great circle that divides visible stars from non visible stars
Celestial meridian
divides east and west runs north south through observers zenith
Three ways to locate stars
- constellations
- declination
- azimath and altitude
Declination
angle between point on celestial sphere and equator.
Altitude
- angle above horizon
- always less than 90 degrees
Retrograde motion
planets moving from east to west ; Mars, Jupiter, Saturn
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
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
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
Zenith
this is the point perpendicular up or above observer.
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.
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.
Visible Light
400 nm to 700 nm
Doppler Shift
Oncoming is shorter, outgoing is longer
radial velocity
Wave goes towards person blue shifted and shorter. Wave goes away longer and red shifted.
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.
Two things that tell how much energy is emitted from an object.
temp. and area
Apparent properties do not depend distance and intrinsic properties depend on distance.
True or False
False
How to find Luminosity?
L=(alpha)Area x temperature to the fourth also look on H-R diagram
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
What star properties 2 are not instrustic and which one is?
Brightness and distance Mass is.
Binary Stars 3
1. Tell us mass.
2. Pair of stars that orbit each other.
3. gravitionally bound together
Thermnuclear fusion
2 nuclei form 1 nucleus and create lots of energy. This needs high temperature, high density, and high speed to happen.
Helium flash
less than 2 solar masses that lets fusion reaction runaway and very exotic
Turnoff point tells age of star
True or false
true
Spectroscopic parallax
Method of determing a star's distance from Earth by measuring its surface temperature, luminosity, and apparent magnitude.
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
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.
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
Assumptions made 2
•Physical laws are constant in space
•Physical laws are constant in time
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.
Blackbody radiation
As temp. increases energy is emitted at all wavelengths. As temp. increases greater light is emitted at short wavelengths.
Cosmology
Study of the universe as a whole. Knowing how large, how old, has it existed, its struture, and history of it.
Blackhole
An object greater than 25 solar masses whose gravity is so strong that the escape veolcity from it exceeds the speed of light
Population one stars are found in the disc. They are o and b stars. They are open clusters.
True.
Population two stars found in halo and are globular clusters. They are older stars.
true
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.
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.
Spiral Arms of milky way
Stable waves that are spiral and don't wrap up in themselves.
Hubble's Law
Everything in the universe is moving away from us and moving fast.
Determing age of universe 3
13.7x10 yeras old.
Hubble's law
Star clusters
cosmic backgroung radiation
Big Bang
Universe began in an exceptionally hot exceptionally small state. As it expanded it cooled allowing nuclei atom, stars, and galaxies to form.
nucleosynthesis
one element and making another element. Star becomes supernova it takes helium and that becomes carbon.
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.
