Monday, December 30, 2013

PHYS 107 ASTRONOMY FINAL 1 REVIEW - OOPSIE

  • Question 1

    0 out of 3 points
    The Hubble Space Telescope has taken the clearest views of the distant Universe because:
    Selected Answer:
    Incorrect 
    it is above the atmosphere and thus is not covered in smog and clouds
    Correct Answer:
    Correct it is above the atmosphere and thus above the blurring caused by atmospheric motions
    Response Feedback:
    Incorrect, the motions in the Earth's atmosphere "smear" out images, telescopes in space are above this distorting effect

  • Question 2

    0 out of 3 points
    What is a standard candle?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct an object of known brightness that can be used to measure the distance to a cluster or galaxy
    Response Feedback:
    Incorrect, it is a variable star like a Cepheid (whose brightness we know from its period) or an object like a Type-I supernova whose brightness we know, so by comparing how bright it appears to how bright it intrinsically is we can determineits distance via the inverse square law.

  • Question 3

    0 out of 3 points
    About what temperature did the cosmic microwave background have at the time of its formation?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 3,000 K
    Response Feedback:
    Incorrect, when it formed the Universe had cooled to roughly 3,000 K, the temperature of the surface of a star.

  • Question 4

    0 out of 3 points
    Mercury's atmosphere is likely non-existent because of its:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct small mass
    Response Feedback:
    Incorrect, its small mass means that the gravitational force is not large enough to retain gas molecules

  • Question 5

    0 out of 3 points
     What do we mean by inflation?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct  A sudden expansion of the universe driven by the energy released when the strong and electroweak forces froze out from the GUT force
    Response Feedback:
      Incorrect, inflation occurs early in the Universe's history when the physical forces become distinct.

  • Question 6

    0 out of 3 points
    Which of the following is the best evidence for the existence of dark matter in the Milky Way:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the orbital speeds of gas clouds outside the orbit of the Sun
    Response Feedback:
    Incorrect, see Figure 9-9 and the discussion beginning on page 181 in the text.

  • Question 7

    0 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:
    Incorrect [None Given]
    Correct Answer:
    Correct The orbits of planets do not change after they are formed
    Response Feedback:
    Incorrect, 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 8

    0 out of 3 points
    Why are objects like Mercury and the moons of Earth, Jupiter and Saturn so heavily cratered?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct Intense bombardment by asteroids and planetesimals subsequent to their birth
    Response Feedback:
    Incorrect, the impact of small bodies leads to cratering and without tectonic activity, melting of ice or weathering the craters remain

  • Question 9

    0 out of 3 points
    Uranus is peculiar because its:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct axis of rotation is so highly tilted
    Response Feedback:
    Incorrect, 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 10

    0 out of 3 points
    How was the CMB (cosmic microwave background) created?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct The burst of radiation from the big bang as it cooled toward 10,000 K.
    Response Feedback:
    Incorrect, when the radiation from the Big Bang cooled to about 10,000 K the hydrogen ions in the early Universe could combine with the electrons to form neutral hydrogen allowing the radiation to escape and travel freely.  It has since been redshifted to radio wavelengths.

  • Question 11

    0 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:
    Incorrect [None Given]
    Correct Answer:
    Correct iron like the Earth
    Response Feedback:
    Incorrect, like the Earth Venus must have a high density iron core

  • Question 12

    0 out of 3 points
    Incandescent light bulbs have a temperature of ~2700 K, this means that their light is emitted mostly:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct at infrared wavelengths
    Response Feedback:
    Incorrect, 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 13

    0 out of 3 points
    A moon must be:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct orbiting a planet
    Response Feedback:
    Incorrect, by definition of a moon.

  • Question 14

    0 out of 3 points
    Particle physicists are interested in the conditions in the early Universe because:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct this allows them to test unified field theories uniting the fundamental forces of nature
    Response Feedback:
    Incorrect, the densities and energies in the early Universe cannot yet (and may never) be replicated in particle accelerators

  • Question 15

    0 out of 3 points
    As seen from the Moon, the Sun rises:
    Selected Answers:
    Incorrect [None Given]
    Correct Answers:
    Correctd. about once a month.
    Response Feedback:
    Incorrect, the Moon rotates in the same time it takes it to orbit the Earth (~ one month), this is why we see only one side of the Moon.

