Term
How is the sky organized? |
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Definition
| Ancient astronomers pictures the stars as all being attached to an imaginary sphere surrounding the Earth called the celestial sphere, with all of the stars being at the same distance from the Earth. It has no physical reality, but it serves as a useful way to visualize the arrangement and motions of celestial bodies. |
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Term
What is the role of constellations? |
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Definition
- Def: an officially recognized grouping of stars on the night sky. Astronomers divide the sky into 88 constellations, mostly named after mythological animals, “characters” or objects.
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Term
| What is the Bayer Designation System? How does it work? |
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Definition
| - Johann Bayer (1603) developed the modern system of star designations. In order for it to work, you must take an of the letters from the Greek alphabet [alpha(brightest), beta(2nd brightest), gama(3rd brightest), delta(4th brightest)] and place it in front of a possessive ending (Ex: Taurus, Leo, Scorpius, ect.) For example: Alpha-Leo is the brightest star in the Leo constellation. |
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Term
| Components of the celestial sphere: |
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Definition
| As the celestial sphere turns, two points on it do not move. These points are defined as the north and south celestial poles. The celestial poles like exactly above the North and South Poles of the Earth |
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Term
| What is the North celestial pole? |
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Definition
| The point on the celestial sphere directly above the Earth’s North Pole. The star Polaris happens to lie close to this point, and other objects in the northern sky appear to circle around this point. |
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Term
| . What is the South celestial pole? |
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Definition
| The imaginary point on the celestial sphere direct over the Earth’s South Pole. Objects on the sky appear to circle around this point as viewed from Earth’s Southern hemisphere. |
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Term
| What is the celestial equator? |
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Definition
| An imaginary line on the celestial sphere lying exactly above the Earth’s equator. It divides the celestial sphere into northern and southern hemispheres |
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Term
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Definition
| The path followed by the Sun around the celestial sphere. The path gets its name because eclipses can occur only when the Moon crosses the ecliptic. |
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Term
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Definition
| The apparent daily motion of celestial objects that rise in the east and set in the west. It is the result of the Earth going west-to-east. |
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Term
What is the difference b/w revolution and rotation?
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Definition
| Revolution = When something ORBITS around something. Rotation = When something is SPINNING on its axis. |
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Term
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Definition
| The time interval from one sunrise to the next sunrise or from one noon to the next noon. That interval is not always exactly 24 hours but varies throughout the year. For that reason, we use the mean solar day (which, by definition, is 24 hours) to keep time. 1 hour = 1/24th of a solar day. |
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Term
What is the sidereal day?
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Definition
| The length of time from the rising of a star until it next rises. The length of the Earth’s sidereal day is 23 hours 56 minutes 4.091 seconds. |
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Term
| What do we observe through the seasons? |
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Definition
The Sun at noon is high in the sky in summer and low in the sky in winter. The earth rotates on the rotation axis. The constancy of our planet’s tilt as we move around the Sun causes sunlight to fall more directly on the Northern Hemisphere for half of the year and more directly on the Southern Hemisphere for the other half of the year. A surface directly facing the Sun receives the most concentrated sunglight and if the surface receives the sunlight at an angle, the light is spread out over a larger area and therefore is less concentrated.
Summer: Long days, short nights. Sun passes higher in the sky = hotter temperatures.
Winter: Short days, long nights. Sun passes lower in the sky = cooler temperatures.
*Summer solstice=June 21st (longest day of the year). Winter solstice=December 21st (shortest “”) |
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Term
Lunar Phases
1. What do we observe? |
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Definition
| - New moon, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent, new moon. Material of the moon is similar to that of Earth and does not contain much iron (just like Earth). Albedo=the amount of light that is reflected from a material. Average reflection of the moon is 11%. |
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Term
| What does synchronous rotation mean? How does it affect what you see of the moon? |
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Definition
| - It is the condition that a body’s rotation period is the same as its orbital period. The moon’s rotational period (how long it takes to spin on its axis) = the moon’s revolution period (how long it takes to orbit around the Earth). Because of the synchronous rotation, we only see one side of the moon. |
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Term
| Why do the phases of the moon occur? |
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Definition
| We see the Moon’s shape change because as it moves around us, we see different amount of its illuminated half. For ex: when the Moon lights approximately opposite the Sun in the sky, the side of the Moon toward the Earth is fully lit. On the other hand, when the Moon lies approximately b/w us and the Sun, its fully lit side is turned nearly completely away from us, and therefore we glimpse at most a sliver of is illuminated side. |
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Term
What are the different types of eclipses?
