... Comet Holmes Grows a Tail . ... 5.11.2007 . ... The comet has diminished in brightness only slightly , and now clearly appears to have a larger angular extent than stars and planets. ... Comet Holmes underwent an unexpected and dramatic increase in brightness starting only two weeks ago. The detail visible in Comet Holmes ' tail indicates that the explosion of dust and gas that created this dramatic brightness increase is in an ongoing and complex event. ... Publications with keywords: tail . ...