Cosmic Treasure Trove of Heavy Metals Found
The Perseus galaxy cluster contains 190 galaxies, and lies about 225 million light-years away.
Credit: Robert Lupton and the Sloan Digital Sky Survey Consortium

An orbiting X-ray observatory has found the largest known reservoir of rare heavy metals in the universe.

The lightweights of the periodic table, hydrogen and helium, are the most abundant elements in the cosmos ? they're the key fuels of stellar engines.

But more familiar to us Earthlings are the heavier elements that make up the rest of the table, though these heftier elements are rare in the universe at large.

Recently, astronomers used the Suzaku orbiting X-ray observatory, operated jointly by NASA and the Japanese space agency, to discover the largest known cache of rare metals in the universe to date.

Suzaku detected the elements chromium and manganese while observing the central region of the Perseus galaxy cluster, which lies 225 million light-years from Earth. The metallic atoms are part of the hot gas, or intergalactic medium, that lies between 190 galaxies within the cluster.

"This is the first detection of chromium and manganese from a cluster," says Takayuki Tamura, an astrophysicist at the Japan Aerospace Exploration Agency who led the Perseus study. "Previously, these metals were detected only from stars in the Milky Way or from other galaxies. This is the first detection in intergalactic space."

The portion of the cluster within Suzaku's field of view is some 1.4 million light-years across, or roughly one-fifth of the cluster's total width. It contains a staggering amount of metal atoms: The amount of chromium is 30 million times the sun's mass, or 10 trillion times Earth's mass. The manganese reservoir weighs in at about 8 million solar masses.

Exploding stars, or supernovas, forge these heavy elements. The supernovas also create vast outflows called superwinds. These galactic gusts transport heavy elements into the intergalactic void.

The Suzaku study data show it took some three billion supernovas to produce the measured amounts of chromium and manganese. And over periods up to billions of years, superwinds carried the metals out of the cluster galaxies and deposited them in intergalactic space.

Scientists hope to use this newfound trove to learn more about star formation and gain a better understanding of how, when, and where the heavy elements formed.

"By measuring metal abundances, we can understand the chemical history of stars in galaxies, such as the numbers and types of stars that formed and exploded in the past," Tamura said.

The Suzaku findings were detailed in a recent issue of The Astrophysical Journal Letters.