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47 Cards in this Set

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What does a phase of the moon represent?
It represents the amount of the moon's day side that we can see from Earth
What are the 3 phases?
Cresecent: we see less than 50% of the moon's dayside
Quarter: We see 1/2 of the moon's dayside (25%)Gibbous: more than 50% of moon's dayside
New Moon Phase
only phase where the moon and sun are in the same direction in the sky (next to each other), we "view" the moon's night side ... but in actuality, the moon seems invisible
First Quarter Phase
7-8 days after new moon
We se 50% of the day side
We see the western/right side of the moon
Full Moon Phase
7-8 days after first quarter
we see 100% of the moon's day side
Only phase where the sun and moon are opposite in the sky
Last Quarter Phase
7-8 days after full moon
We see 50%
We see the Eastern/left side of the moon
What are the intermediate phases of the moon?
Waxing: moon appears more full, and it's during the 1st half of the phase cycle

Waning: we see less of the day side, and it's during the 2nd half of the cycles
What is a solar eclipse?
It is when the shadow cast by the moon hits a portion of the Earth
As a result, we see the moon partly/completely blocking the photosphere
How is a solar eclipse possible?
-The moon and the sun have just about the same angular diameter
- The sun is 400x wider than the moon, but amazingly it is almost 400x further away
What are the necessary conditions for a solar eclipse?
1. New Moon (ocurrs about once a month)
2. Needs to cross the Earth's orbital plane at the same time that it is new moon
Why doesn't an eclipse occur every month?
Because the Moon's orbital plane is inclined by 5 degrees to the Earth's orbital plane ... and during most new moons, the moon is either a little above, or below the Earth's plane. This creates an unfavorable situation and an eclipse cannot happen
What is the saros cycle?
A formula used to predict when another solar eclipse will be - not the NEXT one, just another one

Date of a solar eclipse - plus 18 years, 11 days
How often can we expect solar eclipses to happen?
Anywhere from 0-2 times per calendar year
What are the umbra and penumbra?
Umbra: the inner, darker region of a shadow (very small in comparison to Earth, but still 100 to 200 miles wide) - people on earth in the umbra, experience a total solar eclipse

Penumbra: lighter, outer region of shadow, where people on earth see only a partial eclipse
What is considered the Eclipse of the Century, and why?
July 11, 1991
Not called this because it was any longer or better, just because it's path of totality passed over Hawaii where there were a bunch of the world's largest/best telescopes already established. Chance of a lifetime for solar science - and the first time that an eclipse had actually passed over a major observatory.
What are some problems that could harm scientisits from gathering information during an eclipse - some things they have to worry about???
Weather, Human Error, for the Hawaii one (clouds and volcanic dust)
What did they succeed in finding during the "eclipse of the century"?
They were looking for evidence of magnetic heating in the Corona, by taking high resolution photos of the surface, and FOUND infrared emissions, and a more densely packed inner atmosphere than they previously thought
What are the moon's furthest and closest points called?
Perigee - closest
Apogee - farthest
What makes an Annular Solar Eclipse different?
Though it is in the new moon phase and on the Earth's orbital plane - it is near apogee and so the moon appears smaller than normal. As a result, th emoon cannot cover the Sun's photosphere and we see a ring of it.
Talk about the motion of the shadow in a solar eclipse ...
-The shadow moves because of the Moon's revolution and the Earth's rotation
-The path that it moves in is the "path of totality" (represents the path of the umbra across the earth's surface)
-Duration of the shadow/totality in a given spot is only from 2-4 minutes
What is a lunar eclipse?
The shadow cast by Earth that hits the moon
What is needed for a lunar eclipse to occur?
- Requires a full moon
- The moon must be directly on the Earth's orbital plane
What does a lunar eclipse look like?
As the moon enters the umbra there is no direct sunlight, so we would think it would be invisible?
- Actually, the Earth's atmosphere plays 2 different roles in that is the sunlight passes through it, and the shorter wavelengths are scattered out, leaving only red/orange to pass through. The atmosphere acts like a lens and bens the red/orange around the Earth towards the moon, so we see a redish moon during the eclipse
What are the contents of our Solar System?
- 1 star, our Sun
- 9? planets
- 100+ satellites and moons
- 100,000's asteroids
- millions of comets
Where did the moons in our solar system possibly come from?
- capture
- collision/capture
- "primordial" and have been around since the beginning
Why is there controversy about Pluto being a planet?
*It is the exception to almost all the rules:

