Project overview
The Large Observatory for X-ray Timing (LOFT) is a proposed space mission that has passed the first hurdle for launch by the European Space Agency. We plan to help develop the mission concept further, with the eventual goal of having the mission built and launched into space. The key goal of the mission is to be the best observatory ever built for measuring the variability of the rate at which X-rays are emitted by objects in space, and to that end, LOFT's detectors would be 20 times bigger than those of the biggest X-ray mission ever launched. X-rays from space are especially interesting because they come from only the most energetic particles - those produced in the hottest regions of space, or in shocks taking place at very close to the speed of light. X-rays are produced predominantly in the vicinity of black holes and neutron stars. Black holes are regions of space where the density of matter is so large that light cannot escape. However, when material falls into a black hole, a huge amount of gravitational energy is released, and the material can become extremely hot right before falling in, giving off X-rays. Neutron stars are the densest stars in the universe from which light can escape. They have masses a little larger than the Sun's and radii the size of a city. A teaspoon of neutron star material weighs as much as an elephant. At such high densities, the laws of physics cannot be tested in a laboratory - neutron stars offer unique opportunities to understand the fundamental force laws in a manner which cannot be done in a particle accelerator like the one at CERN. In much the same ways that measurements of the seismic waves from earthquakes have given scientists a means to understand what's inside the Earth, the variations in the X-ray brightnesses of the regions of space near black holes and neutron stars can act to help us understand how matter is falling into black hole or onto neutron stars, or what the internal structures of neutron stars look like. X-ray satellites to date have only scratched the surface of what can be learned from X-ray variability measurements. Furthermore, X-rays do not penetrate the Earth's atmosphere. Therefore, unlike optical and infrared light, which can be observed from ground-based telescopes, X-ray astronomy genuinely requires space-based observatories.