Astronomy Exam 1
Why does the angle of the Sun's rays matter in regard to Earth's seasons?
They are more spread out if they strike at an angle
Different cultures created different calendars because
They used different definition of the day, month, and year
Despite the fact that the Sun's gravitational force on Earth is almost 200 times stronger than the Moon's gravitational force on Earth, the strength of the Moon's tidal force on Earth is more than twice as strong as the Sun's. Why is that?
Tidal forces depend on the difference between the gravitational force on the near side of Earth compared to the far side
The celestial equator is :
directly above the Earth's equator
A light-year is a unit commonly used in astronomy as a measure of
distance
The time it takes a planet to complete its orbit around the Sun is determined by its
distance from the Sun
When the Sun, Earth, and a plaent all lie along a straight line, the planet is at
either opposition or conjunction
When Earth catches up to a slower-moving outer planet and passes it in its orbit, the planet
exhibits retrograde motion
Tides on Earth occur only in the oceans (true or false)
false
A superior planet is one that is
farther from the Sun than Earth
Imagine two objects moving away from you. Object A is faster than object B. You will observe that the light
from object A has a larger shift in frequency
One of the nearest stars is Alpha Centauri, whose distance is 4.4 light-years. The time it takes light to travel from Alpha Centauri to us is
4.4 years
If the plane of the Moon's orbit were the same as the ecliptic (the plane of the Earth's orbit), we would have
One solar eclipse and one lunar eclipse each month
Which of the following is not true about orbits
Orbits are always circular
Galileo observed that Venus had phases that correlated with its size in his telescope. From this information, you may conclude that Venus
Orbits the sun
Just after sunset, a star appears near the eastern horizon. Where will it appear to be after 6 hours
Overhead
Just after sunset, a star appears near the eastern horizon. Where will it appear to be after 6 hours?
Overhead
If you measured the orbital period of the Moon and the distance between Earth and the Moon, then you could calculate
The sum of the masses of Earth and the Moon
Planets with high eccentricity may be unlikely candidates for life because
The temperature varies too much
Imagine that you observe a star/planet system, edge-on. When the planet is moving away from Earth, in which direction is the star moving?
toward Earth
The diffraction limit of a 4-m telescope is _________ than that of a 2-m telescope.
two times smaller
A sidereal day is the time
required for Earth to rotate once on its axis relative to the distant stars
The moon:
rotates on its axis with the same period as its revolution about the Earth
The magnification of a telescope depends on the focal length of the telescope and
the focal length of the eyepiece
If Erath had half of its current radius, how would the strength of lunar tides change
the highs would be lower and the lows would be higher
After greatest wester elongation, before superior conjunction
Waxing gibbous Venus
Polaris, the North Star, is unique because:
it is the only star in the sky that doesn't move throughout the night.
Which of the following is not a reason to put a telescope in space?
to get closer to the stars
The distance between the foci when the eccentricity equals zero is
zero
If you observe the Moon rising in the east as the Sun is overhead, then you know that the phase of the Moon must be
First quarter
If we see a first quarter moon today, what will people on the other side of Erath see later today
First quarter moon
Light has aspects of
both a particle and a wave
Imagine two objects moving away from you. Object A is faster than object B. You will observe that the light
both objects are redshifted
THe connection between gravity and orbits enables astronomers to measure the ______________ of stars and planets
masses
If an object crosses from farther to closer than the Roche limit it,
may be torn apart
As a blackbody becomes hotter, it also becomes __________ and __________.
more luminous; bluer
If you push an object at its center of mass, it
moves away from you
An object that is redshifted is
moving away from us
You are standing at one of the following latitudes on the Earth's surface. At which latitude does the Sun have the highest altitude on June 21, the summer solstice in the Northern hemisphere.
+23.5 (Tropic of Cancer)
During a certain comet's orbit around the Sun, its closest distance to the Sun is 0.6 AU, and its farthest distance from the Sun is 35 AU. At what distance will the comet's orbital velocity be the largest? 1. 1.2AU 2. The comet's velocity is constant no matter what its distance is 3. 17.8 AU 4. .6 AU 5. 35 AU
.6 AU
The eccentricity of the majority of the planetary orbits in our Solar System is approximately
0
The angular resolution of a ground-based telescope (without adaptive optics) is typically
1 arcsecond (arcsec)
About how long does it take Earth to go around its axis once?
