AST101 Sept 18 .
Stars are balls of plasma (a charged gas), which produce energy by nuclear fusion.
Stars are producing a lot of excess energy via nuclear reactions. Planets are not
producing a lot of extra energy.
Planets are rocky, icy, or gassy, and they do not produce much energy. All planets
are smallish spherical bodies.
Terrestrial earth like planet (mars), Prototypical gas giant planets (Saturn), Ice giant
Definition of Planet: 1: Planets orbit stars directly (not other planets) 2: Planets
must be massive enough for their own gravity to compress them into spherical
shapes. 3: Planets must have cleared their orbits. That is, there cannot be a lot of
other stuff orbiting the parent star in orbits very similar to the planet.
Pluto is not a planet because its orbit is full of other object (mainly comets). Pluto
is a dwarf planet.
There are five established dwarf planets: Pluto, Ceres, Makemake, Haumea, and Eris.
Moon is any large body, which orbits a planet. Moon’s are not be definition smaller
than planets technically.
A Nebula is a cloud of gas (bright) and dust (dark). They form solar systems.
What is Science? Science tests falsifiable hypotheses using the scientific method.
The scientific method
3 Experiment or Observation 2 Falsifiable Hypothesis EXAMPLE
1 Model: Astrological Sun signs determine peoples’ career choices
2 Hypothesis: People in the same