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Sunday, October 26, 1997


When Galaxies Collide

A thousand young stars bursting into life

Like lovers who meet with a burst of sparks, pairs of galaxies collide and produce thousands of star clusters before settling down into a united galactic blob.

This is the stunning new photograph to be released by NASA scientists using the orbiting Hubble Space Telescope.

It shows two galaxies colliding in deep space. Scientists are excited about the finding because they think they now understand more about how stars are born and develop.

Big and hot

When stars are born in a placid environment, such as a galaxy where no smash-ups are occurring, the first few stars formed are big and hot, but then star birth tapers off quickly, said Francois Schweizer of the Carnegie Institution of Washington.

[ image: A ground-based telescopic view of the Antennae galaxies]
A ground-based telescopic view of the Antennae galaxies

"But if located in a colliding galaxy ... then the environment is much more violent," Schweizer said. "The galaxy collision crunches the thin gas that pervades all the space between stars, and new stars form all over the place."

Star clusters can each contain a million stars. Once believed to be relics of the earliest days of a galaxy, the clusters now appear in a fairly close double galaxy called the Antennae.

Looking a bit like a huge insect in the sky, the Antennae double galaxy has a heart-shaped nucleus where star clusters are shown shortly after their birth.

New knowledge

Until now, astronomers have had to content themselves with looking at galaxies that merged billions of years ago, which have settled into an elliptical shape.

The Antennae pictures give a better clue to just what happens during a collision.

[ image: A close up view of the galaxies]
A close up view of the galaxies
These findings give support to one theory that holds that all galaxies start as spirals, like our own Milky Way, and smash into other galaxies to eventually form more peaceful elliptical galaxies.

In fact, the Milky Way may be on a collision course with the nearby Andromeda Galaxy, about 2 million light-years away. A light-year is about 6 trillion miles (9.66 trillion km).

But Bradley Whitmore, an astronomer at the Space Telescope Science Institute in Baltimore, said there will be no galactic crash in our part of the universe for about 5 billion years.


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