Lecture 14 4/8/2013 3:49:00 PM
Introduction to the Solar System:
The Doppler Effect:
When we observe lies from an astronomical source, for example, all
the spectral lines of hydrogen, we can compare them with a
reference spectrum from hydrogen gas in the lab.
If the source is moving toward us, the spectral lines will be shifted
to higher frequencies (blueshift) compared to the reference
If the source is moving away from us, the lines will be shifted to
lower frequencies (refshift)
What are the main objects in the solar system:
o The sun includes most of the matter in the solar system.
o Mostly hydrogen and helium
o Terrestrial planets: (Mercury, venus, earth, mars) are small,
rocky, and closer to the sun.
o Jovian planets (Jupiter, Saturn, Uranus, Neptune) are large,
gassy (contain a lot more hydrogen, helium, methane, etc.)
and farther from the sun.
o Jovian planets also have more moons than the terrestrial
o Jovian planets all have rings, but saturn’s are the most
o Order of planets by distance from the sun:
Mercury, venus, mars, Jupiter, satun, Uranus, Neptune.
My very excellent mother just serves us nachos.
Meteoroids, asteroids, comets and dwarf planets.
Other parts of the solar system: the asteroid belt:
Asteroid belt is a region at distances approximately 2-4 au from the
sun, between the orbits of mars and Jupiter. Total mass adds up to about 3x10^21 kg, or 4% of the moons
Includes between 7000,000-1,700,000 objects with diameters of
1km or more.
Rocky and metallic, like terrestrial planets, but some also contain
Actually extremely spread out, not crowded together as in a lot of
Largest asteroid: ceres.
Other parts of the solar system: the Kuiper Belt:
30-50 au from the sun.
small objects like asteroid belt, but 20-200 times as much mass.
Composed mostly of “ices”: frozen water, methane and ammonia.
Includes pluto and several other dwarf planets
Other parts of the solar system: the oort cloud:
2000-50,000 au from the sun (almost 1 ly)
small, icy objects like the Kuiper belt.
Many long-perid comets are believes to come from the oort cloud.
Much less known than other parts of the solar system
What about pluto?
Now a dwarf planet.
What is the difference?
Planets are large enough (and therefore their gravity is strong
o Be pulled to a nearly spherical shape b their own gravity.
o Clear most other objects out of their orbits.
o Large enough to have a spherical shape like planets, but not
enough to clear their orbits. Smaller objects (including most asteroids, comets, meteoroids)
have irregular shapes.
Notable features of the solar system:
Most of the slar syst