The star HE1327-2326 is located 4,000 light years from Earth. Its age is measured by its composition. When the universe was formed, it consisted of hydrogen with some helium. As it evolved, the rest of the chemical elements appeared, formed by nuclear synthesis in stars. HE1327-2326 has almost no metal content in it (just 1/300,000th of the metal content of our own Sun), so must have formed from clouds of gas consisting of almost pure hydrogen and helium, when the universe was young. It may date back to just after the very beginning of the universe, around 13.7 billion years ago.