9 Comments

1. ljk on December 21, 2007 at 13:03

   A novel mechanism for outbursts of Comet 17P/Holmes and other short-period comets

   Authors: Richard Miles

   (Submitted on 20 Dec 2007)

   Abstract: A mechanism is proposed to explain the outburst of comet 17P/Holmes based on; (a) oxidation of water within the porous surface of the comet nucleus to form hydrogen peroxide (H2O2) through exposure to UV radiation, to energetic solar-wind particles and to cosmic radiation, (b) concentration of the H2O2 component through solid-, liquid- and gas-phase processes involving sublimation, evaporation, fractional crystallization, diffusion, supercooling, capillary wetting and migration in voids within the nucleus, and (c) rapid exothermic decomposition of aqueous H2O2 liberating oxygen gas via a surface catalytic reaction through interaction with finely-dispersed transition metals, metal compounds and minerals, in particular those containing Fe, localised within a differentiated multi-component comet nucleus. An accelerated release of gaseous oxygen, concomitant self-heating and volatilisation of hydrocarbons within the nucleus results in its explosive disruption.

   This mechanism may also explain the observation of a repeat outburst of this comet in 1893. Laboratory studies to investigate H2O2 formation in simulated cometary environments and to evaluate H2O2 decomposition on meteoritic samples are recommended.

   Comments: 11 pages, 1 figure, revised version submitted to MNRAS

   Subjects: Astrophysics (astro-ph)

   Cite as: arXiv:0712.3314v1 [astro-ph]

   Submission history

   From: Richard Miles [view email]

   [v1] Thu, 20 Dec 2007 00:47:57 GMT (105kb)

   http://arxiv.org/abs/0712.3314

2. ljk on January 8, 2008 at 0:43

   The comet 17P/Holmes 2007 outburst: the early motion of the outburst material

   Authors: M. Montalto (1), A. Riffeser (2), U. Hopp (1 and 2), S. Wilke (2), G. Carraro (3) ((1) MPE, Munchen, Germany, (2) Universitats-Sternwarte Munchen, Germany, (3) ESO Santiago)

   (Submitted on 6 Jan 2008)

   Abstract: Context. On October 24, 2007 the periodic comet 17P/Holmes underwent an astonishing outburst that increased its apparent total brightness from magnitude V\sim17 up to V\sim2.5 in roughly two days. We report on Wendelstein 0.8 m telescope (WST) photometric observations of the early evolution stages of the outburst.

   Aims. We studied the evolution of the structure morphology, its kinematic, and estimated the ejected dust mass.

   Methods. We analized 126 images in the BVRI photometric bands spread between 26/10/2007 and 20/11/2007. The bright comet core appeared well separated from that one of a quickly expanding dust cloud in all the data, and the bulk of the latter was contained in the field of view of our instrument. The ejected dust mass was derived on the base of differential photometry on background stars occulted by the moving cloud.

   Results. The two cores were moving apart from each other at a relative projected constant velocity of (9.87 +/- 0.07) arcsec/day (0.135 +/-0.001 km/sec). In the inner regions of the dust cloud we observed a linear increase in size at a mean constant velocity of (14.6+/-0.3) arcsec/day (0.200+/-0.004 km/sec). Evidence of a radial velocity gradient in the expanding cloud was also found. Our estimate for the expanding coma’s mass was of the order of 10^{-2}-1 comet’s mass implying a significant disintegration event.

   Conclusions. We interpreted our observations in the context of an explosive scenario which was more probably originated by some internal instability processes, rather than an impact with an asteroidal body. Due to the peculiar characteristics of this event, further observations and investigations are necessary in order to enlight the nature of the physical processes that determined it.

