Monday, December 30, 2013

PHYS 107 ASTRONOMY FINAL REVIEW 2

  • Question 1

    3 out of 3 points
    The most important factor in determining a stars eventual fate is its:
    Selected Answer:
    Correct 
    mass
    Correct Answer:
    Correct mass
    Response Feedback:
    Correct, its mass is tied to the luminosity (since the star is in hydrostatic equilibrium) and thus to the lifetime of the star.

  • Question 2

    1 out of 1 points
    In  5 billion years the Sun will become a black hole:
    Selected Answer:
    Correct False
    Correct Answer:
    Correct False
    Response Feedback:
    Correct, remember lower mass stars like the Sun eventually become white dwarfs

  • Question 3

    0 out of 3 points
    When an atom absorbs a high energy photon and an electron is ejected we call this:
    Selected Answer:
    Incorrect 
    emission
    Correct Answer:
    Correct ionization
    Response Feedback:
    Incorrect, ionization is removing an electron from an atom (creating an ion)

  • Question 4

    0 out of 3 points
    A red giant star like Arcturus must have a:
    Selected Answer:
    Incorrect 
    mass much greater than the Sun
    Correct Answer:
    Correct luminosity much larger than the Sun
    Response Feedback:
    Incorrect, remember the Sun will eventually expand and cool to become a red giant (and thus the other 3 answers must be wrong)

  • Question 5

    3 out of 3 points
    Tonight you observe the planet Saturn at midnight high in the Southern skies, you know that:
    Selected Answer:
    Correct 
    Saturn and Earth must be on the same side of the Sun
    Correct Answer:
    Correct Saturn and Earth must be on the same side of the Sun
    Response Feedback:
    Correct, Saturn must be opposite the Sun at this point.

  • Question 6

    3 out of 3 points
    This is an image of:

    m15_hstheritage.jpg
    Selected Answer:
    Correct 
    a globular cluster
    Correct Answer:
    Correct a globular cluster
    Response Feedback:
    Correct

  • Question 7

    3 out of 3 points
    Uranus is peculiar because its:
    Selected Answer:
    Correct 
    axis of rotation is so highly tilted
    Correct Answer:
    Correct axis of rotation is so highly tilted
    Response Feedback:
    Correct, Uranus is tilted 98 degrees to its orbit and thus moves around the Sun on its "side", but not the part of Uranus pointed at the Sun is not always the same.

  • Question 8

    3 out of 3 points
    As seen from Earth, Jupiter cannot:
    Selected Answer:
    Correct 
    eclipse the Sun
    Correct Answer:
    Correct eclipse the Sun
    Response Feedback:
    Correct, Jupiter cannot come between the Earth and the Sun

  • Question 9

    3 out of 3 points
    Greenhouse gases warm a planet like Earth by:
    Selected Answer:
    Correct 
    retaining more infrared light emitted by the Earth
    Correct Answer:
    Correct retaining more infrared light emitted by the Earth
    Response Feedback:
    Correct, the radiation emitted by the Earth is at longer (infrared) wavelengths compared to the Sun (optical), it is the retention of this radiation that heats the Earth.

  • Question 10

    3 out of 3 points
    The Milky Way is:
    Selected Answer:
    Correct 
    the name of our Galaxy
    Correct Answer:
    Correct the name of our Galaxy
    Response Feedback:
    Correct, from ancient Greek myths

  • Question 11

    3 out of 3 points
    About what temperature did the cosmic microwave background have at the time of its formation?
    Selected Answer:
    Correct 
    3,000 K
    Correct Answer:
    Correct 3,000 K
    Response Feedback:
    Correct, when it formed the Universe had cooled to roughly 3,000 K, the temperature of the surface of a star.

  • Question 12

    3 out of 3 points
    How does the observed density in stars compare with the critical density?
    Selected Answer:
    Correct 
    it is much less
    Correct Answer:
    Correct it is much less
    Response Feedback:
    Correct, the density of material in stars averaged over the enormous volume of space is much less than the density that required to close the Universe (make it re-collapse), although the density of individual stars is much larger than the critical density

  • Question 13

    0 out of 1 points
    Planetary nebulae are the sites of new planet formation:
    Selected Answer:
    Incorrect True
    Correct Answer:
    Correct False
    Response Feedback:
    Incorrect, planetary nebulae are the end stages of the lives of stars like the Sun.  Early astronomers mistook them for forming stars.

