Week 1 Astronomy 3
When the moon is over half lit and appears to be growing larger it is called a...
Waxing gibbous.
The elevation angle of the Celestial Pole from your location is equal to your ______.
latitude
In modern times, like state boundaries on a map, the sky is separated into ___ carefully delineated areas called _______.
88; constellations
What is an annular eclipse?
A solar eclipse where the Moon passes directly between the Sun and the Earth, but cannot completely cover the Sun because the Moon is too far away. Instead. there is a small bright ring around the Moon.
What is the celestial sphere?
A useful mental model for understanding how the stars move through the sky.
All of the planets in the solar system orbit the sun, but in which plane do most of them orbit?
All of the planets orbit the Sun in approximately the same plane.
How much of the Moon's surface is illuminated by the Sun?
Always exactly half.
How much of the Moon's surface is toward the Earth?
Always exactly half.
What causes retrograde motion?
An inner planet passing an outer planet.
If the star directly above you stays fixed all night and the stars do not rise or set, where are you?
At one of the poles
What causes the stars to move in circles across the night sky over the course of a night?
Because the Earth is constantly rotating the stars appear to rotate around it in the opposite direction.
What phase of the Moon appears close to the Sun in the sky, but not in conjunction (the closest approach).
Crescent.
Why does Earth have seasons?
Earth rotates on a tilted axis such that each hemisphere is pointing towards the sun for one half of the year and away from the Sun during the other half.
What phase of the Moon appears far from the Sun in the sky, but not in opposition (the farthest away).
Gibbous.
What determines the phase of the Moon?
How much the 50% of the surface that is illuminated overlaps with the 50% that faces the Earth.
At times even the dark side of the moon is bright enough to see (although still much dimmer than the light side of the moon). Why is this?
Light from the Sun is reflected off of the Earth in the same way we see it reflect off of the moon. This light from the Earth is quite bright and illuminates part of the moon not already illuminated by the Sun.
Which is NOT a reason that it is easier to see a lunar eclipse than a solar eclipse
Lunar eclipses are more common.
Which planets (other than Earth) can be seen using only the naked eye?
Mercury, Venus, Mars, Jupiter, and Saturn.
Relative to the Sun and to the Earth, where is the moon located when it is in the full moon phase?
On the opposite side of the Earth from the Sun.
To a viewer in the outer shadow cast by the moon in a solar eclipse what would the Sun look like during the eclipse?
One side of the Sun would appear to have a dark circular chunk taken out of it while the rest would look about the same.
Earth not only spins on its tilted axis, but also wobbles in a manner similar to the motion of a spinning top. The change in direction of Earth's axis of rotation in space is called...
Precession
Why does an eclipsed Moon look red?
The Moon is reflecting back the filtered and refracted sunlight of all the sunsets seen through the edges of Earth's atmosphere.
Why do stars appear to twinkle when we look at them from Earth?
The air in Earth's atmosphere is unstable and changes the direction of the light that passes through it several times per second. As a result, we on the surface see changes in brightness that we call twinkling.
Why is it that some stars appear to have color while other simply appear to be white?
The color receptors in our eyes are not sensitive enough to detect color in fainter stars and as a result only the brightest stars in the sky appear to have color.
What is the Corona?
The ethereal outer atmosphere of the Sun that is only visible during a total Solar eclipse.
How does Earth's revolution around the Sun affect our view of the stars at night?
The first two options are both correct.
What is retrograde motion?
The motion of planets from east to west relative to the stars over several nights.
During what times of day is the new moon in the sky?
The new moon rises and sets at about the same time as the sun.
Why doesn't a solar eclipse occur every month when the moon is closest to the Sun?
The orbit of the Moon around the Earth is tilted by 5 degrees and therefore does not match up with the orbit of the Earth around the Sun so the moon usually appears either right above or right below the Sun, and only occasionally appears in front of the Sun, eclipsing it.
How do the planets appear to move in the sky?
The planets seem to move around the sky, changing their position relative to the stars with the inner planets moving very rapidly compared to the outer planets.
From Earth it looks as though the Sun and the Moon are about the same size. This is because...
The ratio of the size of the sun to the size of the moon is about the same as the ratio of their respective distances from Earth.
What is the technical name for the line separating the light and dark sides of the moon?
The terminator.
What changes do we see in the stars as a result of the changing direction of Earth's axis of rotation over time?
The time of year in which we see certain stars and constellations changes over the course of many years. The North star used today (Polaris) is different from the one seen by ancient Egyptians, and the pole star thousands of years from now will be different as well. The months in which the Sun passes through each constellation of the zodiac is different from the months it passed through them thousands of years ago.
When a solar eclipse occurs there are two different shadows, one being smaller and darker than the other and sitting inside of the larger shadow. What is the name for the smaller shadow?
The umbra.
Why do the planets not appear to twinkle like stars do?
They are closer to Earth and as a result appear larger, meaning their light is not as distorted as it passes through the atmosphere.
Viewing the moon from a small town in North America you realize that exactly half of it is illuminated on the left side. What phase is this?
Third quarter
Light pollution has negative effects not only on stargazing but also on the behaviors of certain bugs and other animals. What action is necessary to decrease light pollution in a city?
Use a different type of lighting that directs light towards the ground.
