The NASA/ESA Hubble Space Telescope has probed the bright core of Comet 17P/Holmes which, to the delight of sky watchers, mysteriously brightened by nearly a million-fold in a 24-hour period beginning October 23, 2007. Astronomers have used Hubble's powerful resolution to study Comet Holmes core for clues about how the comet brightened. The orbiting observatory's Wide Field Planetary Camera 2 (WFPC2) monitored the comet for several days, snapping images on October 29, 31 and November 4th. Hubble's crisp 'eye' can see details as small as 54 kilometres across, providing the sharpest view yet of the source of the spectacular brightening. The Hubble image at right, taken on November 4, 2007 shows the heart of the comet. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a 'bow tie' appearance. The composite color image at left, taken November 1st by the amateur astronomer Alan Dyer, shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side. (UPI Photo/NASA/ESA/H.Weaver/John Hopkins)