Skip to Navigation | Skip to Content

Astronomical Observatory: Cool Images

The Expanding Dust Shell of Comet 17P/Holmes, L. Molnar

Comet Holmes:
Comet Holmes: 28 October
Comet Holmes: 29 October
Comet Holmes: 30 October
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 yellow color indicates sunlight scattered off of dust. Hence we are seeing the expansion of a cloud of dust. The first graph below shows the expansion of the outer edge of the cloud: a speed of 660 m/s. By the last image, the dust cloud has a diameter 5 times that of Jupiter, the largest planet.

Notice a blob of dust ejected out to the southwest (lower right). It is moving away from the comet center with a transverse speed of 130 m/s (see the second graph below). It seems to have been launched a day or so after the outburst began.

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).

Go back to our Comet Holmes home page or on to our Expanding Gas Cloud page.

Expansion of Comet Holmes Dust Cloud

Motion of Comet Holmes Dust Blob

Right Ascension (J2000) 03h 51m 51s (the first night)
Declination (J2000) +50 13' 42" (the first night)
Dates observed
  1. 27 October 2007, 05:52
  2. 28 October 2007, 03:31
  3. 29 October 2007, 02:32
  4. 30 October 2007, 03:45

(All times Universal Time = EST + 5 h)

Filter used Red, green and blue (RVB)
Exposure times

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




Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Nulla ut nibh.


Lorem ipsum dolor sitamet, consectetuer adipiscing elit. Nulla ut nibh.