Astronomy chapter one Flashcards
What are the three different ways you can observe the night sky?
plain eye, binoculars, and a telescope?
What are the two largest celestial objects we can view?
moon and sun
Why is there a trend of east-to-west motion when observing the sun, moon, and stars?
This basic trend of east-to-west motion is due to Earths rotation on its axis.
What is this trend of the earths rotation called?
Diurnal Motion
What is the approximate rotation time of the earth that relates to the other objects in the sky as well?
23 hours and 56 minutes.
Name the concept that is useful for understanding the positions and motions of stars.
celestial sphere
name the concept that involves expanding the earths equator into space
the celestial equator
what are constellations called that are close enough to the celestial pole that they are visible all night, year-round?
circumpolar constellations
Since the 23 hour 56 minutes period is the length of time it takes the earth to turn as seen from a distant star, this is called a
sidereal day
since stars rise two hours earlier every month, they rise how many hours earlier after six months?
12 hours
Why is it difficult to observe planets, globular clusters, and nebulae when the moon is full?
The moon is about 9 times brighter in its full stage than the first quarter moon. Thus washing out the harder things to see.
The moon rises (on average) about how much later each day?
50 minutes
Why is it ironic that the moon is called “the moon” in regards to the gravitational pull of the earth and sun?
The gravitational pull of the sun on the moon is about twice the pull of the Earth on the moon.
The phases of the moon are not related to the earths shadow, but to the ( ) of the day side of the moon we can see from our position
percentage
It takes how many days for the to go through its phases?
29.3
it takes how many days for its orbital period?
27.5
What is the difference between the sidereal day and the solar day?
solar- 24 hours
sidereal-23 hours 56 minutes
solar-the time it takes the sun to return to its highest point in the sky as viewed from a location on earth.
sidereal- the true rotation of the earth
The motion of the planets is complicated because their apparent motion in the sky is the combination of their what around the sun, plus the what in position due to Earths motion around the sun.
True motion
Apparent shirt
What is responsible for the seasons on earth?
The Earths rotation axis that is tilted relative to its orbit around the sun y 23.4 degrees.
What describes how high above the horizon an abject is (in angle)
Altitude
What describes how far along the horizon an object is to the right of due north<
Azimuth
Equatorial coordinates are based on the what?
Celestial sphere
In particular equatorial coordinates are based on what?
The celestial equator
Describe what the two coordinate systems widely used in astronomy are based on.
Altitude- based on our local horizon, describes the position of an object in the sky with two coordinates
Azimuth- Based on the celestial sphere, the angular distance of a star above the celestial equator is called it “declination”
Stars with a declination that is less than your latitude will pass ( ) of the zenith when they cross the meridian; and stars with a greater declination will pass ( ) of the zenith
south, north
Which RA coordinates can be seen depends on the time of ( ) and the time of ( )
Day, year
Once calibrated on an object whose RA and Dec you know, you can us ( ) circles on a telescope to find any other RA or Dec
setting
What is the best way to get a feel for the motions in the sky?
To get outside and watch
A star wheel or planisphere helps you find stars by lining up the ( ) with the ( ) on the planisphere
date, time
A planisphere helps find constellations, but will not help with ( ) or the ( )
planets, moon
The suns ( ) is zero on the vernal equinox or autumnal equinox, so the sun is above the horizon for exactly ( ) hours
declination, 12
What does the term “Equinox” mean?
equal night
What does the term “solstice” mean?
sun stop
Anyone observing from the ( ) circle will experience 24 hours of sunlight on the summer solstice
artic
In the Northern Hemisphere, days are longer in the ( ) and ( ) seasons, and shorter in the ( ) and ( ) seasons
spring, summer, autumn, winter
The moon orbits roughly in the ( ), not the celestial equator
ecliptic
When will the first quarter moon make its highest arc in the sky?
on spring equinox
A ( ) eclipse, when the moon’s shadow falls on the earth, and a ( ) eclipse, when the earths shadow falls upon the moon.
solar, lunar
What is the generic term for the two points of intersection on any two great circles?
node
The configuration of the sun, moon, and Earth is about the same every 18.031 years, and is called the ( ) cycle
Saros
The earth actually has two shadows. A darker inner shadow called the ( ) and a lighter outer shadow called the ( )
Umbra, penumbra
During a total solar eclipse, the bright surface of the sun ( ) is completely blocked by the moon
photosphere
Any given spot on the earth experiences a total solar eclipse once every ( ) years or so
400
When the moon is farther from the earth, it appears smaller than the sun, and when it passes directly in front of the sun it leaves a thin ring or
annulus
The moon seems to wobble a bit from week to week, which is called
liberation
Planets orbit the sun is slightly ( ) paths with the sun at one focus of the ellipse
Elliptical
The ( ) planets are mars, Jupiter, Saturn, Uranus, and Neptune
Superior
All the planets orbit the sun in the same direction:
Counterclockwise
When a planet is behind the sun its called
Conjunction
What two planets are the two inferior planets whose orbits lie closer to the sun than earth does.
Mercury and Venus
A ( ) transit is when Mercury or Venus cross directly in front of the sun during inferior conjunction
Solar
Comets are icy objects and generally have ( ) orbits
Elliptical
Meteor showers are generally caused by debris left behind by a ( )
comet
The most impressive, reliable meteor shower is the what shower? occurring around August 12th each year
Perseid
The sun traces out a thin figure-eight shape across the sky with each day, which is called
the analemma
The constellation in which the sun is found at equinox shifts with time. This phenomenon is called the
precession of the equinoxes
