Exam 1: ch 1, 2, and 4 Flashcards
1
Q
astronomy
A
the study of all the objects beyond earth and the mechanisms governing them
2
Q
scientific method
A
observations → hypothesis/model → experiments → refine/thrown out hyp./model
3
Q
Sun → earth distance
A
150,000,000 km
4
Q
how many inches in a meter
A
39.4 in
5
Q
how many miles in 1 kilometer
A
0.6 mi
6
Q
what derives the astronomical unit(AU)
A
average sun-earth distance
7
Q
how many km are in 1 AU
A
1.5 x 10^8
8
Q
lightyear
A
the distance light travels in 1 year
9
Q
speed of light (c)
A
c = 3.5 x 10^5 km/s
10
Q
celestial sphere
A
an imaginary sphere around the earth with stars, planets, etc. attached to it
11
Q
zenith
A
directly above where you stand
12
Q
how do the stars rotate
A
- E toW
- the opposite direction the earth spins, around the celestial poles, with the stars keeping their relative position
13
Q
how can you find the altitude (angle above the horizon) of the celestial pole
A
equal to your latitude
14
Q
circumpolar zone
A
at a given location, the portion of the sky that never sets relative to that location
15
Q
how much does the sun’s position in the sky change relative to the stars
A
it moves about 1* per day and returns to its original position after 1 year
16
Q
ecliptic
A
the line traced by the sun across the sky over a year
17
Q
constellation
A
one of the 88 sections of the sky
18
Q
If you are standing at the N pole, where is the celestial equator?
A
your horizon
19
Q
If you are standing on the equator, where are the celestial poles and celestial equator?
A
- the celestial poles are at your horizons
- the celestial equator is at your zenith
20
Q
If you are standing at 50°N latitude, where are the celestial poles?
A
- N celestial pole is 50* N
21
Q
how many degrees across is the moon?
A
0.5* in diamater
22
Q
how much later does the sun rise each day?
A
4 minutes relative to the stars
23
Q
how many constellations intersect the ecliptic?
A
13, but only 12 are talked about
24
Q
why does the ecliptic not lie on the celestial equator?
A
because the earth’s axis is tilted by about 23.5* from the plane of the ecliptic
25
what does the word planet mean in ancient greek?
wanderer
26
how wide is the ecliptic/zodiac
18*
27
asterisms
notable star patterns that do not correspond to the modern constellations
28
neutrinos
close to the speed of light
29
how many light minutes away is the sun
about 8 light minutes
30
star cluster
locations in which stars are grouped together, but not so close that they are in a single system
31
Local Group
both the Milky Way and the Andromeda galaxy are part of this small group of galaxies
32
Virgo Supercluster
what the Local Group is part of
33
parallax
Effect of one object moving relative to another due to motion
34
stellar parallax
is the apparent shift of position (parallax) of any nearby star (or other object) against the background of distant stars
35
Ptolemy
created the geocentric model of the solar system
36
how do the planets move in the sky
they usually move E, but sometimes they turn around and move W for a little while before moving E again
37
retrograde motion
- the orbital motion of an object in the direction opposite the rotation of a central object
- temporary westward motion of the planets
38
cosmology
the study of the structure and origin of the cosmos (or universe)
39
How does the distance to an object affect how much it shifts due to parallax?
The farther away the object is, the less it appears to shift
40
apparent magnitudes
how Hipparchus measured the brightness of the stars, from 1(bright)-6(dim)
41
precession
- refers to any of several slow changes in an astronomical body's rotational or orbital parameters
- "wobble" of the earth's axis
42
how long does it take earth' xis to complete one precession cycle
26,000 years
43
epicycle
in Ptolemy's model, each planet goes around a small circular orbit
44
deferent
in Ptolemy's model, the center of the epicycle orbits the earth on a larger circular path
45
astrology
a system in which the positions of these objects relative to the zodiac could impart knowledge about the present or, more importantly, the future
46
horoscope
the chart that depicts the positions of the Sun, the Moon, and the planets in the sky when that person was born
47
Copernicus
- put forth the heliocentric model of the solar system
- orbits were still circular, not elliptical
48
Galileo
- 1st person to use a telescope
- discovered Jupiter's moons
49
latitude
angle north or south or the equator
50
longitude
angle east or west of the prime meridian
51
what is the equivalent of latitude on the celestial sphere?
declination
52
declination
angle above or below the celestial equator
53
what is the equivalent of longitude on the celestial sphere
right ascension
54
right ascension
measured in time from the location of the vernal equinox
55
vernal equinox
location of the sun on the 1st day of spring
56
how is the celstial sphere vertically divided?
