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Cosmology / Relativity / Gravity Wave Astronomy

Cosmology / Relativity / Gravity Wave Astronomy

One very important space mission has already provided definite answers about cosmology, the quest to understand the origin and fate of the Universe. This is NASA's Wilkinson Microwave Anisotropy Probe, which announced its first results in 2003. We now know that the Universe is 13.7 +/- 0.2 billion years old, and that the cosmic background radiation was emitted when it was only 380 000 years old. More intriguingly, we also know that more than 70% of the mass of the Universe is "Dark Energy", and that this entity now dominates universal expansion, and that its dominance wil grow stronger and stronger with time. In a few years, we will witness the launch of the Planck Surveyor mission (ESA), which will produce the definitive map of the cosmic microwave background, enabling cosmologists to measure the fundamental constants of the Universe with unprecedented precision. In 2011, the SuperNova Acceleration Probe (SNAP) will start measuring the properties of Dark Energy itself, which will allow us to have a fairly good picture of the future of the Universe.

Astronomy has, so far, been the exclusive study of electromagnetic waves and occasionally neutrinos. Ground-based gravitational wave telescopes like LIGO and VIRGO now being completed; and space-based telescopes like LISA should open an entire new window on the Universe, by looking at the gravitational radiation being emitted by extremely large or compact sources, like double black holes, or coalescing neutron stars. By studying neutron stars orbiting black holes, LISA will test some basic predictions of general relativity (GR) to an extreme precision. Several other missions are also going to test GR and its fundamental assumptions: Gravity Probe B, launched in April 2004, and STEP, still being planned, are among the most important. The Space Interferometry Mission will test GR by measuring stellar deflection to a precision of a microarcsecond (a capacity that can also be used to search for extra-solar planets), and BepiColombo will also help testing GR because with its precise measurement of the gravitational field and motion of the planet Mercury (which was the first GR test).