Test One Flashcards
(115 cards)
1
Q
star
A
large glowing ball of gas that generates heat and light through nuclear fission
2
Q
planet
A
moderately large object that orbits a star
- shines by reflected light
- can be rocky, icy, or gaseous in composition
3
Q
moon
A
object that orbits a planet
4
Q
asteroid
A
small rocky object that orbits a star
5
Q
comet
A
small icy object that orbits a star
6
Q
solar system
A
star and all material that orbits it
-includes planets and moons
7
Q
nebula
A
interstellar cloud of gas and/or dust
-where stars are formed
8
Q
galaxy
A
great island of stars in space held together by gravity
-orbits a common center
9
Q
universe
A
sum total of all matter and energy
-everything within and between all galaxies
10
Q
light
A
travels at 300,000 km/s
11
Q
the further away we look into the distance the further we look back in
A
time
12
Q
light year
A
the distance light can travel in one year
speed of light)(1 year
13
Q
the sun is _____ times bigger than Earth
A
100
14
Q
the Milky Way is a part of a local cluster which is a part of a
A
supercluster
15
Q
milky way
A
- about 100,000 light years in length
- about 2,000 light years in height
- 1 of about 100 billion galaxies
16
Q
observable universe
A
14 billion light years
17
Q
cosmic calendar
A
scale on which we compress the history of the universe into one year
18
Q
one AU is _______ km`
A
150 million km
19
Q
Earth’s axis is tilted by _____ degrees
A
23.5
20
Q
how do galaxies move within the universe
A
galaxies are carried along in the expansion of the universe
21
Q
with the naked eye we can see _______ stars
A
2,000+
22
Q
constellation
A
a region of the sky
23
Q
how man constellations fill the entire earth sky
A
88
24
Q
celestial sphere
A
stars at different distances appear to lie on the celestial sphere
-all the constellations cover the entire celestial sphere
25
ecliptic
orbit of the sun through the celestial sphere
26
north celestial pole
straight above Earth's north pole
27
south celestial pole
straight above earth's south pole
28
celestial equator
above earth's equator
| -23.5 degrees
29
altitude
above horizon (local sky)
30
direction
along horizon(local sky)
31
an object's altitude and direction =
its location in local sky
32
meridian
line passing through zenith
33
zenith
point that is directly overhead
34
earth rotates from west to east so stars appear to move from
east to west
35
stars near the north celestial pole are circumpolar and
never set
36
we can't see stars near the
south celestial pole
37
how do constellations depend on latitude
They depend on latitude because your position on Earth determines which constellations remain below the horizon.
38
how do constellations depend on time of year
They depend on time of year because Earth's orbit changes the apparent location of the Sun among the stars.
39
latitude
position north or south of equator
40
longitude
position east or west of prime meridian
41
stars rise and set because of __________'s _______
earth's rotation
42
what is the reason for seasons?
the tilt of earth's axis
43
summer solstice
June
44
winter solstice
December
45
spring equinox
march
46
fall equinox
September
47
what causes phases of the moon
the moon's 27.3 day orbit around the earth
48
new moon
the sun doesn't light up any of the moon
49
waxing crescent
-makes a "P"
50
first quarter
right half side is illuminated by sun
51
waxing gibbous
mostly right side is illuminated by sun
52
full moon
entire moon is illuminated by sun
53
waning gibbous
mostly left side is illuminated by the sun
54
last(third ) quarter
left half side is illuminated by sun
55
waning crescent
makes a lowercase "d"
56
how do we get eclipses
when the moon and earth pass through each others shadows that creates eclipses
57
lunar eclipses only happen with ____ moons
full
58
solar eclipses happen only with ____ moons
new
59
solar eclipses can be ____, ____, ____
partial, total, or annular
60
lunar eclipses can be _____, ______, _____
penumbral, partial, or total
61
we have about ___ eclipse seasons each year
2
62
which cycle do eclipses recur in
Eclipses recur with the 18-year, 11 1/3-day saros cycle, but type (e.g., partial, total) and location may vary.
63
why did the ancient greeks reject stellar parallax
Most Greeks concluded that Earth must be stationary, because they thought the stars could not be so far away as to make parallax undetectable.
64
many current systems have their roots from ancient astronomy such as
```
*Daily timekeeping
• Tracking the seasons
• Calendar
• Monitoring lunar cycles
• Monitoring planets and stars
• Predicting eclipses
```
65
ancient astronomical observations in Africa
Ancient people of central Africa (6500 BC) could predict seasons from the orientation of the crescent Moon.
66
days of the week were named for
the sun, moon, and visible planets
67
ancient astronomy- Egyptian obselisk
Shadows tell time of day.
