The ages of the Universe, the Milky Way, and Earth is the time elapsed since the Big Bang. The Milky Way is estimated to have formed 800 million years after the Big Band, some 13 billion years ago (bya), The Milky way is some 105,700 light years wide, is spiral shaped, and is estimated to contain between 100 and 150 billion stars, along with vast clouds of interstellar gases. About 8 to 11 bya the galaxy Gaia-Enceladus merged with the Milky Way form the current galaxy.

A stars brightness, temperature and elemental composition can give age estimates when compared with models of a stars life cycle. Researchers M. Xiang and H. Rix at the Max Planck Institute of Astronomy surveyed the recorded properties of some 247,000 stars in the inner disk of the Milky Way. They estimated that the thick core of stars around the supermassive Black Hole, (Sagittarius A star) at the center of the Milky Way began forming some 13bya and completed star formation some 2 billion years later.

The age of the Universe can also be estimated using microwave background radiation that estimates the cooling time of the Universe since the Big Bang. Another way is to use the expansion rate of the Universe (Hubble Constant is the rate at which galaxies are moving away from Earth, some 73.8+2.4 Km/sec/Mpc ) by extrapolating backward in time.

Back           Current estimates:      Universe = 13.787+0.02 by       Milky Way = 13.61 by          Earth = 4.542 by

      
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