Download Asteroids and comets

Astronomy Learning Objectives and Study Questions
Chapter 9: Comins and Kaufmann, 10th ed.
1. Cite one observation that justifies grouping Pluto with the other "outer planets" and one that justifies
classifying it as a very different type of body.
2. Calculate the radius of a Kirkwood Gap in the asteroid belt knowing the fraction of Jupiter's orbital period
that corresponds to orbital resonance for that gap.
3. Cite two reasons why astronomers consider it unlikely that the belt asteroids ever were part of a tenth
planet, and explain why these objects never became part of any planetary body.
4. Sketch a diagram of a comet that shows its major parts (nucleus, coma, ion tail, dust tail) as it approaches
the Sun. Be sure to include the comet's orbital path and the direction towards the Sun in your sketch.
5. Explain why astronomers infer two separate reservoirs for comets and briefly describe the shape and size (in
terms of distance from the Sun) of each reservoir.
6. Explain what the three-fold division of most meteorites into stony, iron, and stony-iron families tells us about
the bodies they originated from, and describe what one would look for to recognize a meteorite that had not
been significantly modified since its formation from the solar nebula.
1. The way in which Pluto is most similar to the planets of our solar system is that it
_____.
A. has a strongly eccentric (elongate) orbit
B. has insufficient gravity to clear objects from its neighborhood
C. has an orbit that is strongly inclined to the ecliptic
D. has sufficient gravity to be spherical
E. forms binary system with Charon
2. Most of the asteroids orbit _____.
A. in the ecliptic between Mars and Jupiter
B. in a spherical shell far beyond Pluto
C. in the ecliptic beyond Pluto
D. inside of Earth’s orbit
E. at the Lagrange points near Jupiter
3. The Kirkwood gap for asteroids with orbital periods 3/7 that of Jupiter is located _____ AU from the Sun.
(PJupiter = 11.86 yr.)
A. 3.28
B. 2.82
C. 2.96
D. 2.50
E. indeterminate, cannot tell from the data given
4. Short-term comets enter the inner solar system at low angles to the ecliptic from a doughnut-shaped region
beyond the orbit of Pluto called the _____.
A. asteroid belt
B. Oort cloud
C. comet cloud
D. Kuiper belt
E. Kirkwood’s gap
5. Long-term comets enter the inner solar system at high angles to the ecliptic from a spherical region that
extends out to about 50,000 AU called the _____.
A. Asteroid belt
B. Oort cloud
C. Comet cloud
D. Kuiper belt
E. Kirkwood’s gap
6. As comets enter the inner solar system, their _____ point directly away from the Sun.
A. dust tails
B. ion tails
C. comas
D. hydrogen envelopes
E. nuclei
7. Most meteorites (≈95%) are _____.
A. carbonaceous chondrites
B. chondrites
C. iron meteorites
D. stony meteorites
E. stony-iron meteorites
8. Tiny spherical bodies found in meteorites that are crystallized from droplets of
melt formed in the solar nebula are called _____.
A. crystals
B. chondrules
C. blueberries
D. spherules
E. orbicules
9. The explosion of a comet or small asteroid before it reached the ground produced the distinctive pattern of
damage found at _____.
A. Allende
B. Arizona
C. Chesapeake Bay
D. Chicxulub
E. Tunguska
10. The asteroid impact at Chicxulub that wiped out the dinosaurs occurred about _____ Ma.
A. 35.5
B. 65
C. 250
D. 377
E. 540