ASTRONOMY 101 STUDY GUIDE FALL 2018
FAST FACTS THAT YOU SHOULD KNOW:
The Sun is the center of the solar system. It moves only slightly (mostly due to Jupiter’s gravity)
The planets orbit the Sun in elliptical orbits that are nearly circular. The Earth, in particular, orbits the Sun at a distance of 1 AU, once per year. The outer planets range from 5 to 30 AU from the Sun.
The Moon orbits the Earth at a distance of 0.0025 AU, once every 28 days.
The Earth rotates on its axis once every sidereal day (a bit less than 24 hours). The stars are very far away (the closest is 276,000 AU away).
All of these rotations and revolutions are
the solar system from the north celestial pole The celestial sphere model: The fastest motion of all of these is the rotation of
In the time it takes the Earth to rotate once, the
objects in the sky don’t really move much relative to
Thus, the dominant apparent motion of all things in
the sky is due to the Earth’s rotation underneath
them; things rise in the East and set in the West.
We can pretend that everything in the sky is
attached to a large sphere, rotating around us while
we stay stationary. This isn’t literally true, but is a
This works very well for the stars
This works less well for the Moon, the Sun, and the
planets, since over the course of months and years,
the motions of the Earth and the Moon relative to
them cause them to “move around” the celestial
The two directions along the rotation axis of the
celestial sphere are called the “north celestial pole”
and “south celestial pole”; the northern one points at
the star Polaris.
These are not north and south; north and south are
directions along the surface of the Earth that you can
walk in, while the celestial poles lie up in the sky
(unless you’re on the Equator).
The stuff in the sky appears to rotate
counterclockwise around the NCP and clockwise
around the SCP. From Syracuse, some stars, those We also discuss several other topics like sickle-turbidity test
lying close to the NCP, will be visible all night long;
others will only be visible briefly or not at all (those
lying close to the SCP).
THE SUN We also discuss several other topics like comd 3700,0,12020-11-03,https://studysoup.com/guide/2726638/week-4-and-week-5-assignments,all of the following pieces of information are likely to be found on an operative report except for
Every day, the Earth rotates once, but it also
revolves a little bit – about one degree – around
Sidereal day: the Earth rotates exactly 360 degrees on its axis. (pronunciation: sideereeal, not sidereel)
In one sidereal day, the stars come back to the same apparent positions in the sky The Sun doesn’t quite make it back, slipping a little bit westward every sidereal day Solar day: The Earth rotates 361 degrees on its axis, enough so that the Sun comes back to the same east/west position in the sky.
A solar day: is about 4 minutes longer than a sidereal day
The stars’ apparent positions shift a little bit westward every solar day (since it’s a bit longer than a sidereal day)
We measure days and calibrate our clocks by the solar day, not the sidereal day The twelve constellations in the sky that lie behind the Sun as the Earth orbits it are together called the zodiac; which one lies behind the Sun depends on the time of yeaWe also discuss several other topics like microbiology study guide
The Moon goes around the Earth every 28 day
The Moon doesn’t give off its own light, but reflects
the sun’s light
The relationship of the Moon's phase to its angular distance in the sky from the Sun allows us to establish very exact definitions of when the primary phases occur, independent of how they appear.
The Earth’s axis of rotation is tilted by about 23 degrees with respect to its orbit This causes the seasons in two ways:
1) We also discuss several other topics like thomas peavy
When we are tilted toward the Sun, we have longer days and shorter nights (summer) 2) When we are tilted toward the Sun, we get more direct sunlight than when we are tilted away
Equinox: The two days of the year with equal day and night hours, (one in spring and one in fall) sun shines equally on the northern and southern hemisphere.
Solstice: The two days of the year (one in summer in & one in winter) where there is most daylight hours in one hemisphere and the least daylight hours in the opposite hemisphere.
PATH OF THE SUN: Because of its relation to eclipses, that path is known as the ecliptic. The orbit of the Earth around the Sun. the actual orbit is very close to a circle. There are different “paths” of the sun depending on the month.
EVERYTHING RISES IN THE EAST AND SETS IN THE WEST
PHASES OF THE MOON:
New Moon The Moon's unilluminated side is facing the Earth. The Moon is not visible (except during a solar eclipse).
Waxing Crescent The Moon appears to be partly but less than onehalf illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing.
First Quarter Onehalf of the Moon appears to be illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing.
Waxing Gibbous The Moon appears to be more than onehalf but not fully illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing.
Full Moon The Moon's illuminated side is facing the Earth. The Moon appears to be completely illuminated by direct sunlight.
Waning Gibbous The Moon appears to be more than onehalf but not fully illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing.
Last Quarter Onehalf of the Moon appears to be illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing.
Waning Crescent The Moon appears to be partly but less than onehalf illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing.