If We Could Watch Spiral Arms from a Telescope Situated

question 93

Multiple Choice

If we could watch spiral arms from a telescope situated above the Milky Way over 500 million years, what would we see happen?

• A) Stars will move through the spiral arms, bunching up closer as they pass through. Young hot stars will form and die within the arms before having a chance to move out.
• B) The spiral arms will seem to "wind up", to wrap more and more tightly around the center of the Galaxy.
• C) The spiral arms will eventually dissipate and fade away, since they are a temporary phenomenon that should only last for a million years or so.
• D) The spiral arms will eventually unwind, as centripetal forces send the stars flying outwards into intergalactic space.