from TheIndependent Website
Scientists have known for many years that there is more to the universe than can be seen or detected through their telescopes but it is only now that they have been able to capture the first significant 3D-image of this otherwise invisible material.
Unlike the ordinary matter of the planets, stars and galaxies, which can be seen through telescopes or detected by scientific instruments, nobody has seen dark matter or knows what it is made of, though calculations suggest that it is at least six times bigger than the rest of the visible universe combined.
A team of 70 astronomers from Europe,
America and Japan used the Hubble space telescope to build up a
picture of dark matter in a vast region of space where some of
the galaxies date back to half the age of the universe - nearly 7
The scientists were able to exploit the technique by collecting the distorted light from half a million faraway galaxies to reconstruct some of the missing mass of the universe which is otherwise invisible to conventional telescopes.
One of the most important discoveries to
emerge from the study is that dark matter appears to form an
invisible scaffold or skeleton around which the visible universe has
The three-dimensional map of dark matter
was built up by taking slices through different regions of space
much like a medical CT scanner build a 3-D image of the body by
taking different X-ray "slices" in two dimensions. Data from the
Hubble telescope was supplemented by measurements from telescopes on
the ground, such as the Very Large Telescope of the European
Southern Observatory in Chile and the Japanese Subaru
telescope in Hawaii.
The map stretches half way back to the beginning of the universe and shows that dark matter has formed into "clumps" as it collapsed under gravity.
Other matter then grouped around these clumps to form the visible stars, galaxies and planets.
Astronomers have compared the task of
detecting dark matter to the difficulty of photographing a
city at night from the air when only street lights are visible.
Various experiments on Earth are under way to try to find out what dark matter is made of. One theory is that it is composed of mysterious sub-atomic particles that are difficult to detect because they do not interact with ordinary matter and so cannot be picked up and identified by conventional scientific instruments.
Comparing the maps of visible matter
and dark matter have already pointed to anomalies that could
prove critical to the understanding of what constitutes dark matter.