Advanced LIGO subsystems
are the organizational units of the overall project. Follow the links below to view the mission and progress of each subsystem.

Auxiliary Optics Core Optics
Data Acquisition Data and
Input Optics

Advanced LIGO Science Impacts

The scientific program for LIGO is both to test relativistic gravitation and to open the field of gravitational wave astrophysics. More precise tests of General Relativity (and competing theories) will be made. LIGO will enable the establishment of a brand new field of astronomy, using a completely new information carrier: the gravitational field.

Initial LIGO represents an advance over all previous searches of two or three orders of magnitude in sensitivity and in bandwidth. Its reach is such that, for the first time, foreseeable signals due to neutron-star binary inspirals from the Virgo Cluster (15 Mpc distant) would be detectable. At this level of sensitivity, it is plausible, though not certain, that the first observations of gravitational waves will be made. If signals are not observed with initial LIGO, we will have set challenging upper limits on gravitational wave flux, far beyond the capability of any previously existing technology.

The Advanced LIGO interferometers proposed here promise an improvement over initial LIGO in the limiting sensitivity by more than a factor of 10 over the entire initial LIGO frequency band. It also increases the bandwidth of the instrument to lower frequencies (from ~40 Hz to ~10 Hz) and allows high-frequency operation due to its tunability. This translates into an enhanced physics reach that during its first several hours of operation will exceed the integrated observations of the 1 year LIGO Science Run. These improvements will enable the next generation of interferometers to study sources not accessible to initial LIGO, and to extract detailed astrophysical information. For example, the Advanced LIGO detectors will be able to see inspiraling binaries made up of two 1.4 M neutron stars to a distance of 300 Mpc, some 15x further than the initial LIGO, and giving an event rate some 3000x greater. Neutron star - black hole (BH) binaries will be visible to 650 Mpc; and coalescing BH+BH systems will be visible to cosmological distance, to z=0.4.

The existence of gravitational waves is a crucial prediction of the General Theory of Relativity, so far unverified by direct observation. Although the existence of gravitational radiation is not a unique property of General Relativity, that theory makes a number of unambiguous predictions about the character of gravitational radiation. These can be verified by observations with LIGO. These include probes of strong-field gravity associated with black holes, high-order post-Newtonian effects in inspiraling binaries, the spin character of the radiation field, and the wave propagation speed.

The gravitational wave "sky" is entirely unexplored. Since many prospective gravitational wave sources have no corresponding electromagnetic signature (e.g., black hole interactions), there are good reasons to believe that the gravitational-wave sky will be substantially different from the electromagnetic one. Mapping the gravitational-wave sky will provide an understanding of the universe in a way that electromagnetic observations cannot. As a new field of astrophysics it is quite likely that gravitational wave observations will uncover new classes of sources not anticipated in our current thinking.

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