  • Question 14

    3 out of 3 points
    The Jovian planets retained most of their atmospheres because:
    Selected Answer:
    Correct 
    they were very cold when formed
    Correct Answer:
    Correct they were very cold when formed
    Response Feedback:
    Correct, remember the atmosphere retention simulations from the last homework at:

    http://www.physics.louisville.edu/~jtl/Phys107-2008B/atmo_retention.html

  • Question 15

    3 out of 3 points
    Jupiter's composition is closest to that of:
    Selected Answer:
    Correct 
    the Sun
    Correct Answer:
    Correct the Sun
    Response Feedback:
    Correct, both the Sun and Jupiter are mostly H and He

  • Question 16

    3 out of 3 points
    A Full Moon is at position:

    moonphases_sm.jpg
    Selected Answer:
    Correct 
    e
    Correct Answer:
    Correct e
    Response Feedback:
    Correct, a full Moon is when the Moon is on the opposite side of the Earth from the Sun

  • Question 17

    0 out of 1 points
    Jupiter has only 5 moons:
    Selected Answer:
    Incorrect True
    Correct Answer:
    Correct False
    Response Feedback:
    Incorrect, it has more than 4 dozen Moons

  • Question 18

    1 out of 1 points
    The majority of the mass of the Milky Way is in the form of dark matter:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, the best evidence is the velocities of stars and gas clouds in the outer disk.

  • Question 19

    0 out of 3 points
    An OB star like Rigel moving through the galactic disk is a:
    Selected Answer:
    Incorrect 
    Population II star
    Correct Answer:
    Correct Population I star
    Response Feedback:
    Incorrect, the name given to the stars of the Galactic disk is Population I, the older stars of the halo are Pop II, and the first generation of stars (which we have not yet discovered and may have all "died") are Pop III.

  • Question 20

    3 out of 3 points
    What component of the primordial interstellar cloud became the inner planets?
    Selected Answer:
    Correct 
    The dust grains
    Correct Answer:
    Correct The dust grains
    Response Feedback:
    The inner planets were made from the dust grains in the early Solar nebula which had clumped together to form planetesimals.

  • Question 21

    3 out of 3 points
    What is the largest object in the Solar System?
    Selected Answer:
    Correct 
    the Sun
    Correct Answer:
    Correct the Sun
    Response Feedback:
    Neither globular clusters or supermassive black holes are in our Solar system (they are in the Milky Way galaxy), and by thus by default it is the Sun.

  • Question 22

    3 out of 3 points
    Using the soon to be launched Kepler satellite astronomers detect a planet with a semi-major axis of 1 AU around a G2V star in Cygnus, its period will be:
    Selected Answer:
    Correct 
    1 year
    Correct Answer:
    Correct 1 year
    Response Feedback:
    Right, a G2V star is like the Sun and the planet with a 1 AU orbit is the Earth which has an orbital period of 1 year

  • Question 23

    3 out of 3 points
    You observe a Cephied variable in a distant galaxy, you can now determine the galaxies:
    Selected Answer:
    Correct 
    distance
    Correct Answer:
    Correct distance
    Response Feedback:
    Correct, since Cephieds are standard candles

  • Question 24

    3 out of 3 points
    The cosmic microwave background shows that the Universe evolved from a:
    Selected Answer:
    Correct 
    hot dense state
    Correct Answer:
    Correct hot dense state
    Response Feedback:
    Correct, the Hubble expansion shows that the Universe was once much smaller while the cosmic microwave background must have been made of much higher energy photons before they were redshifted by the expansion of the Universe.

