Comet 73P/Schwassmann-Wachmann 3 (SW3) Bulletin #4

Michael L. Sitko, University of Cincinnati & Space Science Institute

 

 

As of April 21, 39 fragments have received official designations. After exhausting the single letters of the alphabet, the Minor Planet Center has apparently decided to follow the naming convention used for variable stars, adding AA, AB, ÉAP.

 

Major Fragments:

 

C continues to remain relatively stable, but seems to be lagging somewhat behind the magnitudes originally predicted.

 

From Seiichi YoshidaÕs web site http://www.aerith.net/comet/catalog/0073P/2006.html, posted on April 23.

 

 

The detachment observed in B is now well-separated from the main nucleus (see below). The remnant is about 2/3 as bright as the main component right now, but will probably fade.

 

 

B as observed by R. Legustri on April 21 UT

 

 

Images by Carl Hergenrother suggest that G may be undergoing complete disintegration, but the same prognosis was once applied to B.

 

CREATOR: XV Version 3.10a Rev: 12/29/94 Quality = 100, Smoothing = 0

Image (left) and isophotes (right) of G by Carl Hergenrother, from April 21 UT

 

For more  information, see http://www.lpl.arizona.edu/~chergen/73P.html. Note that Carl is taking a well-deserved rest from the telescope, but is expected to be back on April 27.

 

ÒThe fringeÓ is now jumping in the SW3 bandwagon. One person reports that a piece of SW3 will hit the Earth on May 25. Evidence? Crop circles! See:

 

http://news.yahoo.com/s/usnw/20060413/pl_usnw/former_military_air_traffic_controller_claims_comet_collision_with_earth_on_may25_2006104_xml

 

With nonsense such as this floating around, those who are seriously involved with NEO mitigation have their work cut out for them.

 

TECHNICAL NOTES:

M. L. Sitko, B. A. Whitney, and M. J. Wolff (Space Science Institute), C. M. Lisse (Johns Hopkins University), E. F. Polomski (University of Minnesota), R. W. Russell & D. K. Lynch (The Aerospace Corporation) and D. E. Harker (University of California, San Diego) have reported the initial results of spectra of SW3-C using the IRS instrument on the Spitzer Space Telescope. The data, obtained on March 17, show the presence of silicate emission feature that is stronger than that usually observed in Jupiter Family comets. The measured flux at wavelength 10.5 microns (slit size 3".7 x 57") was 0.75 Jy, or magnitude [10.5 microns] = 4.3. [IAUC 8701]

 

D. Harker (University of California, San Diego), D. Wooden (NASA/Ames Research Center), and C. Woodward (University of Minnesota) have observed components C and B using MIRSI on NASAÕs IRTF telescope. Preliminary values for the flux inside a 1.06 circular diameter beam in the N photometric band (10 microns wavelength) was 2.9 Jy for C and 0.3 Jy for B on April 17.

 

W. Reach (Jet Propulsion Lab/Spitzer Science Center) has pieced together a mosaic of the field stretching from C through B and on to G using Spitzer/MIPS. The debris trail can be seen stretching over the entire projected orbit of the fragments, including material leading C.

 

S. N. Milam, A. J. Apponi, L. M. Ziurys, and S. Wyckoff (Arizona Radio Observatory and Steward Observatory) report the detection of HCN in component C, with a column density of 3.4x1011 cm-2 and a production rate of 3.05x1025 s-1. [IAUC 8702]

 

For more information, contact:

Mike Sitko

Dept. of Physics, University of Cincinnati       sitko@physics.uc.edu  Phone: 513.556.0642

& Space Science Institute, Boulder, CO sitko@spacescience.org