Comins DEU 3e Ch 02 Quiz 3 completed
The correct answers are written in bold, italic and underlined.
The most important questions to study for the exam are highlighted.
1. The two most common substances in the universe are
• carbon and oxygen.
• hydrogen and helium.
• hydrogen and nitrogen.
2. The early universe appears to have contained only light elements, mostly hydrogen and
helium, and yet, at the present time, there are significant amounts of heavier elements,
those from which the Earth (and ourselves) are made. From where have these heavy
elements come?
• Repeated energetic collisions of light-element nuclei (cosmic rays) in space that
produced heavier elements by nuclear fusion
• Minor amounts of heavier elements that formed in the initial Big Bang and became
concentrated in certain parts of galaxies to form solar systems such as our own
• Nuclear fusion and element synthesis in the deep interiors of stars
3. Where did the hydrogen come from that is so abundant in the universe today?
• All of it was formed during the Big Bang at the very start of the universe.
• Essentially all of it has been formed inside stars and thrown out into the universe by
supernova explosions.
• Most of it was formed during the Big Bang at the very start of the universe. Since that
time, stars have gradually added more hydrogen to the original amount.
4. Where did the planets come from?
• They formed from material thrown out of the Sun when another small star collided
with the Sun.
• They formed from a nebula of gas and dust, the same nebula from which the Sun
itself formed.
• They formed from a nebula in interstellar space and were captured by the Sun as it
orbited around the Galaxy.
5. What process heated the early solar nebula as it slowly condensed toward a central
protosun?
• Atoms collided with increasing speed as they fell toward the center of the nebula,
creating heat.
• Heat was released by the formation of molecules such as CO2 and NH3 from atoms
and the condensation of ices from gases such as H2O.
• Thermonuclear fusion in the protosun was followed by radiative heating of the
material in the nebula.
6. What is the fundamental law of physics that allowed the planets to form, rather than
having all of the material simply fall into the Sun?
• Conservation of angular momentum
• Conservation of kinetic energy
• The law of action and reaction (Newton's third law)
7. The reason the inner planets are mostly rock and iron and the outer planets are mostly
lighter material like hydrogen and ices is that
• the inner solar system was warm enough that the lighter material vaporized (or
never solidified), leaving rock and iron to form the inner planets.
• rock and iron are heavy and sank toward the center of the solar system.
• rotation in the solar nebula flung the lighter materials into the outer solar system,
leaving the heavier rock and iron to form the inner planets.
8. Which components of the present solar system have probably remained essentially
unchanged since the solar system was formed and can therefore provide valuable clues to
the manner of its formation?
• Comets, asteroids, and meteoritic material
• The terrestrial planets
• The giant planets
9. In the early solar system, how did the formation of the inner planets, such as the Earth,
compare to that of the outer planets, such as Jupiter?
• Both were the same initially, accretion through collisions of larger and larger
planetesimals, but the inner planets stopped there, whereas the outer planets went
on to pull ices and gas directly from the solar nebula.
• Both were very different from the start, the inner planets forming by accretion
through collisions of larger and larger planetesimals and the outer planets by
condensation of ices and gas directly from the solar nebula.
• Both formed by the same process, accretion through collisions of larger and larger
planetesimals, but the planetesimals forming the inner planets were rocky, whereas
those forming the outer planets were composed mostly of ices.
10. At what time and from what source did the majority of the craters on the Moon form?
• During less than the first billion years of the Moon's life, from debris left over from
the formation of the solar system
• Increasing to a maximum impact rate 2.5 billion years ago as collisions between
asteroids produced more and more debris fragments, then dropping off as large
asteroids became rare
• More-or-less uniformly over the life of the Moon due to a roughly constant supply of
rocky and icy debris from the outer solar system
11. The age of the Moon, as determined by radioactive measurements of rocks brought
back by astronauts, appears to be
•
•
•
similar to that of the Earth, about 4.6 billion years.
very much younger than the Earth, indicating that it was probably broken from the
Earth by a collision about 1 billion years ago.
very much older than the Earth, suggesting that it formed elsewhere in the universe
and was subsequently captured by the gravitational field of the Earth.
12. The planets of our solar system, excluding Pluto, move in orbits that
• all lie precisely in one plane, the ecliptic plane, because they were formed in this
configuration.
• are inclined to one another and to the plane of the Earth's orbit by up to 30E, hence
their erratic motions in our sky.
• all lie within a few degrees of one plane.
13. An object less than 1000 km across, composed of rock and iron and orbiting closer to
the Sun than the planet Jupiter, would be called
• a comet.
• a terrestrial planet.
• an asteroid.
14. What does the long, flowing tail of a comet tell us about the solid body of the comet?
• The heat of the Sun produces combustion (burning) on its surface.
• It is composed of ice.
• It is ejecting lava (molten rock) and gas from volcanic eruptions.
15. On the basis of their properties and orbits, the planets of our solar system, apart from
Pluto,
• are all very much alike, having common characteristics.
• are all completely different and individual in character.
• can be classified into two main groups.
16. Suppose a small object is discovered in orbit around the Sun, with a mass of 1 million
kg and a volume of 1000 cubic m. This object is most likely made almost entirely of
• ice.
• rock.
• iron (which is much denser than rock).
17. What major fact leads to the conclusion that the giant planets are composed mainly of
light elements such as hydrogen and helium?
• Their low average density
• Their very low gravitational force
• Their emitted spectra, which are dominated by lines of hydrogen and helium
18. The planet that, in its overall composition and density, is least like any other planet in
our solar system is
• Pluto.
•
•
Jupiter.
the Earth.
19. How have the majority of extrasolar planets (planets orbiting stars outside our solar
system) been found?
• By observations of spectral lines of molecular oxygen, which is highly reactive and
therefore exists in abundance only if produced continuously by life
• By direct photography with the new 8- and 10-m diameter telescopes in Hawaii and
other locations
• By observing their gravitational effect on the star as the planets move around their
orbits
20. How do the majority of the planetary systems that have been found around other stars
compare to our solar system?
• They are very different, containing primarily terrestrial-type planets in both the inner
and the outer regions.
• They are very similar, with Jovian-type planets orbiting in the colder outer regions
and terrestrial-type planets orbiting in the warmer inner regions.
• They are very different, with Jovian-type planets orbiting close to the star.