SPACE - Telescope to Map Dark Matter

"New Space Telescope to Map Dark Matter" by Jenny Marder, PBS Newshour 1/28/2013

Excerpt

This week, NASA announced that it will partner with the European Space Agency' to send a 4,760-pound spacecraft into space.  The Euclid mission space telescope will peer out over billions of galaxies, map and measure the Universe, and investigate the mysteries of dark matter and dark energy.

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

Matter as we know it -- planets, galaxies, stars, 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 (at bottom) by Minute Physics does a nice job explaining the basics.

Even less is known about dark energy.  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.

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

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.