Sun Formed After Stellar 'Baby Boom' in the Milky Way Galaxy

Earth's sun apparently came late to the Milky Way galaxy. In one of the most comprehensive multi-observatory galaxy surveys yet, scientists have discovered that galaxies like our Milky Way underwent a stellar "baby boom" and that our sun is a late "boomer."

The Milky Way's star-birthing frenzy peaked about 10 billion years ago. However, our sun didn't form until about 5 billion years ago. By that time, the star formation rate in our galaxy had slowed to a trickle.

In order to learn a bit more about the history of the Milky Way, the researchers examined other galaxies similar in mass to our own galaxy. The farther into the universe the researchers looked, the further back in time they saw. From the surveys, the scientists assembled an album of images containing nearly 2,000 shots of Milky Way-like galaxies.

"This study allows us to see what the Milky Way may have looked like in the past," said Casey Papovich, lead author of the new study, in a news release. "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 suggest that the Milky Way began as small clumps of stars. Then the galaxy built itself up by swallowing large amounts of gas that ignited a firestorm of star birth.

The findings are published in The Astrophysical Journal.

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