Astrophysics: Gravitation
Faculty
in this area of research:
Gravitational
astrophysics research at MIT focuses on experimental detection of
gravitational radiation as well as theoretical investigations supporting
this research.
MIT and
Caltech have jointly developed the first gravitational-wave observatory,
LIGO (Laser Interferometer Gravitational wave Observatory). Current
estimates of the gravitational wave strain from posited astrophysical
sources (such as supernova explosions, black-hole formation, merging
of neutron stars, and primeval cosmic background fluctuations) require
a strain sensitivity smaller than 10 to the -20 in the 10 Hz to
1 kHz band. To achieve these sensitivities, a very large baseline
system is needed; LIGO comprises two sites separated by continental
distances. Each contains Michelson interferometers in an L-shaped
vacuum system with 4km-long baselines. The interferometers are operated
in coincidence, so as to reject the noise from local environmental
perturbations. Eventually, LIGO may form a network with European,
Japanese, and Australian interferometers to measure the polarization
of the waves and determine source location with sufficient precision
to allow identification by electromagnetic astronomy (radio, optical,
X-ray, and gamma-ray).
MIT faculty
and research staff in the MIT
LIGO laboratory including Rainer
Weiss and Nergis
Mavalvala are working to improve the strain sensitivity of the
initial LIGO interferometer (LIGO-1). Erik
Katsavounidis is developing and applying data analysis algorithms
to search for gravitational wave burst sources. Plans are to upgrade
LIGO with more powerful lasers and improved noise reduction techniques
(LIGO-2) so that its sensitivity will allow detection of coalescing
binary compact objects routinely within a few hundred million light
years distance of the earth.
MIT faculty
are also conducting theoretical research in support of gravitational-wave
astronomy and related areas of gravitational astrophysics.
Scott A. Hughes is computing gravitational waveforms from stars
that spiral into the rapidly rotating, supermassive black holes
lying in the centers of galaxies. Edmund
Bertschinger is studying the dynamics of perturbed relativistic
accretion disks around black holes and neutron stars in order to
better understand the time-variability of X-ray sources.
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