AST 105: FINAL EXAM
114 Cards in this Set
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What does the technique of interferometry allow?
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It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes
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Which of the following is not a good reason to place observatories on remote mountain tops
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to be able to observe at radio wavelengths
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Which of the following statements about electrical charge is true?
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a positive charge and a negative charge will attract each other
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Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms isotopes of each other?
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Atom1: nucleus with 92 protons and 143 neutrons, surrounded by 92 electrons. Atom 2: nucleus with 92 protons and 146 neutrons, surrounded by 92 electrons
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When white light (all wavelengths) passes through a cool cloud of gas, we see....
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an absorption light spectrum
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Which of the following statements about thermal radiation is always true?
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a hot object emits photons with a higher average energy than a cool object
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Which of the following is an example in which you are traveling at constant speed but not at constant velocity?
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driving around in a circle at exactly 100km/hr
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What is the acceleration of gravity of Earth
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9.8 m/s(2) downward
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If you drop a rock from a great height, approximately how fast will it be falling after 5 seconds using the answer to the previous question.
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50 m/s
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Momentum is defined as....
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Mass times velocity
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As long as an object is not gaining or losing mass, a net force on the object will cause a change in....
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velocity
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Which of the following is not a conserved quantity?
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radiation
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What does temperature measure?
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the average kinetic energy of particles in a substance
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Considering Einstein's famous equation E=MC squared, which of the following statements is true?
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a small amount of mass can be turned in to a large amount of energy
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Which of the following statements correctly describes the law of conservation of energy?
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the total quantity of energy in the universe never changes
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According to the universal law of gravitation if you triple the distance between two objects, then the gravitational force between them will....
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decrease by a factor of 9
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Which of the following statements does not use the term angular size or angular size or angular distance correctly?
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the angular distance between those two bright stars in the sky is about 2 meters
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How are wavelength, frequency, and energy related for photons of light?
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Longer wavelength means lower frequency and lower energy
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How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?
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It releases a photon equal in energy to its own energy drop
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From lab measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers. The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nanometers. What can we conclude?
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the star is moving away from us
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The allowed shapes for orbits under the force of gravity are..
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ellipses, parabolas, hyperboles
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Which of the following statements about scientific models is true?
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a model can be used to explain and predict real phenomena
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Why did Ptolemy have the planets orbiting the earth on circles upon circles in his model of the universe?
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To explain the fact that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky
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Which of the following was not observed by Galileo?
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Jupiter's moon
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From Kepler's third law, a hypothetical planet that is twice as far from the Sun as the earth should have a period of.....
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more than 2 Earth years
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Kepler's second law, which states that a planet moves around its orbit it sweeps out equal areas in equal times, means that ...
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a planet travels faster when it is nearer to the sun and slower when it is farther from the sun
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Suppose that, through the malicious act of an eight-dimensional alien being, the strong force was suddenly turned off throughout the universe. What would happen almost immediately to the atoms?
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the nuclei of atoms would fall apart
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What is closest to the average temperature of the surface of the sun?
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6,000K
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Which is closest to the core of the sun?
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10 millionK
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From the center outward, which of the following lists the "layers" of the sun in the correct order?
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core, radiation zone, convection zone, photosphere, chromosphere, corona
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The overall fusion reaction (net effect) by which the Sun currently produces energy is...
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4H-->1He+energy
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Which of the following statements about neutrinos is not true?
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the mass of a neutrino is 30% of the mass of an electron
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Which of the following statements about electrons is not true?
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electrons have about the same mass as protons
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The two families of fundamental particles out of which all ordinary matter is made are...
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leptons and quarks
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What happens when a particle and its corresponding particle of antimatter meet?
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the particle and the antiparticle are annihilated, turning all their mass into energy
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The four fundamental forces are...
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a strong force, weak force, electromagnetic force, gravity
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The two fundamental laws that lie at the heart of quantum mechanics are....
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the uncertainty principle and the exclusion principle
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Which of the following statements best describes the exclusion principle?
