Chapter 8 Exam Questions and Answers
1. What was William Herschel looking for when he discovered Uranus? What made Herschel
particularly suited for discovering planets? In what 2 ways did Uranus reveal itself to Herschel as a
planet? What is it about Uranus' orbit that caused it to be considered a planet instead of a comet?
What is the origin of Uranus' name?
a) William Herschel was cataloguing stars to look for stellar parallax when he discovered Uranus
b) Hershel was particularly suited for discovering planets because he built the largest telescope of his
c) 1) When Herschel increased the magnification of his telescope Uranus increased its size, which
suggest that it was not a star
2) He found that Uranus have moved night to night relative to the stars
d) Uranus had a near circular orbit which would make it a planet, a comet would have an elliptical orbit
e) Uranus was named after the Greek god of the sky, father of Saturn, grandfather of Jupiter
2. What did Kepler believe existed between the large space between Mars and Jupiter? Explain
why Bode's Law supported this idea.
a) When Kepler observed the large gap between Mars and Jupiter, he proposed: it contains an
b) Bodes’ law, where every number in the sequence corresponds to one of the distances between each
planet and our sun. It supported the idea that there was an undiscovered planet between Mars and
Jupiter because every one of Bode’s number supported a planet except one that was between Mars and
Jupiter (2.8). There is something missing, there is a undiscovered planet that corresponds to this 2.8 AU.
3. What is the name of the object found in 1801 between Mars and Jupiter? What was this
object finally classified as, and why? What is this object a part of?
b) Downgraded from planet to asteroid because the word asteroid means they look star-like and that’s
how Ceres appear like but they are not actually stars, they are smaller than a moons
c) Asteroid Belt 4. What caused Adams and Leverrier to suspect the existence of a planet beyond Uranus? When
this planet was found, what was it named, and why?
a) Deviations were detected in the orbit of Uranus
b) The planet was named "Neptune" (Roman sea god), owing to its bluish colour
5. How were the masses of Uranus and Neptune 1st measured? How do their masses compare
with the other planets? Based on the masses and sizes, what do we know about their densities and
a) The masses of Uranus and Neptune was first measured, once their moons were discovered you can
apply Kepler’s 3 law to get at the mass of whatever the moon is orbiting around , in this case it was
Neptune and Uranus. So the mass of the planets were applying Kepler’s 3 law to their moons.
b) Uranus and Neptune are very massive, they are much larger than the Earth but not as nearly as
massive as Jupiter and Saturn.
c) They are light like Jupiter and Saturn and are low density and therefore, gaseous. Therefore we call
these Neptune and Uranus Gas Giants just like Jupiter and Saturn. We call them Ice Giants because a lot
of their material is frozen. But you can refer to them as just Gas Giants. Their composition has a small
rocky core, the rest of the planet is hydrogen gas and frozen based hydrogen based molecules.
6. What is today's theory for why all the planets in our solar system orbit the Sun in the same
direction and in roughly the same plane? What is the observational evidence for this theory?
a) Current theory: after the Sun was born from a spinning, collapsing gas cloud, the remaining gaseous
and rocky particles in the Sun's spinning circumstellar disk coalesced into planets
b) The proof: disks of matter have been found around newborn stars in star-forming nebulae
7. What is today's theory for the asteroid belt? What about planetary rings?
a) The asteroid belt likely the leftover debris from the Sun's circumstellar disk that couldn't coalesce
into a planet due to the opposing gravitational pulls of the sun and nearby giant Jupiter (failed planet,
and it is Jupiter’s fault)
b) Planetary rings (are failed moons) are likely the leftover debris from protoplanetary (disk around a
planet rather than a disk around a star) disks which couldn't coalesce into a moon.
8. What 3 attributes are unique to the 4 planets beyond Mars? What is the current explanation
a) The 4 planets beyond Mars are all gas giants, have numerous moons, and all have rings
b) The reasons: The outer circumstellar disk contained more material allowing the outer planets to
collect more mass and to attract more debris into orbit as mo