Microscopic grains of dead stars are among the oldest known material on the planet - older than the moon, Earth and the solar system itself.

By examining chemical clues in a meteorite's mineral dust, researchers have determined the most ancient grains are 7 billion years old - about half as old as the universe. Rocks don't get much more classic than this.

The researchers studied minerals in the Murchison meteorite, a large space rock that disintegrated in 1969 above cow pastures in Murchison, central Victoria. Dairy farmers collected the fragments and sold kilograms of the meteorite to museums and universities.

The Egg Nebula is a rapidly evolving pre-planetary nebula spanning about one light year toward the constellation of Cygnus. Thick dust blocks the centre star from view, while the dust shells further out reflect light from this star. Credit: NASA, W. Sparks (STScI) and R. Sahai (JPL)

Their research paper shows that scientific collections "include materials that have existed, in essentially their current form, for the better part of the life of the universe", said Gregory Herzog, an expert in extraterrestrial chemistry at Rutgers University, who was not a part of the research team.