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Composition of Elements in the Universe Initially
Hydrogen 75%, Helium 25%, Metals 0% 
Composition of Elements in the Universe Today
Hydrogen 70%, Helium 28%, Metals 3% 
Fuse
To join together 
Star
Ball of gas that generates its own energy in the core by nuclear fusion 
Planet
Object that orbits a star 
Moon
"Rocky or Icy" object that orbits a planet 
Asteroid
Small rocky object that orbits a star 
Comet
Small icy object that orbits a star 
Solar System
Star plus the planets 
Jovian Plantes
The Gas Planets, Jupiter, Saturn, Neptune, Uranus 
Universe
All matter and energy 
The Milky Way Galaxy
Spiral galaxy composed of a highly flattened disk and a central "elliptical" bulge. The disk is about 100,000 light years (30kpc) in diameter. 
How many Stars in the Milky Way galaxy
100 Billion 
How old is the Milky Way Galaxy
13 Billion Years 
How far is the Sun from the center of the Galaxy
27,000 Light Years 
Astronomical Unit
The average distance between the Sun and the Earth (1.5 x 10^11) 
Light Year
The distance light travels in one year (3.0 x 10^8 m/s) 
Age of the Universe
13.75 Billion Years! 
Zenith
The point directly above you 
Horizon 
A great circle on the celestial field, 90 degrees from the zenith 
Nadir
The point directly below the zenith 
Meridan
Great circle moving North-South, and passing through the zenith 
Celestial Sphere
An imaginary around the Earth on which are "pinned" the sun, the moon, planets, and stars 
60 arcminutes
1 degree 
60 arcseconds
1 arcminute 
The planets, the moon orbit
Anti-clockwise 
Daily Motion
The Earth rotates once around its axis each day 
Annual Motion
The Earth rotates around the sun in one year (365 days) 
How far does the sun move in 1 day in regards to the background stars
1 degree to the east 
Why does the sky look blue
Because the Earth's atmosphere scatters Blue light better than Red light 
Ecliptic
The apparent motion of the sun on the celestial sphere 
Celestial Equator
Intersection of the plane passing through the Earth's equator and the celestial sphere. 
Equinox
When the sun crosses the celestial sphere 
Summer Solstice
Sun reaches most northerly point above the celestial equator 
Winter Solstice
Sun reaches most southerly point below celestial equator 
Seasons are caused by:
The tilt in the Earth's axis, and orbital motion of the Earth about the Sun 
Solar Day
Defined by the motion of the Sun 
Mean Solar Day
Defined as an entire day of 24 hours 
Sidereal
With respect to the stars 
Solar
With respect to the Sun 
Sidereal Day
One complete revolution, 23 hours 56 Minutes 
Sidereal Month
The moon that completes one revolution around the Earth 
How much the does the Moon move every day
13 Degrees to the East in regards to the background stars 
Synodic Month
The completion of a full cycle of the moons phases, takes 29.5 days 
Eclipse
One one object moves in front of another object 
Solar Eclipse
When the moon moves in front of the Sun and the Earth 
Total Eclipse
Hides the moon and only the Corona of the Sun is shown 
Annual Eclipse
Occurs when the alignment is perfect but the Moons anguladiameter is too small to fully block the Sun 
Lunar Eclipse
Occurs when the Earth passes in front of the Moon and the Sun, causing Earth's shadow falls on the moon 
The Line of Nodes
Is the intersection of between the two orbital planes 
Speed of Light
3.0 X 10^8 m/s 
Photons
Light particles that have no mass and no charge 
Electromagnetic Radiation
Varying field of Electric and Magnetic waves in the form of light 
Wavelength (Lambda)
Spacing between crests, measured in nm 
Frequency
The number of waves that pass an observer in 1 second, measured in Hz 
C=
(Wavelength)x(Frequency) 
Frequency=
((Planck's Constant)x(C))/(Wavelength) 
Spectrum
Light split into its own separate components or colors 
Spectroscopy
The splitting of light into its component wavelength's 
Refraction
