Astronomy Final Exam
From which location could you observe all of the seas during the course of the year?
Equator
When an astronomer describes the luminosity of a star she is studying, she is talking about:
How much energy the star gives off each second
By far the most abundant element in the giant planets is
Hydrogen
If you were to take a large sample of the four giant planets, the most common element you would find in them is:
Hydrogen
The most common element in the Sun is
Hydrogen
The red color we see on a lot of photographs of nebulae comes from which element?
Hydrogen
Which of the following statements about the main sequence stage in the life of a star is FALSE?
Main sequence stars are rare in the Galaxy, so we are lucky to be living around one
Which of the following does NOT happen when two galaxies collide?
Many of the stars in one galaxy collide with the stars in the other
A spectral line associated with a particular element is measured in the lab to be at a wavelength of 570.2 nm. An astronomer measures it in Star Y's spectrum at a wavelength of 571.0 nm, and in Star Z's spectrum at a wavelength of 570.6 nm. Which statement best describes what is happening?
Both stars are moving away from us, with Star Y receding faster.
According to our textbook, roughly what percent of the mass and energy contents of the universe is made up of dark matter plus dark energy?
95%
A friend of yours (who has not had the benefit of an astronomy course) tells you about a report he has read in a tabloid newspaper. They claim that on the dark side of the Moon, which is never in sunlight, there is a secret base of aliens who cannot stand light, and who send UFO's to Earth under the cover of darkness. Ignoring the UFO claim for a moment, what is the scientific error in this story?
All sides of the moon are illuminated by sunlight in the course of a month; there is no dark side
In the future, several students living on board a space station decide to have a race among different types of electromagnetic radiation. Which of the following travels through space the fastest?
All waves travel through space at the same speed.
The event in the life of a star that begins its expansion into a giant is
Almost all the hydrogen in its core that was hot enough for fusion has been turned into helium
The disks of spiral galaxies have a blue hue because they
Are still undergoing star formation
Which of the following statements about the life of a star with a mass like the Sun is correct?
As the star is dying, a considerable part of its mass will be lost into space
Why do all stars spend most of their lives on the main sequence?
Because the fuel for energy production in this stage of the star's life is hydrogen; and that is an element every star has lots and lots of
Why are astronomers much more interested in the luminosity of a star than its apparent brightness?
Because the luminosity tells us how bright a star really is, while apparent brightness only tells us how bright it happens to look from Earth
Why do different types of atoms (elements) give off or absorb different spectral lines?
Because the spacing of the energy levels is different in different atoms
Which color star is likely to be the hottest?
Blue-violet
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
The faster it is moving away from us
T/F: Given the differences in the temperature, pressure, and composition of their atmospheres, none of the other planets in our solar system is a place where a human could exist without some sort of complicated protective suit.
True
T/F: In an HII region, hydrogen is ionized by the light of nearby stars.
True
T/F: In his second law, Kepler discovered that a planet speeds up as it comes closer to the sun and slows down as it pulls away from the sun.
True
T/F: In one year, the Sun completes a circle around our sky on the ecliptic.
True
T/F: Kepler's third law relates a planet's orbital period to the semi-major axis of the orbit.
True
T/F: The Earth's axis of rotation is not perpendicular to the plane of our orbit around the Sun; the axis is tilted by about 23 degrees
True
T/F: The amount by which the spectral lines of a star is red shifted tells astronomers how fast the star is moving away from us.
True
T/F: The gravity of a star gets weaker with distance, but it never becomes exactly zero.
True
T/F: The vast majority of stars in the Milky Way have masses less than twice the mass of our sun.
True
T/F: We have to learn everything we know about stars by decoding the information in the electromagnetic radiation they send us.
True
If you want to locate someone precisely on the surface of the Earth, you specify her exact latitude and longitude. If you want to locate a star precisely on the sky, you need to specify its exact:
Right ascension and declination
Which planet in the solar system has not been examined by spacecraft instruments that have either flown by or orbited them?
