = R^3 where p is planet's period or orbital revolution about the sun and r is average distance from the sun |
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Term
| Earth closest to sun in ___ |
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Definition
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Term
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Definition
- Clinched heliocentric model
1) Found mountains on the moon
2) Found Sun spots
3) Found that Venus had phases
4) Found 4 moons orbiting Jupiter that all followed Kepler's laws |
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Term
| Isaac Newton's 3 laws of motion |
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Definition
1) A body remains at rest or moves in a straight line at a constant speed unless acted upon by an outside force
2) Acceleration of an object is proportional to force acting on object (F= ma)
3) For every force, there is an equal and opposite reaction force |
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Term
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Definition
| Amount of force earth has for an object with mass |
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Term
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Definition
| Amount of distance an object covers in a certain amount of time |
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Term
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Definition
| Change in object's velocity over time |
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Term
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Definition
Describes nature of gravitational force that keeps planets in orbit around the sun
- f= (Gm1m2)/r^2
- If distance changed by a certain amount, multiply answer by 1/r^2
- Give Kepler's laws a mathematics base in reality |
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Term
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Definition
- intrigued by comet
- thought it was the same comet coming back again and again
- used Newton's laws to predict when and where it would be
- Halley's comet- seen every 76 years |
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Term
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Definition
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Term
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Definition
- people predicted within 1 degree where it would be on sky
- Neptune's presence accounts for Uranus's motion |
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Term
| Search for the 9th planet |
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Definition
- Found by Tombaugh
- We now know Pluto wasn't really causing perturbations in Neptune's motions- they were just spurious motions |
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Term
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Definition
- terrestrial planets
- Mercury, Venus, Earth, Mars
- essentially rocks |
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Term
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Definition
- no atmosphere
- craters
- very hot |
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Term
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Definition
-Closest to earth in terms of mass and size
- Atmosphere almost all CO2
- HELL to live on
- 90 times earth's atmospheric pressure
- Clouds trap heat |
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Term
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Definition
| Formed when an object hit earth, broke off a chunk of earth, and chunk began orbiting Sun |
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Term
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Definition
- 1/10 mass of earth and 1/2 its radius
- Atmosphere pressure 1/100 that of earth
- Atmosphere covered in thin coat of CO2
- liquid water can't exist on surface BUT strong evidence there once was
- Has seasons
- Life may still exist there |
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Term
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Definition
- Jupiter, Saturn, Uranus, Neptune
- Much bigger and massive
- Jupiter's mass 320x earth's mass and its red spot is 2 earth's across
- Gas balls
- LIGHTER DENSITY THAN TERRESTRIAL PLANETS
- Have ring systems
- Saturn's rings the best- covered in ice |
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Term
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Definition
- Chiefly rocks
- Between Mars and Jupiter
- Ceres located in it
- Jupiter's gravity didn't allow a planet to form in this area
- Some asteroids orbit each other
- Formation of asteroids dates back to formation of atmosphere |
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Term
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Definition
- Beyond Neptune's orbit
- Tens of thousands of tiny objects
- Dwarf planets loosely associated with this belt
- Icy rocks
- Comets coming in from ecliptic come from here |
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Term
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Definition
- Beyond kuiper belt
- Trillions of dirty snowballs
- Amonia, CO2, methane inside them
- 50,000 AU from sun
- Dirty snowballs turn to comets |
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Term
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Definition
- When dirty snowballs get close to sun they melt, get ionized, and glow --> leads to tail
- Comet tails ALWAYS point away from the sun
- Tail of comet can stretch 1 AU
- Colma of comet can be 100,000 km in size
- Tail of comet can last weeks to months
- Jupiter can hold a comet in its orbit |
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Term
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Definition
- When earth passes through orbit of dead comet, the debris comets leave behind are there --> meteor showers
- Typical meteor size of grain of sand
- Common
- Last a few seconds
- Craters made by them on earth don't last very long due to erosion |
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Term
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Definition
