Sun joined Milky Way's star-birth party much later

In one of the most comprehensive galaxy surveys yet, astronomers have found that galaxies like our Milky Way underwent a stellar "baby boom" churning out stars at a prodigious rate, about 30 times faster than today.

Our Sun, however, was a late "boomer".

The Milky Way's star-birthing frenzy peaked 10 billion years ago but our Sun was late for the party - not forming until roughly five billion years ago.

The new census provides the most complete picture yet of how galaxies like the Milky Way grew over the past 10 billion years into today's majestic spiral galaxies.

"It allows us to see what the Milky Way may have looked like in the past. 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," explained Casey Papovich from the Texas A&M University in College Station.

Most of that stellar-mass growth happened within the first five billion years of their birth.

The Sun's late appearance may actually have fostered the growth of our solar system's planets.

"The new analysis reinforces earlier research which showed that Milky Way-like galaxies began as small clumps of stars. The galaxies swallowed large amounts of gas that ignited a firestorm of star birth," Papovich noted.

The study reveals a strong correlation between the galaxies' star formation and growth in stellar mass.

"The evidence suggests that we can account for the majority of the buildup of a Milky Way-like galaxy through its star formation," Papovich pointed out.

Elements heavier than hydrogen and helium were more abundant later in the star-forming boom as more massive stars ended their lives early and enriched the galaxy with material that served as the building blocks of planets and even life on Earth.

The study combined observations from NASA's Hubble and Spitzer space telescopes, the European Space Agency's Herschel Space Observatory and ground-based telescopes, including the Magellan Baade Telescope at the Las Campanas Observatory in Chile.

The results appeared in The Astrophysical Journal.