  • Question 16

    0 out of 3 points
    What factor about Mercury best explains its atmosphere or lack thereof?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct Its low mass has made it hard for it to retain any gases at all as an atmosphere.
    Response Feedback:
    Mercury has little atmosphere due to its low gravity (low mass) and closeness to the Sun (and thus high temperature).  Note that Mercury is a relatively slow rotating planet.

  • Question 17

    0 out of 3 points
    We can measure the mass of  the black hole at the center of the Milky Way galaxy by:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct watching the orbits of stars in the center and using Kepler's Third Law
    Response Feedback:
    Incorrect, 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 18

    0 out of 3 points
    Compared to visible light, X-rays have
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correctc. higher energy and shorter wavelengths
    Response Feedback:
    Incorrect, X-rays have very small wavelengths (1 nanometer) and very high energies.

    Remember that energy is inversely proportional to wavelength, so shorter wavelength equals more energy, and one way to remember that X-rays are more energetic is to remember that they can penetrate your body.

  • Question 19

    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 [None Given]
    Correct Answer:
    Correct all of the above
    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 20

    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 [None Given]
    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.

  • Question 21

    0 out of 3 points
    Which of the following has a linear size or radius closest to the radius of a white dwarf?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the Earth
    Response Feedback:
    Incorrect, a white dwarf is roughly the mass of the Sun squeezed into the size of the Earth

  • Question 22

    0 out of 3 points
    Dark energy is:
    Selected Answer:
    Incorrect [None Given]
    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:
    Incorrect, 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 23

    0 out of 3 points
    Tonight you observe the planet Saturn at midnight high in the Southern skies, you know that:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct Saturn and Earth must be on the same side of the Sun
    Response Feedback:
    Incorrect, Saturn must be opposite the Sun at this point.

  • Question 24

    0 out of 3 points
     The distribution of the dark matter in a spiral galaxy is
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
    Incorrect, the spherical halo extends beyond the physical disk

  • Question 25

    0 out of 3 points
    The Milky Way is:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the name of our Galaxy
    Response Feedback:
    Incorrect, the Milky Way is the name of our galaxy (from ancient Greek myths)

  • Question 26

    0 out of 3 points
    A hot glowing solid will emit
    Selected Answers:
    Incorrect [None Given]
    Correct Answers:
    Correctc. a continuous spectrum 
    Response Feedback:
    Incorrect, a hot solid emits a continuous spectrum, approximately as a "blackbody".  

  • Question 27

    0 out of 3 points
    Clusters of galaxies are bound together by:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct gravity
    Response Feedback:
    Incorrect, the attractive force of gravity binds together astronomical objects from planets and stars to galaxies and clusters of galaxies

  • Question 28

    0 out of 3 points
    When we look at the great galaxy in Andromeda we see it as it was approximately:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 2.5 million years ago
    Response Feedback:
    Incorrect, 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 29

    0 out of 3 points
    If we look at a galaxy 4.5 billion light years away we see it as it was:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct when the Earth formed
    Response Feedback:
    Incorrect, remember the Earth formed roughly 4.5 billion years ago and it takes light 4.5 billion years to travel 4.5 billion light years.

  • Question 30

    0 out of 3 points
    The most important factor in determining a stars eventual fate is its:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct mass
    Response Feedback:
    Incorrect, its mass is tied to the luminosity (since the star is in hydrostatic equilibrium) and thus to the lifetime of the star.

  • Question 31

    0 out of 3 points
     Which of the following is not evidence for dark matter?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, the expansion of the Universe is not driven by dark matter

  • Question 32

    0 out of 3 points
    You observe a Cephied variable in a distant galaxy, you can now determine the galaxies:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct distance
    Response Feedback:
    Incorrect, since Cephieds are standard candles we can use the apparent brightness (and their known absolute brightness) to calculate the distance to the star (and thus galaxy)

  • Question 33

    0 out of 3 points
    You have two blackbodies of the same size but differing luminosity, what statement must be true?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the more luminous one is hotter
    Response Feedback:
    Incorrect, 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. This is why the hot O stars are so much more luminous than cooler stars like the Sun.