- 1979- Walter and Louise Alvarez
- Studying a layer of rock in Italy
- Found layer of clay and dark stuff above it- often near soot
- Layer of clay very rich in iridium, which is rare on earth but common in meteorites
- Dates back to 65 million years ago
- Fossils below this layer have lots of life forms
- 70 % of life extinct above this layer
- Impact created a 180 x 300 km crater that has been identified off the Yucatan Peninsula in Mexico
* dates back to impact epoch
* nearby clay layers show enhanced iridium |
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Term
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Definition
- Came very near Jupiter
- Broke into 21 pieces
- As each one hit Jupiter, large heat plumes arose |
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Term
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Definition
| Assesses impact hazards of asteroids or comets |
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Term
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Definition
- Friday April 13, 2029 will pass in between earth and its geosynchronous satellites
- Will come back in 2036 (1/36,000 chance it will hurt earth) |
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Term
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Definition
| (Sun's mass x Energy per burnt mass)/ luminosity |
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Definition
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Term
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Definition
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Term
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Definition
- powers the sun
- 4 H nuclei bombard each other to make 1 He nucleus along with energy and neutrinos
- .7 % of mass going into these reactions doesn't go into He, it goes into energy
- Very high temperatures (15 million K) and very high densities needed to overcome repulsion between positively charged particles
- Hydrogen bomb is the only way fusion happens on earth
- energy obtained from 1 g of fusion is 300,000 times stronger than that from burning 1 g of oil
- happens at inner 10% of sun |
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Term
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Definition
Eternal fight between gravity and energy produced by nuclear reactions that fight off gravity
- right now they're balanced, giving the sun its shape
- like a thermostat |
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Term
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Definition
Process takes energy from core of sun out to about 70 % of the sun's radius- basically to top of radiative zone
- gamma ray photons absorbed, re- emitted, absorved, etc.
- it takes one photon produced at center 100,000 years to get to surface- that's how dense the sun is
- wavelengths slowly move from gamma to UV |
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Term
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Definition
| Cycling that brings heat from top of radiative zone to top of convection zone |
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Term
| We see sun as it was ___ years ago |
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Definition
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Term
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Definition
- Vat filled with chlorine
- Many pass through vat
- Once a day a neutrino and chlorine atom react to make argon
- We thought we were seeing one every three days, which would have meant that in 100,000 years the sun will be 1/3 as bright- called solar neutrino problem
- We now realize that neutrinos come in 3 different "flavors" and only one of the flavors reacts with chlorine to make argon
- Thus, sun will remain constant in next 100,000 years |
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Term
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Definition
- 6,000 K
- lowest layer
- layer from which we see photons (last stop for photons before coming to earth)
- 400 km
- We see absorption lines here |
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Term
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Definition
- 10,000 K
- Above photosphere and is hotter, but LESS DENSE
- Spicules located here: little streams of gas rising in chromosphere best seen during solar eclipse |
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Term
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Definition
- 2 million K
- Only seen during solar eclipse
- VERY LOW density
- particles moving VERY FAST |
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Term
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Definition
- Active Sun
- Larger than earth
- 4,000 K
- Cooler b/c of magnetism- high magnetic fields cool gas in these vicinities, making them appear dark against surface of the sun
- 11 year cycle |
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Term
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Definition
- Can disrupt radio communications
- Can cause power failures
- Cause Northern Lights |
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Term
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Definition
- Best way to measure distances to stars (within 200 parsecs)
- Stars appear to change position b/c of our position changing w/ respect to the star
- Farther the star is from earth, the tinier the parallax angle becomes
- D= 1/p |
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Term
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Definition
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Term
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Definition
| 1 parsec is the distance to a star with p= 1 arc second |
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Term
| Best error we can get from measuring parallax from ground telescopes |
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Definition
- +/- .005 arc seconds
- distance about 40 parsecs |
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Term
| Best error we can get measuring parallax from space telescopes |