  • Question 25

    1 out of 1 points
    Jupiter has moons larger than the planet Mercury:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, Ganymede is larger and Callisto is is the same size as Mercury

  • Question 26

    0 out of 1 points
    Polaris (the "North Star") is a circumpolar star to all observers on the Earth:
    Selected Answer:
    Incorrect True
    Correct Answer:
    Correct False
    Response Feedback:
    Incorrect, Polaris is not visible from the Southern hemisphere.

  • Question 27

    1 out of 1 points
    All globular clusters have the same luminosity:
    Selected Answer:
    Correct False
    Correct Answer:
    Correct False
    Response Feedback:
    Correct, they vary between 100,000 and 1,000,000 stars.

  • Question 28

    3 out of 3 points
    Which of the following has a linear size or radius closest to the radius of a white dwarf?
    Selected Answer:
    Correct 
    the Earth
    Correct Answer:
    Correct the Earth
    Response Feedback:
    Correct, a white dwarf is roughly the mass of the Sun squeezed into the size of the Earth

  • Question 29

    3 out of 3 points
    Why is the cosmic microwave background temperature so cool now?
    Selected Answer:
    Correct 
    The expansion of the Universe has cooled it
    Correct Answer:
    Correct The expansion of the Universe has cooled it
    Response Feedback:
    The radiation has been redshifted (the wavelength of the radiation has been stretched) and thus it is at lower energies - so the cosmic background corresponds to a lower temperature blackbody.

  • Question 30

    3 out of 3 points
    The best evidence that man never landed on the Moon is:
    Selected Answer:
    Correct 
    none of the above - man landed on the Moon
    Correct Answer:
    Correct none of the above - man landed on the Moon
    Response Feedback:
    Correct, remember:

    "If You Open Your Mind Too Much Your Brain Will Fall Out"

  • Question 31

    3 out of 3 points
    When we look at the great galaxy in Andromeda we see it as it was approximately:
    Selected Answer:
    Correct 
    2.5 million years ago
    Correct Answer:
    Correct 2.5 million years ago
    Response Feedback:
    Correct, the Andromeda galaxy (the nearest large galaxy to our own Milky Way) is about 2.5 million light years away, and thus it takes light 2.5 million years to reach us.

  • Question 32

    3 out of 3 points
    Clusters of galaxies are bound together by:
    Selected Answer:
    Correct 
    gravity
    Correct Answer:
    Correct gravity
    Response Feedback:
    Correct, the attractive force of gravity binds together astronomical objects from planets and stars to galaxies and clusters of galaxies

  • Question 33

    3 out of 3 points
    The reason astronomers use near-infrared observations is to:
    Selected Answer:
    Correct 
    penetrate interstellar dust clouds
    Correct Answer:
    Correct penetrate interstellar dust clouds
    Response Feedback:
    Correct, one of the key advantages of near-infrared is its ability to penetrate dust clouds where shorter wavelength opitcal light is absorbed

  • Question 34

    3 out of 3 points
    Particle physicists are interested in the conditions in the early Universe because:
    Selected Answer:
    Correct 
    this allows them to test unified field theories uniting the fundamental forces of nature
    Correct Answer:
    Correct this allows them to test unified field theories uniting the fundamental forces of nature
    Response Feedback:
    Correct, the densities and energies in the early Universe cannot yet (and may never) be replicated in particle accelerators

  • Question 35

    3 out of 3 points
    We can measure the mass of  the black hole at the center of the Milky Way galaxy by:
    Selected Answer:
    Correct 
    watching the orbits of stars in the center and using Kepler's Third Law
    Correct Answer:
    Correct watching the orbits of stars in the center and using Kepler's Third Law
    Response Feedback:
    Correct, remember the following animation from class (image from the UCLA Galactic Center group - This animation was created by Prof. Andrea Ghez and her research team at UCLA and are from data sets obtained with the W. M. Keck Telescopes." Image creators include Andrea Ghez, Angelle Tanner, Seth Hornstein, and Jessica Lu).

