1.
a scientific theory concerning the early development and shape of the universe from a dense state, which began and is still expanding
2.
a region in space where gravity is so strong that even light cannot escape
3.
total amount of light (energy) emitted by a star or other celestial body
4.
the measure of the observed visible brightness of a star
5.
the galaxy which contains our Sun and its solar system, including Earth
6.
clouds of dust and gas; site of star formation; remains of dead or dying stars
7.
observations of galaxies moving away from each other and our own Milky Way galaxy
8.
luminous globe of gas which produces its own heat and light by nuclear reaction made of mostly hydrogen and helium gas
9.
water on the side of the Earth closest to the Moon is most strongly affected by the Moon’s gravitational pull
10.
force of attraction between all masses in the universe, especially the attraction of the Earth's mass for bodies near its surface
11.
occurs at the first and third (last) quarter Moon phases; the Sun is at a right angle to the Moon
12.
occurs at the full and new Moon phases; the Earth, Moon, and Sun are in alignment, pulling the water in the same direction
13.
the rising and falling of the oceans due to the gravitational attraction of the Moon and Sun; usually occurs twice each day
14.
force by which a planet or other body draws objects toward its center
15.
the distance from a star at which liquid water could exist on orbiting planets' surfaces
16.
in a region of space located past Neptune
17.
a small piece of matter from outer space that becomes a streak of light when it falls through Earth’s atmosphere and burns up
18.
most distant region of our solar system
19.
one complete trip of a planet around the Sun