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Definition
- +/- .001 arc seconds
- distance about 200 parsecs |
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Term
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Definition
- Measure of how bright an object appears
- Amount of energy carried by the light through a given area at our distance from the illuminating object in a given time
- Apparent magnitude |
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Term
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Definition
- Measure of how bright an object really is, which is the total amount of energy radiated by the object in a given time
- Absolute magnitude |
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Term
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Definition
B= L/ (4pied^2)
- whatever the factor the distance is changed by, the brightness is multiplied by 1/d^2 |
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Term
| Concepts to remember about magnitude system (3) |
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Definition
1) Large magnitudes (like +12) mean fainter stars and small magnitudes (like -4) mean brighter stars
2) A magnitude difference of 5 is a brightness ratio difference of 100
- The absolute magnitude of a star at a distance of 10 parsecs is equal to its apparent magnitude |
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Term
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Definition
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Term
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Definition
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Term
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Definition
- O stars
- temperature 40,000 K
- hotter --> many UV photons --> ionization because electrons knocked out when UV rays hit atoms |
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Term
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Definition
- M stars
- temperature 3,000 K
- Few if any UV photons --> presence of molecules prove this because UV would have destroyed molecules |
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Term
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Definition
- We classify stars by appearance of spectra
- Different absorption line patterns in spectra
- The pattern of absorption lines are dependent on temperature
- Looking at which ions and atoms are present we can calculate temperature much more accurately than with blackbody radiators
- Hottest and most abundant- Oh Be A Fine Guy Kiss Me- Coolest and least abundant
- Measuring spectral type of star independent of distance |
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Term
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Definition
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Term
| Hertzsprung- Russell Diagram |
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Definition
- Tells us about evolution of stars and distances to stars over 200 parsecs away
-Tells us that Red Giants, Supergiants, and White Dwarfs must be part of story of what happens after a star burns H into He in core
- Positions of stars on diagram is a factor of their SIZE |
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Term
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Definition
- most stars fall along the main sequence
- these stars are still burning H to He with fusion in core |
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Term
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Definition
1) measure apparent magnitude (brightness)
2) Take spectrum
3) Use HR diagram --> see absolute magnitude
4 With m and M find distance |
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Term
| Luminosity goes up if ___ also goes up |
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Definition
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Term
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Definition
- White dwarf that is companion star to brightest star in sky, Serius
- Found by Dearborn observatory |
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Term
| What happens after a protostar forms? |
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Definition
| Chunk of cloud gets hotter and smaller --> compression --> core hotter --> core reaches 15 million K and fusion beings --> protostar becomes star |
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Term
| How long does it take to form a star like the sun? |
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Definition
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Term
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Definition
Tell us about evolution of stars
- ex) Double Star Cluster in Perseus |
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Term
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Definition
- Relatively young
- Over time, stars disperse and go their own way
- Sun may have once been a part of one |
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Term
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Definition
| You can use it to calculate how old the cluster is- point where star no longer has H in core to turn into He |
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Term
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Definition
- No more than 100 light years across
- Hundreds of thousands of stars
- A thousand stars per cubic parsec
- Typical ages: 10 billion years old |
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Term
| Story of stars with less than 8 solar masses once they turn off main sequence |
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Definition
- Sun's atmosphere 90% --> when it formed its core was 90% H, but now it's core is 50% H and 50 % He
- Hydrogen Shell Burning- hydrogen to helium in shell, very productive, can produce more energy than core- burning
- Core contracting to 1/3 its size over 100 million years and temperature of core goes up drastically
- Star becomes Red Giant- large and cool (3,000 K)