Spacecraft have visited all the planets in our solar system
The type of galaxy that sometimes has a distinct bar of stars running across the central region is
Spiral
In which type of galaxy are you likely to observe a significant amount of star formation?
Spiral, irregular
Why do galaxies collide, while stars almost never do?
Stars are much further apart than galaxies are
From horizon to opposite horizon, the sky takes up how much angular distance?
180 degrees
A graduate student is given the assignment to find stars with dusty disks around them. What kind of telescope would it be best for her to use for this purpose?
A large telescope that detects infrared radiation
What happens as an electron falls from a higher level to a lower level in an atom?
A photon is given off.
Astronomers call a ball of matter that is contracting to become a star
A protostar
The Van Allen belt is
A region of trapped charged particles in the earth's magnetosphere
In recent decades, astronomers discovered stars even cooler than the traditional spectral type M stars recently. Astronomers gave these cool stars a new spectral type, L. If you wanted to go out and find more such type L stars, what kind of instrument would it be smart to use?
A sensitive infrared telescope
The radial velocity technique for detecting extrasolar planets involves obtaining
A spectrum of a star and identifying periodic wavelengths shifts in its features
A group of graduate students, bored during a cloudy night at the observatory, begin to make bets about the time that different stars will take to evolve. If they have a cluster of stars which were all born at roughly the same time, and want to know which star will become a red giant first, which of the following stars should they bet on?
A star of spectral type O on the main sequence
Which of the following looks the brightest in the sky?
A star with apparent magnitude -1
An HII region is
A zone around a hot star where hydrogen atoms are ionized
A dashing Romanian count asks his sweetheart to marry him. She says she will give her reply when the Moon is full. If he asked when the Moon was at first quarter, how long will he have to wait?
About a week.
To go from a lower level in an atom to a higher level, an electron must
Absorb a photon of energy.
Which of the following statements about dark matter is FALSE:
Astronomers have a pretty good idea what the dark matter is made of
Where on Earth do stars always circle the zenith (and never rise and set)?
At the North Pole
From a city in the U.S., where in the sky would you look to see a star that is not turning with the motion of the sky in the course of a night?
At the north celestial pole
How fast do electromagnetic waves travel?
At the speed of light.
Solar wind particles can be captured by the Earth's magnetosphere. When these particles spiral down along the magnetic field into the atmosphere, they are responsible for:
Aurorae
Which type of galaxy is observed to contain mostly older stars?
Elliptical
The microlensing technique for detecting extrasolar planets involves obtaining
Brightness measurements of a star and identifying a brief magnification in its brightness.
At an astronomical conference, an astronomer gives a report on a star that interests astronomers because of hints that it may have a planet around it. In his report the astronomer gives the average speed with which this star is moving away from the Sun. How did the astronomer measure this speed?
By looking at the Doppler shift in the lines of the star's spectrum.
The sun's corona is a hot, thin gas. From this information, we should expect that the corona should display a/an
Emission spectrum
On the celestial sphere, halfway between the celestial poles lies the
Celestial Equator
Astronomers now understand that the dark regions or rifts visible in parts of our Galaxy that are otherwise crowded with stars are caused by:
Clouds with a considerable amount of dust which blocks the light of the stars behind them
Which of the following statements about the different types (shapes) of galaxies is correct?
Collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
Suppose a star was discovered that, based on its composition, was believed to be one of the first stars that formed about 13 billion years ago.
Cool, red M-type main sequence star
Which part of the sun's atmosphere is the hottest?
Corona
Astronomers arrange the stars into groups called spectral classes (or types) according to the kinds of lines they find in their spectra. These spectral classes are arranged in order of:
Decreasing surface temperature
According to Kepler's third law, there is a relationship between the time a planet takes to revolve around the. sun and its
Distance from the sun
When astronomers carefully examine the planets found by Kepler and draw conclusions from the Kepler sample, what do they conclude about planets the size of Earth?
