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136 Cards in this Set

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  • Back
  • 3rd side (hint)
Solar System
Sun and all the objects that orbit it
Milky Way Galaxy
Our galaxy!!! Nice chocolate snack. 100 billions stars. Can be seen more easily in the South Hemisphere.
Local Group
Groups of galaxies
Milky Way is one of two largest
Galaxy Clusters
Groups of galaxies with more than a dozen members bound by gravity
Big hot ball of nuclear fusion
Large object that orbits a star
Object that orbits another object (asteroids can have moons too!!!)
Possibly small and rocky object that orbits a star
Possibly small and icy object that orbits a star
Solar System
Technically only applies to our system, however, stupid (sometimes smart too!) scientists sometimes apply it to other systems. Basically a star and its planets
Many stars orbiting a common center
Many galaxies and clusters are packed closely together
Everything out there. Appears to be expanding.
Observable Universe
Everything that can be seen. Only a small part
Astronomical Unit (AU)
Length of the semimajor axis of Earth's orbit (AKA, how far the Earth is from the Sun.) 150 million kilometers.
Distance that light can travel in a year. 9.46 trillion kilometers.
Spinning of an object around it's axis. One day = one rotation. Line between the North and South Pole. Earth rotates West to East.
How long it takes to go around a object. One Year = One Revolution. Travelling at about 60,000 miles per hour.
The universe is expanding. Individual galaxies and clusters are not.
Big Bang Theory
The universe started expanding. Not necessarily an explosion.
Nuclear Fusion
Stuff that makes stars hot and bright. Lightweight atomic nuclei smash together and stick together make heavier nuclei.
When a star runs out of fuel, it makes a big boom.
The Orion Nebula
Giant cloud of dust and gas in which new stars are forming. About 1,500 light years from Earth.
Looking back in time
The farther we look in the distance, the further back we look in time.
Light travelling
Distance = speed X time
1 light-year = (300,000km) X 1 year)
365 Days 24 Hr 60 min 60S
________ X _____ X ______ X ___
1 year 1 day 1 hr 1 min

= 9,460,000,000,000 km
1 light year = speed X time
Ecliptic Plane
Earth's orbit defined in a flat plane around the sun.
Earth's tilt
23 1/2 degrees perpendicular to the ecliptic plane.
An orbit, which is not a perfect circle
Movement relative to nearby stars
70,000 kilometers per hour
Distant from galactic center
28,000 light years.
Galaxy's Halo
Stars only a small part of galaxies. Mass of galaxies seem outside of visible spectrum (stars). Possible dark matter on the outsides
Dark matter
Dark matter
Stuff that's dark, makes up most of the mass of the universe, and not known what it is.
Mass of the universe
Galactic Orbit
230 million years
Milky War-Andromeda Collision
Nearly 10 billion years away if it happens. Moving at 300,000 kilometers per hour.
Galaxies outside of the local group
Appears to be moving from us. The farther it is the faster it is moving
Moving from us
Edwin Hubble
Appears to be moving from us. The farther it is the faster it is moving
Moving from us
Sun-centered solar system in 1543
Claimed Earth moved around the Sun. Put under house arrest in 1633 by the Vatican. Church realized it was wrong, realized Earth was round and went around Sun in 1992.
Where is the center of the galaxy?
Trick question, there is none
Number of stars that can be seen with the naked eye
Specific region of the sky. IAU divides the sky into 88 constellations
Great Celestial Sphere
Greeks believed the Earth was surrounded by giant sphere of stars
North Celestial Pole
Giant Celestial Sphere right above the North Pole
North Pole
South Celestial Pole
Giant Celestial Sphere right below the South Pole
South Pole
Celestial Equator
Extension of Earth's Equator into space
Path the Sun takes per year around Celestial Sphere
Local Sky
The "dome" of the sky we can see
Boundary between the Earth and sky.
Directly overhead, 90 degrees
The half-circle from your north horizon to south horizon.
Angular Size
The size of an object in relation to your field of view. The Moon is about 1/2 degree.
Size in FOV
Angular Distance
Distance that separates objects
Subdivide each degree into 60 arcminutes
34 degrees, 43 arcminutes, 32 arcseconds
Subdivide each arcminute into 60 arcseconds. 34 degrees, 43 arcminutes, 32 arcseconds
North to South measurements. North Pole is 90^N degrees, South is 90^S degrees. Across the Earth
East to West measurements. Greenwich, UK is 0^. Down and Up the Earth.
Down and Up
Prime Meridian
The Longitudal line at Greenwich, UK. Is 0^
Near the North and South Poles, stars do not set, but make clockwise circles in the sky
Attitude of the Celestial Pole
Is equal to your latitude
Path on the ecliptic that passes 13 constellations
Winter Solstice
Northern Hemi receives it's least direct sunlight. Southern Hemi receives it's most direct sunlight. Around December 21 each year.
Spring Equinox
Sun shines equally on both hemispheres. Around March 21.
Summer Solstice
Northern Hemi receives most direct sunlight. Southern receives least direct sunlight. Around June 21 each year.
Fall Equinox
Sun shines equally on both hemispheres. Around September 21.
At what time is the Sun directly overhead?
Trick question, it is never directly above unless you're in the tropics.
Gradial change in the direction of Earth's axis in space. Only orientation that changes, Earth will remain at 23 1/2 degrees. Earth will point to Vega instead of Polaris.
Change of direction
Lunar Phases
Which direction the light hits the Moon, causing shadows on certain sides.
Anytime an object casts a shadow on another
Two points in each orbit at which the Moon crosses the surface
Moon and Eclipses
Lunar Eclipse
When Moon passes in Earth's shadow
Solar Eclipse
When Earth passes in Moon's shadow
Where sunlight is completely blocked by Moon in a Solar Eclipse
Where sunlight is slightly blocked by Moon in a Solar Eclipse
Saros Cycle
Eclipses occur in an 18 years, 11 1/3 day period
18 years, 11 1/3 days
Retrograde Motion
When a planet appears to go backwards because the Earth is in a tighter orbit than the outer planets from Earth.
Stellar Parallax
Apparent shifting of objects from different view points
Shifting of objects
Means "wanderer"
Created a 24 hour day with 12 hour parts. Used water clocks.
In Southern England. Created in 2750 B.C. to 1550 B.C. Sun rises directly over only on Summer Solstice.
Templo Mayor
In Aztec city of Tenochtitlan. Sun rose directly through the notch between the twin temples on the equinoxes.
Metonic Cycle
Every 19 years we get the same lunar cycles
Lunar cycles
Measured the Earth accurately in 240 BC.
Measured something
Geocentric Model
Earth as center of the universe
384 BC - 322 BC. Famous scientist.
His book, the Almagest described a Earth-centered model that remained in use many years later
Heavenly spheres and circles
Ptolemaic Model
Planets made "small circles" in orbit explaining retrograde motion.
Sun-centered solar system. Used AU to measure distances. Still believed in perfect circles of orbit.
De Revolutionibus Orbium Caelestium
Tycho Brahe
Kept records of universe. Best naked-eye records. Hired Johannes Kepler.
Johannes Kepler
Discarded perfect circles. Orbits were ellipses and circles.
Two points to draw an ellipse.
How much a planet deviates from a perfect circle
Circle and ellipses
Kepler's First Law of Planetary Motion
The orbit of each planet about the Sun is an ellipse with the Sun at the one Focus.
Closes to the Sun
Farthest point from the Sun
Semimajor Axis
Average distance from the Sun
Kepler's Second Law of Planetary Motion
As a planet moves around its orbit, it sweeps out equal areas in equal times.
Equal areas
Kepler's Third Law of Planetary Motion
More distant planets orbit the Sun at a slower average speed, obeying the following precise mathematical relationship:

