Comets – III

The Nucleus

Giotto at Halley 1986	Deep Space 1 (DS1) at Borrelly 2001

Stereo image of Wild 2 from Stardust

http://www.physics.uc.edu/~sitko/AdvancedAstro/28-Comets-III/w2_flyby1.gif

The Gas

Sublimation Rates

Actually, the equation above is a bit over-simplified for real work. It neglects the PV work done by the gas as it sublimes and pushes out through the coma. It also ignores conduction of energy downward.

Recent Spacecraft to the Comets

Comet Nucleus Tour – CONTOUR – to Encke in 2003 , but…..

Communication with CONTOUR was lost after it was to fire its engines to leave earth orbit. Images obtained with the Spacewatch Telescope (ironic, isn’t it) indicated that CONTOUR had broken apart, presumably due to a destructive malfunction when during the engine firing.

Stardust (already discussed – more in the next chapter)

Rosetta http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=2279

Launched on March 2, 2004, Rosetta is an ESA mission to orbit and land on a comet. Originally scheduled with 46P/Wirtanen as a target, launch delays forced it to be re-targeted to 76P/Churyumov-Gerasimenko. Global mapping begins August 2014, and the lander is expected to set down November of that same year.

Deep Impact (named before the motion picture came out) http://deepimpact.jpl.nasa.gov/index.cfm We will look at the results of the Deep Impact mission in the next chapter.

Hale-Bopp and Hyakutake

Comet C/1996 B2 Hyakutake

More people probably saw Comet Hale-Bopp than any other comet in recent history. This was due to its tremendous size and absolute magnitude, which made it bright and visible for almost a year.

However, it was Hyakutake that arrived first, and (for those who saw it) provided a more spectacular display, albeit much shorter in duration. It had a long, relatively narrow tail, with the ions providing nice structure to the overall “finger of God” impression that some people described.

One of the nicest pictures of Hyakutake (my opinion)

Image taken by Terry Acomb, at the time a geology student at UC

False-color image of Hyakutake, obtained with a CCD camera in the Cincinnati Observatory 16-ich refractor. It shows the usual “sunward fan”.	Hubble picture of the same thing (a little better than mine)

The importance of Hyakutake (beyond being practice for Hale-Bopp later on) was its close approach to Earth. That allowed many short-lived molecules to be detected. Because Hyakutake arrived before Hale-Bopp, most of the “new’ molecular detections occurred for Hyakutake.

Ron Baalke's Hyakutake web site

Comet C/1995 O1 Hale-Bopp

Ron Baalke's Hale-Bopp web site.