Question

scientists have determined that the universe formed about 13.7 billion years ago. the figure shows a timeline interpretation of the sequence of events. if we look back in time to approximately 500 million years after the big bang event, which of the following statements is correct?
a. stars had formed but no galaxies had formed
b. galaxies had formed but no solar systems had formed
c. solar systems had formed but no planets had formed

Explanation:

To solve this, we recall the timeline of cosmic evolution. After the Big Bang, stars formed first, then galaxies, then solar systems (with planets). 500 million years after the Big Bang, stars would have formed, but galaxies (which are collections of stars) would not have fully formed yet. Option A aligns with this sequence: stars form before galaxies, and solar systems (with planets) form later. Options B and C are incorrect because galaxies form after stars, and solar systems (with planets) form after galaxies.

Answer:

A. Stars had formed but no galaxies had formed