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Question 1
·
In the Drake equation for estimating the possible number of technically advanced civilizations in the Milky Way Galaxy, why does the factor for the rate at which solar-type stars form in a galaxy exclude massive stars with masses greater than about 1.5 times that of the Sun?
| · |
· 1. |
· Such stars are prone to repeated and violent supernova explosions throughout · their lives, which would destroy any developing life-forms. · |
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· 2. |
· Such stars have much shorter lifetimes than it took for intelligent life to develop · on the Earth and hence should probably not be considered. · |
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· 3. |
· Such stars never develop a nuclear furnace in their interiors and hence can never · heat any planet sufficiently to sustain life. · |
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· 4. |
· Such stars would never develop nuclear processes that could produce heavy · elements (e.g., iron) needed for planetary formation. |
·
1 points
Question 2
· The first successful detection of signals from extraterrestrial civilizations was accomplished in which year?
|
· Never—no such signals have been detected yet. |
|
· 1985 |
|
· 1999 |
|
· 1960 |
·
1 points
Question 3
·
What strategies and electromagnetic frequencies are thought to be the most logical for long-range communication across the universe with other intelligent beings?
·
· 1.
· explosion of nuclear devices at specific intervals and in specific patterns across
· Earth when we are closest to a nearby star
·
·
· 2.
· X-ray surveys of space at appropriate times (e.g., when Earth is closest to nearby
· stars in its orbit), in view of the penetrability of space at these wavelengths
·
·
· 3.
· night-by-night photography of nearby stars at hydrogen Balmer wavelengths
·
· 4.
· continuous radio and microwave listening and transmitting at frequencies at
· which the natural radio sky noise background is low
·
1 points
Question 4
· Which of the following statements is NOT considered to be a reason carbon is thought to be the element on which complex extraterrestrial life is likely to be based?
·
· 1.
· Carbon releases a significant amount of energy when it combines with hydrogen.
·
· 2.
· Carbon provides a basis for forming long, complex chains of molecules.
·
· 3.
· Every life-form on Earth is carbon-based, over an immense range of conditions.
·
· 4.
· Carbon forms chemical bonds that are both strong and flexible.
·
1 points
Question 5
· Around which types of stars are we most likely to find planets supporting our kind of life?
·
· 1.
· red giant stars
·
· 2.
· high-mass main-sequence stars
·
· 3.
· low-mass main-sequence stars
·
· 4.
· very low-mass stars
·
1 points
Question 6
· Why is the strategy of searches for extraterrestrial life usually based on carbon chemistry?
·
· 1.
· No other atom can combine easily with the abundant hydrogen and helium
· to form long molecules in interstellar gas.
·
·
· 2.
· Carbon is abundant and is versatile in forming complex, long-chain molecules.
·
· 3.
· Most meteorites that reach Earth are composed of carbon.
·
· 4.
· Carbon dioxide is the main ingredient of planetary atmospheres, both terrestrial
· and Jovian.
·
1 points
Question 7
· Why do we consider only stars with masses less than about 1.5 solar masses in the Drake equation when estimating the number of possible stars in the Milky Way Galaxy around which planets could form that would support our kind of intelligent life?
·
· 1.
· A more massive star would produce so much damaging UV radiation that it
· would sterilize its planets.
·
·
· 2.
· More massive stars would never reach temperatures sufficient to maintain
· life-supporting conditions on the surfaces of its planets.
·
·
· 3.
· More massive stars would have evolved so rapidly that an advanced civilization
· would not have had time to evolve and develop.
·
·
· 4.
· More massive stars would produce massive planets on which life would not be
· possible.
·
1 points
Question 8
· One of the important numbers in determining how many extraterrestrial civilizations there may be at the present time in the Milky Way Galaxy is the following: Out of the stars that have planets, what fraction, fs, has planets suitable for life? (This number is similar to the number ne in the Drake equation.) Based on the extrasolar planets already found by astronomers (see Sections 5-6 and 5-7 of Comins and Kaufmann, Discovering the Universe, 8th ed.), what is a good guess for fs? (Note: If all stars with planets have at least one planet suitable for life, then fs = 1; if no such star anywhere in the Milky Way has a planet suitable for life, then fs = 0.)
·
·
· 1.
· close to fs = 1/2 since about half the stars so far found to have planets have
· planets similar in mass to Earth orbiting the star at about the Earth’s distance
· from the Sun
·
·
· 2.
· fs = 0 since no star has yet been found to have an inhabitable planet
·
· 3.
· fs less than about 1/10 since most stars so far found to have planets have
· high-mass planets (similar to Jupiter or larger) orbiting close to the star,
· which would disrupt the orbit of an inhabitable planet
·
·
· 4.
