Hubble Makes the First Precise Distance Measurement to an Ancient Globular Star Cluster

Astronomers using NASA’s Hubble Space Telescope have for the first time precisely measured the distance to one of the oldest objects in the universe, a collection of stars born shortly after the big bang.

This new, refined distance yardstick provides an independent estimate for the age of the universe. The new measurement also will help astronomers improve models of stellar evolution. Star clusters are the key ingredient in stellar models because the stars in each grouping are at the same distance, have the same age, and have the same chemical composition. They therefore constitute a single stellar population to study.

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Credits: NASA, ESA, and T. Brown and S. Casertano (STScI) ; Acknowledgement: NASA, ESA, and J. Anderson (STScI)

This ancient stellar jewelry box, a globular cluster called NGC 6397, glitters with the light from hundreds of thousands of stars.

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This video zooms into a Hubble Space Telescope view of globular star cluster NGC 6397.

This ancient stellar jewelry box, a globular cluster called NGC 6397, glitters with the light from hundreds of thousands of stars.

The new measurement sets the cluster's distance at 7,800 light-years away, with just a 3 percent margin of error. NGC 6397 is one of the closest globular clusters to Earth.