ASTRO 5 EXAM STUDY GUIDE
QUESTIONS & ANSWERS
Why is a lunar eclipse also called a "Blood Moon"? What is responsible for this
effect? - ANSWER Because its red. Sunlight is refracting around the Earth to
reach the Moon's surface. This light has gone through the Earth's atmosphere,
where some light is scattered out. Since blue light scatters better than red light,
more blue light is removed and a higher ratio of red light reaches the Moon's
surface.
We have 0-2 solar eclipses each year. Why do we not have a solar eclipse every
27.3 days (every moon cycle)? - ANSWER The Moon must be at a node with
the ecliptic since its orbit is tilted (2 times a year)
The Moon must be in New Moon phase (12-13 times a year)
When the Earth is at the point in its orbit when it is closest to the Sun, it is at
perihelion/aphelion (circle one). In what month does this occur? What causes
the seasons? - ANSWER Closest approach (perihelion) occurs in
December/January.
Furthest is Aphelion
The Earth's obliquity (tilt) is responsible for the seasons (make sure you know
why)
The solar day is four minutes longer than the sidereal day, meaning the stars rise
four minutes earlier each day. Why is this? - ANSWER We define the solar day
to be how long it takes for the Sun to be in the same place of the sky. Given that
the Earth is both rotating *and* orbiting around the Sun, the Earth ends up
rotating one extra degree to face the Sun again. So 361 degrees is a solar day, of
24hrs, and 360 degrees is a sideral day of 23H56M.
Why do astronomers prefer describing the positions of the stars using the
celestial sphere instead of using the horizon diagram? - ANSWER The HD
depends on both observer location *and* time and the celestial sphere does not.
, Note: neither is more *accurate* than the other.
What effect does changing longitude and latitude have on the rising and setting
of the stars? - ANSWER Latitude: Which stars are visible
Longitude: rise and set times of stars (think of time zones)
The Earth appears to go through phases as observed from the moon assuming
you're on the half of the moon that is facing the Earth. Why is this? - ANSWER
Just like the Moon, half of the Earth is constantly being illuminated by the Sun.
Depending on where the Moon is in orbit around the Earth, different parts of the
planet will be observable.
The Mnajdra temple in Malta was constructed such that the Sun shown down
the middle of the temple on the equinoxes, and to the left and right during the
June and December solstices, respectively. Why does the Sun shine in the same
spot for the equinoxes, but in different positions for the solstices? - ANSWER
This is due to the Earth's tilt. During the equinoxes, the Sun is in the same place
in the sky (the ecliptic is intersecting with the celestial equator), but during the
solstices, the Sun is either lower in the sky (Winter solstice in northern
hemisphere) or higher in the sky. The Sun's path at the same time every day
throughout the year follows an analemma
What are the names of the two angles used to describe the positions of stars on
the celestial sphere? - ANSWER Right ascension and declination
The Sun's blackbody spectrum peaks around 540nm, which is in the green. Why
does the Sun appear yellow to us instead of green/white? - ANSWER The
Earth's atmosphere is scattering more blue light than red light, so the Sun
appears redder.
Describe the two different ways that light is made. Give an example (either in
everyday life or in astronomy) of these different emissions. - ANSWER
Thermal emission (hot stove) and electron transitions in an atom (running a
current through sodium for a lightbulb)
In what phases of the Moon can the Moon and Sun be in the sky at the same
time? - ANSWER All phases except Full Moon (cannot observe Moon during
New Moon, but it is in the sky while the Sun is)
QUESTIONS & ANSWERS
Why is a lunar eclipse also called a "Blood Moon"? What is responsible for this
effect? - ANSWER Because its red. Sunlight is refracting around the Earth to
reach the Moon's surface. This light has gone through the Earth's atmosphere,
where some light is scattered out. Since blue light scatters better than red light,
more blue light is removed and a higher ratio of red light reaches the Moon's
surface.
We have 0-2 solar eclipses each year. Why do we not have a solar eclipse every
27.3 days (every moon cycle)? - ANSWER The Moon must be at a node with
the ecliptic since its orbit is tilted (2 times a year)
The Moon must be in New Moon phase (12-13 times a year)
When the Earth is at the point in its orbit when it is closest to the Sun, it is at
perihelion/aphelion (circle one). In what month does this occur? What causes
the seasons? - ANSWER Closest approach (perihelion) occurs in
December/January.
Furthest is Aphelion
The Earth's obliquity (tilt) is responsible for the seasons (make sure you know
why)
The solar day is four minutes longer than the sidereal day, meaning the stars rise
four minutes earlier each day. Why is this? - ANSWER We define the solar day
to be how long it takes for the Sun to be in the same place of the sky. Given that
the Earth is both rotating *and* orbiting around the Sun, the Earth ends up
rotating one extra degree to face the Sun again. So 361 degrees is a solar day, of
24hrs, and 360 degrees is a sideral day of 23H56M.
Why do astronomers prefer describing the positions of the stars using the
celestial sphere instead of using the horizon diagram? - ANSWER The HD
depends on both observer location *and* time and the celestial sphere does not.
, Note: neither is more *accurate* than the other.
What effect does changing longitude and latitude have on the rising and setting
of the stars? - ANSWER Latitude: Which stars are visible
Longitude: rise and set times of stars (think of time zones)
The Earth appears to go through phases as observed from the moon assuming
you're on the half of the moon that is facing the Earth. Why is this? - ANSWER
Just like the Moon, half of the Earth is constantly being illuminated by the Sun.
Depending on where the Moon is in orbit around the Earth, different parts of the
planet will be observable.
The Mnajdra temple in Malta was constructed such that the Sun shown down
the middle of the temple on the equinoxes, and to the left and right during the
June and December solstices, respectively. Why does the Sun shine in the same
spot for the equinoxes, but in different positions for the solstices? - ANSWER
This is due to the Earth's tilt. During the equinoxes, the Sun is in the same place
in the sky (the ecliptic is intersecting with the celestial equator), but during the
solstices, the Sun is either lower in the sky (Winter solstice in northern
hemisphere) or higher in the sky. The Sun's path at the same time every day
throughout the year follows an analemma
What are the names of the two angles used to describe the positions of stars on
the celestial sphere? - ANSWER Right ascension and declination
The Sun's blackbody spectrum peaks around 540nm, which is in the green. Why
does the Sun appear yellow to us instead of green/white? - ANSWER The
Earth's atmosphere is scattering more blue light than red light, so the Sun
appears redder.
Describe the two different ways that light is made. Give an example (either in
everyday life or in astronomy) of these different emissions. - ANSWER
Thermal emission (hot stove) and electron transitions in an atom (running a
current through sodium for a lightbulb)
In what phases of the Moon can the Moon and Sun be in the sky at the same
time? - ANSWER All phases except Full Moon (cannot observe Moon during
New Moon, but it is in the sky while the Sun is)