- When core reaches 100 million K, you can start the triple alpha process: through series of reactions He nuclei are smashed together to form carbon, oxygen, and energy
- Core now 1/3 it's original size
- Sun will be red giant for 1 billion years
- Gas that surrounds the core through either single or series of flashes or energy blows away its outer parts- a NEBULAE results
- NEBULAE lasts about 50,000 years
- Star becomes white dwarf- which is the core that is left behind- very hot, and small |
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Term
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Definition
- Core composed of mostly carbon with some oxygen
- All have masses less than 1.4 Solar masses
- Typical one is size of earth
- More mass = smaller size
- Very dense
- Eventually becomes black dwarf- carbon rich object that is essentially a diamond |
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Term
| Degenerate Electron Pressure |
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Definition
- A safety valve pressure that holds off gravity
- All gravity wants to do is squish stars down to nothing
- You can only push electrons so close together until there's a force that stops it --> star reaches stability point |
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Term
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Definition
| Max mass of white dwarf is 1.4 solar masses because it's past this mass that gravity can overcome electrons |
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Term
| White dwarf in binary star system where the amount of mass piled up on it doesn't pass 1.4 solar masses |
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Definition
- Roche Lobes here- gravitational fields around star
- When Main sequence companion star becomes Red Giant, it begins to dump mass on the white dwarf
- Flows like water down a drain- Accretion disk formed
- Temperature gets higher and it gets denser --> H reaches 10 million K---> surface of white dwarf ignites and release of energy --> NOVA |
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Term
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Definition
- nuclear explosion on surface of white dwarf
- new star appears
- with best telescopes we can see 3 - 5 with naked eye per year
- can ONLY occur in BINARY star systems
- Surface explosion--> doesn't destroy white dwarf or disturb companion star |
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Term
| Red Giant Star and White Dwarf that gets enough mass piled up on it that it passes Chandrasaekhar limit |
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Definition
- Matter piling up on White Dwarf
- White Dwarf reaches 1.4 solar masses
- gravity squeezes White Dwarf until it becomes very hot
- Carbon made into energy
- Doesn't expand as it heats up --> entire thing blows up
- Type 1A supernova!!! |
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Term
| Fait of stars with initial masses bigger than 10 solar masses |
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Definition
- Never becomes white dwarf
- Become supergiants (radius over 2 AU)
- Left with core massive enough to contract C and O in star
- core mass of 2 solar masses of silicon produced
- Silicon burned into iron in one day --> lots of energy made
- Iron doesn't burn, so very quickly the iron core goes into free fall collapse because nothing left to stop gravity
- 1/10 of a second the core becomes 5 billion K
- Photons break up iron --> core collapses faster
- Neutroonization: Iron core converted to neutrons, releasing many neutrinos
- In 1/4 second the star becomes 20- 30 km (size of city)
- Because of degenerate pressure, inside of star begins to collapse on core while neutrinos are coming to collide with it --> inside bounces off core carrying energy with it and a shock wave blows matter out of the star
- TYPE 2 SUPERNOVA
- Neutron rich core survives explosion |
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Term
| Type 1A Supernova Characteristics |
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Definition
- need binaries
- powered by thermonuclear energy
- brighter than Type 2
- Can be distinguished by spectra |
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Term
| Type 2 Supernova Characteristics |
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Definition
- Result when massive stars die (can happen in binary but doesn't have to)
- Powered by core collapse
- Fainter than Type 1A
- Distinguished by spectra
- Flood of neutrinos released |
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Term
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Definition
- type 2 supernova went off in another galaxy and it was seen by naked eye
- we detected neutrinos from this object
- over 100,000 light years away |
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Term
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Definition
- Core created from Type 2 supernova
- Size of city (20 km)
- Very dense |
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Term
| Evidence of Existence of Neutron Stars |
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Definition
- Jocelyn Bell
- Pulses coming every 1.3 seconds
- Thought it was extraterrestrial life- called LGM-1- but then we found more pulses so it couldn't be
- called pulsars
- Found one at Crab Nebula center that beeped every .033 seconds
- Pulsars became called neutron stars |
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Term
| Conservation of Angular Momentum |
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Definition
- As object that spins becomes smaller, it spins faster
- So as star collapses into neutron star, it gains speed |
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Term
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Definition
- Squeeze together as star compresses --> magnetic field increased by factor of 1 billion
- Neutron star has an intense magnetic field
- Charged protons and electrons in vicinity of pulsar interact with magnetic field (electrons in particular) and get spun --> emit radiation
- Relativistic electrons: move so fast that that they release synchroton radiation: sweep across the sky as pulsar beeps rapidly
