C/2001 K5 (LINEAR)

C/2001 K5 (LINEAR) was reported as an asteroid on May 17th 2001 but was placed on the NEO confirmation page as its movement was unusual. On May 27th 2002 the Tichas at Klet noticed that the asteroid was slightly difuse and thus a comet. Within a few horas of the Klet observations Tim Spahr also found the object to be cometary in appearance.

Examination of the MPC archive also found images taken by LINEAR on April 30th. The comet was magnitude 16.7 when discovered and at approximately 6AU from the Sun. The comet is dynamically new with a perihelion at 5.18AU on October 11th 2002. The nominal aphelion distance is approximately 3 light years.

Despite the large perihelion distance the comet has maintained a well-developed coma and still shows a quite large and active coma in April 2003.

The light curve

There is considerable dispersion in the light curve although the reason for this is not at all clear. The comet appears to have outburst in Spring 2002 and to have declined steadily from that maximum since then.

We can see that the rate of increase of brightness is very fast. This despite the fact that as the comet approaches and gets larger the small 10" aperture loses light.

Nominally the absolute magnitude of the comet is extremely bright (-7.7), this though is due to the fact that the comet brightened very rapidly with increasing heliocentric distance. In fact, the true size of the comet is probably somewhat larger than average, but not exceptional.

The minimum geocentric distance was reached when the comet was at opposition in June 2002 and at this point it reached its brightest magnitude. Since then, as the comet recedes from the Earth it has started to fade despite still approaching perihelion. The reason is that the decrease in heliocentric distance in the months approaching perihelion is very small and thus the comet hardly brightens intrinsically. In contrast, as the comet moves away from opposition its geocentric distance increases sufficiently to more than compensate for the slight approach to the Sun.

When we separate the observations by observer to attempt to understand the reason for the discrepancies we see some unusual inconsistencies.

Little difference is seen between the total magnitude estimates (apertures up to 30") and the estimates in the standard 10" aperture. In fact, some "CCD Total Magnitude" measures are actually fainter than the measures in a 10" aperture. There may be some strong colour effects present in the data.

 CCD observations in a 10 arcsecond aperture by:

CCD aperture photometry in apertures of 0'.2, 0'.25, 0'.2, 0'.5 by:


Última actualización 12/06/2003
Por M.R.Kidger