Mission Complete! WMAP In 'Graveyard Orbit'

astroengine writes "The Wilkinson Microwave Anisotropy Probe (WMAP) has, quite literally, changed our view of the Universe. And after nine years of mapping the slight temperature variations in the cosmic microwave background (CMB) radiation, its job is done and NASA has commanded the probe to fire itself into a 'graveyard orbit' around the sun. WMAP measured the most precise age of the universe (13.75 billion years), discovered more evidence supporting dark energy and dark matter theories, and found one or two mysteries along the way."

Comments

So long.....

[tpstigers]

..... and thanks.

Re:Dark Matter (Gravity); please explain

[ETEQ]

I guess no one knows such things, but I wonder what would prevent it from clumping up like normal baryonic matter. Maybe it's too diffuse to form dark matter nebulae, but those are only held together by gravity too, right? Or would fast-moving particles just fly apart before gravity could act? Or maybe we just can't see the clumps. Or maybe it's a happy medium—loosely bound to the galaxy but nothing more...

Actually, the explanation for this one is pretty simple: it's because the dark matter is dark. The reason why baryonic matter collapses into a (relatively) tiny disk in the center of a much larger dark matter halo is that baryonic matter emits light... and light carries off energy. So baryonic matter quickly loses all the energy it can while still conserving angular momentum, and the result is a disk-like structure (spiral galaxies). Once it collapses into a disk, the density becomes high enough that it can further clump into nebulae and stars and such. Dark matter, on the other hand, is much lower density and hence isn't able to collapse efficiently (i.e. its Jean's Length is much longer, if you want to think in terms of some simple math).