- Only see pulsar if this radiation beam is in line of sight |
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Term
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Definition
| - Like earth quakes on stars --> spins faster for a little |
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Term
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Definition
- If remnant core after Type 2 supernova explosion has a mass bigger than 3 solar masses, gravity wins and crushes it out of existence
- Core crushed to dimensionless point called singularity
- You can define sphere and singularity
- Black Hole left behind
- Gravity so strong- basically equal to speed of light
- Nothing that gets into black hole can escape
- Represents severe warpage of space time |
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Term
| The radius of a black hole is called ____ |
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Definition
|
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Term
| Einstein's Theory of General Relativity |
|
Definition
- helps us understand black holes
- think of 4 dimensional area
- mass tends to curve space around it --> more mass means more curve
- ex. light bent from star to earth --> star appears to have different position (shift of 1.75 arc seconds of star on edge of sun due to this effect)
- Black holes severely curved |
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Term
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Definition
- Time distorted in vicinity of very strong gravitational fields like black holes
- time within black hole passes very slowly from point of view of someone from outside looking in |
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Term
| 3 main Black Hole characteristics |
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Definition
1) Mass
2) Angular Momentum
3) Electric charge |
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Term
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Definition
| Area surrounding black hole that you could pass through if you were traveling fast enough |
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Term
| What happens to black hole if put in binary star system? |
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Definition
| It could be orbited by a Red Giant- we can't see them but we can tell x- rays are spiraling into black hole --> gas reaches temperature of 2 million K before going into black hole and emitting x- rays |
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Term
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Definition
| As mass dumped on object (black hole, neutron star, white dwarf) it begins to orbit around it and spiral into it |
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Term
| Why are black holes probably at galactic centers? |
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Definition
| Infrared telescopes can see through dust and see stars near galactic center --> they are orbiting something --> this thing must have mass of 3.8 million solar masses stuffed into space smaller than 1 AU --> must be black hole |
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Term
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Definition
- Mass of gas and dust between stars is 15 % of mass in Universe
- Lots more gas than dust |
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Term
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Definition
| Blue haze due to inter stellar dust grains |
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Term
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Definition
- Dust scatters blue light off stars so they appear blue
- Occurs because stars are IN CLOUD |
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Term
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Definition
| Blue light scattered out by dust in gas cloud as light comes through --> stars appear red |
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Term
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Definition
- star factories
- millions of solar masses of gas and dust
- 150- 300 light years on sky
- cores shielded from external radiation --> very cold (10 K)
- very high densities
- cores have over 150 species of molecules- rich molecular organic chemistry |
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Term
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Definition
| UV radiation from O or B stars goes into clouds and excites electrons --> when they come back down they release photons |
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Term
| What determines difference between nova and supernova? |
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Definition
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Term
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Definition
| Einstein put it in equations to keep universe static |
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Term
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Definition
| Can cut through inter- stellar dust, but optical light can't |
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Term
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Definition
- Most abundant thing in inter- stellar medium
- Emit radio waves that allow us to trace them
- Spins of electrons and protons affect radio waves
* More energy when spins parallel (in same direction)
* Less energy when spins anti- parallel (in opposite directions)
- Takes 11 million years for electron to flip spin and then it emits photon --> we can see this radiation at this time ( wavelength = 21 cm is released)
- we can map H atoms across galaxy --> galaxy does have specific morphology --> like a spiral |
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Term
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Definition
- All the action happens here
- Dots of young O and B stars concentrated here |
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Term
| Spiral Density Wave Theory |
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Definition
- Analogy: Expressway construction crew slowly moving down highway --> traffic builds up
