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A team of astronomers from the University of Texas at Austin McDonald Observatory recently estimated the age of one of the oldest stars in the Milky Way, HE 1523-0901, at 13.2 billion years. They used radioactive decay dating techniques. This star is close to the estimated age of the universe, 13.7 billion years.  

A team of astronomers from the University of Texas at Austin McDonald Observatory recently estimated the age of one of the oldest stars in the Milky Way, HE 1523-0901, at 13.2 billion years. They used radioactive decay dating techniques. This star is close to the estimated age of the universe, 13.7 billion years.  

The team leader, Dr. Anna Frebel, said that it was hard to pin down the age of a star, but that it can be inferred that chemically primitive stars must be very old, since they would have been born before many later generations of stars had provided chemical enrichment to the galaxy. A very few old stars contain huge amounts of some chemical elements, including radioactive thorium and uranium, and astronomers can use known rates of decay to deduce the ages of the stars.

The team leader, Dr. Anna Frebel, said that it was hard to pin down the age of a star, but that it can be inferred that chemically primitive stars must be very old, since they would have been born before many later generations of stars had provided chemical enrichment to the galaxy. A very few old stars contain huge amounts of some chemical elements, including radioactive thorium and uranium, and astronomers can use known rates of decay to deduce the ages of the stars using uniformitarian assumptions.

Frebel's team measured the uranium in HE1523-0901 using the UVES spectrograph on the Kueyen Telescope. This is one of four that together comprise the Very Larte Telescope based in Chile. She explained that although uranium had been discovered in two other stars, HE 1523-0901 also contains thorium. Uranium has a half-life of 4.5 billion years while thorium has a half-life of 14 billion years. However, HE 1523-0901 also contains other elements that can be anchored to the radioactive elements - europium, osmium and iridium. This combination provided Frebel with six 'cosmic clocks' that could be used to check each other.

Frebel's team measured the uranium in HE1523-0901 using the UVES spectrograph on the Kueyen Telescope. This is one of four that together comprise the Very Larte Telescope based in Chile. She explained that although uranium had been discovered in two other stars, HE 1523-0901 also contains thorium. Uranium has a half-life of 4.5 billion years while thorium has a half-life of 14 billion years. However, HE 1523-0901 also contains other elements that can be anchored to the radioactive elements - europium, osmium and iridium. This combination provided Frebel with six 'cosmic clocks' that could be used to check each other.