AST 1002 EXAM 1 STUDY GUIDE
astronomical unit (AU) - Answers - The average distance of Earth from the Sun. Precise
radar measurements yield a value for the AU of 149,603,500 km
light year - Answers - The distance that light, moving at a constant speed of 300,000
km/s, travels in 1 year. One light year is about 10 trillion kilometers
celestial sphere - Answers - Imaginary sphere surrounding Earth to which all objects in
the sky were once considered to be attached
celestial equator - Answers - The projection of Earth's equator onto the celestial sphere
summer solstice - Answers - Point on the ecliptic where the Sun is at its northernmost
point above the celestial equator, occurring on or near June 21.
winter solstice - Answers - Point on the ecliptic where the Sun is at its southernmost
point below the celestial equator, occurring on or near December 21
north celestial pole - Answers - Point on the celestial sphere directly above Earth's
North Pole
south celestial pole - Answers - Point on the celestial sphere directly above Earth's
South Pole
Right ascension - Answers - Celestial coordinate used to measure longitude on the
celestial sphere. The zero point os the position of the Sun at the vernal equinox.
Measured in hours, minutes, and seconds, and it increases in the eastward direction
declination - Answers - Celestial coordinate used to measure latitude above or below
the celestial equator on the celestial sphere. The celestial equator is at a declination of
0 degrees, the north celestial pole is at +90 degrees, and the south celestial pole is at -
90 degrees
constellation - Answers - A human grouping of stars in the night sky into a recognizable
pattern
solar day - Answers - The period of time between the instant when the Sun is directly
overhead to the next time it is directly overhead. 3.9 minutes longer than the sidereal
day
sidereal day - Answers - The time needed between successive risings of a given star
Reason for the seasons - Answers - The tilt of Earth's rotation axis relative to the ecliptic
is responsible for the seasons we experience. The 23.5 degrees tilt of the Earth's
rotational axis
, new moon - Answers - all but invisible in the sky, the moon appears to wax (grow) a
little each night
quarter moon - Answers - half of the lunar disk (the circular face we would see if the
Moon were completely illuminated) can be seen
full moon - Answers - at full moon, the entire sunlit face can be seen
lunar phases - Answers -
precession - Answers - The slow change in the direction of the rotation axis of a
spinning object, caused by some external gravitational influence
parallax - Answers - The apparent motion of a relatively close object with respect to a
more distant background as the location of the observer changes
If a star has a Declination of +30 degrees, in which celestial hemisphere is it located
and how far the celestial equator? - Answers - Northern hemisphere, 30 degrees from
the celestial equator
What are the names of the two points in the celestial sphere where the Sun crosses the
celestial equator? - Answers - autumnal and vernal equinox
Declination of the Sun for Summer solstice? - Answers - 23.5 north
Declination of the sun for winter solstice - Answers - 23.5 south
What is the relative location of the Moon, Sun and Earth for the different phases of the
Moon? - Answers -
Where is the Sun in respect to the Moon when it is full Moon? - Answers - the moon is
in earth's shadow
Where is the Sun when it is new Moon? - Answers - the moon is in between the sun and
earth
Where is the Moon in respect to the Sun's position for a lunar eclipse? - Answers - when
the sun and moon are in exactly opposite directions as seen from earth, earth's shadow
sweeps across the moon, temporarily blocking the sun's light and darkening the moon
For a solar eclipse? - Answers - the moon passes directly in front of the sun
Why we don't see a solar or lunar eclipse every month? - Answers - The Moon's orbital
plane is tilted 5 degrees to the ecliptic (plane in which Earth orbits the Sun).
astronomical unit (AU) - Answers - The average distance of Earth from the Sun. Precise
radar measurements yield a value for the AU of 149,603,500 km
light year - Answers - The distance that light, moving at a constant speed of 300,000
km/s, travels in 1 year. One light year is about 10 trillion kilometers
celestial sphere - Answers - Imaginary sphere surrounding Earth to which all objects in
the sky were once considered to be attached
celestial equator - Answers - The projection of Earth's equator onto the celestial sphere
summer solstice - Answers - Point on the ecliptic where the Sun is at its northernmost
point above the celestial equator, occurring on or near June 21.
winter solstice - Answers - Point on the ecliptic where the Sun is at its southernmost
point below the celestial equator, occurring on or near December 21
north celestial pole - Answers - Point on the celestial sphere directly above Earth's
North Pole
south celestial pole - Answers - Point on the celestial sphere directly above Earth's
South Pole
Right ascension - Answers - Celestial coordinate used to measure longitude on the
celestial sphere. The zero point os the position of the Sun at the vernal equinox.
Measured in hours, minutes, and seconds, and it increases in the eastward direction
declination - Answers - Celestial coordinate used to measure latitude above or below
the celestial equator on the celestial sphere. The celestial equator is at a declination of
0 degrees, the north celestial pole is at +90 degrees, and the south celestial pole is at -
90 degrees
constellation - Answers - A human grouping of stars in the night sky into a recognizable
pattern
solar day - Answers - The period of time between the instant when the Sun is directly
overhead to the next time it is directly overhead. 3.9 minutes longer than the sidereal
day
sidereal day - Answers - The time needed between successive risings of a given star
Reason for the seasons - Answers - The tilt of Earth's rotation axis relative to the ecliptic
is responsible for the seasons we experience. The 23.5 degrees tilt of the Earth's
rotational axis
, new moon - Answers - all but invisible in the sky, the moon appears to wax (grow) a
little each night
quarter moon - Answers - half of the lunar disk (the circular face we would see if the
Moon were completely illuminated) can be seen
full moon - Answers - at full moon, the entire sunlit face can be seen
lunar phases - Answers -
precession - Answers - The slow change in the direction of the rotation axis of a
spinning object, caused by some external gravitational influence
parallax - Answers - The apparent motion of a relatively close object with respect to a
more distant background as the location of the observer changes
If a star has a Declination of +30 degrees, in which celestial hemisphere is it located
and how far the celestial equator? - Answers - Northern hemisphere, 30 degrees from
the celestial equator
What are the names of the two points in the celestial sphere where the Sun crosses the
celestial equator? - Answers - autumnal and vernal equinox
Declination of the Sun for Summer solstice? - Answers - 23.5 north
Declination of the sun for winter solstice - Answers - 23.5 south
What is the relative location of the Moon, Sun and Earth for the different phases of the
Moon? - Answers -
Where is the Sun in respect to the Moon when it is full Moon? - Answers - the moon is
in earth's shadow
Where is the Sun when it is new Moon? - Answers - the moon is in between the sun and
earth
Where is the Moon in respect to the Sun's position for a lunar eclipse? - Answers - when
the sun and moon are in exactly opposite directions as seen from earth, earth's shadow
sweeps across the moon, temporarily blocking the sun's light and darkening the moon
For a solar eclipse? - Answers - the moon passes directly in front of the sun
Why we don't see a solar or lunar eclipse every month? - Answers - The Moon's orbital
plane is tilted 5 degrees to the ecliptic (plane in which Earth orbits the Sun).
