Space
The study of what is beyond Earth is called this.
Astronomy
These planets make up the "Outer" planets
Jupiter, Saturn, Neptune, and Uranus
This determines what a star eventually becomes.
Its mass
In order to keep the same face toward Earth, the moon must rotate this many times every orbit.
Once
The Milky Way is an example of this type of galaxy.
Spiral
Because of how vast space is, astronomers use these two units of measurement to measure distances in space.
Astronomical Units (A.U.) and light years
Besides the sun, this planet is the brightest object in our sky.
Intermediate stars have a lifespan of about this long.
10 billion years
This moon formation hypothesis is the most widely accepted among astronomers.
Giant Impact Hypothesis
A lump of rock that is pulled down by Earth’s gravity.
Meteorite
An A.U. is approximately this many kilometers.
About 150 million km
The Sun's mass is primarily composed of these two elements.
Hydrogen (75%) and Helium (25%)
A high mass star will end up as a black hole or this when it collapses upon itself.
Neutron Star
This term describes how tides are caused by gravity pulling on the bodies of water on the Earth.
Tidal Bulges
Most of these are found in an area known as the Oort Cloud, far beyond the orbit of Pluto.
Comets
A light year travels about this many kilometers per second.
The sun makes up this percentage of the total mass of our solar system.
99.8%
All stars begin their lives as this.
A nebula
This phase of the moon occurs twice per orbit, are differentiated by terms "waxing" and "waning," and occur just before and after a full moon.
Gibbous
Scientists use this equation to calculate the odds of intelligent alien life.
The Drake Equation
This galaxy is the closest galaxy to the Milky Way
Andromeda
This is found at both of Mars' poles.
Solidified carbon dioxide
An H-R diagram arrange stars based on these two things.
Luminosity and temperature
This allows the moon to be visible to us on Earth.
Sunlight
There are between this many and this many stars in the Milky Way Galaxy.
100 - 300 billion stars