[meteorite-list] Did a Collision Cause Comet 17P/Holmes'MysteriousOutburst?

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Thu, 8 Nov 2007 03:48:15 -0700 (MST)
Message-ID: <1295.>

Hi Jerry, Sterling, and list:

Sterling. Have I done something wrong. I just got an error message stating
that "mailbox disabled for this recipient." L-

No pun intended, but the "solid theory" is actually a good one. I was
making comets in class yesterday and we tried getting pictures of me
popping film canisters (back in the dark ages cameras had this long
plastic stuff that you actually "loaded" into the camera and then, after
taking your pictures had to have them "developed"). It is very dramatic,
especially the Fuji film canisters that have a much tighter fitting top.
You put a little water a a small piece of dry ice (frozen carbon dioxide)
into it and close the top. The solid warms up, turns to gas and --- pop.
Like popping a champagne cork. It gets the students' attention. The top
actually slams off of our 15 foot class ceiling and lands well up the rows
of students.

At room temperature, solid carbon dioxide weighs 1.6 g/cc and the gas is
0.00198 g/cc. Therefore the volume change is over 800 times. If you try
holding that under the surface of a comet (even with temperatures a little
less) that builds up a lot of pressure --- a really big burp!

Why this comet seems to burp every hundred years or so rather than just
having a jet of material like any "normal" comet is something that I (or
probably anyone else at the moment) understands.


