Astronomy Exam 3 Study Guide: Chapters 16-20
Exam 3 Study Guide: Chapters 16-18
Astronomy Basics
What is Astronomy?
Astronomy is the study of the universe, encompassing matter, energy, space, and time.
Geocentric vs. Heliocentric Models
The geocentric model placed Earth at the center of the solar system, while the heliocentric model correctly positioned the Sun at the center.
Contributions of Key Astronomers
- Copernicus: Proposed the heliocentric model.
- Brahe: Made accurate measurements of stars and planets.
- Kepler: Developed laws of planetary motion and elliptical orbits.
- Galileo: Observed celestial bodies with a telescope and discovered Jupiter’s moons.
- Newton: Explained gravitational forces and planetary motion, solidifying the heliocentric model.
Solar System Formation and Planets
Formation of Solar Systems
Solar systems are believed to form from a nebula, a cloud of gas and dust, that collapses under gravity, leading to the formation of stars and planets.
Classifications of Planets
- Terrestrial Planets (Inner): Mercury, Venus, Earth, Mars. They are small, rocky, dense, and have solid surfaces.
- Jovian Planets (Outer): Jupiter, Saturn, Uranus, Neptune. They are large, have strong magnetic fields, many moons and rings, and are composed mainly of gas.
- Dwarf Planets: Ceres, Pluto, Haumea, Makemake, Eris.
Requirements for Planet Classification
A planet must orbit the Sun, have sufficient mass for a nearly spherical shape, and be the dominant body in its orbit, clearing its neighborhood.
Other Celestial Objects
Solar vs. Lunar Eclipse
A solar eclipse occurs when the Moon passes between the Sun and Earth, blocking sunlight. A lunar eclipse happens when Earth is between the Sun and Moon, casting a shadow on the Moon.
Formation of Earth’s Moon
The leading theory suggests a Mars-sized object collided with Earth, ejecting debris that coalesced to form the Moon.
Moons of Jupiter and Saturn
Jupiter and Saturn have numerous moons with diverse characteristics, including volcanic activity (Io), subsurface oceans (Europa), and thick atmospheres (Titan).
Meteoroids, Meteors, and Meteorites
- Meteoroid: An object in space.
- Meteor: A meteoroid entering Earth’s atmosphere, creating a shooting star.
- Meteorite: A meteor that survives the atmosphere and impacts Earth’s surface.
Comets
Comets are small bodies of dust and ice. As they approach the Sun, they develop a head and tail due to vaporization.
Stars and Energy Production
Stellar Energy Generation
Stars produce energy through nuclear fusion, where light atoms combine to form heavier atoms, releasing energy.
Chapters 19 & 20: Earth’s Atmosphere
Composition of Earth’s Atmosphere
The main components are:
- Nitrogen (78%)
- Oxygen (21%)
- Argon (0.9%)
- Water vapor (variable)
- Carbon dioxide (0.039%)
Layers of Earth’s Atmosphere
- Troposphere: Lowest layer, contains weather phenomena.
- Stratosphere: Contains the ozone layer.
- Mesosphere: Coldest layer.
- Thermosphere: Hottest layer.
Importance of the Ozone Layer
The ozone layer absorbs harmful ultraviolet (UV) radiation from the Sun, protecting life on Earth.
Sunlight Distribution on Earth
The equator receives the most direct sunlight, while the poles receive the least.