Favorite Astronomy Resources

Astronomical Research

Institutions, Organizations, Observatories

Astronomy as a Hobby

Eight Lunar Phases

Lunar phases refer to the shapes of the illuminated portion of the Moon.  These shapes are caused by the positions of the Moon relative to the Sun as viewed by observers on Earth.

There are four main phases and four intermediate phases of the moon.  Each phase refers to the amount of illumination the Sun casts on the lunar surface.

The four main phases of our Moon are new moon, first quarter, full moon, and third quarter. 

In all phases. View assumed from the center of the earth. 
(Geometrically impossible, but best demonstration of 
monthly libration caused by moon’s motion By Tomruen 
[Public domain], via Wikimedia Commons

Learn more about the phases of the moon.
Learn about Sputnik.
Learn about the exoplanet Gliese 581.