galactic nucleus


The center of a galaxy, usually small, very bright, and containing a high density of stars and other objects.♦ An active galactic nucleus is a nucleus that emits more radiation than can be explained in terms of stars alone. Blazars and quasars are thought to be active galactic nuclei; the nuclei of Seyfert galaxies are also active, and are thought to contain an extremely massive black hole.

QUIZZES

DON’T VACILLATE! VANQUISH THIS WORD OF THE DAY QUIZ!

It’d be a real faux pas to miss this quiz on the words from August 3–9, 2020!
Question 1 of 7
What does “vacillate” mean?
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.