Long-lasting spiral density waves occur in the disk of a spiral galaxy when:
A) the spiral merges with another galaxy
B) the galaxy is too close
C) the galaxy's disk is regularly disturbed
D) none of the above

Question

Quizplus · Accepted Answer

Long-lasting spiral density waves occur in the disk of a spiral galaxy when the galaxy's disk is regularly disturbed, which can occur through interactions with other galaxies or through gravitational interactions within the galaxy itself. However, in order for the waves to persist for a long time, the disturbances need to occur regularly and not be a one-time event, ruling out options A and B.

Long-Lasting Spiral Density Waves Occur in the Disk of a Spiral