   Comments: 5 pages, 3 figures, A&A accepted

   Subjects: Astrophysics (astro-ph)

   Cite as: arXiv:0801.0864v1 [astro-ph]

   Submission history

   From: Marco Montalto [view email]

   [v1] Sun, 6 Jan 2008 16:17:56 GMT (670kb)

   http://arxiv.org/abs/0801.0864

3. ljk on February 28, 2008 at 16:06

   Comet Holmes is still around, though getting fainter:

   http://www.eanet.com/kodama/astro/2008/0216/6-11a.htm

4. ljk on March 12, 2008 at 10:24

   Cometary activity at 25.7 AU: Hale–Bopp 11 years after perihelion

   Authors: Gy. M. Szabo, L. L. Kiss, K. Sarneczky

   (Submitted on 10 Mar 2008)

   Abstract: Eleven years after its perihelion, comet C/1995 O1 (Hale-Bopp) is still active. Between October 20–22, 2007, we detected a diffuse coma of 180×10^3$km in diameter with a slight elongation toward N/S direction. The integrated brightness was 20.04 mag in R_C, implying Af\rho=300 m and albedo x dust surface $a_RC$=4300 km^2. The coma was relatively red at V-R=0.66 mag, which is consistent with that of the dust in other comets. The observed properties and the overall fading in brightness between 10 AU and 26 AU follow the predicted behaviour of CO-driven activity (Capria et al. 2002). This is the most distant cometary activity ever observed.

   Comments: 13 pages, 5 figures, 1 table, ApJ Letters, in press

   Subjects: Astrophysics (astro-ph)

   Cite as: arXiv:0803.1505v1 [astro-ph]

   Submission history

   From: Gyula Szabo [view email]

   [v1] Mon, 10 Mar 2008 22:21:42 GMT (176kb)

   http://arxiv.org/abs/0803.1505

5. ljk on April 9, 2008 at 8:40

   Large excess of heavy nitrogen in both hydrogen cyanide and cyanogen from comet 17P/Holmes

   Authors: D. Bockelée-Morvan, N. Biver, E. Jehin, A. L. Cochran, H. Wiesemeyer, J. Manfroid, D. Hutsemékers, C. Arpigny, J. Boissier, W. Cochran, P. Colom, J. Crovisier, N. Milutinovic, R. Moreno, J. X. Prochaska, I. Ramirez, R. Schulz, J.-M. Zucconi

   (Submitted on 8 Apr 2008)

   Abstract: From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of October 24, 2007, we derive 14 N/15N = 139 +/- 26 in HCN, and 14N/15N = 165 +/- 40 in CN, establishing that HCN has the same non-terrestrial isotopic composition as CN. The same conclusion is obtained for the long-period comet C/1995 O1 (Hale-Bopp) after a reanalysis of previously published measurements. These results are compatible with HCN being the prime parent of CN in cometary atmospheres.

   The 15N excess relative to the Earth atmospheric value indicates that N-bearing volatiles in the solar nebula underwent important N isotopic fractionation at some stage of Solar System formation. HCN molecules never isotopically equilibrated with the main nitrogen reservoir in the solar nebula before being incorporated in Oort-cloud and Kuiper-belt comets. The 12C/13C ratios in HCN and CN are measured to be consistent with the terrestrial value.

   Comments: Accepted for publication in the Astrophysical Journal (Letters) 4 pages

   Subjects: Astrophysics (astro-ph)

   Cite as: arXiv:0804.1192v1 [astro-ph]

   Submission history

   From: Jacques Crovisier [view email]

   [v1] Tue, 8 Apr 2008 07:32:40 GMT (67kb)

   http://arxiv.org/abs/0804.1192

6. ljk on October 24, 2008 at 9:36

   From SpaceWeather.com

   FLASHBACK: One year ago today, on Oct. 24, 2007, Comet 17P/Holmes shocked astronomers when it suddenly exploded, brightening a million-fold to naked-eye visibility. Within three days of the blast, the comet was bigger than Jupiter, and within three weeks it was larger than the sun itself. Spanish photographers Vicent Peris and José Luis Lamadrid recorded this view on Nov. 1, 2007, using little more than a 7-inch telescope:

   http://www.spaceweather.com/comets/gallery_holmes_page9.htm

   What happened to Comet Holmes? Just-released observations by NASA’s Spitzer Space Telescope define the mass and velocity of the explosion: “The energy of the blast was about 1014 joules and the total mass was of order 1010 kg,” says Bill Reach of Caltech. In other words, Holmes exploded like 24 kilotons of TNT and ejected 10 million metric tons of dust and gas into space. These numbers fit a model favored by Reach in which a cavern of ice some hundred meters beneath the comet’s crust changed phase, from amorphous to crystalline, releasing in transition enough heat to cause Holmes to blow its top.