  • Question 34

    0 out of 3 points
    Dark matter is composed of:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct no one knows for sure
    Response Feedback:
    Incorrect, this is one of the current unsolved mysteries in astronomy

  • Question 35

    0 out of 3 points
    What component of the primordial interstellar cloud became the inner planets?
    Selected Answer:
    Incorrect [None Given]
    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.

    The ice and hydrogen gas were largely ejected from the inner Solar system by the light and the Solar wind early in the formation of the Solar system.

  • Question 36

    0 out of 3 points
    If we see a cluster with O and B stars we know that it:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct must have formed recently
    Response Feedback:
    Incorrect, O and B stars have very short lifetimes and so must have formed recently.

  • Question 37

    0 out of 3 points
    Which of the following has a linear size or radius closest to the radius of Betelguese?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the orbit of Mars
    Response Feedback:
    Incorrect, 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.

    Remember the in class demo assumed the Sun was the size of a small ball when we said Betelguese was the size of the classroom.

  • Question 38

    0 out of 3 points
     At present, what is the primary way that astronomers carry out SETI programs (that is, search for extraterrestrial intelligence)?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, we are searching for radio signals from intelligent life

  • Question 39

    0 out of 3 points
    About how old is the Solar System?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 5 billion years
    Response Feedback:
    Incorrect, the best evidence from the ages of rocks on Earth as well as the asteroids coupled with models of the Sun's evolution yield an age of about 4.55 billion years.

  • Question 40

    0 out of 3 points
    When astronomers discuss "metals" they are referring to:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct all elements except hydrogen and helium
    Response Feedback:
    Incorrect, for historical reasons all elements except hydrogen and helium are termed "metals" by astronomers.

  • Question 41

    0 out of 3 points
    What is the largest object in the Solar System?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct The Sun
    Response Feedback:
    Incorrect, the Sun conatins most of the mass of the Solar system (~99%),  as well as being 10x larger than the next largest object (Jupiter), if you answered the central black hole you are thinking of the galaxy.

  • Question 42

    0 out of 3 points
    The greenhouse effect on Earth is currently:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct a largely natural process keeping the Earth at a temperature above freezing
    Response Feedback:
    Incorrect, the greenhouse effect is important in keeping the Earth habitable, but could potentially be dangerous to human civilization

  • Question 43

    0 out of 3 points
    Pluto is now classified as a dwarf planet because:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct it is in the Kuiper belt
    Response Feedback:
    Incorrect, Pluto has not "cleared" its orbit.  Note that it croses Neptune's orbit not that of Uranus.

  • Question 44

    0 out of 3 points
    How does the observed density in stars compare with the critical density?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct it is much less
    Response Feedback:
    Incorrect, 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 45

    0 out of 3 points
    As seen from Earth, Jupiter cannot:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct eclipse the Sun
    Response Feedback:
    Incorrect, Jupiter cannot come between the Earth and the Sun

  • Question 46

    0 out of 3 points
     Harlow Shapley concluded that the Sun was not located at the center of the Milky Way Galaxy by
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, he used halo objects generally un-obscured by dust in the plane of the galaxy

  • Question 47

    0 out of 3 points
    Greenhouse gases warm a planet like Earth by:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct retaining more infrared light emitted by the Earth
    Response Feedback:
    Incorrect, 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 48

    0 out of 3 points
    Why is the cosmic microwave background temperature so cool now?
    Selected Answer:
    Incorrect [None Given]
    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 49

    0 out of 3 points
     Which of the following methods used to determine the mass of a cluster of galaxies does not depend on Newton's law of gravity?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, gravitational lensing depends on Einstein's theory of general relativity

  • Question 50

    0 out of 3 points
     What produces the 21-cm radio line that we can be used to map the Milky Way Galaxy?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, the 21cm line comes from neutral hydrogen