1 day
One astronomical unit (AU) is about 149,600,000 km. This distance is equal to _____ meters.
1.496 X 10^11
Two stars are of equal luminosity. Star A is 3 times as far from you as star B. Star A appears ______ star B.
1/9 as bright as
What is the surface temperature of a star that has a peak wavelength of 290 nm?
10,000 K
Which of the following is the best location for an infrared telescope on the ground?
10,000 ft about sea level
Assume that the Sun rises at 6:00 AM. About what time does the Third Quarter Moon rise?
12:00 midnight
The Voyager 1 spacecraft is currently 18 billion km from Earth and heading out of our Solar System. How long does it take radio messages from Voyager 1 to reach us?
17 hours
If you discovered a planet orbiting another star, and the planet had an orbital period of 2 years and a semimajor axis of 2 AU, what would be the mass of its parent star? You can assume the planet's mass is much less than the star's mass.
2.0 MSun
About how long does it take the Moon to orbit Eath
29 days
Suppose Betelgeuse, the bright star in the shoulder of Orion, rises above the eastern horizon at 3:00 A.M. on a particular night. Then five nights later it will rise at _____ A.M..
2:40 AM
Assume that a planet just like Earth orbits the bright star named Sirius. If this Earth-like planet orbits with a semimajor axis of 1 AU and an orbital period of 7 months, what is the mass of Sirius?
3 MSunn
The number 384,000,000 can also be written in scientific notation
3.84 X 10^8
In 2008, the Cassini spacecraft made a flyby of Enceladus, one of the icy moons of Saturn. If the spacecraft's high-resolution camera had an angular resolution of 3 arcsec and it flew at an altitude of 23 km above Enceladus's surface, how large an object could be resolved on the surface?
30 cm
The Sun and the Moon have an angular diameter of about
30' (30 arcminutes)
The speed of light in a vacuum is approximately
300,000 km/s
About how long does it take Earth to orbit the Sun
365 days
What wavelengths of light can the human eye see
380 nm to 750 nm
If the Moon were 2 times closer to the Earth than it is now, the tides would be _________ times stronger
4
The light-gathering power of a 4-meter telescope is _____________ than that of a 2-meter telescope
4 times larger
If the Moon were 2 times closer to Earth than it is now, the gravitational force between Earth and the Moon would be
4 times stronger
Light with a wavelength of 600 nm has a frequency of
5 x 10^14 Hz
Assume the Sun sets at 6:00pm. About what time does the New Moon set
6:00 PM
If you find that the Hα line in a star's spectrum occurs at a wavelength of 656.45 nm, what is the star's radial velocity? Note that the rest wavelength of this line is 656.30 nm.
70 km/s away from you
A brick pizza oven is emitting blackbody radiation that peaks at 3840 nm. How hot is the oven?
755K
If an event were to take place on the Sun, how long would it take for the light it generates to reach us?
8 minutes
A theoretical model is
A detailed description in terms of known physical laws or theories
A spaceship is traveling toward Earth while giving off a constant radio signal with a wavelength of 1 meter (m). What will the signal look like to people on Earth?
A signal with a wavelength less than 1 m
Copernicus's heliocentric model provided 1. A simpler explanation of retrograde motion 2. a way to estimate the planet-Sun distances in terms of the Earth-Sun distance 3. a way to estimate how long it took each planet to orbit the sun
All answers are correct
A theory is: 1. A hypothesis that has withstood many attempts to falsify it 2. Tied to known physical laws 3. Able to make testable predictions
All options are correct
Just after sunset, a star appears near the western horizon. Where will it appear to be after 6 hours
Below the western horizon
For a system in which a planet orbits a star, the center of mass is located
Along the line between the planet and the star, closer to the star
For a pair of objects, the center of mass is located
Along the line between the two objects, closer to the more massive object
Why is an iron atom a different element from a sodium atom?
An iron atom has more protons in its nucleus than a sodium atom has
The term satellite in astronomy means
Any low-mass object that is orbiting a more massive object
IF the Moon was New last Sunday, what phase will it be this Sunday
At or very near First Quarter
Where on the Earth can you see the north celestial pole on the horizon?
At the equator
Where on Earth can you see the north celestial pole at the zenith?
