Spacecraft sees infant galaxies in ageing universe

These images show a typical young galaxy, teeming with hot, newborn stars and exploding supernovas. The supernovas are seen as white flashes of light. Picture / Reuters

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 massive amounts of ultraviolet light they emit as they furiously form stars out of gas, astronomers said.

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

A light-year is about 10 trillion km, 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 which has been orbiting Earth since its launch in April 2003, looking to see how stars formed.

Seeing newborn galaxies now, at relatively close range, is 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 which 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," Alice Shapley, an astronomer at the University of California, Berkeley said.

The sample of newborns detected by the new spacecraft is so similar to those from the early times of the universe that it could be an effective tool to study galactic evolution from what amounts to a ring-side seat, Shapley said.

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 does not mean that another galactic birth surge is under way, Heckman said.

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

- REUTERS