Chilean telescope uncovers one of the oldest star clusters in the galaxy

Color composite GSAOI+GeMS image of HP 1 obtained using the Gemini South telescope in Chile. North is up and East to the left. Gemini Observatory/AURA/NSF; composite image produced by Mattia Libralato of Space Telescope Science Institute

An ultra-high definition image captured by the Gemini South telescope in Chile has uncovered one of the oldest star clusters in the Milky Way. The cluster, called HP 1, could give clues to how our galaxy was formed billions of years ago.

“Ultra-sharp adaptive optics images from the Gemini Observatory allowed us to determine the ages of some of the oldest stars in our Galaxy,” Leandro Kerber of the Universidade de São Paulo (USP) and Universidade Estadual de Santa Cruz, Brazil, said in a statement. “HP 1 is one of the surviving members of the fundamental building blocks that assembled our Galaxy’s inner bulge.”

The team used a technique called adaptive optics which removes the distortions in light caused by Earth’s atmosphere. That allows the telescope to see stars in great detail, which allows their age to be determined. The HP 1 cluster is estimated to be 12.8 billion years old.

“This star cluster is like an ancient fossil buried deep in our Galaxy’s bulge, and now we’ve been able to date it to a far-off time when the Universe was very young,” said Stefano Souza, a Ph.D. student at the USP, who worked on the research team, said in a statement. “These are also some of the oldest stars we’ve seen anywhere.”

HP 1 is known as a globular cluster, which is a collection of stars bound together by gravity. Globular clusters tend to be located near the center of the galaxy, but HP 1 and other similar clusters imaged by Hubble have shown that they can also be found further out in the galactic bulge. As a very old cluster, HP 1 is lacking in heavy elements like metal, and this was the first clue that it could be used as a chemical tracer of our galaxy’s evolution.

“HP 1 is playing a critical role in our understanding of how the Milky Way formed,” Kerber said. “It is helping us to bridge the gap in our understanding between our Galaxy’s past and its present.”

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