Guest Author - Lea Terry

Scientists have long looked to the stars for answers about history--that of our planet, and that of the universe. The images seen through telescopes are millions or billions of years old by the time they reach us, because they travel at the speed of light, and so through them we can literally view our past. And meteorites, which aren’t touched by geological changes and the passage of time like other celestial bodies are, are valued for the glimpse they provide into the beginnings of our solar system.

Now, a star recently dated at 13.2 billion years old may let us travel almost to the beginning of the universe, according to findings, reported in the May 10 issue of Astrophysical Journal. The star, HE 1523, belongs to our own Milky Way galaxy, and at 13.2 billion years old is slightly younger than the universe, which is estimated to be 13.7 billion years old. Our solar system is thought be only about 4.6 billion years old.

HE 1523 was dated using methods similar to those used to date archeological remains and artifacts. The researchers obtained images of the star with the European Southern Observatory's Very Large Telescope, over a period of 7.5 hours. From the star’s spectrum, researchers could determine how much uranium and thorium were still present, helping them determine its age. Because they knew that the elements have half-lives of 4.7 billion years and 14 billion years, respectively, measuring how much the star contained gave them a more accurate estimate of its age. It’s the same technique used in carbon dating, which uses carbon-14, a radioactive form of carbon, and is commonly used to date rocks and fossils.

HE 1523 is a giant red star, and is probably nearing the end of its life. Although it is the oldest dated star, it is probably not the oldest in existence: the composition of other stars leads astronomers to believe they are even older. Astronomers don’t know exactly how far away it is, but it can be seen with a telescope from the Southern Hemisphere.