The most violent and energetic phenomena in the Universe include gamma-ray bursts, supernova explosions, black holes, neutron stars, and the as yet unidentified cosmic accelerators which produce the highest energy photons and cosmic rays.
Viewed in X-rays the night sky glows brightly and uniformly in all directions. The origin of this 'cosmic X-ray background' was one of two great puzzles set by the very first observations of X-rays from beyond the Solar System by Riccardo Giacconi and his team back in 1963. (For which Giacconi won the Nobel Prize in Physics in 2002 (see:Riccardo Giacconi .) To solve the puzzle required sensitive X-ray telescopes, culminating in the Chandra X-ray Observatory .
Nearly a century after their 1912 discovery by Victor Hess the origin of these energetic particle streaming to us from space remains controversial. Where in the universe is there an accelerator far more powerful than anything we can build on Earth? Supernova remnants, young stars, microquasars and even quasars have been suggested.
As a rapidly spinning young neutron star (a "pulsar") slows down, it deposits its enormous reservoir of rotational energy into its environment via a relativistic wind, producing an observable pulsar wind nebula (PWN). PWNe are a rich source of information. Most fundamentally, they provide a direct probe of the high-energy processes through which a neutron star's considerable reservoir of rotational energy is eventually deposited into its environment.
Little known Astronomy facts (secrets): When neutron stars were first discovered by astronomers, they were called 'LGM' - for Little Green Men. This was because they were found be be sending out very fast, very bright, periodic radio pulses, and different ones were pulsing at different speeds - they actually looked like they might be space beacons, similar to lighthouses, that space-faring LGM were using as navigational aids. We know now that they are a perfectly natural (not engineered) phenomenon, but they are still highly interesting and exotic.
The Milky Way contains a few hundred million black holes, which were formed by the collapse of very massive stars. Each of these stellar black holes weighs about 10 times as much as our sun. A very few of these black holes are closely orbited by an ordinary star that is slowly bleeding matter onto the black hole. As this gas falls toward the black hole, it is heated by strong gravity and friction to a temperature of millions of degrees thereby producing a brilliant source of X-rays that is brighter than 10,000 suns.
The most luminous beacons in the the universe are quasars. They are powered by the release of gravitational energy as matter falls onto supermassive black holes at the centers of galaxies. This energy release is far more efficient than the nuclear fusion reactions that power stars, so that quasars can be seen all the way across the observable universe.
Supernova remnants (SNRs) have long been considered the primary sites for the acceleration of cosmic rays up to 10 TeV. The evidence lending support to this belief is based on several strong arguments. First, supernova blast shock are one of the few galactic sites capable of sustaining the cosmic ray population against loss by escape and nuclear interactions.
Jets and shocks are important topics in modern astrophysics. Newly-formed stars eject highly collimated jets of gas into molecular clouds. When a massive star explodes, its rapidly expanding atmosphere produces a shock wave in the surrounding material. SSP scientists use observations and theory to study the formation and evolution of jets and shocks.
Theoretical studies support astronomical observations at all wavelengths, directly address topics of astrophysical importance, and pursue related studies in fundamental physics and atmospheric science.