The first galaxies formed about 13.5 billion years ago, only a few hundred million years after the Big Bang. After the birth of the universe, matter consisted mainly of hydrogen and helium. Gravity gradually pulled enormous clouds of gas together, causing them to collapse and form the first stars. These stars eventually gathered into vast cosmic structures: the first galaxies.
The earliest galaxies were smaller, hotter, and far more unstable than modern galaxies. Within them, the first massive stars were born. These stars shone intensely but lived short lives. When they exploded as supernovae, they scattered heavier chemical elements throughout space, elements that would later become essential for the formation of planets and life.
Over billions of years, small protogalaxies collided and merged, creating larger galaxies such as our own Milky Way. Today, scientists study these ancient galaxies with powerful space telescopes like the James Webb Space Telescope in order to better understand the earliest stages of the universe’s evolution.
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