Free Astronomy Magazine July-August 2015

JULY-AUGUST 2015 SPACE CHRONICLES peaked 10 billion years ago, but our Sun was late for the party, not forming until roughly 5 bil- lion years ago. By that time the star formation rate in our galaxy had plunged to a trickle. Missing the party, however, may not have been so bad. The Sun's late appearance may actually have fostered the growth of our solar system's planets. Elements heavier than hydrogen and he- lium were more abundant later Our Sun came late to the Milky Way's star-birth party by NASA I n one of the most comprehen- sive multi-observatory galaxy surveys yet, astronomers find 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, how- ever, is a late "boomer." The Milky Way's star-birthing frenzy T his illustration depicts a view of the night sky from a hypothetical planet within the youthful Milky Way galaxy 10 billion years ago. The heavens are ablaze with a firestorm of star birth. Glowing pink clouds of hydrogen gas harbor countless newborn stars, and the bluish-white hue of young star clusters litter the landscape. The star-birth rate is 30 times higher than it is in the Milky Way today. Our Sun, however, is not among these fledgling stars. The Sun will not be born for another 5 billion years. [NASA, ESA, and Z. Levay (STScI)]