    2008orbits_animfull.gif

  • Question 36

    3 out of 3 points
    Consider a comet which was recently discovered near the orbit of Jupiter at a distance of 5 AU from the Sun, if astronomers find that it is in an elliptical orbit around the Sun and passes within 1 AU of the Sun, then which of the following statements must be true:
    Selected Answer:
    Correct 
    the semi-major axis of its orbit must be at least 3 AU
    Correct Answer:
    Correct the semi-major axis of its orbit must be at least 3 AU
    Response Feedback:
    Correct, this comet must travel at least 6 AU from side to side of its orbit (1 AU on one side and 5 AU on the other), so its semi-major axis (half the long axis of the ellipse) must be 3 AU.

    Note that period of 1 year = 1 AU and period of 11 years ~ 5 AU by Kepler's Third Law (P2=a3)

  • Question 37

    3 out of 3 points
    How do we know how old the Solar System is?
    Selected Answer:
    Correct 
    By measuring the products of radioactive decay in old rocks and meteors
    Correct Answer:
    Correct By measuring the products of radioactive decay in old rocks and meteors
    Response Feedback:
    Correct, this is known as radiometric dating and uses many elements not just the well-known carbon-14 method used to date relatively recent organic materials (such as achaeological remains).

  • Question 38

    3 out of 3 points
    Why are objects like Mercury and the moons of Earth, Jupiter and Saturn so heavily cratered?
    Selected Answer:
    Correct 
    Intense bombardment by asteroids and planetesimals subsequent to their birth
    Correct Answer:
    Correct Intense bombardment by asteroids and planetesimals subsequent to their birth
    Response Feedback:
    Correct, the impact of small bodies leads to cratering and without tectonic activity, melting of ice or weathering the craters remain

  • Question 39

    3 out of 3 points
    A moon must be:
    Selected Answer:
    Correct 
    orbiting a planet
    Correct Answer:
    Correct orbiting a planet
    Response Feedback:
    Correct, by definition.

  • Question 40

    3 out of 3 points
    The interstellar medium of galaxies today show more "metals" than that seen in distant galaxies because:
    Selected Answer:
    Correct 
    more supernovae have gone off to enrich the gasover the past few billion years
    Correct Answer:
    Correct more supernovae have gone off to enrich the gasover the past few billion years
    Response Feedback:
    Correct, remember two things:
    1) when we look at distant galaxies we are seeing them as they were in the past
    2) the Universe started out with H and He and no heavier elements like C, N, O, Si, Fe

  • Question 41

    3 out of 3 points
    Dark energy is:
    Selected Answer:
    Correct 
    inferred to exist because distant supernovae are fainter than the otherwise should be due to the expansion of the Universe
    Correct Answer:
    Correct inferred to exist because distant supernovae are fainter than the otherwise should be due to the expansion of the Universe
    Response Feedback:
    Correct, dark energy is what astronomers call the energy that is causing the expansion of the Universe to accelerate, which results in distant supernovae being even further from the Sun than they would be given due to the expansion of the Universe.

  • Question 42

    1 out of 1 points
    The Sun has a lifetime much longer than a B-type star like Regulus:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, remember massive stars are much more luminous than the Sun and so use up their fuel very quickly ("live fast and die young")

  • Question 43

    3 out of 3 points
    The surface of Venus is mostly low density rock, while the average density is similar to that of Earth, the interior of Venus must therefor be:
    Selected Answer:
    Correct 
    iron like the Earth
    Correct Answer:
    Correct iron like the Earth
    Response Feedback:
    Correct, like the Earth Venus must have an iron core

  • Question 44

    0 out of 3 points
    Which diagram shows the emission of the lowest energy photon?

    atoms.jpg
    Selected Answer:
    Incorrect 
    C 
    Correct Answer:
    Correct A
    Response Feedback:
    Incorrect, emission is when an electron goes from an outer (higher energy) orbital to an inner (lower energy) orbital giving off energy in the form of a photon, the smaller the jump the less energy released.

  • Question 45

    0 out of 3 points
    Tonight you go outside and see a star at the position marked (labeled as "position at 6pm"), at noon you would expect to see the star at the position labeled:

    circumpolar1_crop.png
    Selected Answer:
    Incorrect 
    b
    Correct Answer:
    Correct c
    Response Feedback:
    Incorrect, this is a circumpolar star and takes 24 hours to circle the pole - for the direction of motion remember it will "rise" in the East.

