“Origin of the Solar System”
(Ch. 19, p. 396-400, p. 407-423)
Goal of the Lecture:
To use the fundamental characteristics of the solar system as
support for the solar nebula hypothesis for the origin of the solar system.
is to discuss planetary evolution within the context of condensation from the solar
I: Origin of the Solar System
Solar Nebula Hypothesis
are clouds of gas and dust in space that mark the birthplace of stars ("star
- the dust
is composed of small amounts of various ices, oxides, carbon and some heavier
elements such as iron.
(size of the dust is about the size of smoke particles, just a few atoms
- the gas
is almost entirely
(which you know as the simplest element, consisting
of one proton and one electron).
- hydrogen makes up about 75% of all the mass in the universe.
Elemental abundance in cosmos
(Fig. P-14 in textbook, 7
ed., figure P-11 in 6
the dominance of hydrogen and helium on both the log plot and linear plot.
H and He
dominate the sun and the Jovian planets.
Note the common occurrence of C, N, O (the stuff of life) and the relative abundance of
Si, Al, Mg, Ca, Fe, S, Na, K that form rocky planets and moons.
- “the atoms of which we are made are just a tiny impurity in the cosmos”
- the elements we’ll talk about most in this class are the common ones that comprise a
large part of the solar system: H, He, O, Si, Fe, C, N
(if you don’t recognize the element
symbol, look them up in the index at the back of the book)
Nebula are “star factories” and the solar nebula from which our solar system formed was a
fragment of a larger interstellar gas cloud.
* The solar nebula hypothesis "proposes that the planets were formed from the disk of
gas and dust that surrounded the sun as it formed."
(i.e., planets form as a byproduct of
star formation from nebula.)