❓ why
Why do elliptical galaxies usually have fewer new stars than spiral galaxies?
Quick Answer
Elliptical galaxies have little cold gas left, and without that gas there is little material to make new stars. Many of them are dominated by old stars that formed long ago.
The Full Story
Unlike spiral galaxies, ellipticals are mostly smooth and rounded, with very little cool gas and dust. Star formation needs cold molecular gas, so when that supply is used up, heated, or removed, new stars stop forming efficiently. Many ellipticals likely grew through mergers that disrupted disks and exhausted or expelled gas. As a result, their light is dominated by older, redder stars.
Key Facts
1.Star formation requires cold molecular gas
2.Many elliptical galaxies contain mostly old stars
3.Galaxy mergers can reduce or disrupt star-forming disks
YouTube Angle
Suggested video title for this topic:
"Why do some galaxies go quiet and stop making stars?"
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