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
b) Hershel was particularly suited for discovering planets because he built the largest telescope
of his time
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
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?
a) Ceres 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 compositions?
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 for this?
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 moons and rin