Studied by 1 personAstronomers use the term "dark matter" to refer to
very abundant, but very mysterious, matter that is inferred to exist only because of the effects it has on the motions of our galaxy and other galaxies
Why can't astronomers use optical telescopes to view all parts of our Milky Way galaxy?
Abundant gas and dust clouds obscure the view within the mid
As space in the universe gradually expands and stretches, _______________ are separating from one another.
all clusters of galaxies
"Precession" refers to
wobbling while spinning
"Revolution" refers to
moving in a path around something
"Rotation" refers to
spinning in place
The Sun's apparent yearly path around the celestial sphere is called
the ecliptic
An observer in the Northern Hemisphere watches the sky for several hours. Due to the motion of Earth, this observer notices that the stars near the north celestial pole appear to move
counter
An observer in the Southern Hemisphere watches the sky for several hours. Due to the motion of Earth, this observer notices that the stars near the south celestial pole appear to move
clockwise
If the Sun sets in the northwest, then it will rise the next day
from the northeast
If the Sun sets in the southwest, then it will rise the next day
from the southeast
An observer on Earth's north pole would see
Polaris almost directly overhead.
Facing south from San Francisco, you see stars
arc across the sky moving from left to right
Facing east from San Francisco, you see stars
rise higher in the sky, moving from the lower left toward the upper right.
Facing west from San Francisco, you see stars
rise higher in the sky, moving from the lower right toward the upper left
Longitude measures
one's east
Latitude measures
one's north
Winnipeg, Canada, and Puebla, Mexico, have nearly the same longitude, but they have very different latitudes. Therefore,
tonight's evening sky in these two places will have completely different sets of constellations
The time it takes the Earth to complete exactly one orbit around our Sun is called the
sidereal year
The time between one spring equinox and the next is called the
tropical year
The time it takes our Earth to spin exactly once on its axis is called the
sidereal day
In Earth's Southern Hemisphere, the summer season begins in
December
The Earth is farthest from the Sun in the month of
July
The "ecliptic" is
the apparent yearly path of the Sun across the celestial sphere
A star that rises from the northeast will set
in the northwest
A star that rises from the southeast will set
in the southwest
From where on Earth might you observe a star rising from the west?
You cannot see this from anywhere on Earth because the whole Earth rotates from west to east.
The imaginary line running from due north, through directly overhead, to due south is called __________.
the meridian
The ________ is the point on the celestial sphere that is directly above an observer.
zenith
Our Sun takes ___________ to orbit around the center of the Milky Way galaxy.
hundreds of millions of years
Planets, such as Venus or Jupiter, that are visible in Earth's sky
may appear only within the constellations of the Zodiac
Declination measures
an object's position on the celestial sphere, measured as an angle north or south of the celestial equator
Right ascension measures
an object's position on the celestial sphere, measured as an angle east of the spring equinox
An observer on Earth's equator would see
that the celestial equator passes directly overhead
Most of the atoms that compose the mass of the Earth (and of your body) were created by
nuclear fusion inside stars that are now long dead
The average distance between the planet Mercury and the Sun is approximately 58,000,000 km. How might this distance alternatively be expressed?
Both of the above answers (C and D) are correct, but Answer C uses powers
The average distance between the Earth and the Sun is approximately 150,000,000 km. What is this in powers
of
The average distance between the Earth and the Moon is approximately 380,000 km. How might this distance alternatively be expressed?
Both Answers B and D are correct, but Answer B uses powers
How many "nm" are in a "cm"?
10,000,000
What is 3 × 103 multiplied by 4 × 108?
1.2 × 1012
10 km/sec divided by 5 sec equals
2 km/sec2
5 km/sec divided by 10 km/sec equals
0.5 km2/sec2
Suppose a new dwarf planet in our Solar System is discovered to be 12 billion kilometers from the Sun. How many AU from the Sun would this be?
80 AU
The diameter of an atom of hydrogen is 0.00000000011 meters. Which of the following shows another way to write this value?
none of the above OR 0.11nm
One "megasecond" equals how many days? (approximately)
11.574 days
One "milliyear" equals how many hours? (approximately)
8.766 hours
One "kilosecond" equals how many minutes?
16 2/3 minutes
On a scale in which the distance from the Earth to the Sun is represented by one inch, a light
year would be most nearly equal to
The diameter of the Milky Way galaxy is roughly 80 million times larger than which of these?
the diameter of Pluto's orbit around the Sun
The planet Earth is, on average, 150 million kilometers from the Sun. How many light
years from the Sun is this?
If the current "cosmic year"
Water is a chemical combination of atoms of hydrogen and oxygen. For water that is found here on Earth, those atoms of hydrogen were first created
in the Big Bang, almost immediately after the universe began.
When astronomers look at galaxies that are 10 billion light
years away from us, they see
Which of these is the largest?
the distance from here to the nearest star other than our Sun
When astronomers look at galaxies that are 10 million light
years away from us, they see
Astronomers estimate that there are somewhere between 1021 and 1023 planets in the observable universe. Be conservative and suppose there are just 1021= 1,000,000,000,000,000,000,000. Now suppose that life is so rare that only one planet in a million supports life (or has a moon that supports life). If that were so, then how many life
bearing planets would there be in the observable universe?
On a scale where the Sun is five feet wide, the Earth would be most comparable in size to ____________, and the Earth would be located roughly ____________ away from the Sun.
a half
Roughly how many times smaller is the full diameter our Milky Way galaxy compared to the full diameter of the portion of the universe that we can observe?
