Astronomy Exam #1
Terms
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- 1 Astronomical Unit
-
93 Million miles
1 AU = distance from sun to earth - Ecliptic
- path sun travels in one year
- Andromeda Galaxy
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Farthest object naked eye can see
2.2 Mly away - Circumpolar Constellations
- Never Rises, Never Sets
- Plane of equator and ecliptic are ____ degrees apart
- 23 1/2
- Precession
- Gravitational force from sun and moon make the axis change it's tilt at times -- makes the spin axis go around in a circle
- Rotation
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Rotation of the earth on its spin axis.
One day. - Revolution
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Rotation of earth around the sun.
One year. - We always see the same side of the moon. Why?
- Moon rotates once on its spin axis in the same time as it revolves once around Earth.
- New Moon
- Completely dark.
- Quarter Moon
- Half lit up
- Full Moon
- Completely lit up
- Waxing moon
- crescent or gibbous getting bigger between new moon and quarter moons
- Waning moon
- crescent or gibbous getting smaller
- Sidereal Period
- Time for the moon to go once around relative to the STARS
- Synodic Period
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New moon to new moon
Earth has moved. Have to go further to catch back up to sun and get all three object lined up the same way. - Lunar Eclipse
- Moon covered up by Earth
- Solar Eclipse
- Sun covered up by moon
- Lunar eclipses only occur with a _____ moon.
- Full
- Fully eclipsed moon is ________ in color
- copper-red
- Lunar eclipses take about ____
- Six hours
- A solar eclipse in totality last only _______
- 2-3 minutes
- Can see _______ and _______ when photosphere is covered during eclipse.
- chromosphere and corona
- Annular Eclipse
- Partial Eclipse
- Line of Nodes
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Where planes of orbit of earth and moon cross
Line of nodes must point at sun for an eclipse - From Lunar Eclipses the ancient Greeks knew ________
-
the earth is a sphere
due to earth's shadow cast on the moon - Eratosthenes
- Figured out circumference of the earth
- Aristarchus of Samos
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Thought he figured out distance to sun - 20 times distance to the moon.
First person to predict the sun was the center of the solar system. - Parallax
- Cannot be seen with naked eye - only with telescope.
- Distance to the nearest star
- 1 parsec
- Naked Eye Planets
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Mercury
Venus
Earth
Mars
Jupiter
Saturn - Non-naked Eye Planets
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Uranus
Neptune
Pluto - Planets are found in a 16 degree band around the ______
- ecliptic
- Retrograde Motion
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Reverse Motion
Planets at their brightest
Due to differing speeds - _____, ______, ______ can be found anywhere on the ecliptic relative to the sun
- Jupiter, Mars, Saturn
- _______ never more than 28 degrees from the sun
- Mercury
- _____ never more than 47 degrees from the sun
- Venus
- Apparant Magnitude
-
brightness of an object
Negative magnitudes: more negative, brighter - North Celestial Pole moves about 1 degree every 70 years due to ______
- precession
- Elongation
- Planet as far from sun as it could possibly be (as it appears from Earth)
- Opposition
- the configuration of a planet when it appears opposite the sun in the sky
- Conjunction
- the arrangement of a planet in the same part of the sky as the sun
- For the outer planets, retrograde motion occurs at _________.
- Opposition
- Thales of Miletus
- The universe is a rational place and the human mind can understand the way it works.
- Pythagoras
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Mathematics is the way to understand the universe.
Greeks were big on symmetry. - Plato
- Uniform Circular Motion for objects in the sky
- Eudoxus
- Built first model of the universe with spheres moving in Uniform Circular Motion
- Aristotle
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Earth is changeable and imperfect; the heavens are permanent and perfect.
Earth is at rest at the center of the universe (Geocentric Model) - Hipparchus
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Made a systematic catalog of about 850 stars.
First person to notice Precession.
Divided stars into brightness ranges - magnitude.
Mag 1 - Brightest
Mag 6 - Dimmest - Ptolemy
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had the confusing stupid model of the planets.
Earth in the center of the universe
Compendium of Greek Astronmical Knowledge - Copernicus
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Sun-centered solar system (Heliocentric Model)
Orbits of the planets were still circles.
Determined relative distances between planets and the stars - Closer in the planet to the sun, the ______ it is moving.
- Faster
- Tycho Brahe
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No telescope, naked eye observations. Made the best observations that had ever been made of the planets over 20 years.
Observed a supernova. - Johannes Kepler
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Copernican Model
Theory must fit the data within the accuracy of the measurements. - Kepler's First Law
- The planets move on ellipses with the sun at one focus.
- Kepler's Second Law
- A line from a planet to the sun sweeps over equal areas in equal intervals of time, thus the planet must be moving at different speeds at different parts of the orbit.
- Kepler's Third Law
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Period of the orbit squared = length of semi-major axis cubed
"Harmonic Law"
Planets with bigger orbits move slower. - Galileo Galilei
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First person to use a telescope to observe the sky.
Moon has mountains and valleys.
Milky Way is made from many faint stars.
Galilean Moons (4) of Jupiter clearly orbit Jupiter, not the Earth.
Sunspots on the sun - not perfect.
Saw that the sun was rotating.
Venus goes through a full set of phases (proved Copernicus right) - Galileo on Physics
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Falling objects accelerate.
Law of Inertia - Law of Inertia
- An object with a given velocity will maintain that velocity unless acted on by a force
- Issac Newton
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Calculus, Motion, the Law of Universal Gravity
Linked motion on Earth to motion in the sky. - Newton's First Law
- Law of Inertia
- Newton's Second Law
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Acceleration is a change in a velocity (change in speed or direction)
F = ma - Newton's Third Law
- To every action, there is an equal and opposite reaction.
- Newton - Law of Universal Gravitation
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F = G Mm
r squared - Bound Orbits
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Circle, Ellipse
Conic Sections - Unbound Orbits
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Parabola, Hyperbola
Conic Sections - Orbits must have:
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1.Tangential Velocity
2. Falling
Gravity produces acceleration.