* Astronomy

Blobrana · L

RE: Comet Hale-Bopp

Blobrana · L

Title: Cometary activity at 25.7 AU: Hale--Bopp 11 years after perihelion
Authors: Gy. M. Szabo, L. L. Kiss, K. Sarneczky

Eleven years after its perihelion, comet C/1995 O1 (Hale-Bopp) is still active. Between October 20--22, 2007, we detected a diffuse coma of 180x10³ km in diameter with a slight elongation toward N/S direction. The integrated brightness was 20.04 mag in R_C, implying Af
ho=300 m and albedo x dust surface a_RC=4300 km². The coma was relatively red at V-R=0.66 mag, which is consistent with that of the dust in other comets. The observed properties and the overall fading in brightness between 10 AU and 26 AU follow the predicted behaviour of CO-driven activity (Capria et al. 2002). This is the most distant cometary activity ever observed.

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Blobrana · L

In 1997, Comet Hale-Bopp's intrinsic brightness exceeded any comet since 1811. Since it peaked on the other side of the Earth's orbit, however, the comet appeared only brighter than any comet in two decades. Visible are the two tails shed by Comet Hale-Bopp.

The blue ion tail is composed of ionized gas molecules, of which carbon monoxide particularly glows blue when reacquiring electrons.
This tail is created by the particles from the fast solar wind interacting with gas from the comet's head. The blue ion tail points directly away from the Sun.
The light coloured dust tail is created by bits of grit that have come off the comet's nucleus and are being pushed away by the pressure of light from the Sun.
This tail points nearly away from the Sun.
The photograph was taken in March 1997.