Newspaper article The Christian Science Monitor

New Grasp of Galaxies: Varied - and Violent

Newspaper article The Christian Science Monitor

New Grasp of Galaxies: Varied - and Violent

Article excerpt

Some 75 years ago, Edwin Hubble trained his telescopes at a faint point of light in the constellation of Andromeda and revolutionized astronomy. Where others had only seen a star or cloud of cosmic dust, he saw a whole new system of stars, for the first time proving that galaxies exist outside our Milky Way.

Today, at the turn of a new century, the orbiting telescope that carries Hubble's name is leading another astronomical renaissance. And this time, the research is changing fundamental ideas about some of the most massive objects of creation.

Individually, none of the new discoveries is as groundbreaking as Hubble's seminal find. Taken together, however, they represent a significant advancement of our understanding of every aspect of galaxies - from what they are to how they are formed. Moreover, while the data are in some cases raising as many questions as they answer, they are also showing scientists that galaxies are far more varied and violent than ever imagined.

"In some ways, the changes have been pretty dramatic," says John Gallagher, an astronomer at the University of Wisconsin in Madison.

During the past 15 months:

* Scientists have found a black hole at the center of the Milky Way. Once thought to be merely galactic exotica, black holes have now been located in the center of more than three dozen galaxies, leading researchers to suggest they may play some integral role.

* The location of a gas cloud at the edge of the universe - big enough to create 100 billion suns - has forced astronomers to rethink theories on galaxy formation.

* Pictures from Hubble have offered new clues about how galaxies evolve.

* Infrared data have shown that some galaxies were born much earlier than previously believed possible.

Across the board, scientists' perceptions of galaxies today are vastly different than they were even a few decades ago. Indeed, some researchers are even going so far as to challenge the very idea of what a galaxy is.

A clump of dark matter

Last week, a team from the University of Cambridge in England suggested that 99 percent of the universe's galaxies may not even be visible. The idea is that galaxies aren't collections of stars, but rather clumps of dark matter - a substance that has never been proved to exist, but that scientists say makes up 90 percent of the mass of the universe. Without the explanation of dark matter, for instance, the gravitational actions of the cosmos don't make sense.

Huge amounts of dark matter are apparently at work in typical galaxies, but smaller amounts may be collected throughout the universe with no stars in them. Says Cambridge astronomer Neil Trentham: "We're biased toward seeing big things with a lot of light."

Back in Hubble's day - and for some time after that - galaxies were seen as "island universes" of stars and dust, created in the distant past as a single, monolithic unit and then left to spin serenely through space for the rest of time. …

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