AY 110 02 - FALL 07 - Holtzman

Review list for second midterm

• Understand Newton's laws of motion and the law of gravity; understand how the law of gravity can be used to calculate the relative strength of gravity at different places, for example, your weight on different planets.

• Understand how Newton's laws can be used to understand orbits, and that Kepler's laws are a natural consequence of Newton's more basic laws about how things move. Understand Kepler's laws.

• Understand orbits: why objects can go around each other when the force of gravity is an attractive force between the two objects. Understand how our model for the formation of the Solar System leads to expectation that planets will have initial transverse velocities and thus will orbit the Sun rather than fall into it.

• Understand how masses of astronomical objects are inferred using our understanding of gravity and measurements of motions of objects. In particular, understand how we measure masses of planets and stars. Know ROUGHLY how massive these objects are: e.g., how massive are different planets compared to the Earth, and how massive are different stars compared to the Sun. Understand how we measure masses of galaxies, and know why we believe that there is a large amount of dark matter in the Universe.

• Understand the concept of gravitational lensing and qualitatively how it can be used to infer masses of objects. Know what a black hole is.

• Light. Know about the general properties of light, and the different forms that light can take (the electromagnetic spectrum), and how different kinds of light are characterized by different wavelengths or different energies. Know about the different kinds of spectra (continuous, emission line, absorption line) that objects can produce. Understand the types of spectra that different astronomical objects produce (e.g., stars produce absorption line spectra, etc.)

• Understand thermal (blackbody) radiation (continuous radiation from warm dense sources) and how it can be used to infer temperatures of objects.

• Understand the effect of dust in the interstellar matter (and in the Earth's atmosphere) on the colors of starlight. Know why the sky is blue and why the sun can appear to change color between midday and sunset.

• Understand basic atomic structure and how the different elements differ at the atomic level. Understand that atoms move and that the speed of their motion is related to the temperature. Know that normal matter in the Universe is primarily composed of hydrogen, with some helium, and very little of everything else.

• Understand how emission and absorption lines are produced, and how they are related to orbits of electrons in atoms. Understand how we can observationally determine physical properties by studying emission and absorption lines. In particular, know how we can estimate temperatures and compositions of stars.

• Understand how the total brightness of stars depends on the temperature, size, and distance of the star. Understand how we can use our previous estimates of temperatures (from colors and/or spectra) and distances (from parallax) to determine sizes of stars; know about dwarf stars and giant stars.

• Understand what a HR (color-magnitude) diagram is, and where stars fall in this diagram. Understand the terminology: main sequence, red giant, white dwarf.