First Light

Before galaxies could begin to form, the light gases from the Big Bang must have been through a certain amount of processing. Astronomers think this was done by a generation of giant stars—the "megasuns." Unlike today's stars, they

THE LoNG look back

The farther away we look, the farther back in time we are seeing. The most distant objects yet photographed are those captured in the Hubble Ultra-Deep Field—primitive galaxies less than a billion years after the Big Bang.

would have been pure hydrogen and helium. This would have allowed them to grow much larger, reaching several hundred times the mass of the Sun. As they ran out of fuel and detonated in enormous explosions, they scattered heavier elements throughout the universe and left black holes that might have been the starting points of galaxies.

THE STRucTuRE oF THE uNIvERSE

If all the matter in the universe started out evenly spread and then fell together under the influence of gravity alone, galaxies would not have formed for billions of years. The large-scale structure of filaments and voids throughout the universe would not have developed at all. There has simply not been enough time since the Big Bang for them to have been formed by gravity, so they must have been there from the very beginning.

FILAMENTS AND GALAxIES THRouGH TIME

Explaining the origin of the universe's large-scale structure of filaments and voids is a key challenge for any theory of creation. This computer simulation shows how the filaments and voids might have developed and formed individual clusters and galaxies.

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The universe at 500 million years old

Just half a billion years after the Big Bang, the large-scale structure of filaments and voids is in place. The seeds of galaxy clusters are forming in the regions where material is most dense.

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