Hubble detects ring of dark matter!!

Astronomers using the Hubble Space Telescope have discovered a ghostlyring of dark matter that formed during a titanic collision between twomassive galaxy clusters. Because ordinary matter in the cluster showsno evidence of such a ring, this discovery is among the strongestevidence yet for non-baryonic dark matter. Clusters of galaxies are the largest gravitationally bound structuresin the universe. They typically contain hundreds or thousands ofgalaxies, forming at the knots of the filamentary sponge-likedistribution of matter on very large scales. Numerical simulationsshow how the accretion of matter from the filaments to the knots makegalaxy clusters grow in size. This one-dimensional accretion (along afilament) results in frequent, near head-on collisions among clustersor groups of galaxies, whereas interactions between individualgalaxies usually occur only when there is significant rotation.

The galaxy cluster Cl 0024+17 – some 5 x 109 light-years away (z =0.4) – is supposed to have experienced exactly such a head-oncollision 1 or 2 thousand million years ago. The first evidence ofthis was obtained in 2002 by Oliver Czoske, from the University ofBonn, and collaborators. By studying the velocity distribution of thegalaxies in the cluster, they found two distinct groups with oppositevelocity, suggesting that there are two sub-clusters moving away fromeach other along the line-of-sight. Their numerical simulationsconfirm the collision scenario and suggest a sub-cluster mass ratio of2:1. In 2004, when the dark-matter distribution in Cl 0024+117 was studied there was no such a peculiar cluster of galaxies. Ring-like distribution was never seen in other clusters.It is indeed tricky to derive the dark-matter distribution in acluster from the distortion it causes on the shape of backgroundgalaxies, but the analysis of this weak gravitational lensing nowseems to be well under control, with the release of the first 3D mapof the dark matter distribution (CERN Courier January/February 2007)

Quark Star... A new Object!!

The breakdown of matter into its tiniest quark components in a star's core may have triggered the brightest supernova ever seen. If correct, this would be the first time anyone has seen the birth of an exotic object called a quark star.On 18 September 2006, astronomers observed the record-breaking supernova, called 2006gy, and were shocked to find that it was intrinsically about 100 times brighter than typical stellar explosions.
To explain its extreme power, its discoverers invoked an unusual argument based on the creation of pairings of matter and antimatter particles inside a massive star. Some physicists say that when matter is crushed to extreme densities, it settles into a soup of individual quarks. A cubic centimetre of this new type of matter – dubbed 'strange’ would weigh as much as a billion tonnes and would have the unusual property of converting any ordinary matter that touches it into more strange matter, releasing energy in the process.
The energy released by converting the core of a star into strange matter would cause an explosion called a quark nova, observed for the first time in SN 2006gy. the event begins when a massive star blasts away its outer layers in an ordinary supernova explosion. In the process, the star's core collapses to become a dense object called a neutron star. some neutron stars last only a short time because their magnetic properties cause their spin rates to drastically slow down. Because centrifugal force can no longer support the neutron star's core, it collapses even further, transforming into strange matter.The transformation releases a tremendous amount of energy, blasting the neutron star's outer layers into space at close to light speed. The layers then slam into debris from the original supernova, creating an intense glow bright enough to explain the observations of SN 2006gy.
"Strange matter may exist or it may not, It's not proven theoretically – it's an open issue.” Evidence for the quark nova scenario could come from continued monitoring of the aftermath of SN 2006gy, which could show signs of rare elements with an atomic weight greater than 130.