These images taken by the NASA/ESA Hubble Space Telescope reveal Comet Holmes’s bright core. The images show that the coma, the cloud of dust and gas encircling the comet, is getting fainter over time. The coma was brightest in the image taken on 29 October 2007. It was two times fainter than on 31 October and nine times dimmer on 4 November (compared to the observations on 29 October).
The coma is getting fainter because it is expanding. A huge number of small dust particles were created during the 23 October outburst. Those particles have since been moving away from the nucleus and filling interplanetary space. The coma therefore is becoming more diffuse over time.
The nucleus, however, is still active and is producing a significant amount of new dust. So the region around the nucleus is still much brighter (at least 10 times brighter) than it usually is at this point in the comet’s orbit.