ASTR 10, Vista College, Spring 2004

Instructor: Dr. Korpela


What Was Important - Material for Exam #2

Feb 26

These notes may seem long, but I've tried to summarize the ideas, instead of just saying "know this", especially where the information is a little scattered in the text.

Solar System Formation

  • Moon Origin:
  • Atmospheres:

    March 11-The cycles that shape planets

    This class focussed on the processes that shape the the surfaces and atmospheres of the terrestrial planets. We discussed how certain cases apply specifically to certain planets.

    Giant Impacts

  • Meteors and Meteorites:
  • Asteroids:
  • Comets:
  • Rings: Recent Debris
  • Impacts

    Geologic and Atmospheric processes that shape the planets.

  • Feedback: Understand the difference between positive and negative feedback, and how one leads to a stable situation and how one leads to an out of control situation.
  • Convection:

    Mar 18 -

    Life in the Universe.

    Properties of life on Earth


    Evolution is the process by which life changes over time. It is due to imperfections in the replication process.

    The history of life on earth

    Life elsewhere in the solar system

    Life in other solar systems

  • Drake's Equation: A way to estimate the number of communicative civilizations we expect. Lists all the factors involved so we can evaluate which are the most important.
  • The factors are: (1) number of stars in the galaxy (2) probability of planets in stable orbits (3) number of planets with orbits in the "life zone" (4) probability that life will originate if the conditions are suitable (5) probability life will evolve to be intelligent (6) fraction of star's lifetime during which the life form is communicative
  • The fraction of a star's lifetime during which a life form (if it exists) is communicative is the most uncertain!. Technological survival between 100 years and 1 million years gives a different answer by a factor of 10,000!
  • Optimistic estimates give 750,000 communicative civilizations in our galaxy, while pessimistic estimates give only 2 communicative civilizations PER 4 million galaxies!

    Mar 25-The properties of stars

    April 1- Stellar Structure

  • Hydrostatic (aka Gravitational) Equilibrium is the balance between pressure and gravity, and is extremely important to understand. It is what keeps a star the size that it is.
  • A star is shining because it is hot, and so is losing energy. To remain stable in size, it must have an internal energy source. This source is FUSION.
  • Know the conditions required for fusion (very high temperature and pressure), and why it results in energy.
  • Also know that the rate of fusion depends upon temperature and pressure and why this is so.
  • Know that fusion turns 4 H atoms into 1 He atom, and releases neutrinos, positrons, and gamma ray photons. Don't stress over the details of the fusion reaction chains (understand that a CHAIN is required).
  • Understand the results of the solar neutrino experiment, and what it tells us about our models of the Sun, and about particle physics. Note that studying the way the sun vibrates (helioseismology) also provides supporting evidence for our model of the Sun.
  • The "Pressure-Temperature Thermostat" regulates the rate of fusion burning. This is another example of "negative feedback".
  • Know and understand the ingredients that go into the calculation of a stellar model - there are only four! Mass, Energy Generation, Hydrostatic Equilbrium and Energy Transport
  • Understand how gravitational equilibrium explains the Mass-Luminosity relation of main sequence stars and why there is a lower limit to the mass of main sequence stars.