   Holmes has exploded twice in recorded history–in 1892 and 2007. Two caverns down, how many to go? No one knows. Browse the gallery for a preview of what the next blast might look like:

   Comet Holmes Photo Gallery:

   http://www.spaceweather.com/comets/gallery_holmes.html

7. ljk on January 19, 2009 at 23:48

   Why did Comet 17P/Holmes burst out?

   Authors: W. J. Altenhoff, E. Kreysa, K. M. Menten, A. Sievers, C. Thum, A. Weiss

   (Submitted on 18 Jan 2009)

   Abstract: Based on millimeter-wavelength continuum observations we suggest that the recent ‘spectacle’ of comet 17P/Holmes can be explained by a thick, air-tight dust cover and the effects of H2O sublimation, which started when the comet arrived at the heliocentric distance <= 2.5 AU.

   The porous structure inside the nucleus provided enough surface for additional sublimation, which eventually led to the break up of the dust cover and to the observed outburst.

   The magnitude of the particle burst can be explained by the energy provided by insolation, stored in the dust cover and the nucleus within the months before the outburst: the subliming surface within the nucleus is more than one order of magnitude larger than the geometric surface of the nucleus — possibly an indication of the latter’s porous structure.

   Another surprise is that the abundance ratios of several molecular species with respect to H2O are variable. During this apparition, comet Holmes lost about 3% of its mass, corresponding to a ‘dirty ice’ layer of 20m.

   Comments: 6 pages, 1 figure. Accepted for publication in A&A

   Subjects: Astrophysics (astro-ph)

   Cite as: arXiv:0901.2739v1 [astro-ph]

   Submission history

   From: Axel Weiss [view email]

   [v1] Sun, 18 Jan 2009 21:41:53 GMT (42kb)

   http://arxiv.org/abs/0901.2739

8. ljk on August 16, 2009 at 0:43

   Continuous Monitoring of Comet Holmes from Before the 2007 Outburst

   Authors: E. E. El-Houssieny (1), R. J. Nemiroff (1), T. E. Pickering (2) ((1) Department of Physics, Michigan Technological University, Houghton, MI, USA, (2) MMT Observatory, University of Arizona, Tucson, AZ, USA)

   (Submitted on 11 Aug 2009)

   Abstract: The outburst and subsequent brightness evolution of Comet 17P/Holmes has been observed using the MMT Observatory’s All-Sky Camera (Pickering 2006) on Mt. Hopkins near Tucson, Arizona, USA.

   The comet was picked up at the limiting visual magnitude of 5.5 on October 24.38 and tracked by the camera continuously until sunrise four hours later.
   During this time the comet brightened to visual magnitude 3.5.

   Comet Holmes was next observed just after sunset on October 25.23 at visual magnitude 2.5 where it remained approximately constant over the next three days. The comet then began to dim slowly and was followed into the early months of 2008 with periods of dense time coverage.

   Comments: 6 pages, 4 figures

   Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

   Cite as: arXiv:0908.1450v1 [astro-ph.EP]

   Submission history

   From: Ehab El-Houssieny Mr. [view email]

   [v1] Tue, 11 Aug 2009 04:34:00 GMT (2354kb)

   http://arxiv.org/abs/0908.1450

9. ljk on September 17, 2009 at 12:47

   September 15, 2009

   Mini Comets Ejected from Comet Holmes Caused Outburst

   Written by Nancy Atkinson

   Comet 17P/Holmes caused a sensation in October and November 2007 when overnight, it brightened enough to be visible with the naked eye and became the largest cometary outburst ever witnessed. Using a special filter on the Canada- France- Hawaii Telescope in Hawaii, astronomers were able to peer inside Comet Holmes to determine why the comet became so bright.

   Images and animations show multiple fragments were ejected and rapidly flew away from the nucleus of comet Holmes.

   Full article here:

   http://www.universetoday.com/2009/09/15/mini-comets-ejected-from-comet-holmes-caused-outburst/