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Two fermions cannot occupy the same quantum state at the same time
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List the major classes of the EM spectrum form highest to lowest frequency
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Gamma rays
X-rays
Ultraviolet (UV)
Visible
Infrared
Microwaves
Radio
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List the three kinds of spectra
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Continuous
Emission
Absorption
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List the simplified steps of the scientific method
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Make an observation
Ask a question
Suggest a hypothesis
Make a prediction
Perform a test or experiment(test the hyp.)
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What is the difference between science and religion?
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science seeks to explain the natural world while religion seeks to explain the supernatural world
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List Newton's three laws of motion
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1. An object moves at constant velocity if there is no net force acting upon it
2. Force = Mass x Acceleration (F=ma)
3. For any force, there is always an equal and opposite reaction force
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List Kepler's three laws of planetary motion
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1. the orbit of each planet around the Sun is an ellipse with the Sun at one focus
2. As a planet moves around its orbit, it sweeps out equal areas in equal times
3. More distant planets orbit the Sun at slower average speeds, obeying a precise mathematical relationship (p(2)=a(2))
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What is the simple formula that relates frequency and wavelength?
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Frequency X Wavelength = Speed
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List the three classes (forms) of energy
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1. radiative
2. kinetic
3. potential
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What type of star is our sun?
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Low mass star
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Which two are the basic premises for the special theory of relativity?
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the laws of nature are the same for everyone and the speed of light is the same for everyone.
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Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
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Mass they are formed with
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If the distance between us and a star is doubled, with everything else remaining the same, the luminosity
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remains the same, but the apparent brightness is decreased by a factor of four
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Which of the following statements about apparent and absolute magnitudes it true?
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a star with apparent magnitude 1 is brighter than one with an apparent magnitude 2. The absolute magnitude of a star is another measure of its luminosity. A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth. The magnitude s…
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Which of the following statements about spectral types of stars is true?
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the spectral type of a star can be used to determine its surface temperature. A star with spectral Type A is cooler than a star with spectral type B. A star with a spectral type of F2 is hotter than a star with spectral F3. The spectral type of a star can be used to determine its color.
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What happens to the rotation of a molecular cloud as it collapses to form a star?
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The rotation rate increases and results in a disk of material around a protostar.
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What is the the range of star masses for high-mass stars?
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Between 8 and 150 solar masses
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Compared to the star it evolved from a red giant is..
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cooler and brighter
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At approximately what temperature can helium fusion occur?
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100 million K
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Which of the following sequences correctly describes the stages of life for a low-mass star?
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Protostar, main-sequence, red giant, white dwarf
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What type of stars end their lives a supernovae?
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stars that are at least several times the mass of the sun
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You discovery a binary star system in which one member is a 15Msun main sequence star and the other star is a 10Msun giant. Why should you be surprised , at least at first?
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the two stars would be the same age so the more massive one should have become a giant first
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a teaspoonful of white dwarf material on Earth would weigh
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a few tons
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A teaspoonful of neutron star material on Earth would weigh
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more than MT Everest
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Which of the following is closest in size to a neutron star
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a city
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What is the basic definition of a black hole?
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any object from which the escape velocity equals the speed of light
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According to the general relativity, why does the earth orbit the Sun?
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the earth is following the straightest path possible, but spacetime is curved in such a way that this path goes around the Sun.
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Which of the following is false?
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the speed of light slows down near the black hole
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What does the equivalence principle say?
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the effects of gravity are exactly equivalent to the effects of acceleration
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No stars have been found with masses greater than 300 times our Sun because...
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they would generate so much power that they would blow themselves apart
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On a Hertzsprung-Russell diagram, where would we find stars that are cool and dim?
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Lower right
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What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
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the core contracts and becomes a black hole
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A 10-solar-mass main-sequence star will produce which of the following remnants?
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black hole
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What is the ultimate fate of an isolated pulsar?
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It will slow down, magnetic field will weaken, and it will become invisible
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Imagine that you are sitting in a closed room (no windows, no doors) when, magically, it is lifted from the earth and sent accelerating through space with an acceleration of 1g (9.8 m/s(2)). According to Einstein's equivalence principle, which of the following is true?
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you wont feel any change and will have no way to know that you've left earth
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When does a protostar become a true star?
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When nuclear fusion begins in the core
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What are the standard units for luminosity?