- Pressure/ Density wave rotates bunching up gas and dust --> stars form there --> O and B stars
- The waves pile up due to mechanical action of things blowing up
- When stars blow up as supernova- it helps propagate actions of pressure waves |
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Term
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Definition
- Young, and metal rich
- Participate in the activity that occurs in the spiral density wave theory
- Disc stars |
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Term
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Definition
- Old, metal poor stars
- Located in Globular Clusters |
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Term
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Definition
- found we weren't at center of galaxy
- used globular clusters
- said that if we were at the center of the galaxy, globular clusters should be distributed symmetrically around sky
BUT
- he measured the distances to globular clusters
- he had to invent new way o get distances sp he used the Period- Luminosity relation for star called the RR Lyrae star
- this star pulsates small to big over and over again in regular manner (period of 1/2 day) (M= .5)
- If absolute magnitude is .5 and period is 1/2 day we can look for stars like this, find apparent magnitude, and measure distances
- found we are 25,000 light years from center of galaxy |
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Term
| Distance from us to center of galaxy |
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Definition
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Term
| Period- Luminosity Relation |
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Definition
- Cepheid Variable- bigger and smaller etc.
- Relation between pulsations and luminosity |
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Term
| Velocity of sun orbiting Milky Way Galaxy center |
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Definition
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Term
| how long it takes sun to make one orbit |
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Definition
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Term
| How much mass is in sun's orbit around galactic center |
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Definition
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Term
| Relationship between distance b/w us and galactic center and Mass |
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Definition
| As one goes up, so does the other |
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Term
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Definition
- Plot of how fast things are moving at certain distances from galactic center
- Milky Way Galaxy has flat rotation curve |
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Term
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Definition
- As distance b/w us and galactic center goes up, so does mass
- BUT as you go further out there are way less stars, but mass has continued to increase
- Due to dark matter
- Flat Rotation curve indicative of dark matter |
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Term
| 3 Main Things about Milky Way |
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Definition
1) Disc of Milky Way (where all action happens) has radius of 50,000 light years
2) 4 million solar mass black hole at center of Milky Way
3) Halo of Milky Way
- 200 Globular Clusters
- Mostly empty space
- Dark matter larger than size of disc of milky way itself |
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Term
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Definition
- Saw fuzzy, fixed objects that rotated with the stars while looking for comets
- Catalogued these
- Along disc of Milky Way he found amorphous, irregular fuzzy objects with emission lines
- Above and below plane of Milky Way in halo found symmetrical fuzzy objects with absorption lines moving at high velocity away from Milky Way (spherical, elliptical, spiral) |
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Term
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Definition
- Debate over whether the fuzzy objects Charles Messier found in sky were other galaxies or part of ours
- 1920
- Harlow Shapley vs. Hebe Curtis
- No one won |
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Term
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Definition
- Ended Great Debate
- used Mt. Wilson 100 inch telescope
- Could estimate distance of stars in Andromeda- they were much farther away than anything in Milky Way |
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Term
| Basic Characteristics of Galaxies |
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Definition
- Conglomerations of stars
- Galaxies within a billion light years - 90% have spiral or elliptical shapes
- Some of spherical ones have bar in center like the Milky Way and some have nice spherical centers
- Almost all spirals and large ellipticals have large black holes in the middle |
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Term
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Definition
Shape: Pancake and bulge
Diameter: 50,000 - 200,000 ly
Color: Blue spiral arms (population 1)
Inter stellar Mass: Lots
Star formation: Lots
Internal Motion: Rotating
Texture: Knotty |
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Term
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Definition
Shape: Sphere or football
Diameter: 1,000- 500,000 ly
Color: Yellow- red (population 2)
Inter stellar Mass: Virtually none
Star formation: Very little
Internal Motion: Beehive- follow own orbits buzzing around each other
Texture: Smooth |
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Term
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Definition
- Anything not spiral or elliptical
- No real symmetry
- Ex.) Large Magellenic Cloud and Small Magellenic Cloud |
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Term
| How long is local group across? |
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Definition
