Comet Hale-Bopp images obtained

with the 0.8-m telescope

of the Observatoire de Haute-Provence

last update May 11, 1997

The images of Comet Hale-Bopp were taken with a CCD TK 512x512 at the Cassegrain focus (F/D=15) of the 80 cm telescope of the Observatoire de Haute Provence. Picture sampling: 0.42"/pixel, field 3.6'x3.6'. Pictures processed with ESO-MIDAS and QMiPS32 softwares.

Hale-Bopp between May 7 and May 9, 1997 :

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.

Hale-Bopp between Apr. 14 and Apr. 21, 1997:

Twenty days after its perihelion, Hale-Bopp becomes gradually fainter, but it keeps a strong activity. Famous concentric dust hoods and spriral jets are again easily visible.

The two following Hale-Bopp images have been obtained on April 18, 1997 with the 0.8-meter telescope at the Observatoire de Haute-Provence, behind a "dust" narrow band filter (on the left) and a CN filter (on the right). The "dust" filter blocks all gaseous emissions spectrum-lines, whereas the CN filter is centered on the cyanid (CN) emission line at 387.1 nm. Contrary to the "dust" image, CN images shows a strange spiral jet in the other side of dust shells.

Hale-Bopp on Apr.18, 1997, 19h30 UTC. Sum of five 20s-exposures, with a "dust" filter (centered on 484.5 nm, FWHM= 6.5 nm). Field: 3,5'	Hale-Bopp on Apr.18, 1997, 19h45 UTC. Sum of eleven 40s-exposures, with a CN filter (centered on 387.1 nm, FWHM= 5 nm). Field: 3,5'
"Dust" image after a rotationnal-shift-difference processing. Over six dust shells are visible.	The same processing used on the CN image. A large spiral jet in visible on the opposite side of the sun.

This long spiral jet surrounding inner coma on over one whorl is also visible on B, V and R filtered images taken on April 14. These spectal bands are larger and contain several gaseous emisions lines. So, CN is not the only component of this spiral jet, all cometary gas are probably present in the jet.

Other images showing this spiral jet have also been obtained at the Pic-du-Midi Observatory.

Hale-Bopp on Mar. 26, 1997, 19h10 UTC:

In few days, Hale-Bopp will reach its maximum of activity. Its magnitude is now about -0.7 ! Hale-Bopp is spectacularly visible with naked-eye, even from big cities. We can easily see the white dust tail and the blue gaseous tail on over 20°.

Three concentric dust shells are now visible with a small telescope.

Result of a sum of three 10s-exposures with a red "dust" filter (684 nm), showing a dust jet curved by the nucleus rotion. Field of 3'x3', North is down, East is on the right.

A logarithmic LUT gives a more visual look.

Hale-Bopp on Mar. 12, 1997, 4h55 UTC:

Sum of seven 10s-exposures with a red "dust" filter (684 nm) showing a spiral dust jet in the inner coma. The nucleus rotation axis is aligned with the line of sight, so the speed nucleus rotation (period of 11.47 hours) give some spiral dust jets. Field of 3'x3', North is down, East is on the right. Observer: Luc Arnold.

The same image after a logarithmic LUT. You can compare this visual look CCD image with Luc Arnold's drawings.

Hale-Bopp between Jan. 30 and Feb. 12, 1997:

A must-see: two animations of Hale-Bopp (animated gif) !!!

Formation of a new dust envelope close to the nucleus (from Jan. 30/97 to Feb. 12/97).

Expansion of the outside envelopes (from Jan. 30/97 to Feb. 12/97)

Comet Hale-Bopp becomes brighter and brighter. To the naked eye, its nucleus appears as a blurred star, magnitude 3, in the vicinity of Altaïr, the tail is perfectly visible on more than 5 degrees toward Vega.

At the focus of a telescope the inner coma appears as an elongated kidney shape perpendicular to the direction of the sun. At each end two powerfull dust jets take off and curve under the solar wind. The concentric envelopes are more contrasted and in greater number than before, they become really visible on original pictures.

Opposite, a rotational-shift-difference processing shows 10 jets at least (p.a. 28°, 86°, 108°, 138°, 167°, 209°, 288°, 315°, 337° et 358°).

A comparison of images taken between Jan. 30/97 and Feb. 9/97 does not show any noticeable rotation of the dust jets, because the line of sight has not moved during this period.

Opposite image processed with a unsharp-masked technique shows the complex structure of the coma on Feb 7/97, at 5:30 UTC. Eight or nine envelopes circle the nucleus in a parabolic shape locally disturbed by powerfull dust jets. Envelopes are 9" apart (about 12 300 km.). An envelopes expansion is clearly visible on an images sequence processed by unsharp-masked technique. Thus the period for a new envelope to be formed seems to be about 5.2 day. The real period is about 11.47 hours, and has been measured by J. Lecacheux, F. Colas and L. Jorda at Pic-du-Midi Obervatory. On this sequence, we see a stroboscopic visual effect.

On the following images sequence, we witness the "live" birth of a new envelope next to the nucleus. A blanket of dust is ejected toward the South-West (P.A.=209°). Picture field: 57"x70", the North is on the right and the East is at the bottom.

This periodic formation of dust envelopes is quite a mystery. We can think of a nucleus area becoming periodically very active with each exposition to the sun.