Deep secrets of star birth revealed

Bright knots of blue-white, hot, newborn stars

By BBC News Online science editor Dr David Whitehouse

A new analysis of the deepest views of the cosmos ever taken by an optical telescope suggests that stars burst into existence dramatically and suddenly.

The new finding indicate that there was a "stellar firestorm" when the Universe was young, as myriads of stars were formed in far greater numbers than we see today.

The Hubble Space Telescope sees a galaxy undergoing violent starburst

"If this can be verified, it will dramatically change our understanding of the Universe," said Dr Anne Kinney, of the US space agency, Nasa.

The deepest ever views of the cosmos were made by Kenneth Lanzetta, of the State University of New York at Stony Brook, and colleagues.

They base their conclusions on a new analysis of galaxies seen in the Hubble Deep Fields, the two most distant and clearest views of the billions of galaxies in the Universe, taken in 1995 and 1998 respectively.

Looking at galaxy colours, Dr Lanzetta believes that the farthest objects in the deep fields must be bright knots of blue-white, hot, newborn stars embedded in primordial galaxies.

Star light, star bright

He says that these are only the "tip of the iceberg" of an effervescent period of star birth that is unlike anything the Universe will ever see again.

The new finding may change our understanding of how the Universe evolved. It was thought that the rate of formation of stars increased gradually over a few billion years before it began tailing off.

Proving that countless numbers of stars began forming so early after the birth of the Universe could cause us to rethink a lot of our theories

Dr Kenneth Lanzetta, State University of New York

But things may have happened differently and certainly more dramatically.

It appears that the Universe made a significant portion of its stars in a torrential firestorm of star birth only a few hundred million years after the Big Bang.

Although stars continue to be born today in galaxies, the current stellar birthrate could be a trickle compared with what it was when the Universe was young.

When it was only a few hundreds of millions of years old, the cosmos may have undergone a voracious burst of star formation, converting primordial hydrogen into bright stars at an unprecedented rate.

'Firework display'

Astronomers say that during this time, the sky would have looked very different from the vast stretches of galaxies around us today. Everywhere the sky would have been ablaze with bright knots of hot, blue stars in a Universe-wide "firework display".

Many of the stars were grouped into primitive galaxies but unlike today there was very little dust in them, because the heavier elements the dust is composed of had not yet been made inside stars.

This lack of dust affected the way they appeared, making their identification possible in the Hubble Deep Field images.

Dr Lanzetta said: "Because stars are the building blocks of galaxies and the birthplace of solar systems, proving that countless numbers of stars began forming so early after the birth of the Universe could cause us to rethink a lot of our theories."

Dr Lanzetta next plans to use Hubble's Advanced Camera, to be installed in early 2002, for surveys to look even deeper into the Universe to try to directly verify his team's observations and conclusions.

Hubble's deep view of the Universe: Billions of galaxies