  Light from thermal black body radiators such as stars exhibits photon
bunching behaviour at sufficiently short timescales. However, with available
detector bandwidths, this bunching signal is difficult to be directly used for
intensity interferometry with sufficient statistics in astronomy. Here we
present an experimental technique to increase the photon bunching signal in
blackbody radiation via spectral filtering of the light source. Our
measurements reveal strong temporal photon bunching in light from blackbody
radiation, including the Sun. Such filtering techniques may revive the interest
in intensity interferometry as a tool in astronomy.
