Over the years, astronomers have found about 150 ancient star clusters embedded in our Milky Way Galaxy. These tight groupings of stars hail from the early years of the universe and are thought to be fossils of mergers past, the stuff the Milky Way gobbled up in order to grow.

Now, not expecting to find any more, researchers have spotted one of these globular clusters, as they are called, practically in our back yard.

The cluster is between 10 billion and 13 billion years old. It is a mere 9,000 light-years away and resides in the main plane of the galaxy.

The globular cluster was found with NASA's Spitzer Space Telescope, which records infrared light. It did not stand out in other images of the region (see inset) because the galaxy's main plane contains a lot of dust, which blocks visible light.

"It's like finding a long-lost cousin," said Chip Kobulnicky, a professor of physics and astronomy at the University of Wyoming, Laramie, and lead author a report on the finding that will be published in the Astronomical Journal. "We thought all the galaxy's globular clusters had already been found."

Globular clusters are valuable for studying the age and formation history of the galaxy. They are sprinkled around the center of the galaxy "like seeds in a pumpkin," astronomers say.

The newfound cluster contains several hundred thousand stars, most of them older and more massive than our Sun.

"I couldn't believe what I was seeing," said Andrew Monson, a graduate student at the University of Wyoming, who first spotted the cluster. "I certainly wasn't expecting to find such a cluster."

The cluster, catlogued as GLIMPSE-C01, is in the direction of the constellation Aquila.

Credit: NASA/JPL-Caltech/H. Kobulnicky (Univ. of Wyoming)