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Definintion of science
- 1. Systematic study of the world
- 2. A way of knowing about the
- physical world
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Characteristics of science 3
- - empirical data
- - provisional explanation
- - specific to general
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Differences between siderdal day and solar day 3
- - earth is always orbiting the sun
- - solar day is longer than
- siderdal day (1/365th)
- - earth rotates one degree in a siderdal day
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Celestial horizon
great circle that divides visible stars from non visible stars
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Celestial meridian
divides east and west runs north south through observers zenith
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Three ways to locate stars
- - constellations
- - declination
- - azimath and altitude
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Declination
angle between point on celestial sphere and equator.
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Altitude
- - angle above horizon
- - always less than 90 degrees
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Retrograde motion
planets moving from east to west ; Mars, Jupiter, Saturn
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Kepler laws 3
- - planets move in elliptical with sun at focus
- - line joining sun and planet sweeps out equal areas in equal time
- - sideral period squared=cube of distance to sun
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Newton's law of motion 3
- - body at rest will go in straight line
- - rate of change of velocity=mass of body being accelerated
- - force a exerts on force b; b exerts equal and opposite force on a
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Newton's law of universal gravitation 2
- - mass attracts other mass in the universe
- - force of one mass exerts on another=mass of two bits and is inversely proportional to the
- distance between them
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Zenith
this is the point perpendicular up or above observer.
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Why does a circle have 360 degrees rather than 100?
- the circular track of the
- Sun's annual path across the sky
- took about 360 days to complete one year.
- Consequently, they divided the circular path into 360 degrees to track each day's passage of the Sun's whole journey.
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How can spectrum of light tell a star's chemical compostion?
each element produces its own pattern of spectra lines and with a spectrograph you can see the lines.
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Visible Light
400 nm to 700 nm
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Doppler Shift
Oncoming is shorter, outgoing is longer
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radial velocity
Wave goes towards person blue shifted and shorter. Wave goes away longer and red shifted.
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Atmosphere and light 3
- 1.More likely to scatter shorter wave lengths.
- 2.Blue light will scatter 60x more than red light.
- 3.Person behind equals unscatter, People below equals scatter.
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Two things that tell how much energy is emitted from an object.
temp. and area
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Apparent properties do not depend distance and intrinsic properties depend on distance.
True or False
False
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How to find Luminosity?
L=(alpha)Area x temperature to the fourth also look on H-R diagram
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7 properties of a star
- 1. surface area
- 2. distance stellar parallax
- 3. temperature spectral type
- 4. luminosity absolute magnitude H-R diagram
- 5. chemical composition
- 6. brightness
- 7. radial veolcity
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What star properties 2 are not instrustic and which one is?
Brightness and distance Mass is.
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Binary Stars 3
- 1. Tell us mass.
- 2. Pair of stars that orbit each other.
- 3. gravitionally bound together
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Thermnuclear fusion
2 nuclei form 1 nucleus and create lots of energy. This needs high temperature, high density, and high speed to happen.
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Helium flash
less than 2 solar masses that lets fusion reaction runaway and very exotic
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Turnoff point tells age of star
True or false
true
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Spectroscopic parallax
Method of determing a star's distance from Earth by measuring its surface temperature, luminosity, and apparent magnitude.
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Stellar Evolution
- Stellar evolution is the sequence of changes in the characteristics of a star resulting from the physical processes occurring within it.
- It is the physical “life history” of a star
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Why is stellar evolution difficult to study? 2
- 1. Stars may exist for billions of years (e.g. Sun is about 4.5 x 109 years old).
- 2. Humans live for less than 102 years. Meaning that humans can observe less than 1/107(1 10 millionth) of a star like Sun’s life.
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3 types of spectra
- 1. Continuous Spectrum - light like the rainbow
- 2. Absorption Line Spectrum - dark lines on a continuous spectrum starlight
- 3. Emission Line Spectrum - mostly dark, no continuity
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Assumptions made 2
- •Physical laws are constant in space
- •Physical laws are constant in time
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Are stars forming today?
- Yes Astronomers
- have seen stars that have just arrived on the main sequence, as well as infrared images of gas and dust clouds in the process of forming stars.
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Blackbody radiation
As temp. increases energy is emitted at all wavelengths. As temp. increases greater light is emitted at short wavelengths.
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Cosmology
Study of the universe as a whole. Knowing how large, how old, has it existed, its struture, and history of it.
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Blackhole
An object greater than 25 solar masses whose gravity is so strong that the escape veolcity from it exceeds the speed of light
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Population one stars are found in the disc. They are o and b stars. They are open clusters.
True.
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Population two stars found in halo and are globular clusters. They are older stars.
true
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Why do we see milky effect?
Vision is blocked by dense matter. You look far enough you can't make out what you see other than billions of stars.
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Ceheipd variable stars 2
- 1.Determined M31 galaxy
- 2. Giant stage stars that are unstabe that get bright or dimmer and expands and contracts over time.
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Spiral Arms of milky way
Stable waves that are spiral and don't wrap up in themselves.
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Hubble's Law
Everything in the universe is moving away from us and moving fast.
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Determing age of universe 3
13.7x10 yeras old.
- Hubble's law
- Star clusters
- cosmic backgroung radiation
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Big Bang
Universe began in an exceptionally hot exceptionally small state. As it expanded it cooled allowing nuclei atom, stars, and galaxies to form.
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nucleosynthesis
one element and making another element. Star becomes supernova it takes helium and that becomes carbon.
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Pulsars
Light is emitted out of poles, beams are intense. Star rotates like a lighthouse and evertime it rotates towards earth a pulse of light will be visible.
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