Dark Matter Mapped in 3-D, Scientists Report

January 8, 2007

A new three-dimensional map of the universe's dark matter provides compelling evidence that the mysterious substance is the scaffolding upon which stars and galaxies are assembled.

Scientists are still not sure exactly what dark matter—an invisible form of matter that does not give off or reflect light yet accounts for the vast majority of mass in the universe—is made of. (Related: "Dark Matter Proof Found, Scientists Say" [August 22, 2006].)

But "without dark matter as we are seeing here, the universe wouldn't exist as it is today," Richard Massey, an astronomer at the California Institute of Technology (Caltech) in Pasadena, said at press briefing yesterday in Seattle, Washington.

Massey likened the dark matter to scaffolding that both holds the universe together as it expands after the Big Bang and provides a framework for the assembly of normal matter.

The map was published online yesterday by the science journal Nature. Massey and his colleagues presented details of the study at the 209th meeting of the American Astronomical Society in Seattle, Washington.

"For the first time we have been able to map out the large-scale distribution of this invisible, mysterious dark matter," Massey said.

Searching the COSMOS

The map was derived from nearly a thousand hours of observations of 575 overlapping patches of sky with the Hubble Space Telescope's high-resolution cameras (see an interactive Hubble diagram). The imaging was part of a project called COSMOS—the Cosmic Evolution Survey.

(Related: "Hubble Repair Mission Approved by NASA" [October 31, 2006].)

"It's the largest project that's ever been done by the space telescope," noted Caltech team member Nick Scoville, principal investigator for COSMOS.

Additional space and ground telescopes in Hawaii and Chile helped give the map its depth and color.

Richard Ellis, also a Caltech team member and a co-principal investigator for COSMOS, said the research collectively shows "what an important role dark matter plays in shaping the universe."

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