Comet Holmes

From Hubble site here.

Hubble first observed Comet 17P/Holmes on June 15, 1999, when there was virtually no dusty shroud around the nucleus. From that observation, astronomers deduced that the nucleus had a diameter of approximately 2.1 miles (3.4 kilometers), about the length of New York City's Central Park. Astronomers hope to use the new Hubble images to determine the size of the comet's nucleus to see how much of it was blasted away during the outburst.

Hubble's two earlier snapshots of Comet Holmes also showed some interesting features. On Oct. 29, the telescope spied three "spurs" of dust emanating from the nucleus, while the Hubble images taken on Oct. 31 revealed an outburst of dust just west of the nucleus.

The Hubble images, however, do not show any large fragments near the nucleus of Comet Holmes, unlike the case of Comet 73P/Schwassmann-Wachmann 3 (SW3). In the spring of 2006 Hubble observations revealed a multitude of "mini-comets" ejected by SW3 after the comet increased dramatically in brightness.

Ground-based images of Comet Holmes show a large, spherically symmetrical cloud of dust that is offset from the nucleus, suggesting that a large fragment did break off and subsequently disintegrated into tiny dust particles after moving away from the main nucleus.

From NASA here.