COBE All-Sky Map 1992

The Cosmic Background Explorer (COBE) satellite was launched in 1989, twenty five
years after the discovery of the microwave background radiation in 1964. In 1992, the COBE
team announced that they had discovered “ripples at the edge of the universe”, that is, the first
sign of primordial fluctuations at 380,000 years after the Big Bang. These are the imprint of the
seeds of galaxy formation. These appear as temperature variations on the full sky map that
COBE obtained (shown above). Red areas represent areas with slightly higher temperatures
and blue areas a slightly lower temperature than the mean.