Earth-sized planets are common, but so are planets somewhat bigger than Earth
We now know that the orbit of a stable planet around a star like the Sun is always in the shape of:
Ellipse
After the core of a massive star becomes a neutron star, the rest of the star's material
Explodes outward as a supernova
T/F: A star this is moving away from the solar system will show spectral lines that are blue-shifted compared to a star at rest relative to us.
False
T/F: All the planets in the solar system are similar in terms of what materials they are mostly made of.
False
T/F: Astronomers now believe that all galaxies start out as irregulars, evolve in their youth into ellipticals, and then become spirals as they mature and reach old age.
False
T/F: The Earth's period of rotation is equal to 1 year.
False
T/F: The Sun revolves around (orbits) the earth in about 356 days.
False
T/F: The eight planets may be different in size, but they all have roughly the same density.
False
T/F: The term HI refers to hydrogen that is ionized once by electromagnetic radiation that hits it.
False
T/F: The terms luminosity and apparent brightness mean the same thing when it comes to stars.
False
T/R: Right now, astronomers have NO way to measure the location or amount of dark matter among the visible galaxies of regular matter.
False
One piece of evidence that can help astronomers sort out how the planets in our solar system formed is
Finding circumstellar disks of material around nearby stars
What phase of the moon must it be to have a lunar eclipse?
Full moon
Which of the following has the highest frequency?
Gamma rays
During the process of differentiation:
Heavier materials sink toward the centers of planets that are in a liquid or gas state
The radical velocity technique has a particular selection bias making it most easily able to specifically detect
High-mass planets
If you want to find stars that are just being born, where are the best places to search?
In giant molecular clouds.
The idea that objects tend to continue doing what they are already doing is called the law of:
Inertia
You are alone in a large, completely dark auditorium on Earth. What kind of telescope should I use from the other side of the auditorium to detect the electromagnetic radiation emitted by your body?
Infrared
The direct imaging technique for detecting extrasolar planets involves obtaining
Infrared images of a planet with the light from its host star blocked out.
Using a good pair of binoculars, you observe a section of the sky where there are stars of many different apparent brightnesses. You find one star that appears especially dim. This star looks dim because it is:
It could be more than one of these; there is no way to tell which answer is right by just looking at the star
Why is an absorption spectrum especially useful for astronomers?
It has dark lines in it that allow astronomers to determine what elements are in the star
In general, the further planets are from the Sun, the cooler they are. What other factor can have a significant influence on a planet's surface temperature?
Its atmosphere
How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on
Its mass
The transit technique has a particular selection bias making it most easily able to specifically detect
Large-diameter planets
The image shown here depicts Jupiter with aurorae around its north pole. What is this evidence of?
Jupiter's intense magnetic field
Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?
K
How do astronomers learn what elements are present in a given star?
Look at the absorption lines in its spectrum.
The spacecraft that sent back the most detailed radar images of Venus and showed us features as small as a football field is:
Magellan
An exhausted-looking astronomer comes off the mountain where her observatory is located and tells you she has been doing photometry all night. What has she been up to?
Measuring the brightness of different stars
Suppose astronomers wanted to double-check their conclusions derived from the Moon about the bombardment history of the inner solar system. Which solar system object would be the most useful to obtain another cratering record?
Mercury
When a planet, in its orbit, is closer to the sun, it:
Moves faster than average
Astronomers were surprised to find so many Jupiter-mass planets so close to their stars. According to their best theories and models, such "hot Jupiters"
Must have formed further out from the star and must have "migrated inward" early on
Suppose Star A has an apparent magnitude of +2.0 and Star B has an apparent magnitude of +0.5. From this information only, what can we say about the luminosities of the two stars?
Nothing can be said about the stars' luminosities from this information only
A crucial difference that helps explain why Venus is so hot and the Earth isn't is that:
On venus, there was eventually no ocean to remove carbon dioxide from the atmosphere
The material that would eventually make all the major bodies in our solar system first gathered together into smaller pieces which astronomers call:
Planetesimals
An astronomy student, for her PhD, really needs to estimate the age of a cluster of stars. Which of the following would be part of the process she would follow?
