Milky Way's Baby Pictures Pieced Together Using Photos of its Younger Siblings

NASA has uncovered the first visual clues into how the Milky Way came to resemble a pinwheel.

Using the Hubble Space Telescope's deep-sky surveys, astronomers were able to piece together an 11-billion-year history using images of 400 galaxies similar to the Milky Way, making special note of changes in their physical appearance at various stages of development.

"For the first time, we have direct images of what the Milky Way looked like in the past," study co-leader Pieter G. van Dokkum of Yale University, said in a statement. "Of course," he noted, "we can't see the Milky Way itself in the past."

To get around this, the scientist turned to galaxies located billions of light years away and on track to one day resemble our own galaxy. "By tracing the Milky Way's siblings, we find that our galaxy built up 90 percent of its stars between 11 billion and 7 billion years ago, which is something that has not been measured directly before," Dokkum said.

They also determined that the Milky Way likely began as a faint, blue object filled with a lot of gas and not much else. That gas later fueled rampant star production, with the blue color indicative of rapid star formation. When the universe was roughly 4 billion years old, star formation peaked at an average of 15 new stars every year, compared to its current rate of one star a year.

The galaxy probably started as a flat disk with a bulge in the middle before both transformed into its current spiral, the researchers concluded. "You can see that these galaxies are fluffy and spread out," said study co-leader Shannon Patel of Leiden University in The Netherlands. "There is no evidence of a bulge without a disk, around which the disk formed later."

Today, the bulge is home to a supermassive black hole that scientists believe grew up with the galaxy.

"In these observations, we're capturing most of the evolution of the Milky Way," explained team member Joel Leja of Yale University. "These deep surveys allow us to see the smaller galaxies. In previous observations we could only see the most luminous galaxies in the distant past, and now we can look at more normal galaxies."