Analysis of past comet apparitions

55P/Tempel-Tuttle

1998


Until May we received 66 observations of 12 section members of comet 55P/Tempel-Tuttle. Adding 170 international estimates yield the following results. At perigee comet Tempel-Tuttle was an easier object than expected, especially when observed under a dark sky.

The brightness evolution was very steep but astonishingly continuous and can be best described by the formula

m = 8.3m + 5×log D + 24.7×log r

Heliocentric Magnitude development, pre-perihelion

This yields a maximum brightness of 7.8m at perigee. Prior to perihelion the brightness developed quite furious, due to the great value of n and the rapidly shrinking distance to earth. Thereafter the great value of n resulted in a very slow decline of the apparent magnitude, which reached 9.0m at the end of the apparition.

In contrast, the apparent coma diameter showed a mirror image prior and after perigee, reaching about 15' at perigee. At the start of the apparition the coma was very vague (DC 0-1), but condensed more and more in the following weeks. At perigee it was already condensed (DC 3) and continued until end of February to DC 5. At that time the apparent coma diameter had decreased to only 3', displaying a 13-14 mag weak false nucleus. The absolute coma diameter increased from 100.000 km at the last days of December to 250.000 km at perihelion.

Reports of a visually visible tail were very rare and even on photographs the comet did not display more than a faint, short gas tail.

Observations by P. Lamy and his team indicate a diameter of the nucleus in the order of 3.5 km (IAUC 6851).

Total Brightness and Coma Diameter

Andreas Kammerer

Observations


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