The image was created by compositing 11 individual ACIS-I exposures for a cumulative exposure time of over one million seconds, in the period 1999–2000, by a team led by Riccardo Giacconi.[2] This region was selected for observation because it has much less galactic gas and dust to obscure distant sources.[3] Further observations taken between 2000 and 2010 have resulted in a total of exposure of over four million seconds.[4] An additional four million seconds of exposure are scheduled to be undertaken by the end of 2015, resulting in an integrated exposure time of eight million seconds.