276,000
Anatomically modern humans (homo sapiens) have lived on this planet for perhaps as long as 200,000 years. What fraction of the age of the Earth is this?
roughly 44 millionths of Earth's total age
Why do constellations have angular sizes but not true sizes?
Constellations extend to infinite distances outward from Earth.
From a middle
north latitude place, such as California, the stars rise
From a middle
south latitude place, such as Australia, the stars set
From a middle
south latitude place, such as Australia, the stars rise
Suppose that a 400 km wide asteroid passes close enough to Earth that, when viewed through a telescope, it covers an angle of one arcsecond. Approximately how close did the asteroid pass?
82.5 million km
Suppose you have a job with the Coast Guard, and one night you receive a radio distress call from a small boat that is lost at sea. Hoping to give some information about their location, the caller claims that they have observed stars arcing clockwise around the star Polaris, which they have measured to be 20° above their horizon. From this information, you determine that
the people on the boat must be confused about which star is Polaris, and you won't be able to learn what latitude they are at until they get it right.
Suppose the Hubble telescope observes one of Jupiter's moons to have an angular size of one arcsecond. If, at the time of this observation, the distance to Jupiter is approximately 750,000,000 km, then approximately how big across is this moon?
3600 km
Suppose you wake up one morning to find that the axis of Earth's rotation has been changed by evil, practical joking aliens to be perfectly level within the plane of Earth's orbit around the Sun The seasons and seasonal variations throughout the year then would be
much more severe
The location of the Sun at the moment of the Summer Solstice is a point
Both Answers B and C are correct (on the ecliptic and in the constellation of Gemini)
The location of the Sun at the moment of the Fall Equinox is a point
Both answers A and B are correct (on the celestial equator and on the ecliptic)
The location of the Sun at the moment of the Spring Equinox is a point
Both answers A and B are correct (on the celestial equator and on the ecliptic)
If we set the length of one day equal to the time it takes Earth to spin exactly once on its axis, then
every year would need to be a day longer than it is now
The city of Mumbai, in India, is at a latitude of 19° North. The mid
day Sun passes directly overhead (zenith) as seen from Mumbai on
The latitude of Boston, Massachusetts, is 42½° North. On the day of the Summer Solstice, how high does the Sun reach in the sky as seen from Boston at mid
day?
If you observe the north celestial pole to be 60° above the northern horizon, what is your latitude on Earth?
60° N
The city of Belo Horizonte, in Brazil, is at a latitude of 20° South. The mid
day Sun passes directly overhead (zenith) as seen from Belo Horizonte on
If the Sun rises from precisely due east, then
it must be the day of either the spring equinox or the fall equinox
Which of the following is not an effect of Earth's precession?
The position of Polaris changes relative to the stars, The angle between the ecliptic and the celestial equator changes
Which of the following is/are happening?
The Local Supercluster is expanding
Which of the following could be used to determine your latitude on Earth?
Any one of the above could be used to determine your latitude (the altitude of a celestial pole above your horizon, which constellations are visible in the sky, how stars appear to move as they rise)
Approximately how many times has our Solar System gone around the Milky Way galaxy since dinosaurs first evolved?
just once
Approximately how many times has our Solar System gone around the Milky Way galaxy since our Solar System was born?
20 times
If we adjusted our calendars so that the average length of a calendar year was equal to the time between one spring equinox and the next spring equinox, then
nothing would change. Our calendar is already adjusted this way
If you observe at different times while remaining in the same place, then from what places on Earth is it possible to observe the entire celestial sphere?
anywhere along Earth's equator
If the Earth did not rotate, we could still define the _________ but we could not define the _________.
ecliptic; celestial equator
If the Moon is in the waning crescent phase, then two weeks later it will be
in the waxing gibbous phase
If the Moon is in the waxing gibbous phase, then two weeks later it will be
in the waning crescent phase
That fact that we always see the same face of the Moon tells us that
the Moon's rotation period is the same as its orbital period around the Earth
The "nodes" of the Moon's orbit are where
the Moon's orbital path crosses the ecliptic plane
What might the phase of the Moon be when a lunar eclipse is happening?
full
What might the phase of the Moon be when a solar eclipse is happening?
new
The types of possible solar eclipses are
total, annular, and partial
If the Moon's umbra reaches the Earth, then
a part of the Earth is darkened and sees a solar eclipse
a part of the Earth is darkened and sees a solar eclipse
the Moon's orbital path crosses the ecliptic plane
The Metonic cycle is
a roughly 19 year period used to keep lunar calendars synchronized with Earth's seasons
In the Greek geocentric model, the apparent retrograde motion of a planet occurs when
the planet moves closer to Earth as it follows the path of a small circle that turns around a larger circular path that goes around the Earth
Who was the first known person to suggest that the Earth goes around the Sun?
Aristarchus
Who created a successful model to explain the complex motions of the planets in the sky that kept the Earth's position fixed at the center of the Solar System?
Ptolemy
Who first discovered that the orbital paths of the planets were ellipses and not circles?
Kepler
Kepler's 2nd Law
states that a planet sweeps out equal areas of its orbit in equal intervals of time
Kepler's 3rd Law
describes a relationship between a planet's average distance from the Sun to the time it takes that planet to orbit around the Sun
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