    Look at the web simulation:

    http://astro.unl.edu/naap/motion2/animations/ce_hc.swf

  • Question 46

    0 out of 3 points
    The moons of Mars were likely formed:
    Selected Answer:
    Incorrect 
    as a result of the impact of a large body on Mars
    Correct Answer:
    Correct in the asteroid belt before their later capture
    Response Feedback:
    Incorrect, these irrgularly shaped objects are likely captured asteroids

  • Question 47

    0 out of 1 points
    The Universe appears homogeneous and isotropic to our eyes:
    Selected Answer:
    Incorrect True
    Correct Answer:
    Correct False
    Response Feedback:
    Incorrect, it is only when you average over large volumes that the Universe is shown to be  homogeneous and isotropic.

  • Question 48

    3 out of 3 points
    The greenhouse effect on Earth is currently:
    Selected Answer:
    Correct 
    a largely natural process keeping the Earth at a temperature above freezing
    Correct Answer:
    Correct a largely natural process keeping the Earth at a temperature above freezing
    Response Feedback:
    Correct, the greenhouse effect is important in keeping the Earth habitable, but could potentially be dangerous to human civilization

  • Question 49

    3 out of 3 points
    Dark matter is composed of:
    Selected Answer:
    Correct 
    no one knows for sure
    Correct Answer:
    Correct no one knows for sure
    Response Feedback:
    Correct, this is one of the current unsolved mysteries in astronomy

  • Question 50

    0 out of 3 points
    Observations of young stars show features like this because:

    betapic_eso_big.jpg
    Selected Answer:
    Incorrect 
    a and b
    Correct Answer:
    Correct b and c
    Response Feedback:
    Incorrect, the collapse of the cloud to form the star results in some material falling into a disk due to rotation, and it is out of this material that new planets form.

  • Question 51

    3 out of 3 points
    Which of the following is the best evidence for the existence of dark matter in the Milky Way:
    Selected Answer:
    Correct 
    the orbital speeds of gas clouds outside the orbit of the Sun
    Correct Answer:
    Correct the orbital speeds of gas clouds outside the orbit of the Sun
    Response Feedback:
    Correct, see Figure 9-9 and the discussion beginning on page 181 in the text.

  • Question 52

    3 out of 3 points
    The Hubble Space Telescope has taken the clearest views of the distant Universe because:
    Selected Answer:
    Correct 
    it is above the atmosphere and thus above the blurring caused by atmospheric motions
    Correct Answer:
    Correct it is above the atmosphere and thus above the blurring caused by atmospheric motions
    Response Feedback:
    Correct, the motions in the Earth's atmosphere "smear" out images

  • Question 53

    1 out of 1 points
    Pulsars are rotating white dwarfs:
    Selected Answer:
    Correct False
    Correct Answer:
    Correct False
    Response Feedback:
    Correct, pulsars are rotating neutron stars.

  • Question 54

    1 out of 1 points
    Jupiter's moon Io has volcanoes:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct

  • Question 55

    3 out of 3 points
    Jupiter contains approximately what fraction of the mass of the planets:
    Selected Answer:
    Correct 
    70%
    Correct Answer:
    Correct 70%
    Response Feedback:
    Correct, Jupiter contains most of the mass in the planets, although remember it is a small fraction of the Sun

  • Question 56

    3 out of 3 points
    If we look at a galaxy 4.5 billion light years away we see it as it was:
    Selected Answer:
    Correct 
    when the Earth formed
    Correct Answer:
    Correct when the Earth formed
    Response Feedback:
    Correct, remember the Earth formed roughly 4.5 billion years ago

  • Question 57

    3 out of 3 points
    Incandescent light bulbs have a temperature of ~2700 K, this means that their light is emitted mostly:
    Selected Answer:
    Correct 
    at infrared wavelengths
    Correct Answer:
    Correct at infrared wavelengths
    Response Feedback:
    Correct, the cooler temperature (relative to the Sun) means that these bulbs emit most of their light at longer - infrared - wavelengths.  This is why they are so inefficient.

