New Space Telescope to Map Dark Matter

BY Jenny Marder  January 28, 2013 at 12:11 PM EST

This artist’s concept shows the Euclid spacecraft, which will launch to an orbit around the sun-Earth Lagrange point L2. Image by ESA/C. Carreau.

Update: Jan 29 | This week, NASA announced that it will partner with the European Space Agency to send a 4,760-pound spacecraft into space to peer out over billions of galaxies in an effort to map and measure the universe. Its purpose: to investigate the mysteries of dark matter and dark energy.

The Euclid mission space telescope is half the width of Hubble, but its cameras will sweep across wide swaths of the sky to cover an area 200 times greater.

“In its lifetime, the Hubble Space Telescope has only imaged a few square degrees in the sky,” said Jason Rhodes, lead scientist for the mission’s U.S. component. “Euclid will image 15,000 square degrees in the sky…Instead of looking at small patches, we’ll be looking at a third of the sky.”

We thought we’d take this as an opportunity to remind ourselves, what is dark matter? And what is dark energy?

Put simply, dark matter holds things together and dark energy drives things apart.

The stuff we consider normal matter — planets, stars, rocks, the atoms that make up the human body, in short, everything that we know and see — accounts for only a fraction of total matter. The rest is made up of a mysterious force called dark matter, which was first described in 1932, but has never been directly seen or observed.

Dark matter is spread throughout all of space. It is five times more abundant than standard matter. It engulfs our galaxy and others. It does not interact with light – hence its name. But scientists believe it does interact with ordinary matter through gravity, binding galaxies together like invisible glue. They know that it’s there, because of the gravitational force it exerts on other objects.

This video by Minute Physics does a nice job explaining the basics.

Even less is known about dark energy. In the pas 15 years, we’ve learned that the universe is expanding at an accelerating rate, and it’s believed that dark energy is at the root of this cosmic expansion. Universal expansion, astronomers believe, depends on a tug of war between gravity trying to slow things down and dark energy trying to speed things up. While there are still many questions about what exactly dark energy is, the commonly held theory is that it makes up most — about three-quarters — of the energy in the universe. Stars and galaxies constitute only a small fraction — about 5 percent.

“Whatever we’re calling dark energy, it could be a new force, it could be a property of space itself, and it could be that we don’t understand how gravity works,” Rhodes said. “All we know is there are some interesting observational consequences… that the universe is expanding faster and faster.”

One of the primary goals of Euclid would be to constrain those theories, to rule many of them out and understand better this mysterious force.

Euclid will consist of a telescope operating alongside two scientific instruments, designed to map two billion galaxies. The hope is that mapping these galaxies will give scientists more insight how the galaxies evolved and how the universe’s acceleration changed over time, in turn revealing clues into the nature of dark matter and dark energy.


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