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astronomy > Exam 1: ch 1, 2, and 4 > Flashcards

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

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2
Q

scientific method

A

observations → hypothesis/model → experiments → refine/thrown out hyp./model

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3
Q

Sun → earth distance

A

150,000,000 km

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4
Q

how many inches in a meter

A

39.4 in

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5
Q

how many miles in 1 kilometer

A

0.6 mi

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6
Q

what derives the astronomical unit(AU)

A

average sun-earth distance

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7
Q

how many km are in 1 AU

A

1.5 x 10^8

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8
Q

lightyear

A

the distance light travels in 1 year

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9
Q

speed of light (c)

A

c = 3.5 x 10^5 km/s

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10
Q

celestial sphere

A

an imaginary sphere around the earth with stars, planets, etc. attached to it

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11
Q

zenith

A

directly above where you stand

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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
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13
Q

how can you find the altitude (angle above the horizon) of the celestial pole

A

equal to your latitude

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14
Q

circumpolar zone

A

at a given location, the portion of the sky that never sets relative to that location

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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

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16
Q

ecliptic

A

the line traced by the sun across the sky over a year

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17
Q

constellation

A

one of the 88 sections of the sky

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18
Q

If you are standing at the N pole, where is the celestial equator?

A

your horizon

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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
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20
Q

If you are standing at 50°N latitude, where are the celestial poles?

A
  • N celestial pole is 50* N
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21
Q

how many degrees across is the moon?

A

0.5* in diamater

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22
Q

how much later does the sun rise each day?

A

4 minutes relative to the stars

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23
Q

how many constellations intersect the ecliptic?

A

13, but only 12 are talked about

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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

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25
Q

what does the word planet mean in ancient greek?

A

wanderer

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26
Q

how wide is the ecliptic/zodiac

A

18*

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27
Q

asterisms

A

notable star patterns that do not correspond to the modern constellations

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28
Q

neutrinos

A

close to the speed of light

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29
Q

how many light minutes away is the sun

A

about 8 light minutes

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30
Q

star cluster

A

locations in which stars are grouped together, but not so close that they are in a single system

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31
Q

Local Group

A

both the Milky Way and the Andromeda galaxy are part of this small group of galaxies

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32
Q

Virgo Supercluster

A

what the Local Group is part of

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33
Q

parallax

A

Effect of one object moving relative to another due to motion

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34
Q

stellar parallax

A

is the apparent shift of position (parallax) of any nearby star (or other object) against the background of distant stars

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35
Q

Ptolemy

A

created the geocentric model of the solar system

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36
Q

how do the planets move in the sky

A

they usually move E, but sometimes they turn around and move W for a little while before moving E again

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37
Q

retrograde motion

A
  • the orbital motion of an object in the direction opposite the rotation of a central object
  • temporary westward motion of the planets
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38
Q

cosmology

A

the study of the structure and origin of the cosmos (or universe)

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39
Q

How does the distance to an object affect how much it shifts due to parallax?

A

The farther away the object is, the less it appears to shift

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40
Q

apparent magnitudes

A

how Hipparchus measured the brightness of the stars, from 1(bright)-6(dim)

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41
Q

precession

A
  • refers to any of several slow changes in an astronomical body’s rotational or orbital parameters
  • “wobble” of the earth’s axis
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42
Q

how long does it take earth’ xis to complete one precession cycle

A

26,000 years

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43
Q

epicycle

A

in Ptolemy’s model, each planet goes around a small circular orbit

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44
Q

deferent

A

in Ptolemy’s model, the center of the epicycle orbits the earth on a larger circular path

45
Q

astrology

A

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
Q

horoscope

A

the chart that depicts the positions of the Sun, the Moon, and the planets in the sky when that person was born

47
Q

Copernicus

A
  • put forth the heliocentric model of the solar system
  • orbits were still circular, not elliptical
48
Q

Galileo

A
  • 1st person to use a telescope
  • discovered Jupiter’s moons
49
Q

latitude

A

angle north or south or the equator

50
Q

longitude

A

angle east or west of the prime meridian

51
Q

what is the equivalent of latitude on the celestial sphere?

A

declination

52
Q

declination

A

angle above or below the celestial equator

53
Q

what is the equivalent of longitude on the celestial sphere

A

right ascension

54
Q

right ascension

A

measured in time from the location of the vernal equinox

55
Q

vernal equinox

A

location of the sun on the 1st day of spring

56
Q

how is the celstial sphere vertically divided?

A
  • 24 hours
  • 15* per hour
57
Q

how is declination divided?

A

split each degree into 60 arc minutes and each arcminute into 60 arcseconds

58
Q

how is right ascension divided?