| - 3,000,000 light years across |
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Term
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Definition
- nearest rich cluster of galaxies
- 7,000,000 light years across
- 60,000,000 light years away from us |
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Term
| What kinds of galaxies are most common in rich clusters and why? |
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Definition
Ellipticals
- Ellipticals only have old stars
- 11- 13 billion years ago there were many protogalaxies interacting with each other within rich clusters --> collisions frequent and huge star formation --> in doing so, cleans out interstellar matter and gas --> Only stars left --> No new gas to make new stars |
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Term
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Definition
- Collisions not very frequent
- Local Group is example
- Rotates, shrinks, collapses --> disc --> gas piles up --> stars form gradually --> spiral galaxies made (like Milky Way) |
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Term
| In general, which shape of galaxies is most common? |
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Definition
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Term
| What happens when spirals smash into each other? |
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Definition
| STARBURST- entire galaxy will eventually erupt in explosion of supernovas --> formation of elliptical galaxy |
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Term
| What happens when large galaxy collides with small galaxy? |
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Definition
| big one will be disrupted or big one absorbs little one |
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Term
| As universe expands what happens to space between clusters and space between galaxies? |
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Definition
- Space between clusters expands but not space between galaxies
- Movement can tell us about mass of clusters |
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Term
| What percentage of matter in galaxy clusters is dark matter? |
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Definition
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Term
| Evidence of Dark Matter (3) |
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Definition
1) Flat Rotational Curve of galaxies
2) Velocities of galaxies within clusters- we can measure how much mass must be in galaxy- this is much greater than what we know is there
3) Gravitational Lenses- as light from distant galaxies comes through the images get distorted
--> we can record mass |
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Term
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Definition
- Weakly- Interacting Massive Particles
- Most astronomers believe these cause dark matter
- our best guess, but we still haven't found them |
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Term
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Definition
- Unstable supergiant that's brighter when bigger and fainter when smaller
- relationship between period and luminosity
- so bright we can see them in other galaxies with telescope
- assumed Cepheid variables in our galaxy are same as ones in other galaxies (so he could use Period- Luminosity radiation and measured how bright it was to get distance)
- Hubble measure distance to Andromeda Galaxy doing this
- Hubble could take cepheids out to 20 million ly |
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Term
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Definition
| - What astronomers call objects whose velocities we think we know (i.e. cepheid variables) |
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Term
| How far can we reach cepheids with Hubble Telescope? |
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Definition
| Out to 60 million ly (Virgo Cluster) |
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Term
| How do we measure distances beyond 60 million ly? |
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Definition
- Use Type 1A Supernova
- Northing brighter in Universe
- We don't have control over which galaxies have this particular standard candle
- When Type 1A supernova is at max brightness, it always has same luminosity
- We have found galaxies up to 10 billion light years away |
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Term
| extragalactic distance scale |
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Definition
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Term
| extragalactic distance scale |
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Definition
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Term
| Hubble used spectrum of galaxies to measure distances and velocities, and found that almost all showed ____ shifts |
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Definition
- RED
- More distant galaxies showed biggest red shift |
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Term
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Definition
V= Hd where:
- v is velocity of galaxy
- H is Hubble's Constant- expansion rate of universe
- d is distance to galaxy
*If we know Hubble's constant, all we have to do to get distance is get its velocity
* Universe must be expanding |
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Term
| Andromeda has what shift and why? |
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Definition
| Blue due to what's happening within our cluster |
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Term
| How do we deal with the fact that velocity of galaxies close to us can be affected by things happening in the cluster? |
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Definition
- 15 to 20 years ago some scientists though hubble's constant was 100 and some thought it was 50 (10 billion years old vs. 20 billion years old)
- Answer: the midpoint- universe 13.7 billion years old |
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Term
