Astronomy Chapter 1

consists of the sun and all the objects that orbit it: the planets and their moons, and counless smaller objects including rockey asteriods and icy comets

large disk shaped collection of stars (Galaxy: great island of stars in space containing a few huungred million more stars)

milky way is one of the two largest among the 40 galazies- thus local

local group of galaxies, superclusters

the average distances between galazies are increaing with time

galazie was tightly compressed and reached a point of epansion thus the beginning

A star is born when gracity compresses the material in a cloud ot the point where the center becomes dense and hot enough to generate energy

a large, glowing ball of gas that generates heat and light thourhg nuclear fusion in its core. Sun is a star

large object that orbits a star and shines primarily by reflecting light from the star

an object that orbits a planet. satellite is used to refer to any object orbiting another object

a relativly small and rocky object that orbits a star

a small icy object that orbits a star

A star and any planets and other materials that orbit it. Roughly half of all star systems contain two or more stars.

the portion of the entire univers that can be seen from Earth, at least in prinicple. The observable universe is probably only a tiny portion of the entire universe.

the average distance between Earth and the Sun, which is about 150 million kilmeters. 1AU is the length of the semimajor axis of the Earth's Orbit.

The distance that light can travel in 1 year, which is about 9.46 trillion kilometers.

The spinning of an jobect around its axis.

The orbital motion of one object around another.

Earth's orbital path defines a flat plan