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watts
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Which of the following statements about an open cluster is true?
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all stars in the cluster are approximately the same age
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The helium fusion process (triple alpha process) results in the production of..
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carbon
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What happens to the core of a star after a planetary nebula occurs?
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It becomes a white dwarf
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What is the CNO cycle?
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a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
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Which of the following statements best describes what is "relative" in the theory of relativity?
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The theory says that measurements of motion make sense only when we state what they are measured relative to
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Which of the following is not a prediction made by the theory of relativity?
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Observers in different reference frames may disagree about the basic laws of nature
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The faintest star visible to the naked eye has an apparent visual magnitude of about
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+6
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On the main sequence, stars obtain their energy
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by converting hydrogen to helium
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What kind of star is most likely to become a white-dwarf supernova?
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a white dwarf star with a red giant binary companion
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Each of the following is a prediction of the theory of relativity. Which one is crucial to understanding how the Sun provides light and heat to the Earth?
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E=MC(2)
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You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following except...
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rotation rate of the star
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A spaceship is moving past us at a speed close to the speed of light. If we could measure the mass of the spaceship as it goes by, what would it be?
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Its mass is greater than its mass
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List 4 possible triggers of star formation in a molecular cloud
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OB Association, Supernova, Cloud Collision, Jeans Instability
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What do astronomers consider heavy metal?
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all elements besides hydrogen and helium
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Where are most heavy metals made?
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in stars and supernovae
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What is the thickness of the disk of the milky way?
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1000 light years
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Which of the following comprise the oldest members of the Milky Way?
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Globular clusters
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What kind of objects lie in the halo of our galaxy?
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Globular clusters
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What makes up the interstellar medium?
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gas and dust
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Approximately how long does it take the sun to orbit the milky way?
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230 million years
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What is the steps of the star-gas-star cycle
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Atomic H Clouds
Molecular Clouds
Star Formation
Nuclear Fusion in Stars
Returning Gas
Hot Bubbles
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What is a standard candle?
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an object for which we are likely to know the true luminosity
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Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest?
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parallax, main sequence of fitting, Cepheid variables, Tully-Fisher relation, Hubble's law
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Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately..
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100 billion
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Why are cepheid variables important?
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Cepheids are pulsating variable stars and their pulsation periods are directly related to their true luminosities. Hence, we can use cepheids as standard candles for distance measurement
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How many more stars does a starburst galaxy form in one year than the milky way?
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about 100
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What is a quasar?
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the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
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If an object doubles its luminosity in ten hours, how large can the emitting source of light be
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about 10 light hours across
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The most active galactic nuclei are usually found at large distances from us; relatively few nearby galaxies have active galactic nuclei. What does this imply?
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active galactic nuclei tend to become less active as they age
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Why should galaxy collisions have been more common in the past than they are today?
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Galaxies were closer together in the past as the universe was smaller
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Which of the following types protogalactic is most likely to form an elliptical galaxy?
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A dense cloud with very little angular momentum
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Why do we believe starburst galaxies represent a temporary stage in galaxy evolution?
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Such galaxies produce so much light that they would have consumed all their gas long ago if they had always been forming stars at this high rateSuch galaxies produce so much light that they would have consumed all their gas long ago if they had always been forming stars at this high rate
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If an object doubles it luminosity in 10 hours how large can the emitting source of light be?
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about 10 light years across
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List 5 elements of the periodic table that can covanlently bond with 3 or more other elements.Circle the best one for forming complex life and explain why in a couple sentences
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Boron
Carbon
Nitrogen
Phosphorus
Silicon
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Two fundamental laws that lie at the heart of quantum mechanics
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uncertainty principle and the exclusion principle
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The characteristic that distinguishes fermions from bosons
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their spin
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What is the upper limit to the mass of a white dwarf?
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1.4 solar masses
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what type of star is most likely to become a white-dwarf supernova?
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A white dwarf star with a red giant binary companion
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What is the upper limit to the mass of a neutron star?
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There is an upper limit less than 3 solar masses, but we do not yet know precisely what it is
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In relativity, two people share the same frame of reference only if...
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they are not moving relative to each other
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AST 105: Final