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Horizons Exploring the Universe
Ch. 1-3
79
Astronomy
Undergraduate 1
09/26/2011

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Cards

Term
who came up with the magnitude scale?
Definition
Hipparchus
Term
what is the equation to determine the intesity ratio of two stars with different magnitudes?
Definition
subtract the larger magnitude (dimmer) from the smaller magnitude and enter it into calculator as 2.512 ^ (answer from subtraction)
Term
what is the equation to determine the magnitude difference of two stars?
Definition
enter in calculator: LOG(dimmer star/brighter star) and multiple this by 2.512
Term
How big is an AU?
Definition
about 150,000,000 km
Term
how are stars named?
Definition
by their Greek letter for brightness in that constellation (alpha=brightest, beta=2nd brightest)
Term
At what magnitude do we start to have difficulty seeing stars?
Definition
about 6
Term
what's ano word for zenith?
Definition
altitude
Term
what's ano word for zenith?
Definition
altitude above the horizon
Term
what is the meridean?
Definition
it goes North to South and splits the sky east and west
Term
what is nadir?
Definition
directly below you
Term
what's the horizon?
Definition
90 degrees from the zenith
Term
what is a light year?
Definition
the distance light can travel in a year
(about 10 trillion km)
Term
how many arcminutes are in one degree?
Definition
60' arcminutes
Term
how many arcseconds are in an arcminute?
Definition
60" arcseconds
Term
what is one finger about equivalent to in degrees?
Definition
one degree
Term
what is a fist about equivalent to in degrees?
Definition
10 degrees
Term
what is a stretched out palm about equivalent to in degrees?
Definition
20 degrees
Term
You live at a latitude of 73° N. What is the angle
between the northern horizon and the north celestial
pole?
Definition
73 degrees
Term
Where in the sky (North, South, East, or West) would stars appear to be moving counterclockwise at the north pole?
Definition
North
Term
Where in the sky (North, South, East, or West) would stars appear to be moving upwards (rising) at the north pole?
Definition
East
Term
Where in the sky (North, South, East, or West) would stars appear to be moving in a rainbow-shaped motion at the north pole?
Definition
south
Term
how much of the night sky is north of the celestial equator?
Definition
exactly half
Term
to what degree is our earth's axis tilted?
Definition
23.5 degrees
Term
what is precession?
Definition
the "wobble" of the earth's rotation that occurs about every 26,000 years
Term
what is the ecliptic?
Definition
the sun's apparent path on the sky
Term
What DOES NOT contribute to the changes in the seasons?
Definition
the "distance" from the sun
Term
What does determine the seasons?
Definition
the amount of sun and the angle of the sun (more direct sunlight/longer day=warmer)
Term
What is perihelion?
Definition
the point when the earth is closest to the sun
Term
what is aphelion?
Definition
the point when the earth is furthest from the sun
Term
What three factors contribute to the Milankovich hypothesis?
Definition
Eccentricity of Earth’s orbit around the Sun
(varies over period of ~100,000 years)
• Precession (period of ~26,000 years)
• Inclination of Earth’s axis versus orbital plane
Term
what IS the Milankovich Hypothesis?
Definition
Changes in all
three of the factors are responsible for
long-term global climate changes (ice ages)
Term
How do the planets move?
Definition
All planets in
almost circular
(elliptical) orbits
around the Sun,
in approx. the
same plane
(ecliptic) AND
Sense of
revolution:
counter-clockwise
Term
Which planets are almost never visible with the naked eye?
Definition
uranus and neptune
Term
about when would you see Mars?
Definition
shortly after sunset or shortly before sunrise for a short while
Term
about when would you see Venus?
Definition
for a few hours after sunset or before sunrise
Term
The moon has an angular diameter of 0.5°.
What is the moon's angular diameter in minutes
of arc?
Definition
30
Term
If you were standing on the moon, what phase would the earth be in?
Definition
the opposite of the moon (if it's a new moon, it's a full earth, etc.)
