By Dr David Whitehouse
BBC News Online science editor
Observations made with the Hubble Space Telescope (HST) indicate the first stars formed as little as 200 million years after the Big Bang - much earlier than previously thought.
The earliest stars - artist's impression
The evidence comes from data showing large amounts of iron present in very distant, ancient quasars. This iron must have been made in the massive explosions that ended the lives of the first generation of stars in the cosmos.
The discovery is the first major scientific result to emerge from the Nicmos instrument that was revived during the Hubble servicing mission by the space shuttle in 2002.
It indicates that the raw materials for life - elements such as carbon - were present from a very early stage in the history of the Cosmos.
Stars are nuclear factories that process lighter elements such as hydrogen and helium into heavier elements such as nitrogen, carbon, and iron. When some stars explode in supernova explosions, this iron is scattered into space where it can become part of a new generation of stars.
The HST observations show massive amounts of iron in very distant and ancient quasars - galaxies with intense activity at their cores due to the presence of a supermassive black hole.
Hubble's work pushes back the era of the very first stars in the Universe to as early as 200 million years after the Big Bang.
This is much earlier than previously thought, though it is in agreement with very recent results from the Wilkinson Microwave Anisotropy Probe, which looks at the background radiation from the young Universe.
In October 2002, a team led by Wolfram Freudling used the HST to observe three of the most distant quasars known. The light from them had travelled for 12.8 thousand million years before reaching Hubble's detector, having left the quasars 900 million years after the Big Bang.
The spectra show clear signs of the large amounts of iron. This is the first time that elements created in the first generation of stars have been found.
Wolfram Freudling said: "Iron is a good indicator of the evolutionary state of a quasar. This element is not created during the Big Bang but in stars later on.
"We believe that the iron we detected with Hubble was created in the very first generation of stars which formed soon after the Big Bang."
The detection of iron so early in the Universe's history has profound implications.
Michael Corbin, of the Space Telescope Science Institute, said: "The presence of iron shows that basic ingredients for planets and life were present, at least in some places, very early in the history of the Universe.
"This is much earlier than the formation of the Earth itself 4.6 thousand million years ago."