Class Notes (1,200,000)
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AST101H1 (500)
Lecture

September 20


Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
Michael Reid

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150 bill ly is relatively close in terms of the universe
stars: balls of plasma which produce energy by nuclear fusion (plasma = superheated
gas, superheated so electrons float around freely) produces a lot of energy in its core
planets: rocky (mercury, venus, earth, and mars- terrestrial), icy (uranus and neptune,
really cold in the center - ice giants), gassy (actually balls of liquid, Saturn and Jupiter -
jovians) (from our solar system) and don’t produce much energy
planet:
1. planets orbit stars directly (not other planets)
2. planets must be massive enough for their own gravity t compress them into spherical
shapes
3. !!!planets must have cleared their orbits, that is, there can’t be a lot of other stuff
orbiting the parent star in orbits very similar to the planet!!
in Pluto’s orbit, there’s a lot of comets
Pluto’s a dwarf planet, not based on size, but clarity of orbit.
Ceres, Makemake, Haumea, (5 dwarf planets)
moon: large body which orbits a planet
of the terrestrial planets, noly earth has a moon
Titan’s (a moon of saturn) bigger than mercury
nebula: a cloud of gas (bright and dust (dark). make new solar systems
the scientific method:
falsifiable, can’t be vague
start anywhere in theory- hypothesis - experiment or observation - theory - hypothesis
loop
model: astrological Sun signs determine peoples’ career choices - hypothesis: people in
a given career should have the same Sun sign - observation: canadian prime ministers
have random signs - new model: career choices are determined by socioeconomic class
Beauty/elegance in science. inspiration, people due trying to make things work, it needs
to be worthwhile. simple, elegant, beautiful things make more sense
nebula pictures much easier to interpret when they’re simple and beautiful
“beautiful”? to perceive it you have to speak the language
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