Which of the following statements about our modern ideas of how spiral galaxies form and develop is TRUE?
A) the central bulges of spiral galaxies formed first and their disks formed later
B) star formation in the spiral galaxies is much higher today than it was 8 billion years ago
C) spiral galaxies formed pretty quickly after the Big Bang and already looked then the way they look today
D) spiral galaxies have evolved until today they are all "red and dead", containing just old stars and showing almost no current star formation
E) spiral galaxies cannot have a central super-massive black hole, so astronomers don't understand just how they formed

Question

Quizplus · Accepted Answer

According to current understanding, the central bulges of spiral galaxies formed first through violent mergers of smaller galaxies, and their disks formed later through accretion of gas and dust. This process took billions of years and continues to shape and evolve spiral galaxies today. Option B is incorrect as the opposite is true - star formation was much higher in the early universe compared to today. Option C is incorrect as spiral galaxies took billions of years to form and have undergone significant changes since their formation. Option D is incorrect as many spiral galaxies still have ongoing star formation, and while some may become "red and dead" in the future, not all will. Option E is incorrect as supermassive black holes are commonly found at the centers of spiral galaxies, and their presence is considered necessary for the formation and evolution of such galaxies.

Which of the Following Statements About Our Modern Ideas of How