Term
in what direction does the moon across the sky?
Definition
eastward (rises in the west)
Term
at about what time does a last quarter (3rd quarter) moon rise?
Definition
midnight
Term
The ____ moon is visible above the eastern
horizon a couple of hours before sunrise.
Definition
waning crescent
Term
how long is the synodic period?
Definition
29.5 days (how long it takes the moon to reach the same spot relative to the sun)
Term
how long is the sidereal period?
Definition
27.3 days (how long it takes to orbit earth)
Term
On a clear night when an observer in Los Angeles
sees a first quarter Moon, an observer in London
would see _____.
Definition
the same thing. :|
Term
what is the lighter shadow the earth has called?
Definition
penumbra
Term
what is earth's darker shadow called?
Definition
umbra
Term
if the entire moon enters the umbra we have a _____.
Definition
total lunar eclipse
Term
During a total eclipse, the Moon has a
faint, red glow, why?
Definition
it's reflecting sunlight
scattered in the Earth’s atmosphere.
Term
what phase must the moon be in to have a total lunar eclipse?
Definition
full
Term
would the sun be hidden behind the earth if you were standing on the moon during a total lunar eclipse?
Definition
yes
Term
true or false: the sun and moon have equal angular diameters?
Definition
true
Term
what can be seen during a total solar eclipse?
Definition
the corona (chromosphere and prominence)
Term
What is Perigee?
Definition
when the moon is closest to the earth
Term
what is apogee?
Definition
when the moon is furthest from the earth
Term
what's another way of saying total solar eclipse?
Definition
annular
Term
when does an annular solar eclipse occur?
Definition
when the earth is at perihelion and the moon is at apogee
Term
about how long is the saros cycle?
Definition
about 18 years
Term
In early astronomy, it was almost universally believed
that ____________.
Definition
the earth was at the center of the universe (geocentric)
Term
What are some clues of ancient astronomy?
Definition
Stonehenge, the Mayans, the Anasazi, etc.
Term
If the Earth's tilt were 13.5 degrees instead of 23.5 degrees, the path of the Sun would be
Definition
Not as far north in summer nor as far south in winter.
Term
Just as the Sun sets, the shadows are:
Definition
Always the same length BUT pointed to a different compass point according to the season.
Term
how many degrees does the moon's position change from one day to the next?
Definition
13
Term
TRUE OR FALSE The full moon is never visible at noon.
Definition
true
Term
The amount of time between two solar eclipses visible from the same location is about
Definition
54 years
Term
Imagine that Earth did not turn on its axis.
What would be true about the ecliptic?
Definition
It would still be defined and could be seen from all points on Earth, but only when they faced the sun
Term
Imagine the earth did not turn on its axis what else would be true?
Definition
The day would be the same length as the year.
Term
In one cycle of lunar phases, each crescent and gibbous phase has a duration of about how long?
Definition
one week
Term
If you could see the sun and stars during the daytime for several weeks, you would notice that the sun is doing what?
Definition
moving slowly eastward relative to the stars
Term
About how many days must elapse between first-quarter moon and third-quarter moon?
Definition
14-15
Term
TRUE OR FALSE During a solar eclipse, the moon casts a shadow on Earth.
Definition
true
Term
The sun is about ____ times the diameter of Earth.
Definition
100
Term
Earth is about ____times the diameter of the moon
Definition
4
Term
What types of distances are typically listed in astronomical units (AU)?
Definition
distances in the solar system
Term
A total solar eclipse occurs when the moon is...?
Definition
new and near the ecliptic
Term
If the moon is at one of its nodes, it must be...?
Definition
near the ecliptic
Term
Where is the sun in the winter?
Definition
south
Term
what was parallax?
Definition
shifting stars
Term
what is the deferent?
Definition
a larger circle in Ptolemy's theory
Term
what is the epicycle?
Definition
a small circle in Ptolemy's theory
Term
what is the equant?
Definition
the planets' speeds vary because the circle is slightly off center in Ptolemy's theory
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