The Sun formed after our galaxy's busiest period of star formation

A new survey of spiral galaxies has shown that their periods of fastest star formation occurred within their first five billion years.
By Andrew McDonald | Apr 10, 2015
According to a NASA statement, a new study led by Casey Papovich of Texas A&M University in College Station has found that the Sun formed long after the end of the Milky Way's era of maximum star generation.

The research team used an array of observatories and techniques to survey over 24,000 galaxies. The FourStar Galaxy Evolution Survey by the Magellan Baada Telescope at the Las Campanas Observatory in Chile, Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) by the Hubble Space Telescope, and the Spitzer Space Telescope were used to ascertain the galaxies' stellar masses. CANDELS images also revealed the sizes and evolution of galaxies, while Spitzer and the Herschel Space Observatory revealed the rates at which stars formed in those galaxies.

In all, this broad approach allowed the researchers to build up a database of almost 2,000 images of galaxies similar to the Milky Way, covering over 10 billion years of cosmic evolution. This extensive database showed the evolution of Milky Way-like galaxies in great detail. These spiral galaxies underwent an era of prolific star formation within the first five billion years of their history, around 30 times faster than new stars are formed today. The implication for our solar system is that the Sun, at about 5 billion years old, did not form until after the Milky Way's peak period of star formation had ended.

"This study allows us to see what the Milky Way may have looked like in the past," Papovich said. "It shows that these galaxies underwent a big change in the mass of its stars over the past 10 billion years, bulking up by a factor of 10, which confirms theories about their growth. And most of that stellar-mass growth happened within the first 5 billion years of their birth."

The new findings were published in the April 9 edition of The Astrophysical Journal.

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