The Neutron Star

I've always been interested in discovering the fundamental properties of the most basic of matter, but had never thought to look to the skies. The neutron star is absolutely phenomenal. When a Supergiant doesn't create enough pressure from its core,  it collapses. A neutron star is formed when a degenerate core of a Supergiant nears a limit, the Chandrasekhar limit, and collapses. The core is so massive, that the gravitational force-which is normally much weaker than the strong force- overpowers and pulls the matter closer. Even though there is no fusion within the core, there is still neutron degeneracy pressure that holds the star up. While they are no where near as massive as Supergiants, if there were even a modest neutron star of 1.4 M (that's about 10^57 neutrons) with a radius of about 10 Km, it's average density (deeper in the core has an even greater density) would be 6.65e17 Kg m^-3. This is huge even compared to the typical density of the atomic nucleus of 2.3e17 Kg m^-3. Such a mass would result in the acceleration of an object due to gravity to be 1.86e12 m s^-2 or 190 BILLION times that of Earth. This is so big that if one were to drop an object from a mere meter above the surface of a neutron star, using classical Newtonian mechanics, the object would crash into the surface at a speed of 1.93e6 m/s or .06 times the speed of light. This means that the result of so much mass in a compressed volume requires an accurate description of a neutron star to necessarily include special and general relativity.
It is clear hat such high densities have an odd effect on matter. The fluid of free neutrons within the neutron star can spontaneously pair, changing into bosons, such that they no longer are restricted by the pauli exclusion principle. This is significant because it means that this fluid could be a superfluid, one which has no resistance. So a swirling puddle of free neutron pairs could spin forever without ever slowing down. Also, as density continues to increase, it is possible for both the pairing of neutrons and protons to create a superconductor that carries no electrical resistance.

Galactic Car Crash

Above: Abell 520   Green: Hot gas which is evidence of collision. Blue is where majority of mass is, which is dominated by dark matter. Starlight from galaxies, derived from observations by the Canada-France-Hawaii Telescope, is colored orange

It is not terribly uncommon for galaxies to collide with one another, but astronomers using data from the Hubble space telescope have observed a puddle of dark matter left behind from two massive cluster galaxies. `There is a very low density of stars within galaxies. The galaxies are filled with different gases and when two galaxies collide, it is likely that the stars pass by each other without interacting, but generally the gas collides and is left behind. the results found involving dark matter, however, could challenge current theories about dark matter that predict galaxies should be anchored to the invisible substance even during the shock of a collision. While dark matter may be invisible, the effects can be seen. Dark matter can bend light moving by, essentially magnifying objects behind it called lensing. This technique led to a puzzle when observing Abell 520 though; the dark matter in  had collected into a "dark core," containing far fewer galaxies than would be expected if the dark matter and galaxies were anchored together. This means that many of the galaxies originally with the dark matter has gone drifting somewhere else. This challenges our understanding of dark matter which means more research and innovative ideas will have to be created to better understand dark matter. The current problem however is that there are not very many collisions between local galaxies which is the primary way of studying how dark matter effects its surroundings. The other main galaxy cluster, the bullet cluster, is inconsistent with Abell 520. The dark matter and the galaxies bound to it were different in each case. The different instances could mean that "some" dark matter is sticky and smashes with dark matter- slowing it down, while other types of dark matter can pass through each other without interacting much. One other possible issue from abell 520 is the limitation of hubble. It is entirely possible that there are in fact galaxies within abell 520, but they are so relatively faint that hubble is not able to resolve them.

Astrophysics Experiment for Grating and Imaging Spectroscopy,

Astrophysics Experiment for Grating and Imaging Spectroscopy (AEGIS), is a concept for a high-throughput, high-resolution, moderate cost, X-ray spectrometer. This is for a new high energy astrophysics mission proposed to NASA. High resolution spectroscopy has enhanced much of our astrophysical knowledge and AEGIS should have over 40 times the resolution in its .2-1 Kev (100-600nm) range compared to other projects such as the XMM-Newton RGS or Chandra Gratings. Greater resolutions allows AEGIS to distinguish between multiple bright light sources that are close to each other while also allowing more precise measurements. AEGIS will be the first observatory with sufficient resolution at E < 1 KeV to resolve thermally broadened lines in hot plasmas (T>10^7K) AEGIS will be able to observe so well because it uses advanced X-ray optics. The results from AEGIS, along with Hubble, will give an accurate description of the intergalactic medium. By observing light at high energies, AEGIS may be able to answer questions about: large scale structures and their evolution, how matter behaves near high density objects such as neutron stars, and what happens close to high gravity objects like black holes.