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Dark matter

This is a map of dark matter in the Universe. It was made from data obtained using the gravitational lensing technique. It...Read More >>This is a map of dark matter in the Universe. It was made from data obtained using the gravitational lensing technique. It reveals a web of dense (light) and empty (dark) regions. The invisible dark matter is seen coloured in pink, covering an area of sky around 420 times the size of the Full Moon.Scientists think that a large part of the total mass of the Universe—about 85% of it—cannot be accounted for by the mass of objects we can see or detect. Only the small remaining fraction, 15%, is made up of atoms, the building blocks of galaxies, stars, planets and living things. Scientists call the mysterious "invisible" portion of the Universe dark matter. Dark matter cannot be detected using telescopes, because it does not give out or absorb light or any other form of electromagnetic radiation. This is why it is described as "dark." It is likely that dark matter is made up of types of subatomic particle that have yet to be discovered, called "Wimps".


Spinning galaxies

The effect of dark matter on galaxy rotation{more}
Scientists know that galaxies appear to spin too quickly to hold themselves together. They should fly apart, yet they do not. Something else therefore is providing the gravitational force needed. Scientists say that it is invisible dark matter that is providing the mass that gives galaxies this gravitational force.
This image, taken by the Hubble Space Telescope, is of one of the most massive galaxy clusters known: Abell 1689. The enormous...Read More >>This image, taken by the Hubble Space Telescope, is of one of the most massive galaxy clusters known: Abell 1689. The enormous gravitational pull of the cluster's dark matter, combined with that of trillions of stars, actually bends and magnifies the light of other galaxies far beyond the cluster, like an incredibly powerful lens. This is called gravitational lensing. Some of the faintest objects pictured may lie over 13 billion light years away, the most distant objects visible to us.

Gravitational lensing

The first scientist to suspect the existence of dark matter was William Thomson, Lord Kelvin, in 1884. Estimating the mass of the galaxy to be greater than the mass of visible stars contained in it. Lord Kelvin concluded: "Many of our stars, perhaps a great majority of them, may be dark bodies."

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