absorption nebula


A mass of interstellar gas and dust that absorbs most or all of the light from the stars behind it. Absorption nebulae appear as irregular dark patches and collectively cover about two percent of the sky. Some absorption nebulae, especially the Coalsack near the constellations Centaurus and Southern Cross, are visible to the naked eye. Also called dark cloud dark nebula See more at nebula.

QUIZZES

IS YOUR DESERT PLANT KNOWLEDGE SUCCULENT OR DRIED UP?

Cactus aficionados, don't get left in the dust with this quiz on desert plants. Find out if you have the knowledge to survive this prickly foray into the desert!
Question 1 of 7
This tall, horizontally branched cactus is probably the most recognizable cactus in Arizona. What is it called?
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.