The Expanding Gas Cloud of Comet 17P/Holmes , L. Molnar
|Full color images of Comet Holmes taken October 27, 28, 29, and 30, 2007|
The four images above were taken 3-6 days after the outburst of Comet 17P/Holmes began. The cyan color indicates emission from gas molecules such as CN, C3, C2 and NH2. Hence we are seeing the expansion of a cloud of gas. (The central portions of each image are saturated--this is the brightly reflecting dust from the comet.) The graph below shows the expansion of the outer edge of the cloud: a speed of 1500 m/s. By the last image, the dust cloud has a diameter 11 times that of Jupiter, the largest planet.
On the 27th, the comet was 150 million miles from Earth. The physical size of the solid nucleus (likely a dark object) is estimated to be no more than 10 km across (about the size of the city of Grand Rapids).
|Right Ascension (J2000)||03h 51m 51s (the first night)|
|Declination (J2000)||+50 13' 42" (the first night)|
(All times Universal Time = EST + 5 h)
|Filter used||Red, green and blue (RVB)|
Average of 30 images, each 1 second the first night, 2 seconds the second and third nights, and 5 seconds the last night.
Daniel W. E. Green, 2007a October 24, International Astronomical Union Circular No. 8886. "Comet 17P/Holmes" [Official announcement of the discovery of the 2007 outburst]
Daniel W. E. Green, 2007b October 26, International Astronomical Union Circular No. 8887. "Comet 17P/Holmes" [First measurements of the comet's light spectrum]
Gary W. Kronk. updated October 2007. "17P/Holmes" [A page within a cometography website with both historical information and current images.]
Seiichi Yoshida. "17P/Holmes (2007)" [A plot of the comet brightness with time.]
Content posted 31 October 2007, by L. Molnar