Studied by 116 people
Astronomical Unit
the average distance between the sun and the earth
Light year
the distance that light travels in a year
the celestial sphere
An imaginary sphere (dome) that models the projection of objects in the sky
Horizon
Line where the dome meets the earth
Zenith
Top of the dome, above your head.
Ecliptic Tilt
on the celestial sphere and is the apparent path of the sun over the course of the year.
Tropical Year
Based on the seasons
Sidereal year
Based on the earth’s orbit around the sun. (the true year)
Zodiac
the 12 constellations the sun moves through during the year.
Constellation
Bright stars that are grouped together
Eratosthenes
First person to get a fairly accurate determination of the Earth’s diameter.
Hipparchus
Discovered the position in the sky of the north celestial pole had altered over the previous century → precession “slow shift” of Earth’s axis.
Claudius Ptolemy
proposed a model for the solar system to explain retrograde motions of the planets
Epicycles
a small circle whose center moves around the circumference of a larger one.
Geocentric model
earth lays at the center of the universe
Aristotle
proposed geocentric model
Aristarchus of Samos
proposed that planets revolved around the sun but was ignored because of Aristotle’s following
Heliocentric Model
Planets orbit in circles around the sun
Galileo
built and used the telescope
Kepler’s first law ( The law of orbits )
Planet’s move around the sun in elliptical orbits (ellipses): ea. planets orbit about the sun is an ellipse.
Ellipse
Oval shaped path that celestial objects follow as they orbit the sun
Eccentricity
The determination of how oval an ellipse is. → length of the major axis
Kepler’s 2nd law
A planet moves faster when closer to it’s sun and slower when it’s farther
Kepler’s 3rd Law
the farther a planet is from the sun, the longer it’s orbital period.
Major axis
Diameter of the ellipse, stretching from one end to the other.
Semi major axis
Half of the major axis
Isaac newton
Father of the laws of motion
Angular momentum
The spinning power of an object (spinning or moving in a circle) The faster or heavier the more angular momentum.
Gravity
general force of attraction
Gravitational force
attractive forces between masses.
Aphelion
Farthest distance from sun and moves slowly
Perihelion
Closest distance to sun and moves fast
Escape speed
Speed needed to move away from Earth forever
refraction
the bending of light passing through air or water
solar day
earth’s rotation relative to the sun
sidereal day
earth’s rotation relative to distant stars
synchronous rotation:
rotates once on its axis while simultaneously orbiting earth once. → keeps the same face toward earth
sidereal month
time it takes moon to make a full 360 around earth
synodic month
time it takes moon to complete cycle of phases
Giant Impact Theory
proposes that the moon was formed from the debris of a massive collision between earth and another celestial body.
Solar Eclipse
Sun covered by moon
Lunar Eclipse
Moon dimming.
Annular Eclipse
ring of light
Total Solar Eclipse
Sun completely hidden
Penumbra
sun partially visible
umbra
sun completely blocked.
Electromagnetic Radiation
transmission of energy through space
Mechanical Wave
wave that needs a medium to travel through (ie. sound and water waves)
Electromagnetic Wave (EM)
wave that travels through vacuum, without medium (ie. radio, light, microwaves)
Photon
tiny packets of energy that makeup light
Inverse Square Law for Light Propagation
light becomes weaker the further it travels from its source
Electromagnetic Spectrum
range of EM radiation
Blackbody Radiation
type of light emitted by an object and absorbs light
Wien’s law
as an object gets hotter, its peak wavelength become smaller
Stefan-Boltzmann Law
as the temperature of an object increases, it radiates more energy.
Spectrometer
device to measure and analyze the properties of light such wavelength and energy
Atom
building block of all matter
Doppler Effect
wavelength of light shortens toward source, lengthens away from it.
Reflector
telescope using mirrors
Refractor
telescope using lens
Note 
Flashcard (22)