Astronomy Prologue
Terms
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- Connections of the brightest stars in to configurations
- constellations
- the appearance of stars as if they were glued to a ceiling overhead led to the the idea of the
- celestial sphere
- What is the major reason the idea of the celestial sphere is INCORRECT?
- stars are not all in one celestial sphere they have a certain depth to them. from Earth, stars appear to be in two dimensions in reality the stars of a given constellation may be very far apart.
- Celestial sphere also explains how the stars move at night...
- Since stars do not seem to "move" independently they all "move" (although again they dont move, we move) as one unit, early astronomers believed the celestial sphere passed from east to west across the unmoving earth.
- What structure do all stars in the sky do all stars seem to rotate about (in other words what fixture does NOT move)? why?
- Polaris (the north star). it lies on the earth's rotational axis.
- From a modern standpoint what causes the motion of the stars in the sky?
- The apparent motion of stars is a result of the earth's rotation NOT that of the imaginary celestial sphere.
- In celestial cordinates, how are alpha, betta, gamma etc. designated within a constellation?
- The brightest stars in a constellation are assigned: ALPHA, then betta and so on.
- More precise celestial coordinates include ______ which is the equivalent to earth's lattitude measures and ____________ which is equivalent to earth's longitude measurement.
- declination , right acension
- How is declination measured?
- From the celestial equator (0 degrees) the angle (in degrees) from parallel to the celestial equator to the object. F.e: North pole + 90 and south pole = -90.
- Solar day
- 24 hours. the time from one moon to the next moon.
- siderial day
- Each day the earth rotates around the sun and on its axis. rotation around its axis is = to 360 degrees but the movement around the sun causes it to travel a little bit more than 360 degrees to make it to the exact same place. about 4 minutes shorter. (23 hrs 56 min)
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Zodiac signs
-how did they come about. - the view of the night sky changes as Earth moves in its orbit about the sun. At different parts of the year, different constellations can be seen.
- what accounts for the Earth's seasons?
- the 23 1/2 degree tilt on which the Earth rotates. Thus 1/4 of the year (3 months) it is summer in the north/south hemisphere and the opposite in the other.
- how come the season's alternate depending on where a person lives?
- because the tilt makes one hemispher closer to the sun than the other. NOT THAT THE EARTH GETS CLOSER IN ONE PART OF THE YEAR.
- Points in time where the ecliptic intersects with the celestial sphere. these are called...
- equinox
- Vernal equinox
- occurs in the spring (between Summer and winter) ~ March 21st
- Automnal equinox
- occurs in the fall (September 21)
- Siderial year vs tropical year.
- The earth has a tropical year of 365 days (time required for earth to make one full rotation around the sun. Siderial year also takes into account the gravitational forces that cause the earth to "wobble like a top" and cause it to take 365 days and 20 minutes. These are SLOW CHANGES OVER LONG LONG PERIODS OF TIME.
- How far is the moon from earth in miles?
- 240,000 miles
- What is the disstance to the nearest star?
- 2e 13 miles
- What is the distance to the closest constellation? What is its name?
- Andromeda; 2e 19.
- How long does it take for the light from the sun to reach earth?
- 8 minutes (8 light minutes)
- How far in light years is the nearest star (other than the sun)?
- 4 light years
- What is important to remember about what we observe from distant planets?
- we see distant objects as they were in the past!
- when we see the stars moving in the sky, what are we really observing?
- The motion of the stars is the result of the Earth’s rotation
- How many degrees per day does earth cover in its orbit around the sun?
- 360 degrees/year /365 days/yr= about 1 degree/day
- during winter why are their shorter days?
- because the sun rises lower in the sky
- What is the idea of the "precession of the equinox?"
- The gravitational force tug-of-war on earth between the moon and the sun has lessened the earth's tilt
- Our calender is based on what
- lunar orbit
- At what time does the moon rise if there is a full moon?
- Noon
- what is a solar eclipse?
- This is where the moon blocks the solar light from reaching earth.
- From where can a solar eclipse be seen?
- Only in select places around earth.
- What occcurs in a lunar eclipse?
- This is where the Earth comes between the sun and the moon.
- Where on earth can a lunar eclipse be seen?
- From anywhere that the moon can be seen.
- Solar eclipses occur at ________ moon while lunar eclipses occur at ________ moon.
- New ; Full
- Why isn't their an eclipse every month?
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Because the moon is on a tilt from earth.
Eclipses only occur when the moon crosses the earth's ecliptic during a new moon (solar eclipse) or during a full moon (lunar eclipse)