### planet:

Bigger planet
* have larger gravities and can hold on to more atmosphere
  - more heat, and it takes longer for bigger planets to cool down
* require higher velocities for an object to escape their gravitational pull.

Different planet
* have different pole stars because their axes are oriented differently.
* require epicycles of different sizes.

### planet:

Extrasolar planet
* Learn about planets that orbit stars.
* Many extrasolar planets appear to have highly eccentric elliptical orbits
  - are known to move in highly elliptical orbits
  - have masses far greater than Jupiter
* are planets outside our own solar system.
* can have many different forms compared to our solar system.
* emerge from the dark.
+ Extrasolar planet, Types
+ Kepler-22b, Orbit: Exoplanets
  * No information is available about the shape of the planet's orbit. Many extrasolar planets are known to move in highly elliptical orbits. We only know that the semi-major axis of its orbit is within its host star's habitable zone. If Kepler-22b has a highly elongated orbit it may well only spend a small fraction of its time within this habitable zone, which would cause extreme temperature differences on the planet and make it inhospitable.

Gas giant
* are also very much larger than terrestrial planets
  - astronomical objects
* do form farther out.

Giant planet
* are huge reservoirs of hydrogen, a major constituent of comets.
* can significantly influence terrestrial planet formation.
* carry the lion's share of angular momentum in a stellar system.

Inferior planet
* can never be at opposition to the sun, from Earth's point of view
  - pass in front of the sun
* have orbits that are closer to the Sun than is Earth's orbit.
* is also different from minor planet or dwarf planet.
* take more time to go around the Sun than superior planets.

Inner planet
* are small and rocky, while the outer planets are large and gaseous.
* symbolize important aspects of personality.

Jovian planet
* All Jovian planets have rings around their equators and at least eight moons.
* are far from the Sun
  - further from the sun than terrestrial planets
  - large planets
  - much larger than terrestrial planets
  - very large and massive, and are primarily made of gases
* have high masses
  - long days
  - stronger magnetic fields

Larger planet
* are farther from the sun.
* have stronger gravity, so can hold on to their atmosphere better so more erosion.
* tend to have more satellites, both large and small, than smaller planets.

Massive planet
* More massive planets cool more slowly than less massive planets
  - have more gravity, so they cause more wobble
* can cause slight tidal distortions to their host stars.

Superior planet
* All superior planets travel slower in their orbits than does Earth.
* are at quadrature twice in their orbits
  - brighter at opposition, when moving retrograde
* can have only superior conjunctions with the sun.
* have orbits that are farther from the Sun than Earth's orbit.

Terrestrial planet
* All terrestrial planets are different when it comes to their interaction with the solar wind
  - thought to have had a similar process in their early histories
  - show evidence of volcanism, though manifestation is different
* are built from heavier elements such as silicon, iron and magnesium
  - rough-surfaced, and most planets are at least slightly oblate
  - smaller than Jovian planets
* have iron cores and rocky surfaces.
* lose whatever hydrogen and helium they have.

Uranian planet
* are a special sort of gas giants , they have more hydrogen and helium.
+ Planet, In the Solar System, Types of planets
  * Jupiter, Saturn, Uranus, Neptune. Uranian planets are a special sort of gas giants, they have more hydrogen and helium.