Plot an H-R diagram for the stars in the cluster
The star that is currently closest to the North Celestial Pole is:
Polaris
The north star Polaris has been useful in the modern era for determining one's latitude in the northern hemisphere. However, when explorers sailed south of the equator they were no longer able to use Polaris to determine their latitude. Why?
Polaris dropped below the horizon that far South.
The slow tipping of the Earth's axis in a circle with a period of about 26,000 years is called:
Precession
I want to examine the surface of a planet which is completely covered by a thick layer of clouds all the time. What wavelength of electromagnetic radiation would I be smartest to use:
Radio waves
Which of the following has the longest wavelength?
Radio waves
When a star or galaxy is moving away from us, we observe the Doppler effect by seeing the lines in its spectrum
Redshifted (shifted toward the red end of the light spectrum)
When a planet temporarily moves westward in the sky over the course of several weeks or months (instead of eastward, as it typically does), we call it:
Retrograde motion
The main sequence is called this because it is where some 90% of stars we see are located on an H-R diagram.
Stars spend most of their life as main sequence stars, and a relatively short amount of time as red giant stars.
Why was the Kepler mission not able to find planets smaller than Mars, even though it was in space (and had no Earth atmosphere to deal with)?
Such planets make dips in the light of the star that are too small for Kepler to detect
If you could see the new moon, at what time of day would it rise?
Sunrise
Why is there a 4-minute difference between the solar day and the sidereal day?
The Earth is going around the Sun in the course of a year.
If the Earth goes around the Sun, why is the ecliptic not lined up with the celestial equator?
The Earth's axis is tilted by about 23 degrees from the vertical.
As a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first?
The O and B type stars
Which of the following statements about the mass of the Sun during its lifetime is correct?
The Sun will lose a significant amount of mass during and after its red giant phase
How do astronomers currently think the amount of detectable (observable) matter in the universe compares to the amount of dark matter and dark energy?
The amount of detectable matter is far less than the amount of dark matter & energy
Why does the moon show phases in the course of a month?
The angle the moon makes with the sun changes and we see differing amounts of reflected sunlight
The figure illustrates the drop in a star's apparent brightness over time as an exoplanet transits (a "light curve"). The size of the planet is not shown to scale. Suppose the planet had a larger mass but the same radius. How would the light curve look different?
The drop would be identical to that shown in the figure (no difference)
The figure illustrates the drop in a star's apparent brightness over time as an exoplanet transits (a "light curve"). The size of the planet is not shown to scale. Suppose the planet had a smaller radius (and is much smaller than its star), but the same mass. How would the light curve look different?
The drop would be shallower but basically the same width
Which statement below best explains why the James Webb Space Telescope was optimized for infrared viewing in order to study early galaxy formation in the universe?
The earliest galaxies are the most distant, and universal expansion has redshifted their spectra into infrared wavelengths.
The Sun's apparent path around the celestial sphere is called
The ecliptic
The ground state in an atom is
The electron orbit with the lowest possible amount of energy.
What incident in a massive star's life sets off (begins) the very quick chain of events that leads to a supernova explosion?
The fusion of iron
You are observing a binary star system and obtain a series of spectra of the light from the two stars. In this spectrum, most of the absorption lines shift back and forth as expected from the Doppler Effect. A few lines, however, do not shift at all, but remain at the same wavelength. How can we explain the behavior of the non-shifting lines?
The lines come from interstellar matter between us and the star, not from the stars themselves
Suppose two stars have the same apparent brightness but one is more distant than the other. What can you say about these two stars relative to each other?
The more distant star is more luminous.
To measure how dense a planet is (to know whether it is made of rock or gas and liquid) they must be able to measure the planet's mass from the Doppler shift and
The planet's radius using the transit method
The process by which Venus became so much hotter than the Earth is called:
The runaway greenhouse effect
The period of the moon's rotation on its axis is:
The same as its revolution around the Earth.
