Hale Bopp

The Observatoire de Haute-Provence

We have recently observed rapid changes in the inner coma of Hale-Bopp: dust shells become less visible, whereas new radial jets are growing around the nucleus. This new coma structure looks like to the february one's (see below).

On May 8, 1997, a huge concentration of dust is ejected from the nucleus toward the anti-solar direction. (Hale-Bopp on May 8, 1997 at 19h44 UTC. Sum of 5 exposures of 2s each, with I filter, unsharp masking. Field of view: 3.6'x3.6'. North is on left, East is up.)

The two following sequences show the evolution of the coma on three days. On the first sequence, we can see three original images obtained with an infrared filter on May 7, 8 and 9. The last sequence shows the corresponding rotational-shift-difference processed images. The speed of ejection is very high. 24 hours after the ejection, the dust spreads on over 50000 km from the nucleus.

Lastly, we can note the rapid expansion of the curved jet (in the direction of the sun). On May 9, this jet is twice longer than on May 7.

This dust ejection doesn't appear at each nucleus rotation, so it's certainly an unique and an exceptional phenomenon.