  • Question 58

    1 out of 1 points
    A closed Universe is one that re-collapses at some point in its history:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, this is the definition of a closed Universe.

  • Question 59

    3 out of 3 points
    You have two blackbodies of the same size but differing luminosity, what statement must be true?
    Selected Answer:
    Correct 
    the more luminous one is hotter
    Correct Answer:
    Correct the more luminous one is hotter
    Response Feedback:
    Correct, remember the luminosity goes as temperature to the fourth power times the radius squared for a blackbody, and the the more luminous object must be hotter.

  • Question 60

    1 out of 1 points
    Ceres is a dwarf planet:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, remember that while Ceres is large enough to be pulled by self-gravity into a "round" shape it is in the asteroid belt and thus has not cleared its orbit of similarly size bodies.

  • Question 61

    0 out of 1 points
    The temperature of the cosmic microwave background (CMB) varies widely (by a factor of 10 or more) across the sky:
    Selected Answer:
    Incorrect True
    Correct Answer:
    Correct False
    Response Feedback:
    Incorrect, the temperature varies by only a small fraction (about 1 part in 100,000)

  • Question 62

    1 out of 1 points
    The average density of "normal" matter like atoms and neutrinos is much less than the critical density required to close the Universe:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, "normal" matter is a small fraction of what makes up the Universe both dark matter and dark energy are much larger fractions of the Universe.

  • Question 63

    1 out of 1 points
    What do astronomers infer from the motion of the distant galaxies?
    Selected Answer:
    Correct 
    The Universe is expanding.
    Correct Answer:
    Correct The Universe is expanding.

  • Question 64

    3 out of 3 points
    When astronomer's refer to inflation, they are discussing:
    Selected Answer:
    Correct 
    the rapid increase in the size of the very early Universe
    Correct Answer:
    Correct the rapid increase in the size of the very early Universe
    Response Feedback:
    Correct, inflation was (possibly) a period of rapid expansion very early in the history of the Universe leading to the extreme homogenaity and isotropy of the Universe.

  • Question 65

    3 out of 3 points
    Why do all the planets orbit the Sun in the same direction?
    Selected Answer:
    Correct 
    They formed from material all circulating in the same direction in the primordial Solar Nebula
    Correct Answer:
    Correct They formed from material all circulating in the same direction in the primordial Solar Nebula
    Response Feedback:
    Correct, the direction of rotation was set by the initial rotation of the primordial cloud.

  • Question 66

    3 out of 3 points
    When astronomers discuss "metals" they are referring to:
    Selected Answer:
    Correct 
    all elements except hydrogen and helium
    Correct Answer:
    Correct all elements except hydrogen and helium
    Response Feedback:
    Correct, for historical reasons all elements except hydrogen and helium are termed "metals" by astronomers.

  • Question 67

    3 out of 3 points
    Which of the following has a linear size or radius closest to the radius of Betelguese?
    Selected Answer:
    Correct 
    the orbit of Mars
    Correct Answer:
    Correct the orbit of Mars
    Response Feedback:
    Correct, supergiant stars like Betelguese are extremely large (600-800 times larger than the Sun) and if located in the Solar system would engulf the terrestrial planets and ateroids and reach almost to Jupiter.

  • Question 68

    1 out of 1 points
    A Solar eclipse can occur only during a full Moon:
    Selected Answer:
    Correct False
    Correct Answer:
    Correct False
    Response Feedback:
    Correct, remember a Solar eclipse is when the Moon is between the Sun and the Earth and there for occurs during new Moon.

  • Question 69

    3 out of 3 points
    How do the planets near the Sun differ from those farther out?
    Selected Answer:
    Correct 
    The ones nearest the Sun are generally smallest
    Correct Answer:
    Correct The ones nearest the Sun are generally smallest
    Response Feedback:
    Correct, remember that the Terrestrial planets are significantly smaller than the Jovian planets.  You might be tempted to say rotate faster by remember that Jupiter rotates in only 10 hours.