At the north pole
A spaceship approaches Earth at 0.9 times the speed of light (0.9c) and shines a powerful searchlight onto Earth. How fast will the photons from this searchlight be moving when they hit Earth?
At the speed of light, c
In the heliocentric model of the Solar System, which planets exhibit retrograde motion?
Both superior and inferior planets
The horizon is defined
By the idrection perpendicular to a line to the zenith
Kepler's second law says that if a planet is in an elliptical orbit around a star, then the planet moves fastest when the planet is
Closest to the star
If you are standing in a fixed location, you may notice that the pitch of a passing train's whistle changes. What produces this effect?
Doppler effect
At the center of the geocentric model of the Solar System is the
Earth
What causes the angle of the Sun to change over the year?
Earth's North Pole always points in the same direction in space. Sometimes this is toward the SUn, and sometimes its away from the Sun
Ultraviolet radiation with wavelengths shorter than about 200 nm are hard to observe primarily because
Earth's atmosphere easily absorbs it
There is an angle between the ecliptic and the celestial equator because
Earth's axis is tilted with respect to its orbit
A lunar eclipse occurs when _____________ shadow falls on ______________
Earth's, the Moon
The Moon and a particular star appear in the same place in the sky one night. Where will the Moon be located one week from now?
East of the star
What is the parth of the Sun across the sky called?
Ecliptic
If you observe the Moon rising in the east as the Sun is setting in the west, then you know that the phase of the Moon must be
FUll
Suppose tonight is new moon. You are standing on the Moon, facing the Earth. What phase Earth do you see?
Full Earth
Superior conjunction
Full Venus
Best time to observe an inferior planet in the evening
Greatest easter elongation
How did Ptolemy "fix" the geocentric system?
He introduced epicycles
How does the speed of light traveling through a medium (such as air or glass) compare to the speed of light in a vacuum?
It is always less than the speed of light in a vacuum
What does it mean for a planet to be at opposition?
It is closest to Earth in its orbit
Assume that at sunset today, Jupiter appears to be 20 degrees away from the Sun. If the sidereal period of Jupiter is 12 years, when will it next appear in this same position relative to the Sun?
In 12 years
Suppose you are suddenly transported to a planet that had 1/4 the radius of Earth but the same mass as Earth. Your weight would _________ by a factor of _________.
Increase; 16
_________ hypothesized that planetary motions could be explained by a force arising from the attraction between the mass of the planet and the Sun that decreased with the square of the distance between them.
Isaac Newton
What does it mean for a star to be circumpolar?
It never sets below the horizon
If an object is moving in a circular orbit at a constant speed, which of the following is false?
Its acceleration is zero
Suppose you read in the newspaper that a new planet has been found. Its average speed in orbit is 33 km/s. When it is closest to its star it moves at 31 km/s, and when it is farthest from its star it moves at 35 km/s. This story is in error because
Kepler's seconds law says the planet must move fastest when it is closest, not when it is farthest away
Which of the following are the inferior planets?
Mercury and Venus
Which planet is the only one that could be in opposition (Mercury, Venus, Earth, Mars)
Mars
Which of the following was not discovered by Galileo using a telescope
Mars has a polar ice cap similar to Earth
Which of the following are superior planets
Mars, Jupiter, Saturn
Which planet has a synodic period relative to Earth that is longer than its sidereal period?
Mercury
If you have two moons that have the same radius, but Moon A is denser and has 2 times the mass of Moon B, how do their escape velocities compare?
Moon A has an escape velocity that is 1.4 times larger than Moon B
When using the scientific method, a hypothesis that would explain a particular observation
Must be able to be tested
As seen from the Moon, how often does the Earth set
Never
INferior Conjunction
New Venus
In science an idea that cannot be tested is
Not a scientific idea
A star appears circumpolar at a location at +30° latitude. How will it appear from -30° latitude?
Not visible at all
___________ is the idea that the simplest explanation for a phenomenon is usually the correct one.
Occam's razor
Kepler's third law for our Solar System can be expressed mathematically as
P^2 = A^3
Retrograde motion is seen when _______________ due to Earth's motion
Planets change the direction in which they move across the night sky
Kepler's second law says that
Planets move fastest when they are closet to the Sun
Who of the following was not a proponent of the heliocentric model of the solar system
Ptolemy
Greatest easter elongation
Quarter Venus
The Doppler shift can be used to determine the _________ of an object.
