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Artist's timeline chronicling the history of the universe.
This artist's timeline chronicles the history of the universe, from its explosive beginning to its mature, present-day state.
Astronomers do not know if the very first objects were either stars or quasars. The first stars, called Population III stars (our star is a Population I star), were much bigger and brighter than any in our nearby universe, with masses about 1,000 times that of our sun. These stars first grouped together into mini-galaxies. By about a few billion years after the Big Bang, the mini-galaxies had merged to form mature galaxies, including spiral galaxies like our own Milky Way. The first quasars ultimately became the centers of powerful galaxies that are more common in the distant universe.
Credit: NASA/JPL-Caltech
Special Restrictions: Caption shortened from NASA original.
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