- 24 hours
- 15* per hour
57
how is declination divided?
split each degree into 60 arc minutes and each arcminute into 60 arcseconds
58
how is right ascension divided?
each hour is split into 60 arcminutes, and each minute is split into 60 arcseconds
59
how does the local coordinate system work
– the altitude is the angle above your horizon
– the azimuth is the compass direction relative to your location
60
Foucault pendulum
a pendulum swinging along a straight line will appear to rotate as time goes on; this only happens if it is the Earth that rotates (“the Earth rotates under the pendulum”)
61
when is a hemisphere experiencing summer
when that hemisphere is "leaning toward" the sun
62
why does the tilt create season
because the sunlight hits the hemisphere that is "leaning toward" the sun more directly, and for longer, so it heats up more
63
summer solstice
- June 21
- N tilted toward the sun (summer), S tilted away (winter)
64
autumnal equinox
- September 21
- Neither hemisphere is pointed toward the sun, so equal sunshine
- autumn/fall in N, spring in S
65
winter solstice
- December 21
- S is tilted toward the sun (summer), N is tiled away (winter)
66
Vernal equinox
- March 21
- Neither hemisphere pointed toward the sun
- Spring in the N, autumn in the S
67
N pole qualities
day for 6 months (3/21 - 9/21) then night for 6 months (9/21 - 3/21)
68
arctic circle qualities
- (lat. 66.5*N)
- anywhere above has 24 hrs of day on the summer solstice
69
Tropic of cancer qualities
- (lat. 23.5*N)
- Sun passes through zenith on the summer solstice
70
Tropic of Capricorn qualities
- (lat 23.5*S)
- sun passes through zenith on the winter solstice
71
Antarctic circle qualities
- (lat. 66.5*S)
- anywhere below has 24 hrs of day on the winter solstice
72
S pole qualities
day for 6 months (9/21 - 3/21) then night for 6 months (3/21 - 9/21)
73
how are seasons determined at the equator
by rainfall, not sunlight
74
how are seasons determined at the equator?
by rainfall, not sunlight
75
solar day
one rotation of the earth with respect to the sun
76
sidereal day
one rotation of the earth relative to the stars: 23 hr 56 min
77
apparent solar time
based on positions of the sun on your location
78
mean solar day
the average length of apparent solar day over a year
79
international date line
- lies roughly along longitude 180*; zig-zagging to avoid land
- It compensates for time changing 24hrs going around the earth
- When moving east, decrease the date
- If moving W, increase the date
80
why can we see some sunlight before sunrise and after sunset?
because the atmosphere refracts (bends) the sunlight around the horizon
81
day
rotation period of earth
82
solar month
time for moon to complete its cycle of phases; 29.5306 days
83
tropical year
orbital period of earth; 365.2422 days
84
Julian calendar
- year is 365.25 days
- 3 out of every 4 years is 365 days
- 1 out of every 4 years in 366 days
- Mainly a solar calendar, but the lengths of months are a relic of lunar timekeeping
85
Gregorian Calendar
- a year that is 365.2425 days long
- changes to leap years
86
leap year rules
- If the year is divisible by 4, it is a leap year
- Unless it is divisible by 100
- But if is divisible by 400, it is a leap year
87
phases
Over a month, the moon appears to change size because of which portion is lit
88
order of moon phases
New, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent
89
rule for waxing vs waning
- When lit portion of the moon is on right, it is waxing
- When on left, it is waning
90
sidereal month
the time it takes for the moon to go around the earth once, relative to the stars, 27.3217 days
91
synchronous rotation
The moon rotates on its axis at the same rate that it orbits earth
92
how much does the moon move in the sky each day
about 12*
93
what direction does the moon travel
- eastward
- travels its own diameter in about 50 minutes
94
what causes tides
moon's gravity on earth
95
oblate spheroid
when earth distorts slightly due to moon's gravity
96
tidal buldge
- This difference in gravitational pull causes water to “pile up” on the side of the earth facing the moon
- Same thing happens on the opposite side of earth, there are 2 bulges
- Over the course of the day, earth rotates once, so every location passes through both bulges each day
- The sun also rises tides on earth, but the effect is less than that of the moon
97
spring tides
When E, M, S are all lined up, we get particularly high high tides and low low tides
98
neap tides
when M and S are at right angles, their tidal effects partially cancel, and we get less extreme tides
99
how can eclipses occur
- because the S and M have the same apparent size in the sky
- because the diameter of the Sun is about 400x that of the Moon and the Sun is 400x farther away, so each object covers about 1/2°in the sky
100
solar eclipse
When M is directly between S and E, M casts a small shadow on part of E
101
lunar eclipse
- when M passes into E shadow, the entire night side of E sees an eclipse
- can last as long as 100 minutes
102
umbra
Darker middle part of the shadow
103
penumbra
- the lighter outer portion of the shadow
- extends out about 3,000 km on either side of the eclipse path
104
why don't we get eclipses every month
because the orbit of M is 5* off from the orbit of the earth
105
annular eclipse
the Moon is slightly farther away, it cannot cover the entire Sun, so we get a ring of Sun around the Moon
106
total solar eclipse
- the Moon is slightly closer than usual and it covers the entire Sun
- in this case, the umbra of the Moon’s shadow actually reaches the surface of the Earth
107
duration of totality (total eclipse visible)
never longer than 7 minutes
108
penumbra
- the lighter portion
- extends out about 3,000 km on either side of the eclipse path
