NATS1745 6.0 History ofAstronomyChapter 8 Exam Review
1. What was William Herschel looking for when he discovered Uranus? He was
classifying the stars to aid the search for stellar parallax. Discover a stellar
What made Herschel particularly suited for discovering planets? He had the
biggest telescope of that time, the longer the tube the more magnified the object
was. He could see deeper in the sky and produce larger images.
In what 2 ways did Uranus reveal itself to Herschel as a planet? Near circular
orbit around the sun which qualifies it as a planet. ~20AU from the sun (orbital
period of 84 years)
What is it about Uranus' orbit that caused it to be considered a planet
instead of a comet? Uranus was moving in an orbit nearly circular to the sun.
Comets have elongated eccentric orbits whereas Uranus had circular orbits. What
is the origin of Uranus' name? Greek God of the Sky, father of Saturn, grandfather
2. What did Kepler believe existed between the large space between Mars and
Jupiter? Explain why Bode's Law supported this idea. Kepler proposed that
the large gap between Mars and Jupiter contained an undiscovered planet. Bode’s
Law: the orbital radii of the 6 known planets follow a sequence of numbers.
Bode’s sequences were very close to the actual distances. The number at 2.8AU at
no corresponding planet, which falls within that gap which suggested that there
might be an undiscovered planet.
3. What is the name of the object found in 1801 between Mars and Jupiter? The
object was named “CERES.”
What was this object finally classified as, and why? This object was
downgraded from a planet to an asteroid when it was found to be smaller than
What is this object a part of? This object is a part of the circular belt that
contains hundreds of asteroids discovered between Mars and Jupiter.
4. What caused Adams and Leverrier to suspect the existence of a planet
When this planet was found, what was it named, and why? This planet was
found in 1846, named Neptune (Roman Sea God), due to its bluish color.
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?
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? The Solar System Formation theory –
tells us that all of the star planets come from the same spinning circumstellar disk which means they move in the same direction and since circumstellar disk is flat,
they all belong in the same plane. 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?
The asteroid belt is 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 the nearby giant Jupiter. The planetary rings are likely the leftover debris
from protoplanetary disks which couldn’t coalesce into a moon.
8. What 3 attributes are unique to the 4 planets beyond Mars? All 4 planets