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Stars burst to life before Hubble's lens

October 21, 1997
Web posted at: 1:11 p.m. EDT (1711 GMT)
galaxies colliding photo -  click for larger version

BALTIMORE (CNN) -- NASA's Hubble Space Telescope has uncovered more than 1,000 bright, young star clusters bursting to life in a brief but intense "fireworks show" at the heart of a pair of colliding galaxies, the Space Telescope Science Institute in Maryland said Tuesday.

The photographs Hubble relayed back to Earth may tell scientists how a collision between our own galaxy and the Andromeda galaxy, expected in several billion years, could alter the two systems.

The pictures also provide further support for a scientific theory that if one disk-shaped, or spiral, galaxy collides into another, the result is an elliptical galaxy with far more stars than either of the original galaxies contained, including many star clusters.

Galaxies realign, stars form

It was once commonly believed that these globular star clusters were remnants from the start of a galaxy's creation. Now, most scientists think that the ages of the clusters may provide a clock for estimating the age of a collision -- not the age of the original galaxy.

galaxies colliding photo -  click for larger version

Scientists who support this theory believe that the additional star clusters are formed when massive clouds of hydrogen gas -- measuring tens to hundreds of light-years across -- in the spiral galaxies are compressed and then ignite, triggering the new stars' sudden formation.

The Hubble pictures came from nearby galactic-scale collisions, including the Antennae galaxies, so called because a pair of long, luminous tails resembling an insect's antennae were formed when they began their ongoing collision.

Although the Antennae are relatively close to Earth in astronomical terms, ground-based telescopes were only able to see the brightest of the clusters created by the crash, and even in those cases could not show that the clusters were compact.

But Hubble's resolution and sensitivity allowed NASA scientists to uncover more than 1,000 exceptionally bright young star clusters there.

In fact, even before its February upgrade, Hubble was able to see more than any ground-based telescopes, NASA said. That mission improved Hubble's "vision" into the infrared range. Overall, NASA officials estimate the Hubble, launched in 1990, has cost $3 billion.

Milky Way also headed for crash

If Hubble were around to witness it, the far-seeing telescope might snap similar pictures of the Milky Way and the Andromeda galaxy when they crash into each other.


The two galaxies are on a collision course, closing the gap at a speed of 300,000 miles per hour. As Andromeda is currently 2.2 million light years away, the collision will happen no sooner than 5 billion years in the future, by which point the sun may have burned out, reducing the Earth to a lifeless lump of rock.

Even if there were someone here to observe the collision, they would be unlikely to see it from beginning to end. NASA scientists say the crash will probably take several billion years to run its course.

During the collision, they predict, molecular hydrogen clouds will compress and explode, triggering the formation of thousands of new star clusters. The galaxies' gravitational pulls will draw Andromeda and the Milky Way into one elliptical galaxy, with thousands of old and new stars mingling together.

The turmoil will be such that in the end, they say, an observer would see no sign of the former, majestic spiral galaxies that our ancient civilization knew as the Milky Way and Andromeda.


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