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Kebsis
2004-Nov-27, 08:46 AM
When those comets left scarres on Jupiters surface, why did they do so? How did they leave black scarres on gas?

Evan
2004-Nov-27, 08:56 AM
Jupiter doesn't have a surface that we can see. As for the black appearance, that was caused by a change in albedo by the interaction of the comet fragments with the upper atmosphere of Jupiter. It isn't necessarily black. The surface of the moon has approximately the same reflectivity as black asphalt pavement but it doesn't look black, does it? Sort of like sunspots.

John Kierein
2004-Nov-27, 10:28 AM
At the April APS Astrophysics conference there was a guy who claimed that this comet was made of anti-matter which caused the bigger than expected explosions on Jupiter. In fact he thinks most comets are anti-matter so when Deep Impact hits it'll really cause a big explosion. Maybe that's what the "Whatzit" flash is. Transitory one time events like these are hard to explain. He also believes that when comets hit the sun they cause CMEs for this reason.
Many, if not all, of the comets that Lou Frank sees hitting earth may be just cosmic rays hitting his instrument; but gamma ray bursts could indeed be antimatter hitting matter. We know such things occur above the galactic plane because we see the signature of electron-positron anihilation. Gamma ray bursts could be due to higher order antimatter like atoms or molecules hitting matter.

Kebsis
2004-Nov-27, 12:15 PM
Excuse me if I'm mistaking what you said but are you stating that you feel comets might be made of anti-matter?

ngc3314
2004-Nov-27, 02:08 PM
When those comets left scarres on Jupiters surface, why did they do so? How did they leave black scarres on gas?

The dark splotches were some combination of cometary matter and gases from below the cloudtops blasted back upwards by the final explosion. Much of this stuff was channeled into the hot, ionized trail produced by the incomingcomet, directing it upward at about 45 degrees (one Hubble image just shows the faintly glowing trail, in fact), shooting back several thousand kilometers above the cloudtops before the local gravity pulled them back deeper into the atmosphere. The particles, then hanging in the wind, slowly dispersed and dropped - planetary scientists were interested in following the spots' development to measure winds above the Jovian cloudtops, in fact. They got really hard to see after a month or two, although faint traces remained in the UV (where small particles block light most effectively) for longer.

And to respond to another bit of this thread - there cannot be a significant amount of antimatter in the solar system (of the Milky Way, for that matter), or we'd be bathed in the gamma-ray annihilation signature (especially the 511-keV gamma ays from electron-positron annihilation). The solar wind is ordinary matter, as we know from grabbing samples, and where it impinged on comets we do not see the annihilation radiation. Likewise, it's a big deal when the line shows up in our Galaxy - like the Great Annihilator near the galactic center, which is pumping out at least anti-electrons only to have them quickly annihilate on surrounding ordinary matter. This annihilation radition is also seen from diffuse material in the Milky Way, with an important part (and, AFAIK, maybe all) coming from positrons prodced in cosmoc ray interactions with interstellar matter.

R.A.F.
2004-Nov-27, 08:12 PM
At the April APS Astrophysics conference there was a guy who claimed that this comet was made of anti-matter which caused the bigger than expected explosions on Jupiter.

That is an "against the mainstream" belief, and as such, any discussions concerning "Anti-matter comets" belongs on that forum not on the "general astronomy" forum. (My nit-pic for the day. :))

Wolverine
2004-Nov-27, 09:20 PM
At the April APS Astrophysics conference there was a guy who claimed that this comet was made of anti-matter which caused the bigger than expected explosions on Jupiter. In fact he thinks most comets are anti-matter so when Deep Impact hits it'll really cause a big explosion. Maybe that's what the "Whatzit" flash is. Transitory one time events like these are hard to explain. He also believes that when comets hit the sun they cause CMEs for this reason.
Many, if not all, of the comets that Lou Frank sees hitting earth may be just cosmic rays hitting his instrument; but gamma ray bursts could indeed be antimatter hitting matter. We know such things occur above the galactic plane because we see the signature of electron-positron anihilation. Gamma ray bursts could be due to higher order antimatter like atoms or molecules hitting matter.

Why was this posted (albeit with very subtle changes) on two different threads dealing with entirely separate topics? (separate discussion) (http://www.badastronomy.com/phpBB/viewtopic.php?p=371336#371336)