Astronomy 161 -- Winter 2008 (Prof. Stanek)
Midterm 2 Study Guide (Friday, February 8)
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Classes to review:

Newton's Laws
Applying Newton's Laws
Light
Spectra
Telescopes
Solar System Survey
Origin of the Solar System

Key Concepts:

Newton's Laws:
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Three Laws of Motion:

(1) An object remains at rest, or moves in a straight line at constant
    speed, unless acted on by an outside force.
(2) The acceleration of an object is directly proportional to force,
    and inversely proportional to mass.
(3) For every action, there is an equal and opposite reaction.

Law of Gravity:

(4) The gravitational force between masses M and m, separated by
    distance r, is

    F=G(Mm/r^2)

Applying Newton's Laws:
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(1) Newton modified and expanded Kepler's Laws of Planetary Motion.
(2) Kepler described how planets move; Newton explained why they move.
(3) Tides are caused by the difference between the Moon's
    gravitational force on different sides of the Earth.
(4) Tidal forces are slowing the Earth's rotation & enlarging the
    Moon's orbit.

Light:
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(1) Visible light is just one form of electromagnetic radiation.
(2) Light can be though of as a wave or as a particle.
(3) Light forms a spectrum from short to long wavelengths.
(4) A hot, opaque object produces a continuous blackbody spectrum.

Spectra:
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(1) A hot, transparent gas produces an emission spectrum.
(2) A cool, transparent gas produces an absorption spectrum.
(3) Every type of atom, ion, and molecule has a unique spectrum.
(4) The most abundant elements in the universe are hydrogen and helium.
(5) The radial velocity of an object is found from its Doppler shift.

Telescopes:
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(1) Telescopes use either a lens or a mirror to gather light.
(2) The main purposes of a telescope are to gather light and resolve
    detail.
(3) Radio and microwave telescopes use a reflecting dish to focus waves.
(4) Telescopes in orbit avoid the distorting effects of the atmosphere.
(5) Ultraviolet, X-ray, gamma ray, and most infrared light is visible
    only from orbit.

Solar System Survey:
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(1) The terrestrial planets are made primarily of rock and metal.
(2) The Jovian planets are made primarily of hydrogen and helium.
(3) Moons (a.k.a. satellites) orbit the planets; some moons are large.
(4) Asteroids, meteoroids, comets, and Kuiper Belt objects orbit the Sun.
(5) Collision between objects in the Solar System cause impact craters.

Origin of the Solar System:
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(1) A cloud of gas & dust contracted to form a disk-shaped solar nebula.
(2) The solar nebula condensed to form small planetesimals.
(3) The planetesimals collided to form larger planets.
(4) Radioactive age-dating indicates the Solar System if 4.56 billion
    years old.