The New Scientist has a couple of stories up on neutron stars, the ultradense leftovers of exploded stars that don't have enough mass to form a black hole. Both are interesting in that they show just how much information can be conveyed in the sudden and brief bursts of energy that sporadically erupt from these objects. The first article delves into the phenomenon of short gamma-ray bursts, some of which are thought to be produced by the collision and fusion of two neutron stars. Thanks to the Swift observatory, more of these bursts are being observed, and the profile of the gamma-ray emissions is allowing an estimation of the energy released. Observations by the Swift suggest that some bursts do not radiate evenly, instead shooting out jets of energy. This limited spread of energy lowers to total estimated output down to levels consistent with their source being a neutron star collision. Other bursts radiate in all directions, and so must have a more powerful source, but the article doesn't suggest what those sources might be.
Meanwhile, another high-energy observatory, the Rossi X-ray Timing Explorer, has revealed details about the structure of intact neutron stars. Intact, but not stable, that is. One particular neutron star showed some variation in its output that the researchers suggest is the remnant of a star-quake, an earthquake-like event thought to be caused by the star's intense magnetic fields ripping open its own crust. The lingering variation appears to be caused by the shock waves from this event rebounding within the star. Just like on Earth, these shock waves can tell us something about the internal structure of the star, namely that it has a crust about 1.5km thick, which takes up 15 percent of its 20km diameter. By coming to grips with the crust, the researchers hope to understand what's under it, as some have proposed the intense gravity there wipes out the boundaries of regular atomic components, and leaves a plasma of free-moving quarks behind.