Blue shifted celestial bodies are quite rare. Of the billions of known galaxies, only about 100, including the Andromeda galaxy, are blue shifted.
Redshift and blueshift describe how light changes as objects in space (such as stars or galaxies) move closer or farther away from us. The concept is key to charting the universe's expansion.
Blueshift indicates that an object is moving toward the observer. The larger the blueshift, the faster the object is moving. Redshift indicates that an object is moving away from the observer. The larger the redshift, the faster the object is moving.
The terms redshift and blueshift also apply to any part of the electromagnetic spectrum, including radio waves, infrared, ultraviolet, X-rays and gamma rays. So, if radio waves are shifted into the ultraviolet part of the spectrum, they are said to be redshifted — shifted toward the lower frequencies.
Visit www.space.com to learn more about redshift and blueshift.