Chapter 12- Dwarf Planets and Small Solar System Bodies

Question 1

Ceres

Answer 1

Many astronomers begin to search for other planets after Herschel’s discovery of Uranus in 1781. Downgraded to the first asteroid to its size compared to other bodies discovered nearby. Recently became a dwarf planet

Question 2

Pluto

Answer 2

Irregularities discovered in the orbit of Uranus led to the discovery of Neptune. Some believed they saw discrepancies in Neptune which led to the discovery of Pluto. Originally considered a planet; demoted to dwarf planet.

Satellite Charon is large enough and close enough to Pluto that they are locked into synchronous orbits facing each other.

Thin atmosphere of nitrogen. Frozen methane on surface.

Question 3

What Defines a Planet?

Answer 3

1. A planet has enough gravity to pull itself into a (more-or-less) spherical shape.
2. A planet orbits the Sun (at least in this solar system), but it does not orbit another planet.
3. A planet has enough gravitational influence that it has cleared the debris out of its orbit.Dwarf planets accomplish 1) and 2) but not 3).

Question 4

Kuiper Belt

Answer 4

A disk shaped region out beyond the planetary orbits. Inner part begins at the orbit of Neptune (about 30 AU) and extends to about 50 AU.

This outer edge is rather sharply defined because that radius forms a 2:1 orbital resonance with Neptune. For every two orbits of Neptune, the planet is closest to the same region at radius 50 AU. Any particles there will thus feel repeated tugs from Neptune and that radius has been swept clean.

Question 5

Oort Cloud

Answer 5

Spherical region extending perhaps beyond 50,000 AU from the Sun.

Question 6

Asteroids

Answer 6

There are thousands of asteroids, mostly between the orbits of Jupiter and Mars. All are smaller than the major satellites. Most are just chunks of rocks a few tens of km across.

These (and many of the TNO’s) are the remaining planetesimals and the fragments of collisions in the early solar system. Some cross the orbit of Mars, and many of these cross Earth’s orbit as well.

The Trojan asteroids (named after the heroes of the Trojan War) are trapped at Jupiter’s stable Lagrangian points.

Question 7

Lagrangian points

Answer 7

Any two-body system like Sun-Jupiter or Earth-Moon has five Lagrangian points. L1, L2, and L3 L4 and L5, located in the orbit of the orbiting body, are stable. Many asteroid’s are trapped in Jupiter’s stable Lagrangian points.