On Wed, November 7, 2007 8:09 pm, Jerry wrote:
> Sterling, Larry and List,
> The "burp" theory as proposed by Sterling is as solid as any and more
> likely than most to guesstmate the auspicious, unusual cometary event that
> graced this generation of observers with a front row seat to the great
> mysteries of OUR existence. We, once more, have been priviledged to
> witness a spectcal to generate wonder. Whether, and I doubt we'll ever
> explain this one, a consensus is ever arrived at, I am satisfied that the
> collisional aspect has been addressed and though partitioned into a much
> lower probability, uncertaintity, chaos if you will, has reared its head
> to grade our fears and futures into a more respectable framework to wend
> our way through the rest of our days. Spooky, but throw in a Nakhla Dog, a
> Lama or two, a guy blow off his feet
> and knoked unconscious, another at Tunguska and IT does give one pause.
> Jerry Flaherty
> ----- Original Message -----
> From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
> To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
> Cc: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
> Sent: Wednesday, November 07, 2007 9:42 PM
> Subject: Re: [meteorite-list] Did a Collision Cause Comet
> 17P/Holmes'MysteriousOutburst?
>> Hi, List,
>> You would think with all the new (and old) scientists
>> examining the collisional possibilities of Comet Holmes passing through
>> the Asteroid Belt, some of them might have noticed that Comet Holmes
>> "through" the Asteroid Belt!
>> I'm being sarcastic about this because I made exactly the
>> same mistake myself, until an astronomer, List member Larry Lebofsky,
>> pointed out that because of its high inclination (19.12 degrees), Comet
>> Holmes does not pass through the
>> ecliptic plane in the Asteroid Belt, but way out at the inside edge of
>> Jupiter's orbit, at 4.86 AU.
>> http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=17p&orb=1
>> The vast majority of the asteroids in the Main Belt have
>> inclinations of less than 19 degrees. Of course, it is possible that
>> Holmes could collide with a "less inclined" asteroid; it
>> depends on the orientation of the asteroidal orbit. But, but it's really
>> a very thin chance, with a small subgroup of an already widely scattered
>> population. In non-numerical terms, Comet Holmes essentially passes over
>> (and under) the Asteroid Belt,
>> rather than "through" it.
>> However, Holmes does plunge through the ecliptical plane
>> in the position where thousands of Jupiter Trojan asteroids co-orbit with
>> the planet, making passes that repeat the same orbital configuration
>> every 81-point-something years. The odds of a collision with something
>> in Jupiter's Trojans is dramatically higher than with a Main Belt
>> asteroid.
>> There are two goups of Trojans, ahead and behind Jupiter
>> at 60 degrees, but since they are themselves generously distributed ahead
>> and behind their Trojan points, along about 1/3rd of the Jupiter orbit,
>> Holmes is exposed to such "Trojan"
>> encounters for about 1/3rd of its orbits.
>> The two possible causes of the outburst, collision or thermal,
>> can be summarized as the "Bump" or "Burp" theories. I think an endogenous
>> cause of the outburst is more likely than a collision, as both the great
>> outbursts, the discovery outburst and the present one, occured after
>> perihelion passage with some delay. From June 16, 1892 to November 6,
>> 1892 is 143 days. From May 4, 2007
>> to October 24, 2007 is 173 days. (There are some uncertainties about
>> dates of perihelion.) Passage through the ecliptic plane at 2.05 AU
>> (right at the inner limit of the Asteroid Belt) occurs 4-5
>> months earlier than perihelion. At the times of the outbursts, the comet
>> was high above the ecliptic plane (the ecliptic plane being where
>> collisions would be most likely).
>> Sterling K. Webb
>> ------------------------------------------------------------------------
>> ---
>> ----- Original Message -----
>> From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
>> To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
>> Sent: Wednesday, November 07, 2007 5:46 PM
>> Subject: [meteorite-list] Did a Collision Cause Comet 17P/Holmes'
>> MysteriousOutburst?
>> http://www.newscientist.com/blog/space/2007/11/did-collision-cause-come
>> t-holmess.html
>> Did a collision cause comet's mysterious outburst?
>> Kimm Groshong
>> New Scientist space blog
>> November 06, 2007
>> Comet 17P/Holmes has certainly given sky-watchers - backyard and
>> professional astronomers alike - a thrilling chance to see a cometary
>> outburst on a grand scale. After we posted my story
>> <http://space.newscientist.com/article/dn12880> about on-going
>> speculation about what could have caused this outburst (and the one 115
>> years ago), many readers posted comments related to two questions:
>> Could
>> this have been triggered by a collision with an object in the main
>> asteroid belt? And why can't we see more of a tail on this comet?
>> Here's what I found out: Michael Mumma at the Goddard Center for
>> Astrobiology says such a collision in the asteroid belt is theoretically
>> conceivable. He noted that comet guru Fred Whipple suggested that a
>> collision with a small asteroid could have provided the right amount of
>> energy to produce the ejecta and brightening observed in the comet's
>> 1892 flare-up.
>> But Mumma himself thinks it would be "very surprising" if a collision
>> were the cause of the outburst. He says part of the difficulty in
>> weighing this possibility is that it's very hard to estimate how many
>> small boulders are in the asteroid belt. These tiny objects - on the
>> order of one-metre across - are beyond the detection limits of
>> telescopes.
>> Brian Marsden, former
>> director of the International Astronomical Union's Minor Planet Center
>> <http://cfa-www.harvard.edu/iau/mpc.html>, says plainly that he doesn't
>> believe this to be a viable explanation for the outburst. He says it's
>> hard to believe that this comet, among all those that pass through the
>> asteroid belt, has been struck twice by objects in the belt - once in
>> 1892 and again this year.
>> Many people have been discussing whether or not this comet has a tail.
>> Comets typically have two types of tail - a
>> dust tail and an ion tail. The dust tail is made of fine dust from the
>> comet's main body, or nucleus, that has been swept out by the Sun's
>> radiation. It usually points in the direction from which the comet
>> came. The ion tail is caused by the Sun's magnetic field sweeping ions
>> (which
>> start out as neutral gas particles on the body of the comet) into a line
>> that always points directly away from the Sun.
>> Marsden says the there isn't much of either type of tail. He says it's
>> possible that there just isn't enough very fine dust in the material
>> coming off the nucleus to be pushed by sunlight into a nice dust tail.
>> (He says there may only be "fairly hefty dust" in the comet's coma.)
>> Some people have argued that we can't see the comet's ion tail because
>> the orientation of the Sun, Earth and comet means the tail is mostly
>> pointing away from Earth.
>> But though the tail does look fore-shortened, Mumma says the
>> accumulated surface brightness would be greater seen from one end than
>> if it were seen spread out, from the side. He likened it to looking at
>> the contrail of a plane. If we saw the stream from the side, we would
>> basically see right through it. But if we were in front of or behind the
>> contrail, looking into it, it would appear many times brighter.
>> Marsden says the comet is so far from the Sun that the solar wind is
>> not interacting strongly enough with the ionised gas to produce a
>> fantastic ion tail. But he says it doesn't bother him that it doesn't
>> have much of a tail. After all, the "fuzzy head" is putting on such a
>> great show of its own.
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Received on Thu 08 Nov 2007 05:48:15 AM PST

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