1. Does not orbit in the same plane on the sun's equator as all of the other planets
2. does not have a nearly circular orbit
3. does not rotate in the same direction that it revolves (it rotates clockwise, instead of counter)
4. does not spin quickly
5. does not fit into either of the planet groups (terrestrial and jovian)
What are some major planet characteristics that most of them have in common?
1. all planets orbit the sun in the same direction
2. they orbit in the same plane (through the sun's equator ... except pluto
3. orbit in nearly circular orbits (except mercury, mars, pluto)
4. rotate in the same direction they revolve (counter clockwise) ... except venus, uranus, pluto
5. most planets spin quickly
(except mercury, venus, pluto)
What are the two planet groups?
-Terrestrial: like Earth, including Mercury, Venus, Earth and Mars
-Jovian: like Jupiter, including Jupiter, Saturn, Uranus, Neptune
*also known as the gas giants
T v. J comparison
- distance to sun
T = closer
J = further
T v. J comparison
- temperature
T = warmer
J = colder
T v. J comparison
- revolution speed
T = faster
J = slower
T v. J comparison
- revolution period
T = shorter
J = longer
T v. J comparison
- radius
T = small
J = large
T v. J comparison
- mass
T = small
J = huge
T v. J comparison
- density/composition
T = high density
minerals, metals (iron, nickel, etc)
J = low density
ices, gases (hydrogen, helium)
T v. J comparison
- surface
T = solid
J = gaseous
T v. J comparison
- amount of atmosphere
T = very little to none
J = huge
T v. J comparison
- rings
T = none
J = all have them, yes
T v. J comparison
- # of moons
T = few to none
J = many many moons
T v. J comparison
- rotation period
T = longer period
J = shorter period, spins the fastest
What would we expect about the seasons, but isnt really true?
Because perihelion is the point closest to the sun, we would expect it to be summer, and the opposite, with aphelion being winter. This is actually not the case, because perihelion for us is Jan 3rd (winter) and aphelion is July 6th (summer). Because the aphelion and perihelion are not that much different from that of the avg distance from the sun it's not a huge contributing factor in the change in seasons for us
What's up with a planet's tilt?
Earth = 23 1/2 degrees
Consequence - 1 hemisphere receives more direct sunlight at a given time

Tilt Affects:
- length of daylight hours
- height of sun around noon
- intensity/concentration of sunlight

**In general:
- Greater tilt = more seasonal differences
- Less tilt = less differences
What is significant about March 21 and Sept 21?
The only two days that the sun rises due east and sets due west
- called the equinoxes
- only 2 days of the year that have exactly 12 hrs day and 12 hrs night
Sun stuff from March 21st through Sept 21st
- Sun rises NORTH of due east
- Sun sets NORTH of due west
- daylight hours are greater than 12 hrs. (longer days)
- Sun is very high in the sky around noon
Sun stuff from Sept 21st through March 21st
- Sun rises SOUTH of due east
- Sun sets SOUTH of due west
- daylights hours are less than 12 hrs (shorter days)
- Sun is low around noon
Why is summer, summer?
The days are longer and the usn is high in the sky for several hours, which results in lots of concentrated sunlight and lots of solar energy intake ... which added up over weeks leads to warmer temperatures
Why is winter, winter?
The days are shorter, and even at noon the sun is low (and pretty weak) so the sunlight had a low concentration leading to a low amount of solar enery intake. Added up over many months, it results in it being colder.