Change of comet Holmes (from Oct 27 to Feb 1, 2007)
Continuous composed image of comet 17P/Holmes (from Oct 27 to Dec 14, 2007)
Continuous composed image of comet 17P/Holmes (from Dec 31, 2007)
Fig.1 Change of apparent angular diameter of comet Holmes
white...angular diameter of dust composition yellow...that of greenish ionized composition
Fig. 2 Change of real diameter of comet Holmes
white...real diameter of dust composition yellow...that of greenish ionized composition
Fig. 3 Change of expansion velocity of comet Holmes
This page shows you a continuous composed comet Holmes image and figures indicating the change of coma diameter.
Fig.1 shows the change of apparent diameter measured from individual images, and the change of real diameter calculated from geocentric distance is shown in Fig.2.
We can see that the diameter has almost zero on Oct 24 by extrapolating the diameter vs. time line, the day is almost coincident with that when the comet Holmes had the outburst.
The apparent and real diameters of comet are increasing with time proportionally; the change rate can be estimated about 1.35 arc minutes per day (=95 thousand kilometers per day).
This expanding velocity is equivalent to 2,000 km/h (1,250 mph).
The Fig.3 shows the change of expansion velocity of coma, and the velocity has begun to decrease on and after Nov 16.
It may be apparent effect because the outer region of coma has distributed and been invisible,
but need to chase the change still more to secure conclusive evidence of this fact.
In the year of 2008, the comet has been getting dimmer and dimmer slightly.
And the real expansion velocity is almost stable at about 77,000km/day(=48,000miles/day), a bit decreased from just after its outburst.
(added a postscript on Feb 3, 2008)
This page will be updated during observing period of comet. (last updated on Feb 24, 2008)