  • Question 51

    0 out of 3 points
     Scale the Milky Way down to the size of a compact disc. Which of the following best describes the size, shape, and distance of the Andromeda Galaxy on the same scale?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, both are disk galaxies relatively (cosmically speaking) close together

  • Question 52

    0 out of 3 points
    Eris is classified as a dwarf planet (and not a planet) because:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct it has not cleared its orbit around the Sun
    Response Feedback:
    This is the only part of the definition of a planet that Eris does not meet, and it is "planet-like" in that it does have sufficient self-gravity to be round, and it does orbit the Sun.  However since it is within the Kuiper belt there are numerous bodies near it that are of similar mass, so it has not "cleared its orbit".

  • Question 53

    0 out of 3 points
    Hydrostatic equilibrium means that:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct stars have a higher temperature and pressure in their centers to support the mass of their outer layers
    Response Feedback:
    Incorrect, the concept of hydrostatic equilibrium implies that a star must have a higher pressure in its center to support the weight of the outer layers.

    Despite the inclusion of "static" within this term, it does not imply that nothing can move within a star - see for example convective transport of energy.

  • Question 54

    0 out of 3 points
     How does the interstellar medium obscure our view of most of the galaxy?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
    Incorrect, interstellar dust grains absorb light and then re-radiates it in the infrared

  • Question 55

    0 out of 3 points
    When an atom absorbs a high energy photon and an electron is ejected we call this:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct ionization
    Response Feedback:
    Incorrect, ionization is removing an electron from an atom (creating an ion)

  • Question 56

    0 out of 3 points
    As seen from Mars, the planets Mercury, Venus and Earth can only be seen in which of the following locations in its sky:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct just above the eastern horizon before sunrise
    Response Feedback:
    Incorrect, from Mars, Earth (as well as Venus and Mercury) is an inner planet and so will be seen only near the Sun, all of the other points are either on the opposite side of the sky from the Sun or not the same for every person on the planet (the zenith).

  • Question 57

    0 out of 3 points
    A white dwarf that exceeds the Chandrasekhar limit becomes:
    Selected Answer:
    Incorrect [None Given]
    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 58

    0 out of 3 points
    The moons of Mars were likely formed:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct in the asteroid belt before their later capture
    Response Feedback:
    Incorrect, these irrgularly shaped objects are likely captured asteroids

  • Question 59

    0 out of 3 points
     Why should galaxy collisions have been more common in the past than they are today?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, the Universe was much smaller so the force of gravity was much larger (remember Newtons Law)

  • Question 60

    0 out of 3 points
    A red giant star like Arcturus must have a:
    Selected Answer:
    Incorrect [None Given]
    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 61

    0 out of 3 points
    When astronomer's refer to inflation, they are discussing:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the rapid increase in the size of the very early Universe
    Response Feedback:
    Incorrect, 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 62

    0 out of 3 points
    How do we know how old the Solar System is?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct By measuring the products of radioactive decay in old rocks and meteors
    Response Feedback:
    Incorrect, 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 63

    0 out of 3 points
    The cosmic microwave background shows that the Universe evolved from a:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct hot dense state
    Response Feedback:
    Incorrect, 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 64

    0 out of 3 points
    Using the 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:
    Incorrect [None Given]
    Correct Answer:
    Correct 1 year
    Response Feedback:
    Incorrect, 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 65

    0 out of 3 points
     Which of the following is not a possible solution to the Fermi Paradox?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, the Galactic disk has existed about twice as long as the Sun

  • Question 66

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

    moonphases_sm.jpg
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct e
    Response Feedback:
    Incorrect, a full Moon is when the Moon is on the opposite side of the Earth from the Sun

  • Question 67

    0 out of 3 points
    The horizon is:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct an imaginary plane that separates what is visible in the sky from what is below the Earth
    Response Feedback:
    Incorrect, remember the horizon on Earth is the plane that separates what you can see from what you can't (this is why we call the distance out to which we can see at any point in time in cosmology the "horizon")

  • Question 68

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

    atoms.jpg
    Selected Answer:
    Incorrect [None Given]
    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 69

    0 out of 3 points
    A main sequence star's luminosity comes from:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correcta. fusion of hydrogen into helium in the core
    Response Feedback:
    Incorrect, the main sequence is when a star uses nuclear fusion reactions to convert hydrogen into helium in the core of the star.

