Current Status of Gravitational Wave Astronomy

Gravitational waves were predicted by Albert Einstein almost 100 years ago, but have not been detected directly until now. A recent report by the BICEP2 team on evidence for primordial gravitational waves that may have arisen during the inflationary phase has highlighted the importance of gravitational waves in an astrophysical context. Currently experimental facilities such as LIGO (US) and Virgo (Europe) are undergoing major upgrade for sufficient sensitivity to observe gravitational waves directly, and KAGRA (Japan) is under construction. The most likely event to be observed first is the merger of a binary composed of neutron stars and/or black holes by using advanced configurations of the above detectors that will become available in a few years. In this article, we describe the current status of gravitational-wave research and the outlook for gravitational-wave astronomy which utilizes gravitational waves as one of the messengers that carry information from astrophysical objects to us.