· close to fs = 1 since most stars so far found to have planets have high-mass
· planets (similar to Jupiter or larger) orbiting far from the star, indicating that
· the solar system is probably typical of planetary systems in general
·
1 points
Question 9
· Several lines of evidence now suggest that large and complex organic molecules can exist or could evolve in outer space, from which the building blocks of life could be formed. Which of the following is NOT one of these observational findings?
·
· 1.
· radio astronomical observations of large organic molecules in giant molecular clouds
·
· 2.
· laboratory experiments in which electrical sparks passing through a combination
· of simple gases such as H2O, H2, N2, and CO2 produced large organic molecules
·
·
· 3.
· discovery of organic molecules inside some meteorites
·
· 4.
· discovery by the Viking landers of large organic molecules in the Martian regolith
·
1 points
Question 10
· There are now over 265 known extrasolar planets. When we consider them as possible homes for life, it is important to remember that most of them are
·
· 1.
· hydrogen-rich planets like Jupiter.
·
· 2.
· in extremely elliptical orbits, like comets.
·
· 3.
· Earthlike planets with water on their surfaces.
·
· 4.
· still in the process of forming and thus not old enough to have evolved life.
Question 11
· A starlike object seen on deep sky photographs coincides with an intense radio source and has a spectrum in which the characteristic Lyman pattern of hydrogen spectral lines has been shifted from the ultraviolet to the visible spectral range. What is this object?
·
· 1.
· quasar
·
· 2.
· supernova explosion
·
· 3.
· pulsar
·
· 4.
· black hole
·
1 points
Question 12
· BL Lacertae objects appear to be
·
· 1.
· giant irregular galaxies with neither spiral arms nor the smooth shape of
· elliptical galaxies.
·
·
· 2.
· active galaxies, most of whose energy is emitted by two widely spaced radio
· lobes.
·
·
· 3.
· spiral galaxies with bright, starlike nuclei.
·
· 4.
· elliptical galaxies with bright, starlike nuclei.
·
1 points
Question 13
· The emission lines in quasar spectra were difficult to identify initially because
·
· 1.
· they were very faint and could not be measured accurately.
·
· 2.
· no one expected violet and ultraviolet spectral lines to be shifted so far toward
· the red.
·
·
· 3.
· they appeared to be created by elements that did not exist on Earth.
·
· 4.
· the observed emission lines were so broad because of internal motions in the
· quasar that they were difficult to identify.
·
1 points
Question 14
· What observational evidence seems to indicate the presence of a supermassive black hole at the center of our neighboring galaxy, M31, in Andromeda?
·
· 1.
· slow but measurable motion of the Milky Way Galaxy toward M31 under the
· intense gravitational force of its black hole
·
·
· 2.
· very intense X-ray emission from a very small central core, indicating a very
· hot source
·
·
· 3.
· spectroscopic measurements of extremely high and symmetric Doppler shifts
· from material orbiting rapidly around a massive object near the galactic center
·
·
· 4.
· small but dark region on detailed photographs of M31, showing an area from
· which light cannot escape
·
1 points
Question 15
· The first three strong radio sources, discovered by Reber in the 1930s and 1940s, did NOT include a
·
· 1.
· supernova remnant.
·
· 2.
· distant galaxy.
·
· 3.
· globular cluster.
·
· 4.
· galactic nucleus.
·
1 points
Question 16
· Seyfert galaxies are
·
· 1.
· irregular galaxies with no shape or structure.
·
· 2.
· active galaxies with bright, starlike nuclei.
·
· 3.
· the largest galaxies in the universe.
·
· 4.
· very small elliptical galaxies.
·
1 points
Question 17
· Which of the following is a characteristic of a Seyfert galaxy?
·
· 1.
· A Seyfert galaxy has no spiral arms.
·
· 2.
· The spectrum of a Seyfert galaxy shows particularly narrow absorption lines.
·
· 3.
· The nucleus of a Seyfert galaxy is unusually faint compared with the spiral arms.
·
· 4.
· The nucleus of a Seyfert galaxy is unusually bright compared with the spiral arms.
·
1 points
Question 18
· All quasars appear to be
·
· 1.
· relatively close, very bright objects.
·
· 2.
· moving away from Earth at very high speeds.
·
· 3.
· very distant, intrinsically faint objects.
·
· 4.
· moving toward Earth at very high speeds.
·
1 points
Question 19
· A BL Lacertae object is a(n)
·
· 1.
· rapidly spinning neutron star.
·
· 2.
· active galactic nucleus.
·
· 3.
· eclipsing binary star with a black hole as one component.
·
· 4.
· emission nebula containing a young T Tauri star.
·
1 points
Question 20
· Massive black holes have been discovered in the cores of what kinds of galaxies?
·
· 1.
· giant ellipticals
·
· 2.
· dwarf ellipticals, giant ellipticals, and spirals
·
· 3.
· giant ellipticals and spirals
·
· 4.
· spirals