    Chemical burning (combining oxygen with other elements), stored gravitational energy and radioactive decay are not energy sources for main sequence stars.  Core helium
    and shell hydrogen burning occur after the star has evolved off the main sequence.

  • Question 70

    0 out of 3 points
    An OB star like Rigel moving through the galactic disk is a:
    Selected Answer:
    Incorrect [None Given]
    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 71

    0 out of 3 points
    We know of approximately how many exo-planets today
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 900
    Response Feedback:
    Correct, we currently know of about 900 extra-Solar planets (note 1 was known when I left graduate school 13 years ago)

  • Question 72

    0 out of 3 points
    About how old is the Solar System?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 5,000,000,000 years
    Response Feedback:
    Incorrect, based upon radioactive dating of meteors the best estimate for the age of the Solar system is 4.55 billion years.

  • Question 73

    0 out of 3 points
    The reason astronomers use near-infrared observations is to:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct penetrate interstellar dust clouds
    Response Feedback:
    Incorrect, one of the key advantages of near-infrared is its ability to penetrate dust clouds where shorter wavelength opitcal light is absorbed.

    Remember that dark matter does not interact with light and that hot gas will emit at short wavelengths (high energies) in the X-rays and ultraviolet.

  • Question 74

    0 out of 3 points
    A sidereal day on Earth is not:
    Selected Answers:
    Incorrect [None Given]
    Correct Answers:
    Correctc. longer than a Solar day. 
    Response Feedback:
    Incorrect, all three of (a), (b), and (d) are true.  The sidereal day is defined in answer (a), and because the Earth orbits the Sun in the same direction it rotates the sidereal day is ~4 minutes shorter than the Solar day.

  • Question 75

    0 out of 3 points
    Jupiter's composition is closest to that of:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct the Sun
    Response Feedback:
    Incorrect, both the Sun and Jupiter are mostly H and He

  • Question 76

    0 out of 3 points
    The interstellar medium of galaxies today show more "metals" than that seen in distant galaxies because:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct more supernovae have gone off to enrich the gasover the past few billion years
    Response Feedback:
    Incorrect, 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
    the "extra" few billion years that local galaxies mean that more supernovae go off and thus there are more metals (which are formed in supernovae) in the galaxy.

    Aside: remember to an astronomer all elements other than H and He are "metals"

  • Question 77

    0 out of 3 points
    The majority of the asteroids (the asteroid belt) lie between:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct Mars and Jupiter 
    Response Feedback:
    Incorrect, most of the asteroids lie in a "belt" between Mars and Jupiter, while some have orbits which cross that of the Earth (or even Mercury) most are in this region.  Objects beyond Neptune are in the Kuiper belt or Oort cloud.

  • Question 78

    0 out of 3 points
     Why can't current theories describe what happened during the Planck era?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, despite the efforts of physicists over the last ~80 years we do not yet have a theory linking quantum mechanics and gravity

  • Question 79

    0 out of 3 points
    If astronomers on Earth see tonight a newly formed cluster of O stars in the Andromeda galaxy, alien astronomers in the Andromeda galaxy would most likely see (today) at the same location:
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct a cluster of supernova remnants
    Response Feedback:
    Incorrect, remembering that O (and B) stars live fast and die young, so in the 2 million years that the light from these stars took to reach the Milky Way they will have evolved off the main sequence, become supergiants and then become supernovae leaving behind black holes or white neutron stars.

  • Question 80

    0 out of 3 points
     Why do we call dark matter "dark"?
    Selected Answer:
    Incorrect [None Given]
    Correct Answer:
    Correct 
    Response Feedback:
     Incorrect, it does not emit, scatter or absorb significant amounts of light
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