  • Question 70

    0 out of 1 points
    Compared to visible light, microwave radiation has much longer wavelengths and much lower energies:
    Selected Answer:
    Incorrect False
    Correct Answer:
    Correct True
    Response Feedback:
    Incorrect, microwave radiation is of much longer wavelengths than optical light and thus of much lower energy since the energy of a photon is inversly proportional to its wavelength.

  • Question 71

    0 out of 3 points
    The modified form (by Newton) of Kepler's third law allows astronomers to determine the mass of:
    Selected Answer:
    Incorrect 
    all of the above
    Correct Answer:
    Correct planets around distant stars
    Response Feedback:
    Using the principles of Kepler and Newton, astronomers can determine the masses of all of these objects.  Einstein's General Relativity is used to determine the properties of objects such as black holes and the Universe at large scales.

  • Question 72

    3 out of 3 points
    Pluto is now classified as a dwarf planet because:
    Selected Answer:
    Correct 
    it is in the Kuiper belt
    Correct Answer:
    Correct it is in the Kuiper belt
    Response Feedback:
    Correct, Pluto has not "cleared" its orbit as it is surrounded by similar sized bodies.

  • Question 73

    3 out of 3 points
    Mercury's atmosphere is likely non-existent because of its:
    Selected Answer:
    Correct 
    small mass
    Correct Answer:
    Correct small mass
    Response Feedback:
    Correct, its small mass means that the gravitational force is not large enough to retain gas molecules

  • Question 74

    3 out of 3 points
    About how old is the Solar System?
    Selected Answer:
    Correct 
    5,000,000,000 years
    Correct Answer:
    Correct 5,000,000,000 years
    Response Feedback:
    Correct, based upon radioactive dating of meteors the best estimate for the age of the Solar system is 4.55 billion years.

  • Question 75

    0 out of 1 points
    Type II supernovae are good standard candles:
    Selected Answer:
    Incorrect True
    Correct Answer:
    Correct False
    Response Feedback:
    Incorrect, Type II supernovae are the final stage of a star of mass >8 * M(Sun), and thus vary greatly in brightness depending on the star.

  • Question 76

    3 out of 3 points
    Which of the following assumptions of the original nebular planet formation hypothesis is likely untrue based upon observations of extra-Solar planets?
    Selected Answer:
    Correct 
    The orbits of planets do not change after they are formed
    Correct Answer:
    Correct The orbits of planets do not change after they are formed
    Response Feedback:
    Correct, the original models of planet formation assume that the planets do not change their orbits, however observations of extra-Solar planets show large gas giant planets very close to stars in very eccentric orbits suggesting that they migrated in from further out.

  • Question 77

    0 out of 3 points
    A white dwarf that exceeds the Chandrasekhar limit becomes:
    Selected Answer:
    Incorrect 
    a type II supernova
    Correct Answer:
    Correct a type Ia supernova
    Response Feedback:
    Incorrect, when a white dwarf exceeds 1.4 Solar masses electron degeneracy pressure can no longer support it against gravity and so it collapses and subsequently detonates and explodes as a Type Ia supernova

  • Question 78

    1 out of 1 points
    The evolution of intellegent life on a planet is guarenteed once life forms:
    Selected Answer:
    Correct False
    Correct Answer:
    Correct False
    Response Feedback:
    Correct, there is no reason to think that intellegent life (or even multi-cellular life) will necessarily develop even if life forms on a planet.

  • Question 79

    1 out of 1 points
    The Universe appears homogeneous and isotropic when averaged over large volumes:
    Selected Answer:
    Correct True
    Correct Answer:
    Correct True
    Response Feedback:
    Correct, while it may look very different in every direction, 

  • Question 80

    0 out of 3 points
    Astronomers are interested in particle accelerator experiments such as those conducted at the Large Hadron Collider because:
    Selected Answer:
    Incorrect 
    they will search for particles which may have led to the beginnings of nuclear fusion in the center of stars
    Correct Answer:
    Correct they will search for particles which may have led to inflation in the early Universe
    Response Feedback:
    Incorrect, particle physics experiments like the LHC provide insight into the conditions that must have existed in the early Universe.
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