How do astronomers know how old our galaxy is?
A new estimate of the age of our Milky Way Galaxy suggests it was an original member of the universe, having been born just about as early on as was possible. The overall universe is about 13.7 billion years old. That figure, after decades of wildly varying estimates, was pinned down last year to within 200 million years of accuracy. Scientists used space-based observations of a microwave background radiation that had been unleashed as a dense fog cleared, shortly after the universe’s formation. The background radiation also suggested that the first stars formed about 200 million years after the Big Bang, theorists say, just as the fog lifted on the initial dark ages. Astronomers have known that the Milky Way is among the oldest of galaxies. The new observations suggest it was indeed one of the first to get under construction. The study puts its age at 13.6 billion years, give or take 800 million years. Further studies will be needed to reduce that margin of error. A key to generating
