Astronomers have made their own confirmations of the Big Bang theory. Analyzing the light coming from other galaxies, they have noted shorter and longer wavelengths proportional to the distances of the galaxies from Earth, indicating that they are moving away from the Earth and thus that space itself is expanding. The existence of cosmic microwave radiation, a remnant of hot ionized plasma of the early universe offers more proof of the Big Bang, as does the distribution of heavier and lighter elements through the universe. It took some 200 million years for gravity to begin coalescing these free-floating atoms into the primordial gas out of which the first stars and galaxies would emerge. Over billions of years, such early stars and galaxies phased through their lifecycle, using up their nuclear fuel and collapsing in on themselves, spewing out vast new clouds of matter and energy that would eventually form new generations of stars and galaxies. The sun around which the earth and the solar system rotate is one of these later generation stars, formed roughly five billion years ago.