Astrophysics: Introduction to the Universe

Planets Mnemonics:
My  : Mercury
Very  : Venus
Educated  : Earth
Mother  : Mars
Just  : Jupiter
Served : Saturn
Us  : Uranus
Nothing :Neptune

Relative Planet Sizes

hyperphysics.phy-astr.gsu.edu

Asteroids: A small rocky body that drifts around the Solar system

Meteorite: An asteroid on a collision course with the planet is known as a meteoroid. Small meteors can be vaporized due to friction with the atmosphere. The bits that arrive are called meteorites.

Comet: are mixtures of rock and ice

Stellar Constellation: Are a group of stars that are physically close to each other, created by the collapse of the same gas cloud

Constellation: These are patterns of stars that have been identified.

Light Star: The distance light travels in one year.

Comparing Distances:
Distance of the visible universe: 10^26m

Distance between local galaxies: 10^22 m

Distance of our galaxy: 10^21m

Distance of our solar system: 10^13 m 

Movement of constellations:

Over one night: They appear to be rotating in the sky around a fixed point (the pole star) due to the rotation of the earth

This shows the movement of Orion over one night.

Over a year: The pivot of rotation (i.e.) the pole star appears to have changed position in the sky which is due to the revolution of earth. This means that the constellations appear at different places in the sky depending on the time of the year.