Ringside seats for birth of galaxies

WASHINGTON - Billions of years after a galactic "baby boom", a Nasa spacecraft has detected dozens of newborn galaxies in Earth's part of the universe.

These unexpected cosmic infants were discovered with the Galaxy Evolution Explorer, which managed to spy them because of the huge amounts of ultraviolet light they emit as they furiously form stars out of gas, astronomers say.

The closest of them might be a mere billion light years from Earth, about nine billion light years closer than the baby galaxies scientists had observed previously, said Tim Heckman, an astronomer at Johns Hopkins University in Baltimore.

A light year is about 10 trillion kilometres, the distance light travels in a year.

Astronomers believe the real boom time for galaxy formation was just a few billion years after the theoretical Big Bang explosion thought to have given birth to the universe.

Before the Galaxy Evolution Explorer astronomers did not know whether newborn galaxies were present at all in the universe today or whether this phase of cosmic creation might be over.

The Explorer, known familiarly as Galex, is a space telescope that has been orbiting Earth since its launch in April 2003, looking to see how stars formed.

Seeing newborn galaxies now, at relatively close range, was remarkable, Heckman said: "It's almost like looking out the window and seeing a dinosaur walking by."

Astronomers have long looked for baby galaxies to get some clue to the formation of the Milky Way, the galaxy that contains Earth's solar system. Previous observations have centred on the youngest galaxies that are also the furthest away and therefore hard to study in detail.

"While these newborn galaxies (from the galactic baby boom) are much more numerous in the early universe, we can only obtain crude information about them," said Alice Shapley, an astronomer at the University of California, Berkeley.

The sample of newborns detected by the new spacecraft was so similar to those from the early times of the universe that it could be an effective tool to study galactic evolution from what amounted to a ringside seat.

The new image of the youngest galaxies shows them to be from one-fifth to one-third the diameter of the Milky Way and other mature galaxies. Unlike the Milky Way, with its elegant spiral arms, the baby galaxies are amorphous blobs.

The visible light they emit is about the same as the middle-aged galaxies, but in the ultraviolet realm they shine much more brightly.

This discovery did not mean that another galactic birth surge was under way, Heckman said.

"What we're seeing now is the last dregs of galaxy birth, the stragglers. We don't know what's causing the decline."

- REUTERS