The Solar System Part 1
Terms
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- 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
- 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
- Galaxy Clusters
- Groups of galaxies with more than a dozen members bound by gravity
- Star
- Big hot ball of nuclear fusion
- Planet
- Means "wanderer"
- Moon
- Object that orbits another object (asteroids can have moons too!!!)
- Asteroid
- Possibly small and rocky object that orbits a star
- Comet
- Possibly small and icy object that orbits a star
- Galaxy
- Many stars orbiting a common center
- Supercluster
- Many galaxies and clusters are packed closely together
- Universe
- 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.
- Light-Year
- Distance that light can travel in a year. 9.46 trillion kilometers.
- Rotation
- Spinning of an object around it's axis. One day = one rotation. Line between the North and South Pole. Earth rotates West to East.
- Revolution
- How long it takes to go around a object. One Year = One Revolution. Travelling at about 60,000 miles per hour.
- Expansion
- 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.
- Supernovae
- 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.
- 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 - 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.
- Ellipse
- 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
- Stuff that's dark, makes up most of the mass of the universe, and not known what it is.
- 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
- Edwin Hubble
- Appears to be moving from us. The farther it is the faster it is moving
- Copernicus
- Sun-centered solar system. Used AU to measure distances. Still believed in perfect circles of orbit.
- Galileo
-
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 - Where is the center of the galaxy?
- Trick question, there is none
- Number of stars that can be seen with the naked eye
- 2000-3000
- Constellation
- 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
- South Celestial Pole
- Giant Celestial Sphere right below the South Pole
- Celestial Equator
- Extension of Earth's Equator into space
- Ecliptic
- Path the Sun takes per year around Celestial Sphere
- Local Sky
- The "dome" of the sky we can see
- Horizon
- Boundary between the Earth and sky.
- Zenith
- Directly overhead, 90 degrees
- Meridian
- 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.
- Angular Distance
- Distance that separates objects
- Arcminutes
-
Subdivide each degree into 60 arcminutes
34 degrees, 43 arcminutes, 32 arcseconds - Arcseconds
- Subdivide each arcminute into 60 arcseconds. 34 degrees, 43 arcminutes, 32 arcseconds
- Latitude
- North to South measurements. North Pole is 90^N degrees, South is 90^S degrees. Across the Earth
- Longitude
- East to West measurements. Greenwich, UK is 0^. Down and Up the Earth.
- Prime Meridian
- The Longitudal line at Greenwich, UK. Is 0^
- Circumpolar
- 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
- Zodiac
- 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.
- Precession
- 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.
- Lunar Phases
- Which direction the light hits the Moon, causing shadows on certain sides.
- Eclipse
- Anytime an object casts a shadow on another
- Nodes
- Two points in each orbit at which the Moon crosses the surface
- Lunar Eclipse
- When Moon passes in Earth's shadow
- Solar Eclipse
- When Earth passes in Moon's shadow
- Umbra
- Where sunlight is completely blocked by Moon in a Solar Eclipse
- Penumbra
- Where sunlight is slightly blocked by Moon in a Solar Eclipse
- Saros Cycle
- Eclipses occur in an 18 years, 11 1/3 day period
- 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
- Egyptians
- Created a 24 hour day with 12 hour parts. Used water clocks.
- Stonehenge
- 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
- Eratosthenes
- Measured the Earth accurately in 240 BC.
- Geocentric Model
- Earth as center of the universe
- Aristotle
- 384 BC - 322 BC. Famous scientist.
- Ptolemy
- His book, the Almagest described a Earth-centered model that remained in use many years later
- Plato
- Heavenly spheres and circles
- Ptolemaic Model
- Planets made "small circles" in orbit explaining retrograde motion.
- Tycho Brahe
- Kept records of universe. Best naked-eye records. Hired Johannes Kepler.
- Johannes Kepler
- Discarded perfect circles. Orbits were ellipses and circles.
- Foci
- Two points to draw an ellipse.
- Eccentricity
- How much a planet deviates from a perfect circle
- 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.
- Perihelion
- Closes to the Sun
- Aphelion
- 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.
- 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. - Scientific Method
-
Observations
Question
Hypothesis
Prediction
Test - Discovery Science
- Going out and looking at nature to find something new
- Hypothesis-driven Science
- Proposing an idea and testing it
- Hypothesis
- An "educated guess."
- Occam's Razor
- When we choose the simpliest answer
- Theory
- Explain a wide-range of observations
- Pseudoscience
- Based off evidence not treated scientifically
- Paradigm
- Ideas that fall outside mainstream thought
- Sidereal Day
- 23 hours, and 56 minutes. When the Earth makes one full rotation
- 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
- 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
- Conjunction
- When planets line up with the Sun
- Opposition
- Opposite of the Sun, away from the Earth
- Transit
- 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
- Celestial Coordinates
- Used to pinpoint locations on the celestial sphere
- Declination
- 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
- E=mc^2
- 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)