Radial velocity
How do the wavelength and frequency of red light compare to the wavelength and frequency of blue light?
Red light has a longer wavelength and lower frequency than blue light
The speed of light was first determined by which scientist?
Romer
Star A and star B appear equally bright in the sky. Star A is twice as far away from Earth as star B. How do the luminosities of stars A and B compare?
Star A is 4 times as luminous as star B
An alignment when a planet appears on the opposite side of the Sun from Earth
Superior conjunction
The time it takes for a planet to come back to the same position relative to the Sun is called its _________ period.
Synodic
Which term describes how long it takes the Moon to make a full cycle of phases?
Synodic month
In order to account for retrograde motion, Ptolemy had to resort to what embellishment to his geocentric model for the solar system?
That planets would travel on smaller circles that were superimposed onto their larger, circular orbits around the Earth
When a boat moves through the water, the waves in front of the boat bunch up, while the waves behind the boat spread out. This is an example of
The Doppler effect
Which of the following are in order from smallest to largest?
The Milk Way Galaxy, The Local group, the virgo supercluster
We always see the same side of the Moon because
The Moon rotates on its axis once for each revolution around Earth
Tides on Earth are primarily due to
The Moon's gravitational pull on the Earth
Why do solar eclipses seem much rarer than lunar eclipses
The Moon's shadow is much smaller than the Earth's , so each solar eclipse is only visible within a small area
Which of the following is true about a comet that si on an elliptical orbit around the Sun?
The comet's speed is greatest when its nearest the Sun
Because of _______________, we can conclude that gravity works the same way on Earth as it does on Mars
The cosmological principle
If the wavelength of a beam of light were to double, how would that affect its frequency?
The frequency would be two times lower
If the Moon had twice the mass that it does, how would the strength of the lunar tides change?
The high tides would be higher, and the low tides would be lower.
Which is not true on the vernal and autumnal equinoxes?
The motion of the stars in the sky is different than on other days/
Astronomers argued that the heliocentric model of the Solar System was simpler than the geocentric model, based on
The observed retrograde motions of the planets
Day and night are caused by
The rotation of Earth on its axis
At sunrise, the Moon is about 45° above the eastern horizon. What phase is it in?
Waning crescent
After greatest eastern elongation, before inferior conjunction
Waning crescent Venus
What is the difference between visible light and X-rays
Wavelength; X-rays have a shorter wavelength than visible light
A planet appears overhead near sunrise
Western quadrature
Imagine a planet in a very eccentric elliptical orbit around a star. This planet has no moons, but it has oceans. This planet's orbit not tidally locked. Are there tides?
Yes, because the strength of the tidal force will change with the distance from the star
IF Earth did not have a moon, would we still have tides
Yes, but our tides would be only about half as strong since the Sun's tidal force is about half of the Moon's
When an electron moves from a higher energy level in an atom to a lower energy level,
a photon is emitted
AN atmospheric window is
a region of the electromagnet spectrum that can reach the ground
Which of these stars would have the biggest redshift
a star moving at high speed away from you
A centripetal force is
any force that points toward center of a circular path
Constellations are groups of stars that
are close to each other in Earth's sky
The temperature of an object has a very specific meaning as it relates to the object's atoms. A high temperature means that the atoms
are moving very fast
A star that is noticeably redder in color than another is likely
at a lower temperature than the other
The angular resolution of a ground-based telescope is usually determined by
atmospheric seeing
Imagine that you observe a star/planet system, edge-on. When the planet is moving away from Earth, the light from the star is
blueshifted
An object in a(n) __________ orbit in the Solar System will remain in its orbit forever. An object in a(n) __________ orbit will escape from the Solar System.
bound; unbound
What does amplitude reveal about light
brightness
Which formula denotes how the speed of light is related to its wavelength and frequency?
c = yf
A full moon
can never rise at midnight
Saying that something is quantized means that it
can only have discrete quantities
The Sun, Moon, and stars
change their relative positions over time
An inferior planet is one that is
closer to the Sun than Earth is
Looking down on Earth from above the North Pole, the Moon orbits Earth
counterclockwise
Suppose you are suddenly transported to a planet with 1/4 the mass of Earth but the same radius as Earth. Your weight would _________ by a factor of _________.