The change in the direction of light as it travels from one medium to another 
The different types of visible light
Red (Longest Wavelength), Orange, Yellow, Green, Blue, Indigo, Violet (Shortest Wavelength) 
Types of Electromagnetic Radiation, Highest to Lowest Energy
Gamma, X-Ray, Ultraviolet, Visible, Infrared, Radio 
As radiation passes through a COLD gas it produces (Krichoff Law)
An Absorption Line Spectrum 
As radiation passes through a HOT gas it produces (Krichoff Law)
An Emission Line Spectrum 
Continuous Spectrum
Intensity of visible light changes smoothly with wavelength 
Emission Line Spectrum
Light emitted at only a few wavelength's because the intensity of electromagnetic radiation at that wavelength is greater than neighboring wavelength's 
Absorption Line Spectrum
A continuous spectrum in which dark bands are seen because the intensity of electromagnetic radiation at that wavelength is less than that of neighboring wavelength's 
Blackbody
Perfect absorber and emitter of electromagnetic radiation, which is a function of temperature and wavelength only, emits a continuous spectrum 
A real stellar spectrum
Not a perfect blackbody, it contains absorption lines and/or emission lines 
As a blackbody gets hotter
It moves further to shorter wavelength's 
Wein's (Displacement) Law
Lambda(max)= Constant (2.9 x 10^6 nm K)/Temperature 
As a Blackbody gets hotter
More radiation is emitted at all wavelength's 
Stefan-Boltzmann Law
L= 4(pi)(R)^2(sigma)(T)^4 
Sigma=
5.7x10^-8 
Neutral Atom
An atom with equal protons and neutrons, no charge 
Ground State
ALL electrons are in their lowest energy level 
Excited State
Added energy allows electrons occupy a higher energy level 
A photon is emitted when
Electrons jump to a higher energy level, emission line is produced 
A photon is absorbed when
Electrons jump to a lower energy level, absorption line is produced 
Lyman Series
The transition between the ground and the excited state 
Balmer Series
Transition from the 1st energy level to higher energy levels 
The Doppler Effect
(Lamba)-(Lambdao)/(Lambdao) The Change in Wavelength/The Wavelength measured at the source 
Chromatic Aberration
The light of different colors are focused at different lengths 
Parabolic and Spherical Mirrors
Suffer from Aberrations 
The collecting area of a single telescope
.25(pi)(diameter)^2 
Refracting Telescope
Collects Electromagnetic Radiation by Lenses 
Disadvantages of Refracting Telescopes (4)
1) Costly, 2) Suffer from Chromatic Aberrations, 3) Difficult to mount large lenses, 4) Difficult to make large lenses 
Advantages of Refracting Telescopes (1)
Long focal length gives good plate scale for astronomy 
Reflecting Telescopes
Focus light using mirrors which are parabolic in shape 
Advantages of Reflecting Telescopes
1) No Chromatic Aberration 2) Easy to build 3) Easy to mount 
Disadvantages of Reflecting Telescopes
1) Small fields due to Coma, 2) Resolution used to be limited (Not anymore) (Adaptive Optics) 
Schmidt Telescopes
Focus light using Mirrors and Lenses 
Resolution in Radians
1.22(Wavelength/Diameter) 
Resolution in arcseconds
2.52 x 10^5 (Wavelength/Diameter) 
Interferometry in Radio Telescopes
To improve resolution, two or more telescopes can be used simultaneously 
Kepler's First Law of Planetary Motion
Each planet's path around the sun is an ellipse with the sun at one of the focal points 
Kepler's Second Law of Planetary Motion
A planet moves along its elliptical path with a speed that changes in such a way that a line from a planet to the Sun sweeps out equal areas in equal intervals of time 
Kepler's Third Law of Planetary Motion
The ratio of a cube of a planet's Semi Major Axis, a, to the square of its orbital p, is the same for each planet 
Cosmic Ray
High energy protons coming from outer space, not electromagnetic radiation 
Composition of the Universe
Atoms= 4.6%, Dark Matter= 23%, Dark Energy= 72%

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