A

each hour is split into 60 arcminutes, and each minute is split into 60 arcseconds

59
Q

how does the local coordinate system work

A

– the altitude is the angle above your horizon
– the azimuth is the compass direction relative to your location

60
Q

Foucault pendulum

A

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
Q

when is a hemisphere experiencing summer

A

when that hemisphere is “leaning toward” the sun

62
Q

why does the tilt create season

A

because the sunlight hits the hemisphere that is “leaning toward” the sun more directly, and for longer, so it heats up more

63
Q

summer solstice

A
  • June 21
  • N tilted toward the sun (summer), S tilted away (winter)
64
Q

autumnal equinox

A
  • September 21
  • Neither hemisphere is pointed toward the sun, so equal sunshine
  • autumn/fall in N, spring in S
65
Q

winter solstice

A
  • December 21
  • S is tilted toward the sun (summer), N is tiled away (winter)
66
Q

Vernal equinox

A
  • March 21
  • Neither hemisphere pointed toward the sun
  • Spring in the N, autumn in the S
67
Q

N pole qualities

A

day for 6 months (3/21 - 9/21) then night for 6 months (9/21 - 3/21)

68
Q

arctic circle qualities

A
  • (lat. 66.5*N)
  • anywhere above has 24 hrs of day on the summer solstice
69
Q

Tropic of cancer qualities

A
  • (lat. 23.5*N)
  • Sun passes through zenith on the summer solstice
70
Q

Tropic of Capricorn qualities

A
  • (lat 23.5*S)
  • sun passes through zenith on the winter solstice
71
Q

Antarctic circle qualities

A
  • (lat. 66.5*S)
  • anywhere below has 24 hrs of day on the winter solstice
72
Q

S pole qualities

A

day for 6 months (9/21 - 3/21) then night for 6 months (3/21 - 9/21)

73
Q

how are seasons determined at the equator

A

by rainfall, not sunlight

74
Q

how are seasons determined at the equator?

A

by rainfall, not sunlight

75
Q

solar day

A

one rotation of the earth with respect to the sun

76
Q

sidereal day

A

one rotation of the earth relative to the stars: 23 hr 56 min

77
Q

apparent solar time

A

based on positions of the sun on your location

78
Q

mean solar day

A

the average length of apparent solar day over a year

79
Q

international date line

A
  • 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
Q

why can we see some sunlight before sunrise and after sunset?

A

because the atmosphere refracts (bends) the sunlight around the horizon

81
Q

day

A

rotation period of earth

82
Q

solar month

A

time for moon to complete its cycle of phases; 29.5306 days

83
Q

tropical year

A

orbital period of earth; 365.2422 days

84
Q

Julian calendar

A
  • 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
Q

Gregorian Calendar

A
  • a year that is 365.2425 days long
  • changes to leap years
86
Q

leap year rules

A
  • 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
Q

phases

A

Over a month, the moon appears to change size because of which portion is lit

88
Q

order of moon phases

A

New, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent

89
Q

rule for waxing vs waning

A
  • When lit portion of the moon is on right, it is waxing
  • When on left, it is waning
90
Q

sidereal month

A

the time it takes for the moon to go around the earth once, relative to the stars, 27.3217 days

91
Q

synchronous rotation

A

The moon rotates on its axis at the same rate that it orbits earth

92
Q

how much does the moon move in the sky each day

A

about 12*

93
Q

what direction does the moon travel

A
  • eastward
  • travels its own diameter in about 50 minutes
94
Q

what causes tides

A

moon’s gravity on earth

95
Q

oblate spheroid

A

when earth distorts slightly due to moon’s gravity

96
Q

tidal buldge

A
  • 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
Q

spring tides

A

When E, M, S are all lined up, we get particularly high high tides and low low tides

98
Q

neap tides

A

when M and S are at right angles, their tidal effects partially cancel, and we get less extreme tides

99
Q

how can eclipses occur

A
  • 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
Q

solar eclipse

A

When M is directly between S and E, M casts a small shadow on part of E

101
Q

lunar eclipse

A
  • when M passes into E shadow, the entire night side of E sees an eclipse
  • can last as long as 100 minutes
102
Q

umbra

A

Darker middle part of the shadow

103
Q

penumbra

A
  • the lighter outer portion of the shadow
  • extends out about 3,000 km on either side of the eclipse path
104
Q

why don’t we get eclipses every month

A

because the orbit of M is 5* off from the orbit of the earth

105
Q

annular eclipse

A

the Moon is slightly farther away, it cannot cover the entire Sun, so we get a ring of Sun around the Moon

106
Q

total solar eclipse

A
  • 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
Q

duration of totality (total eclipse visible)

A

never longer than 7 minutes

108
Q

penumbra

A
  • the lighter portion
  • extends out about 3,000 km on either side of the eclipse path

astronomy (3 decks)

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