Astro 1010 Final Exam Study Guide - Chapters 12 & 13

Astro 1010: Final Exam Study Guide

General Information

  • The final exam is comprehensive, covering chapters 1-13 and S1, consisting of 100 multiple-choice questions.
  • Questions are evenly distributed across the covered chapters.
  • This study guide focuses on chapters 12 and 13 (since exam 3).
  • Refer to previous study guides for material from exams 1-3.
  • An equation sheet for the final exam is available on iCollege.

Chapter 12: Asteroids, Comets, and Dwarf Planets

The Asteroid Belt
  • Located between the orbits of Mars and Jupiter.
  • Asteroids are mainly composed of metals and/or carbon-rich rock.
  • The inner and outer edges are determined by orbital resonances with Jupiter.
    • Gaps within the belt are also caused by orbital resonances with Jupiter.
  • Jupiter's gravity prevented the formation of a large, single object in the asteroid belt.
  • The asteroid belt is less crowded than commonly believed.
    • Objects are widely spaced, making collisions rare.
    • The total mass of the main belt is only a fraction of Earth's moon's mass.
Ceres
  • The only dwarf planet within the asteroid belt.
  • Contains 1/3 of the main belt's total mass.
  • It's the only object massive enough to have a spherical shape; other asteroids are irregular.
  • First detected object in the main belt, was initially considered a planet before the remaining objects were discovered and then "demoted" to a dwarf planet.
Ida
  • The first asteroid discovered to have its own moon.
Trojan Asteroids
  • A large population of asteroids outside the main belt, located in Jupiter's L4 and L5 Lagrangian points.
The Kuiper Belt
  • Located beyond Neptune's orbit, but closer to the Sun than the Oort cloud.
  • Kuiper Belt Objects (KBOs) are mostly icy, similar in composition to comets.
  • Short-period comets (T < 200 years) originate from the Kuiper Belt.
  • Inner and outer edges are set by orbital resonances with Neptune.
  • Neptune's gravity prevented a large, single object from forming here as well.
Kuiper Belt Dwarf Planets
  • At least four dwarf planets are located in the Kuiper Belt: Pluto, Eris, Makemake, and Haumea, with several more candidates.
Pluto
  • Has five moons; Charon is half the size of Pluto.
  • Orbit crosses Neptune's, but they will never collide due to a 2:3 orbital resonance.
  • Its orbit is inclined at about 17 degrees from the main plane of the planets.
  • Initially considered a planet before the remaining objects in the belt were discovered, then “demoted”.
Eris
  • Slightly more massive than Pluto; its discovery led to the creation of the "dwarf planet" classification.
The Oort Cloud
  • A spherical distribution of icy objects at the solar system's extreme edge.
  • The origin of long-period comets (T > 200 years).
  • Objects formed in the main disk but were scattered into highly elliptical, randomly oriented orbits by the gas giants early in the solar system's history.
Comets
  • Two main populations:
    • Long-period comets (T > 200 years) have highly inclined orbits and originate in the Oort Cloud.
    • Short-period comets (T < 200 years) have orbits in the main plane and originate in the Kuiper Belt.
  • Only a small fraction of comets enter the inner solar system. The majority reside in the Kuiper Belt or Oort Cloud.
  • Comets are frozen lumps of ice far from the Sun. They develop comas (gaseous atmospheres) and tails when surface ice sublimates near the Sun.
    • Comas form at a minimum distance of 3-5 AU from the Sun.
    • Tails form at a minimum distance of about 1 AU.
  • Comets have two tails:
    • A plasma tail that points directly away from the Sun.
    • A dust tail that curves away from the Sun.
Comet Exploration
  • Deep Impact: Fired a rocket at a comet and analyzed the spectral features of the debris.
  • Stardust: Flew through a comet's coma and returned samples to Earth.
  • Rosetta: Placed a lander on a comet's surface, with partial success.
  • Meteor showers occur when Earth passes through the orbit of a comet.

Chapter 13: Other Planetary Systems

Planet Detection Methods
  • Four main methods:
    • Direct imaging (limited to planets in wide orbits around nearby stars).
    • Astrometry (observing a star's slight motion due to a planet's gravitational pull).
    • Doppler shifts (detecting blueshifts/redshifts in a star's spectra caused by a planet's pull).
    • Transits (observing dips in a star's luminosity as a planet passes in front of it).
First Extrasolar Planet
  • The first extrasolar planet was found orbiting a pulsar, detected by timing the pulsations and noting offsets caused by the planet's gravity.
Kepler Space Telescope
  • Has discovered thousands of extrasolar planets using the transit method.
  • Planets are common; rocky, Earth-sized planets are more common than gas giants.
  • On average, every star has at least one planet.
  • Planets have been found in multi-star systems and orbiting single stars.
Habitable Zones
  • The range of distances around a star where a planet with an atmosphere can support liquid water on its surface.
  • Farther from hot, high-mass stars and closer to cooler, low-mass stars.
  • Roughly 1/5 of sun-sized stars have an Earth-sized planet in their habitable zone.
  • High-mass stars may be less hospitable to life, as they have shorter lifespans
  • Low-mass stars may be less hospitable because planets in their habitable zones may be tidally locked.
Brown Dwarfs
  • An intermediate class of objects more massive than gas giants but with insufficient mass to be stars.
Rogue Planets
  • Objects that formed around a star but were ejected and now orbit the galactic center independently.