Scientists believe they have discovered a stellar "dinosaur egg" on the verge of hatching.
Groups of ancient stars, called globular clusters, are rarely spotted in their newborn phase, and the conditions under which they are formed has remained a mystery, the National Radio Astronomy Observatory reported. Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) discovered what is believed to be the first known example of a globular cluster just before its time of birth. It was spotted in the form of a dense, starless could of molecular gas.
"We may be witnessing one of the most ancient and extreme modes of star formation in the universe," said Kelsey Johnson, an astronomer at the University of Virginia in Charlottesville and lead author on a paper accepted for publication in the Astrophysical Journal. "This remarkable object looks like it was plucked straight out of the very early universe. To discover something that has all the characteristics of a globular cluster, yet has not begun making stars, is like finding a dinosaur egg that's about to hatch."
The object, dubbed the "Firecracker," is located about 50 million light-years away inside the interacting galaxies known of as the Antennae galaxies.
"Until now, clouds with this potential have only been seen as teenagers, after star formation had begun," Johnson said. "That meant that the nursery had already been disturbed. To understand how a globular cluster forms, you need to see its true beginnings."
Most globular clusters are believed to have formed about 12 billion years ago, and our own galaxy holds about 150 of these objects. Star clusters are still forming throughout the universe today, but it's extremely rare to see a globular cluster in this early phase of development.
"The survival rate for a massive young star cluster to remain intact is very low -- around one percent," Johnson said. "Various external and internal forces pull these objects apart, either forming open clusters like the Pleiades or completely disintegrating to become part of a galaxy's halo."
The team believes the newly-observed object contains 50 million times the mass of the Sun in molecular gas. It also appears to be under extreme pressure, supporting past theories suggesting these conditions are necessary for cluster formation.
The findings were published in a recent edition of the Astrophysical Journal.