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Definition
| A total solar eclipse is when the Moon passes directly b/w the Sun and the Earth and blocks our view of the Sun. A lunar eclipse is when the Moon passes through the Earth’s shadow as it moves through the portion of its orbit opposite the Sun. |
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Term
| Why don’t eclipses always occur? |
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Definition
| - Eclipses can occur only when the Moon is within about 1 degree of crossing the ecliptic – the plane of the Earth’s orbit around the Sun. This usually occurs only twice during the year. |
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Term
| How is the duration of totality determined? What makes it longer/shorter? |
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Definition
| The duration of totality is measured in min/sec. It is how long the umbra takes to cross over any given location on the surface of the Earth. The duration can be longer/shorter depending on the size/speed of the shadow. |
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Term
| Describe the observed motions of the planets (how do they move throughout the sky?) |
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Definition
| It was believed that the planets orbited around the Earth in retrograde motion. Like the Sun and the Moon, the planets would usually move from west to east through the stars. |
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Term
Describe the Ptolemeic model (Be able to describe it and how it worked)
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Definition
| The Earth is the center of the universe, all celestial bodies revolve around the Earth, all celestial bodies are perfect and unchanging, and all celestial bodies exhibit uniform circular motion |
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Term
| The Copernican Model (how was it superior to the Ptolemeic model?) |
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Definition
| The Copernican Model placed the Sun at the center of the solar system with the Earth orbiting the Sun with the other planets. |
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Term
| Tycho Brahe (what did he contribute to our understanding of astronomy?) |
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Definition
| Brahe was the first person to make the most accurate measured representation of the sky using tools. |
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Term
| Johannes Kepler ( The Three Laws of Planetary Motion – be sure to apply the knowledge, don’t just memorize them). |
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Definition
- #1=The orbit of a planet around the Sun is in the shape that occupies one of the two foci.
- #2=A planet moves fastest in its orbit when it’s closest to the Sun, and moves slowest in its orbit when its farthest from the Sun.
- #3=The square of the orbital period of a planet is proportional to the cube of its orbital distance. |
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Term
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Definition
- Galileo provided observational support for Heliocentric cosmology. He was the first to use telescopes to observe celestial objects, which led to:
*discovery of a galaxy (Milky Way is full of stars)
*Mountains of craters on the moon
*Discovered that the Sun is a rotating body (“Spots” on the Sun)
*Discovered that it’s okay for an orbit not to go around the Sun (rings of Saturn)
*Discovered the phases of Venus (shows heliocentric model)
*Discovered the fourth largest moon of Jupiter – Galilean Satellites (Showed that you can have a moving body and keep its moons orbiting. (Ex: Both the Earth and the Moon move around the Sun. The Moon continues to orbit around the Earth while at the same time moving around the Sun). |
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Term
What is Newton's 1st Law of Motion?
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Definition
| - #1= “A body at rest remains at rest unless acted upon by an outside force. A body in motion remains in motion moving in a straight line at constant speed unless acted upon by an outside force.” (Ex: When throwing a baseball, gravity is the outside forced curving it down. Air particles and resistance prevents its constant speed). |
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Term
| What is Newton's 2nd Law of Motion? |
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Definition
| - #2= “The acceleration of an object is directly proportional to the applied force and inversely proportional to its mass.” (Ex: F could be the force you feel when accelerating on a turn on the freeway. When (a)=0 there is no direction or velocity so there is no force. (F = m a) *Anytime an object with mass experiences acceleration there has to be a resulting force. |
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Term
| What is Newton's 3rd Law of Motion? |
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Definition
| - #3=For every force there is an equal but opposite force.” (Ex: Hitting a car in a phone booth=BOTH the phone booth and the car are damaged). |
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Term
| 2. What are the approximate dates of sunrise and sunset at the South Pole? Describe the appearance of the Sun from the South Pole on the first day of each season in a year. |
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Definition
| - The dates of sunrise and sunset are March 21st and September 23rd. On March 21st(Vernal Equinox) the Sun crosses the Celestial Equator moving from south-to-north. On September 21st(Autumnal Equinox)the Sun rises exactly due East. On June 21st (Summer Solstice) the Sun is at northern-most point. On Winter Solstice the sun rises south-east, sets south of west. |
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Term
| 3. Describe Galileo's major telescopic discoveries and discuss the significance of each one to the heliocentric model. |
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Definition
- Discovered that the Milky Way is full of stars (discovery of a galaxy)
- Mountains and craters on the Moon
- “Spots on the Sun” (discovered that the Sun is a rotating body)
- Discovered rings of Saturn (discovered that it’s okay for an object to not orbit around the sun)
- Discovered the phases of Venus (shows heliocentric model)
- Discovered the fourth largest moon of Jupiter – Galilean Satellites (showed that you can have a moving body and keep it’s moon orbiting. Ex: Earth can orbit around the Sun while the Moon continues to orbit around the Earth) |
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Term
5. Describe the contributions to astronomy made by a) Copernicus; b) Tycho Brahe; c) Kepler. How were the contributions similar? How were the contributions different?
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Definition
a) Copernicus resurrected the idea of heliocentrism and shows evidence that it could possibly be true. He placed the Sun at the center of the solar system with the planets in the correct order. The Earth revolved around the Sun with the other planets.
b) Brahe was the first person to make a most accurate representation of the sky using measurable tools. |
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Term
| 6. Using Newton's Laws, explain why the Moon does not fall to the surface of the Earth, or why the planets do not fall into the Sun. |
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Definition
| - In addition to falling toward the Sun, the planets are moving sideways, around the Sun. This is the same as if you have a weight on the end of a string and swing it around. You are constantly pulling it toward you, but the motion sideways keeps it swinging around. Like the string, the Sun’s gravity pulls on the planets, but the planets have enough sideways motion to keep them in their orbits. |
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