Astronomers use the term interstellar extinction to refer to:
The scattering and absorption of starlight by dust grains in space.
Suppose you observe a star whose spectrum exhibited neither a redshift nor a blueshift. What could you conclude about this star?
The star has no radial motion with respect to us.
Which of the following is NOT a result of the Earth's precession?
The stars twinkle when seen from the surface of planet earth.
Which of the following is an important part of the reason it is hotter in summer in North American than in winter?
The sun's rays hit the earth more directly in the summer, and spread out less
T/F: Compared to the mass of the sun, the mass of the Earth is pretty insignificant.
True
What would have to change about the Earth to stop our planet from having significantly different seasons?
The tilt of its axis
When stars become giants, which of the following does NOT usually happen?
Their mass grows significantly as they incorporate planets and interstellar matter near the star
On which of the planets (other than Earth) could a human being step out of a spacecraft and survive without any protective gear (special suit, oxygen tanks, etc)?
There is no other planet on which we could survive unprotected
Which of the statements below best describes planetary orbits in our solar system?
They generally have low eccentricity and lie in the same plane.
Which statement below correctly identifies the nebula shown here and explains why it is evidence for recent star formation.
This is an emission nebula; its red color arises from hydrogen emission stimulated by UV photons. These photons only come from massive main sequence stars, and since these stars have short lifetimes they must have formed recently.
When the outer layers of a star like the Sun expand, and it becomes a giant, which way does it move on the H-R diagram?
Toward the upper right
T/F: According to the Cosmological Principle, it does not matter what section of the universe we observe: any section will look the same as any other.
True
T/F: Analyzing the light in the spectrum of a star can tell astronomers the star's temperature, what elements are in it, and its speed in a direction toward us or away from us.
True
T/F: Astronomers have discovered many circumstellar disks around other young stars that resemble what we think the solar nebula looked like as it was forming.
True
T/F: Astronomers today think that dwarf elliptical galaxies may be the most common kind of galaxy in the universe.
True
An astronomer is observing a star which puzzles her. The lines in the star's spectrum indicates that the star is very hot and should therefore be blue. But the star looks reddish in photographs and in measurements of the continuous spectrum. What is one possible explanation of this puzzle?
We are seeing the light of the star through layers of interstellar dust.
How do astronomers know what the outer layers of the Sun are made of?
We take an absorption line spectrum of the Sun, and the absorption lines tell us what elements are present in the outer layers
Imagine that earth had no axial tilt. How would this affect our view of eclipses?
We would continue to see solar and lunar eclipses in the same way we currently do.
Imagine that Earth's orbit was changed to be a perfect circle around the Sun so that the distance to the Sun never changed over the course of one year. How would this affect our experience of the seasons?
We would experience seasons in essentially the same way we do now
Which of the following is NOT a characteristic of a spiral galaxy?
When we take spectra of its stars, they have far less of the heavier elements than the Sun
When a single star with a mass equal to the Sun dies, it will become a
White dwarf
Is it possible for a star's apparent magnitude to be equal to its absolute magnitude?
Yes, if the star is at a specific distance from earth
Is it possible for a star's apparent magnitude to be higher than its absolute magnitude?
Yes, if the star is particularly far from Earth.
During spring vacation, you go on a camping trip with your family. One night, youwake up at 3 am, and see a beautifully clear dark sky, full of stars. You lie down on thesoft grass, looking at the sky. Straight up, above you, you will always see____________.
Your zenith
The point in the sky directly above your head at any given time is called the:
Zenith
If most stars are low-mass stars, and low-mass stars typically eject a planetary nebula, why then do astronomers see relatively few planetary nebulae in the sky?
planetary nebulae expand rapidly and soon become too faint to be visible
When a star first begins the long path toward becoming a red giant, a layer of hydrogen around the core begins to undergo fusion. If this layer was too cold to do fusion throughout the main sequence stage, why is it suddenly warm enough?
the core is collapsing under its own weight and heating up from the compression; this heats the next layer up