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Definition
- Show importance of Hubble's constant
- Look like stars
- Spectrum doesn't show many absorption lines (unlike stars) but does show emission lines
- Show red shift
- Plugged into V= Hd --> enormous distances but bright enough to see with Hubble telescope
- Use relativistic not classical
-Quasars are light days to light months in size but can produce 10- 1,000 milky way luminosities
- Supermassive black holes at heart of quasars powering them |
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Term
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Definition
| - Where did universe come from, how is it evolving, and what is its fate? |
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Term
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Definition
- According to Newtonian physics, we must be living in infinite universe because we haven't been pulled into a blob (which is what would happen in finite universe)
- because space goes on forever with stars and galaxies scattered throughout
it, your line of sight must eventually hit a star
- no matter where you look in the sky, you should ultimately see a star
- therefore, the entire sky should be as bright as an average star
- the fact that this isn’t so is called Olber’s Paradox
- tells us that there is something wrong with Newton’s picture of a static, infinite universe
- problem: Newton's view of universe, in which time and space have no complications
- In Einstein's universe, space, time, and matter intimately related to each other
- Einstein applied general theory of relativity to entire universe
- Einstein's calculations told him the universe should be expanding or contracting
- Einstein invented the cosmological constant and put it in his equations to act like pressure to keep universe from expanding or contracting
- 10 years later, Hubble proved universe was expanding |
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Term
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Definition
- Explains how wherever you are, everything else seems to be moving away and that things farther apart move faster
- Center of universe and edge of universe are TIMES NOT PLACES |
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Term
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Definition
| - Photons expand in wavelength as they move they move through space because expansion of universe pulls it |
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Term
| We only see expansion in space between ______ |
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Definition
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Term
| Answer to Olber's Paradox |
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Definition
| Sky black b/c when you look out at universe at night you can see a time when there were no stars or the galaxies that were there were so redshifted and stretched that we see no light |
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Term
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Definition
- expands slowly --> slows down --> collapses --> near galaxies show blue shifts --> universe crushed into singularity --> fire
- curves back on itself
- density > critical density |
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Term
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Definition
- ends in ice because all lights in universe go out because everything gets so far apart
- curves away from itself
- density < critical density |
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Term
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Definition
- no curvature
- density = critical density |
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Term
| Rocket must go faster than ____ to leave earth |
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Definition
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Term
Amount of matter in universe
- just shining
- counting black matter |
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Definition
- just shining: omega = .03
- counting black matter: omega = .3 |
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Term
| Why is universe expanding faster now than in the past? |
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Definition
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Term
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Definition
- governs universe
- galaxies expanding much faster now than long ago- this is why dark energy necessary!
- acts like cosmological constant Einstein put in his equations
- what is it?
1) Indefinite expansion
2) Big Rip
3) Big Crunch
- Indefinite expansion/ cosmological constant approach will happen |
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Term
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Definition
| universe is infinite with galaxies spread throughout |
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Term
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Definition
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Term
| Evidence of Big Bang Model (4) |
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Definition
1) expanding universe
2) distribution of quasars with distance
- lots far away, none nearby
3) Abundance of helium
- 25% of universe everywhere we look
- if all He produced by stars --> there should be more He in older galaxies, but there isnt! --> this He must have come from the Big Bang
4) Cosmic Microwave background radiation
- 3000 K
- galaxies we see at great distances should look different in Big Bang Model and they do!
- 300,000 years after Big Bang, particles become 3 K because of red shifting of galaxy |
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Term
| Most of extra- solar planets found today have ____ mass planets... none like ____ |
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Definition
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Term
| How many sun type stars outside galaxy have planets? |
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Definition
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