Astronomy - Chapter 1
While watching a star, you see it moves 15 degrees across the sky. How long have you been watching it?
1 hour
The Milky Way galaxy contains about ________ stars.
100 billion
Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. (Click "Show Moon with flat orbit" to see this situation.) In this hypothetical situation, approximately how many solar eclipses would occur each year?
12
In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____.
2
How long is the precession cycle?
26,000 years
How many arc seconds are in a degree?
3600
Listed following are the latitudes of several locations on Earth. Rank these latitudes based on the maximum altitude (on the meridian) at which the celestial equator passes through the local sky, from lowest altitude (nearest the horizon) to highest altitude (farthest above the horizon). - latitude 50d N - latitude 30d N - latitude 70d N - latitude 40d N - latitude 10d N
70 50 40 30 10
Into how many constellations is the celestial sphere divided?
88
1. A solar eclipse that occurs when the new moon is too far from Earth to completely cover the Sun can be either a partial solar eclipse or an
Annular eclipse
If you could change the layout of the solar system, what would cause a lunar eclipse to occur at least once every month in this hypothetical situation?
Change the Moon's orbital plane so it is in the same plane as Earth's orbit around the Sun.
What celestial line is a product of the Earth's orbit around the Sun?
Ecliptic
Constellations:
Groups of stars making an apparent pattern in the celestial sphere
First Quarter Moon:
It is highest in the sky at sunset. It is the half Moon of the evening sky. It rises about noon. It occurs about a week after new Moon.
What condition is necessary for an ANNULAR solar eclipse?
New Moon on ecliptic at apogee
What condition is necessary for a TOTAL solar eclipse?
New Moon on ecliptic near perigee
What condition is necessary for a PARTIAL solar eclipse?
New Moon on ecliptic, with us in the penumbral shadow
What is the name of the point on the celestial sphere that all stars seem to circle around, when viewing the sky from North America?
North Celestial Pole
Where on Earth would you be if Polaris were directly overhead?
North Pole
Why is there a two-day difference in the sidereal and synodic months?
The Earth is also revolving around the Sun, so the Moon must "catch up."
Ecliptic:
The Sun appears to move about a degree per day eastward long it. The major planets stay close to it, but not always on it. It is tilted 23.5 degrees with respect to the equator. The year is marked by the Sun's return to the same place along it.
The angular size of an object depends on ___
The object's actual size and its distance from us Submit
What conditions must exist for a LUNAR ECLIPSE to occur?
The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.
What conditions must exist for a SOLAR ECLIPSE to occur?
The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane.
2. Anyone looking from the night side of Earth can, in principle, see a
Total lunar eclipse
4. A ____ can occur only when the Moon is new and has an angular size larger than the Sun in the sky.
Total solar eclipse
5. A partial lunar eclipse begins when the Moon first touches Earth's
Umbra
Where did most of the chemical elements that make up our bodies come from?
Vanished Stars
If you are in the Moon's umbral shadow, then you will witness...
a total solar eclipse
Early astronomers picture the Earth as stationary, with the ________ spinning, moving the stars along with it.
celestial sphere
The Last Quarter phase of the Moon...
crosses the meridian at sunrise.
The celestial sphere appears to move fastest above the ________.
equator
Where on Earth can you observe all the stars in the sky over an entire year?
equator
The places where the Sun crosses the equator are called the...
equinoxes
The two days when the Sun rises due east and sets due west are the ________.
equinoxes
Some type of solar eclipse will happen about...
every six months at new Moon.
A lunar eclipse can only happen during a ________ Moon.
full
A lunar eclipse can only happen during a ___
full moon
The distances to other stars are best measured in ________.
light years
Summer solstice
longest day (most daylight) of the year the noontime Sun reaches its highest point of the year
A solar eclipse can only happen during a ________ Moon.
new
A solar eclipse can only happen during a ____
new moon
6. A point at which the Moon crosses Earth's orbital plane is called a
node
3. During some lunar eclipses, the Moon's appearance changes only slightly, because it passes only through the part of Earth's shadow called the
penumbra
That Polaris will not always be the pole star is due to...
precession shifting the celestial pole.
The four extra minutes in the solar day are due to our ________ around the Sun.
revolution
Winter solstice
the Sun crosses the meridian 23.5 degrees lower in altitude than the celestial equator sunset occurs at its farthest point south of due west for the year the noontime Sun casts the longest shadows Submit
Fall equinox
the Sun has declination 0 degree today, but will have a negative declination tomorrow
Spring equinox
the Sun rises due east today, but will rise slightly north of due east tomorrow
The Sun's lowest position in the sky occurs during the ________.
winter solstice