68
ancient astronomy- stonehenge
predict solstices and equinoxes
69
most sophisticated geocentric model
ptolemaic model
| used for 1,500 years
70
Eratosthenes
measured the circumference of the earth relatively accurately in 240 BC
71
ptolemaic model
The Ptolemaic model had each planet move on a small circle whose center moves around Earth on a larger circle
72
copernicus
proposed a sun centered model in 1543
- used model to determine layout of solar system
- no more accurate than ptolemaic model because Copernicus used perfect circles
73
Tycho Brahe
made the most accurate naked eye measurement of planetary positions
- still didn't detect stellar parallax
- still thought earth was the center of the solar system
74
kepler
tried to match Tycho's observations but got discrepancies which led him to figure out ellipses
75
Kepler's 1st law
orbit of each planet around sun is an ellipse with the sun at one focus
76
what is an ellipse
it looks like an elongated circle
77
Kepler's 2nd law
as planet moves around its orbit it sweeps out equal areas in equal times
-aka planets travel faster near the sun and slower the further it is from the sun
78
Kepler's 3rd law
more distant planets orbit the sun at slower average speeds
p^2 = a^3
p= orbital period in years
a= average distance from sun
79
Galileo
overcame three major objections of the theorists of his time
80
Galileo overcoming the nature of motion
Galileo showed that objects will stay with earth as it moved and would stay in motion unless a force acts to slow them down (Newton's first law of motion).
81
galileo overcoming the concept of heavenly perfection
Using his telescope, Galileo saw:
• SunspotsonSun ("imperfections")
• Mountainsandvalleys on the Moon (proving
it is not a perfect sphere)
82
galileo overcoming the parallax
Galileo showed stars must be much farther than Tycho thought — in part by using his telescope to see the Milky Way is countless individual stars.
-If stars were much farther away, then lack of detectable parallax was no longer so troubling.
Galileo also saw four moons orbiting Jupiter, showing that not all objects orbit Earth.
83
eccentric
how stretched out an ellipse is
- a measure of how an orbit deviates from circular. A perfectly circular orbit has an eccentricity of zero; higher numbers indicate more elliptical orbits.
84
foci
on both sides of the center of an ellipse
85
retrograde motion
Astronomers use the term to refer to the occasional backwards motion of the planets as seen in Earth's sky. When used in this way, retrograde motion is entirely an illusion caused by the moving Earth passing the outer planets in their orbits.
86
phases of venus
Galileo observed the phases of Venus and showed that it orbits the sun and not the earth
87
hallmark of science #1
Modern science seeks explanations for observed phenomena that rely solely on natural causes.
88
hallmark of science #2
Science progresses through the creation and testing of models of nature that explain the observations as simply as possible.
89
hallmark of science #3
A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations.
90
Occam's razor
“one should not increase, beyond what is necessary, the number of entities required to explain anything”
91
sidereal day
• The amount of time it takes the Earth to spin
once with respect to the distant stars.
• 23 hours 56 minutes
92
solar day
• The amount of time time takes the Earth to
spin once with respect to the Sun.
• 24 hours
93
synodic month
The amount of time it takes the Moon to
repeat its phase (i.e., new to the next new).
• 29.5 days
94
sidereal month
The amount of time time takes the Moon to complete one orbit with respect to the background stars.
• 27.3 days
95
sidereal year
The amount of time it takes the Earth to orbit the Sun once with respect to the background stars.
96
tropical year
The amount of time time takes the Earth to go from the March equinox one year to the March equinox the next year.
97
sidereal period
The amount of time it takes a planet to orbit the Sun, measured with respect to the background stars.
98
synodic period
The time from when a planet is aligned with the Sun in our sky until it is again aligned similarly.
99
apparent solar time
Noon is the time when the shadow on a sundial is shortest.
100
mean solar time
Noon is set to the average time when the shadow on a sundial is shortest
101
standard time
Mean solar time in the center of your time zone
102
universal time
Mean solar time at `0 degrees longitude
| Useful for navigation and astronomy.
103
why do we have leap years?
Because there are ~365.25 days in a year, a calendar based based on 365 days will get out of synch with the seasons
104
Julian calendar
add an extra day every four years
105
Gregorian calendar rules for leap years
Hence the Gregorian calendar: no leap year at full centuries (1800, 1900), only if the year can be divided by 400 (1600, 2000).
106
declination
latitude on celestial sphere
| +/- instead of north and south
107
right ascension
longitude on celestial sphere
| measured in hours
108
sky at north pole
Stars move parallel to your horizon.
| • A star's declination is equal to its altitude.
109
sky at equator
Stars move perpendicular to your horizon.
110
the sun's position during solstices
The Sun circles the sky at an altitude of 23.5o on the summer solstice.
• The Sun circles 23.5o below the horizon on the winter solstice.
111
sun at the equator
The Sun passes through the zenith on noon of the equinoxes.
112
sun at the tropics
The tropic of Cancer and the tropic of Capricorn represent the northernmost and southernmost latitudes where the Sun will pass directly overhead at some point during the year.
113
sun at arctic and antarctic circles
he Arctic and Antarctic circles represent the latitudes above (Arctic) or below (Antarctic) which there will be more than 24 hours of consecutive sunlight during the summer and darkness during the winter.
114
how can you determine your latitude
by finding altitude of celestial pole
115
how can you find your longitude
find apparent solar time and compare it to time at a known longitude
