New images of comet’s core might provide clues about its brightness

November 16th, 2007 - 2:14 pm ICT by admin  

Berlin, Nov 16 (ANI): New images from the Hubble Space Telescope might provide clues about the mysterious brightening of Comet 17P/Holmes.
Using the orbiting observatory’s Wide Field Planetary Camera 2 (WFPC2), astronomers monitored the comet for several days and probed its bright core, that had brightened by nearly a million fold in a 24-hour period beginning October 23 this year.
Images, snapped by the Hubble on October 29, 31 and November 4, clearly displayed the source of the brightness as the nucleus of the comet.
The nucleus, which is the small solid body that is the source of the comet’s activity, is still swaddled in bright dust, even 12 days after the spectacular outburst.
The composite colour image taken on November 1 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.
“Most of what Hubble sees is sunlight scattered from microscopic particles,” explained Hal Weaver of The Johns Hopkins University Applied Physics Laboratory of Laurel, Maryland in the US. “But we may finally be starting to detect the emergence of the nucleus itself in the final Hubble image taken on November 4,” he added.
The central portion of the Novemeber 4 Hubble 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.
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.
Although Hubble cannot resolve the nucleus, astronomers inferred its size by measuring its brightness. Astronomers deduced that the nucleus’s diameter was approximately 3.4 kilometres.
They 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.
The Hubble images however do not show any large fragments near the nucleus of Comet Holmes.
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 broke off and subsequently disintegrated into tiny dust particles after moving away from the main nucleus.
Hubble first observed Comet 17P/Holmes on June 15, 1999, when there was virtually no dusty shroud around the nucleus.
The Hubble space telescope is a joint collaboration between NASA and the ESA. (ANI)

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