decrease 4
If we wanted to increase the Hubble Space Telescope's altitude above Earth and keep it in a stable orbit, we also would need to
decrease its orbital speed
As wavelength increases, the energy of a photon _________ and its frequency _________.
decreases, decreases
A_____________ becomes a ______________when repeated testing of its predictions does not disprove it
hypothesis; theory
If the distance between Earth and the Sun were cut in half, the gravitational force between these two objects would
increase by 4
Which of these types of electromagnetic radiation has the longest wavelength
infrared
The phase of the Moon at a solar eclipse
is always new
If you went to Mars, your weight would be
lower because Mars has lower mass and a smaller radius that together produce a lower gravitational force
The force of gravity than an object has is directly proportional to its
mass
You observe the spectrum of two stars. Star A has an emission line from a known element at 600 nm. Star B has emission lines from the same atom, but the emission line is occurring at 650 nm. One possible explanation for this observation is: that star A is
moving toward us faster than star B
During an annular solar eclipse, the Moon must be
near apogee, because its angular size is smaller
If the Sun is located at one focus of Earth's elliptical orbit, what is at the other focus?
nothing
The radial velocity of a star or other object is measured by
observing the Doppler shift of spectral lines in the light from the object
As two objects orbit one another, they are always
on opposite sides of the center of mass, traveling in opposite directions in space
You see the first quarter Moon on the meridian. Where is the sun?
on the western horizon?
A planet appears overhead at midnight
opposition
Keplers third law is a relationship between an orbiting object's
period and semimajor axis
Einstein showed that the _________ could be explained if photons carried quantized amounts of energy.
photoelectric effect
In Newton's universal law of gravitation, the force is
proportional to both masses
A scientific theory can be shown to be wrong if
scientists gather new data that contradict its predictions
The average distance between a planet and the Sun is given by the _________ of its elliptical orbit.
semimajor axis
The amount of time a planet takes to orbit the Sun is called its _______________ period
sidereal
Galileo observed that Jupiter has moons. From this information, you may conclude that;
some things do not orbit Earth
According to kepler's laws, a comet with a highly eccentric orbit will
spend most of its time far from the sun
You are shopping for telescopes online. You find two in your price range. One of these has an aperture of 20 cm, and the other has an aperture of 30 cm. If aperture size is the only difference, which should you choose, and why?
the 30 cm, because the light-gathering power will be better
The Local Group is the environment around
the Milky Way that contains a few dozen galaxies
Spring tides occur only when
the Moon's phase is new or full
The aperture of a telescope is which of the following
the diameter of the primary lens/mirror
the distance used in Newton's law of gravitation is
the distance between the centers of the object
Where on Earth can you stand and, over the course of a year, see the entire sky?
the equator
In a star with a temperature of 10,000 K, the transition from level 3 to level 1 of hydrogen produces photons with a wavelength of 102.5 nm. In a star three times as hot as the first, this transition produces photons with
the same wavelength
Compare to your mass on Earth, on the Moon your mass would be
the same, mass doesn't change
Why can you see fainter stars with an 8-inch telescope than you can see with your naked eye?
the telescope collects light over a larger area
If two objects are tidally locked to each other
the tides always stay on the same place on each object AND the objects always remain in the same place in each other's sky.
How does the resolution of a telescope depend on its focal length?
there is no relation between resolution and focal length
Astronauts orbiting Earth in the space shuttle experience so-called weightlessness in space because
they are in constant free fall around Earth
Why don't we see cars as bluer when they approach and redder when they recede?
they are too slow
Saturn's rings do not clump together to form a moon because
they lie within Saturn's Roche limit
You see the Moon on the meridian at sunrise. The phase of the Moon is
third quarter
Astronomers can use ground-based telescopes to observe in the majority of which of the following parts of the electromagnetic spectrum
visible and radio
The color of visible light id determined by its
wavelength
Which phase comes immediately before first quarter?
waxing crescent
The "second" high tide in a 24-hour day is caused by
weaker gravity pulling on Earth on the side opposite the Moon
Which of the following properties of an astronaut changes when he or she is standing on the Moon, relative ot when the astronaut is standing on Earth
weight
When a planet exhibits retrograde motion it moves in which direction relative to the stars
westward
Solve the following equation for x in terms of y: y=3x
x=y/3
