ZetaTalk: Hale-Bopp sci.astro debates: European Southern Observatory

http://www.hq.eso.org/
The Enormous Size of Comet Hale-Bopp
30 August 1995

In order to better show the real extent of the surrounding coma, ESO Press Photo 24B/95 displays a photographically enhanced copy of the original plate. In this process, the contrast has been greatly increased so that even very faint areas of the diffuse coma become visible. The comet now appears as a roughly circular, dark object in the front of myriads of stars in this sky area

Recent News and Observations
http://encke.jpl.nasa.gov/RecentObs.html
Charles S. Morris / [email protected]

1995 Sept. 30

At 67x, the comet looked like it had a stellar nucleus, but at 156x this resolved into a small knot of material.

1995 Sept. 23

Bob Ross and Tom Johnston at Edwards, Colorado report - in the 36" at 250x, the comet showed an off center core with stellar nucleus, fan pointing NE. coma about 1.5' diameter.

1995 Sept. 16

On the second night, there was a stellar nucleus ... that wasn't there the first night.

1995 Aug. 25

Do not be confused by the coma diameters. The measured diameter is at the point of the central condensation (or stellar nucleus) and is measured perpendicular to the tail. The coma fans out behind this point (into the tail) which makes the coma look larger. In general, the coma is much smaller than a week ago. Be advised that the massive photometric outburst which occurred earlier this week seems to have permanently altered the general appearance of Comet Hale-Bopp. The object now consists of an extremely faint, diffuse coma (essentially DC=0) which is somewhat elongated N-S. Offset south of the coma's center is an intense, not-quite-stellar nucleus which totally dominates the object.

1995 Aug. 25

Why is Comet Hale-Bopp now so bright?
25 August 1995

It is in fact likely that most of the light observed from the central condensation in the comet's head is sunlight reflected from the particles in this cloud. The nucleus is probably completely hidden from view inside this cloud and we do not see it at all.

When we cannot observe the nucleus of a comet directly, we can only judge its size indirectly from the amount of dust it produces; a larger dust production will normally correspond to a larger nucleus. However, a temporarily high dust production rate during an outburst from the nucleus will lead to an overestimate of its size. In this case, the comet's brightness will begin to fade after a while, as the dust particles ejected during the outburst slowly disperse into space.

Comet Hale-Bopp Is Coming!
By Edwin L. Aguirre
November 1995

Comet Hale-Bopp was easy to mistake for a globular cluster, several of which are identified by Messier or NGC numbers in this Sky & Telescope finder chart. Stars are shown down to 9th magnitude.

Veteran comet watchers Charles Morris and John Bortle, observing at about 70x with a 10- inch reflector from Lockwood Valley, California, and with a 16-inch reflector from Stormville, New York, respectively, also witnessed bewitching nuclear changes. They saw the comet's pseudonucleus evolve from a small, weak condensation within the coma on August 19th to a perfectly stellar, 12th-magnitude point the following night. "The comet seems to be undergoing continuous outbursts one after another, and there is no sign that this activity is letting up," according to Morris.

Correction on Comet Hale-Bopp Jet
Miquel Serra
October 3, 1995

I have good and bad news. First the bad ones. The bad news is that further analysis of previous images (reported in the IAUC) and more images taken tonight has shown that the apparent "rotation was due to the unfortunate juxtaposition of a star with the jet in rather poor seeing. It is now obvious that there is no detectable rotation of the jet and that this may, possibly, be a renewed outbreak of the previous active region. And the good ones are that we have made a new arm movie with images taken on 3th October showing (another time) the jet expansion. Please correct our previous conclusions.