Astro 1010 Final Exam Study Guide - Chapters 12 & 13

Astro 1010 Final Exam Study Guide

The final exam is comprehensive, with 100 multiple-choice questions. Questions are evenly distributed across chapters 1-13 and chapter S1. Chapters 12 and 13 are detailed here, with older topics covered in study guides for exams 1-3. An equation sheet is available on iCollege.

Chapter 12: Asteroids, Comets, and Dwarf Planets

Asteroid Belt

• Located between Mars and Jupiter.
• Asteroids are primarily composed of metals and carbon-rich rock.
• The inner and outer edges are determined by orbital resonances with Jupiter.
  • Gaps exist within the asteroid belt due to orbital resonances.
  • Jupiter's gravity prevented the formation of a large object in this region.
• The asteroid belt is less crowded than perceived.
  • Objects are widely spaced, making collisions rare.
  • The total mass is less than the mass of Earth's moon.
• Ceres
  • The only dwarf planet within the asteroid belt.
  • Contains approximately 1/3 of the main belt's mass.
  • Spherical shape due to its mass, unlike other irregular asteroids.
  • Initially considered a planet, later reclassified.
• Ida: The first asteroid found to have its own moon.
• Trojan asteroids: Located in Jupiter's L4 and L5 Lagrangian points, outside the main belt.

Kuiper Belt

• Beyond Neptune's orbit but closer than the Oort cloud.
• Kuiper Belt Objects (KBOs) are mainly icy, similar in composition to comets.
• Short-period comets (T < 200 years) originate from here.
• Inner and outer edges shaped by orbital resonances with Neptune.
• Neptune's gravity hindered the formation of a single large object here.
• At least four dwarf planets reside here: Pluto, Eris, Makemake, and Haumea.
• Pluto
  • Has five moons, including Charon, which is half Pluto's size.
  • First detected object in the main belt; initially considered a planet before the remaining objects in the belt were discovered, then “demoted”.
  • Its orbit crosses Neptune's but avoids collision due to a 2:3 orbital resonance.
  • Orbit is inclined at about 17 degrees from the main plane of the planets.
• Eris: Slightly more massive than Pluto; its discovery led to the creation of the "dwarf planet" classification.

Oort Cloud

• Spherical distribution of icy objects at the solar system's edge.
• Origin of long-period comets (T > 200 years).
• Objects were scattered into highly elliptical orbits by gas giants early in the solar system's history.

Comets

• Two primary populations:
  • Long-period comets (T > 200 years): Highly inclined orbits, originating from the Oort cloud.
  • Short-period comets (T < 200 years): Orbits lie in the main plane of the solar system, originating from the Kuiper Belt.
  • Only a small fraction of comets enter the inner solar system and the majority reside in the Kuiper Belt or Oort Cloud.
• Comets are frozen ice lumps when distant from the sun.
  • They develop comas (gaseous atmospheres) and tails as surface ice sublimates near the sun.
  • Comas form at a minimum distance of 3-5 AU from the sun.
  • Tails form at approximately 1 AU.
• Comets possess two tails:
  • A plasma tail pointing directly away from the sun.
  • A dust tail curving away from the sun.
• Satellite Exploration of Comets:
  • Deep Impact: Launched a rocket at a comet, analyzing debris' spectral features.
  • Stardust: Flew through a comet's coma, collecting samples for Earth return.
  • Rosetta: Deployed a lander on a comet's surface, with limited success.
• Meteor showers occur when Earth intersects a comet's orbit.

Chapter 13: Other Planetary Systems

Methods for Detecting Exoplanets

• Direct imaging: Limited to planets with wide orbits around nearby stars.
• Astrometry: Detects a star's slight movement caused by a planet's gravitational pull.
• Doppler shifts: Measures the blueshift/redshift of a star's spectra due to a planet's pull.
• Transits: Observes dips in a star's luminosity as a planet passes in front of it.
• The first extrasolar planet was found orbiting a pulsar by observing timing offsets in its pulsations caused by the planet's gravity.

Kepler Space Telescope

• Discovered thousands of exoplanets using the transit method.
  • Planets are common; rocky, Earth-sized planets are more prevalent than gas giants.
  • On average, each star hosts at least one planet.
  • Planets exist in multi-star systems and around single stars.

Habitable Zones

• The distance range around a star where a planet with an atmosphere can sustain liquid water on its surface.
  • Located far from hot, high-mass stars and close to cooler, low-mass stars.
  • Around 1/5 of sun-sized stars have an Earth-sized planet within their habitable zone.
  • High-mass stars may be less conducive to life due to their short lifespans.
  • Low-mass stars may be less hospitable, as planets in their habitable zones become tidally locked.

Other Objects

• Brown dwarf: An intermediate object between a gas giant and a star, lacking sufficient mass for nuclear fusion.
• Rogue planets: Objects ejected from their star systems, orbiting the galactic center independently.