Group items tagged

This is not just a pretty picture, however – the image packs a lot of scientific information. The authors extract the mass distribution in the cluster (which has implications for cosmological models), measure the mass-to-light ratio of the bright galaxy in the center of the cluster, and use the magnifying power of the lens to search for even more distant galaxies. The basic idea is to construct a model of the lens, starting with the cluster galaxies and a dark matter halo; then refine the model to reproduce the multiple images that are seen. Using this refined model it’s possible to predict the location of additional images of a given source, and to identify regions of high magnification that can then be examined for multiple images of other sources. Any additional images that are found can be used to further refine the model and so on.

This galaxy has been lensed by the warp in spacetime created by the cluster. Light from the galaxy, which lies almost directly behind the center of the cluster but much farther away from us, travels along several curved paths through the cluster lens, producing multiple magnified images of the galaxy. The inset box shows a computer generated model of the unlensed source galaxy, enlarged by a factor of four so that the details, including the spiral arm structure, are visible. Without the lensing power of the cluster, we would see this galaxy as a single small blue smudge. In general, lensing will both magnify and distort (shear) images of a background source. This lens is fairly unique in that we see large but relatively intact images of the spiral galaxy, which implies that the mass distribution in the central region of the cluster must be nearly uniform.

First things first, neutron stars, quark stars and black holes are all born via the same mechanism: a supernova. But each of the three are progressively more massive, so they originate from supernovae produced by progressively more massive stars. So, what if a star exploded, producing something a little too massive to be called a neutron star? Well, neutron stars resist collapsing under their own gravitational pull by a characteristic of matter known as neutron degeneracy. This produces an outward force called neutron degeneracy pressure. What if the neutron star born after a supernova is too massive for this neutron degeneracy pressure to hold up against the neutron star's own gravity? In this case, it's up to the quarks that make up the neutrons to take over, preventing the body from collapsing any further. Single neutrons are composed of three quarks (two "down" quarks and one "up" quark). When quark degeneracy pressure kicks in, a quark star may be produced; the free "up" and "down" quarks get converted into "strange" quarks. Therefore, a quark star (also known as a "strange star") is made up of strange matter.

Using what we know from the Standard Model of particle physics, a massive quark star may have enough gravitational energy to start 'burning' strange matter. The quarks inside the core of the quark star may be abused so badly by gravitational pressure that the quarks will be converted into pure energy and neutrinos.

The fascinating thing with this scenario is that the quark star matter will be so dense that even the neutrinos cannot escape. However, this release of energy and generation of neutrinos creates an outward pressure countering the relentless inward gravitational pull.