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Suddenly, universe awash in black holes

An artist's view of a black hole in a globular cluster
An artist's view of a black hole in a globular cluster  

By Richard Stenger

(CNN) -- Scanning the universe with the most powerful orbiting observatories, scientists have discovered different types of black holes in the most unexpected places.

The findings could shed light on how galaxies form and interact with surrounding star groups as well as revamp theories on the evolution of the universe.

Using the Hubble Space Telescope, researchers confirmed for the first time the existence of medium-size black holes, according to NASA, which announced the findings Tuesday.

"Black holes are more common in the universe than previously thought," said Hubble scientist Roeland van der Marel. "These findings may be telling us something very deep about the formation of star clusters and black holes in the early universe."

Van der Marel and colleagues found the elusive class of black holes, previously only the subject of speculation, in the hearts of globular star clusters.

Finding the 'missing link'

The thick star swarms formed billions of years ago, possess the oldest stars in the cosmos and hover around more conventional galaxies such as the Milky Way.

"These new data from the Hubble help us connect globular clusters to galaxies," said Michael Rich of the University of California, Los Angeles, another of the black hole hunters.

One of the black holes, about 32,000 light-years away in the globular cluster M15, has an estimated mass 4,000 times that of the sun.

To compare, small black holes peppered throughout the cosmos have only several times more mass than the sun.

The largest known ones, which lurk in the core of many galaxies, including the Milky Way, are thought to have millions or billions of times the mass of the sun.

"Medium-size black holes are an astronomical missing link," said Steinn Sigurdsson of Pennsylvania State University in University Park.

Many scientists speculate that small black holes served as seeds for larger ones, merging with nearby peers into increasingly larger black holes in galactic cores over the eons.

"These intermediate-mass black holes that have now been found with Hubble may be the building blocks of supermassive black holes that dwell in the center of most galaxies," said Karl Gebhardt of the University of Texas at Austin.

In old galaxies, more surprises

The Chandra X-ray Observatory's view of an old galactic cluster with many more active black holes than expected
The Chandra X-ray Observatory's view of an old galactic cluster with many more active black holes than expected  

In another cosmic search with unforeseen results, scientists using the Chandra X-ray Observatory in space and the Carnegie telescope in Chile detected six times more active supermassive black holes than expected in a cluster of aging galaxies.

Such black holes are thought to be common in young galaxies, where the matter gobblers have plenty of material to satisfy their voracious appetites.

But astronomers presumed such dynamic black holes were rare in older galaxies, their supplies of gas and dust presumably depleted over the eons.

"This changes our view of galaxy clusters as the retirement homes for old and quiet black holes," astronomer Paul Martini said last week.

Martini and colleagues published their findings in the September 10 issue of The Astrophysical Journal Letters.

Black holes are regions of space so staggeringly warped and dense that light cannot escape their grasp. Small ones are thought to be the collapsed remnants of stars much larger than the sun. Supermassive specimens are squeezed into areas about the size of our solar system.




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