p^2 = a^3

where p is planet's orbital period in years and a is its average distance from the Sun in astronomical units.
p^2 = a^3
Used the telescope. Found:
1. Sunspots on the Sun
2. Moon has mountains and valleys by looking at shadows
3. Strong evidence of stellar parallax
4. Jupiter had moons too
5. Phases of Venus
Scientific Method
Discovery Science
Going out and looking at nature to find something new
Hypothesis-driven Science
Proposing an idea and testing it
An "educated guess."
Occam's Razor
When we choose the simpliest answer
Explain a wide-range of observations
Based off evidence not treated scientifically
Ideas that fall outside mainstream thought
Sidereal Day
23 hours, and 56 minutes. When the Earth makes one full rotation
23 hours...
Solar Day
24 hour-day, based off the time it takes the Sun to make one rotation
Earth's Day Orbital Motion
1 degree, makes a 360 degree orbit in 365 days
360 degrees in one year
Synodic Month
When the Sun and Moon "meet" in the sky with every new moon. 29 1/2 days
Sidereal Month
Moon's true orbital period, 27 1/3 days
Sidereal Year
Time it takes to complete one orbit relative to the stars
Tropical Year
Cycle of seasons, 20 minutes shorter than sidereal year
Sidereal Period
Time it takes to orbit the Sun
Synodic Period
Time between being lined up with the Sun
When planets line up with the Sun
Lined Up
Opposite of the Sun, away from the Earth
Transit across the Sun
Greatest elongation
Farthest from the Sun
Apparent Solar Time
The Sun's actual position in the sky, using a sundial.
Mean Solar Time
The average of solar times. 12:00 for a sundial would not match up with a watch. Uses the average of 12:00 to tell time.
Standard Time
Time zones
Daylight Saving Time
1 hour ahead
Universal Time
Also called GMT, UTC, or Zulu. Greenwich's central time.
Leap Year
In the Julian Calendar, every fourth year has 366 days.
Gregorian Calendar
Leap years are skipped unless the century is divisible by 400
Pope Gregory XIII
Declared after Oct 4 would be Oct 15
Oct 15
Celestial Coordinates
Used to pinpoint locations on the celestial sphere
Similiar to Latitude
Right Ascension
Similiar to Longitude
Tropic of Cancer and Capricorn
Boundary of where the Sun aims straight down
Kepler's Third Law Formula
p^2 = a^3
Mass-energy conversion
Kepler's Third Law According To Newton
(m1 + m2)[Sun takes most room, planet is insignificant, it is 1] p2 = a3
Kinetic energy
v = SQRT (2G*M/R)