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nubeoort
2010-Dec-06, 09:46 PM
Hi, I'm doing one work in subject of science.

I have to calculate the loss mass per orbit of 17P Holmes, if I do this, I have a 10/10 (A+).

What I need?

I have:

Mass: 3,3 x 10 ^ 12
Diameter: 3,24 km (R = 1,62 km).
Perihelion: 2,05 UA
Aphelion: 5 UA
Eccentricity (3 decimals): 0,451
Inclination: 19,116º
Temperature at 2,4 UA: 175K
Composition: H2O, HCN, C2H6, and C2H2 in the coma
Density: 0,5 g/cm3 in the bulk.
Heat capacity: No info.


Mineralogical info of the comet's dust:

amorphous carbon 5.63 C
ferromagnesian sul de 1.02 MgFeS
amorphous pyroxene 0.50 (Fe,Mg)SiO3
forsterite 0.46 Mg2SiO4
water ice 0.44 H2O
diopside 0.11 MgCaSi2O6
enstatite 0.14 MgSiO3
water gas 0.09 H2O
smectite 0.06 ( 1
2Ca,Na)0:33(Mg,Fe)3(Si,Al)4O10(OH)2 nH2O
PAH 0.006 CnHm


More info about composition of the last outburst:

"At least 11 molecules OH, CO, CH3OH, H2CO, HCN, CH3CN, HC3N, H2S, SO, HNC and CS. "

" Significant upper limits on the abundances of HNCO, HCOOH, SO2 and OCS"

[http://www.lpi.usra.edu/meetings/acm2008/pdf/8146.pdf]


With this data, can I calculate the loss mass per orbit?

If I do this, I have (A+, 10/10).

Please help me !

antoniseb
2010-Dec-06, 10:15 PM
The data you've given is not enough for a precision answer. It doesn't include information about the albedo of the nucleus and hence the energy absorbed that can be used to heat your frozen volatiles into gasses. It doesn't tell you anything about the ratio of gasses lost to solid matter ejected but still frozen.

You can probably make a good estimate (within a power of ten) by making a few simplifying assumptions.

nubeoort
2010-Dec-07, 09:07 AM
Oh, I miss some data:


Albedo: 0,04.
The proportion of gas.... : I have the mineral rate, but I haven't got the data of the gas proportion. I have the water and carbon rate, in the first post.


Here, one text of the AANDA:

" Aims. On October 24, 2007 the comet 17P/ Holmes underwent an outburst that was extraordinary in both duration and size. We attempted to determine the cause of the outburst by acquiring and analyzing high resolution spectra of the comet.

Methods. On two nights, October 25 and December 2, we acquired four high resolution spectra in the visible range at the Telescopio Nazionale Galileo in La Palma. The oxygen lines intensity ratio was estimated for the observation performed on October 25, and computed for the observation performed on December 2.

Results. Many emission lines were detected in the spectra, most of them attributable to C2, NH2, CN and CH. The atomic O green line and one of the red doublet lines were detected in a spectrum acquired on October 25. All the three atomic O lines were detected in a spectrum acquired on December 2. The value obtained for the first night, 0.1 ± 0.11, implies that the H2O molecule was the main parent of the emission lines, while the value obtained for the second night, 0.3 ± 0.1, implies that the main parent was CO or CO2 instead than H2O.

Conclusions. Our results imply that in the days around the outburst the water production was exceptionally high for that heliocentric distance. By December, however, the behavior of 17P/ Holmes had returned to that of a comet orbiting at 2.6 AU from the Sun, in which state the activity is probably sustained mostly by gases more volatile than water, such as CO and CO2. "



Here, a little pdf of composition: http://vela.astro.ulg.ac.be/themes/solar/Comets/Archives/table_isotopes_20052009.pdf


Mineralogical info of the comet's dust:

amorphous carbon 5.63 C
ferromagnesian sul de 1.02 MgFeS
amorphous pyroxene 0.50 (Fe,Mg)SiO3
forsterite 0.46 Mg2SiO4
water ice 0.44 H2O
diopside 0.11 MgCaSi2O6
enstatite 0.14 MgSiO3
water gas 0.09 H2O
smectite 0.06 ( 1
2Ca,Na)0:33(Mg,Fe)3(Si,Al)4O10(OH)2 nH2O
PAH 0.006 CnHm

And the data of the first message (density, composition, and mass, orbit...).


With this data, can I calculate the loss mass per orbit?

With an error percentage of 1/20 - 1/10 ?

antoniseb
2010-Dec-07, 12:26 PM
Can you calculate the amount of heat that the nucleus absorbs during perihelion vs. aphelion?
I noticed that your chart didn't show quantities of carbon dioxide, or other volatiles (methane, ethane, ammonia, etc.) You would want to estimate what fraction of the orbit the comet was getting warmed enough to release these from their frozen state from near the comet's surface. You only showed water.

I'm guessing the point of your effort is to show that the Holmes outburst was extraordinary.

nubeoort
2010-Dec-07, 12:33 PM
Hello,

I don't know this data! The work is: calculate the loss mass per orbit of 17P Holmes.

But I think: I don't have all the data for calculate this.

With this data I can't calculate this, true?

antoniseb
2010-Dec-07, 02:56 PM
... But I think: I don't have all the data for calculate this.
With this data I can't calculate this, true?

Personally, I think the task of calculating it would be pretty difficult, but not impossible. Getting it within 10% might be unrealistic given the data available. I'm a physicist, and something of a generalist, and there might be people here who are comet specialists who haven't responded yet.

Among the things you'd have to guess at would be how large are the areas of the nucleus with the thinnest insulating layers, and how much can the Sun heat up volatile ices that make up the comet. You might need to guess at the nucleus' rotation rate. You'll have to make a good guess as to the mass of the nucleus.

The minerals you've cited are a little bit of a red herring, but it would be helpful to know their specific heat.

nubeoort
2010-Dec-07, 03:36 PM
Ok, but I accept an error of 10% (more or less). More things:

Rotation: 7-12h , about 10,3 hours.
Mass: Core: 3,9 Blob: 2,7 Shell: 3,3 (x 10 ^12)

Total comet mass: 3,3 x 10 ^12 (10^11kg outburst = 3%)=(10x33= 3,3 x 10^12). [http://arxiv4.library.cornell.edu/PS_cache/arxiv/pdf/1001/1001.4161v2.pdf]


Temperature of the comet at 2,4 UA: 175 K .

Grain temperature: Core 185 Blob 200 Shell 400 (Kelvins)


Nucleus composition: only water and and dust (H2O and dust) .


More info (the explosion do the sublimation of the H2O and dust and) :

An international astronomy team, led by Drs. Dominique Bockelee-Morvan and Nicolas Biver at Observatoire de Paris in France and Drs. Darek Lis and Ruisheng Peng at Caltech used the 10.4-meter Leighton telescope at the Caltech Submillimeter Observatory and the IRAM 30-meter telescope at Pico Veleta (Spain) in order to investigate the composition of the comet and better understand what happened to the comet.
First observations using the IRAM 30-meter radio telescope (Pico Veleta, Spain) on October 26th revealed intense lines of the CS radical and of the molecules of carbon monoxide (CO), methanol (CH3OH) and hydrogen cyanide (HCN), which originate from the sublimation of the cometary ices.

The quantities of observed gases released by 17P/Holmes were at that date almost similar to those released by comet Hale-Bopp at its closest approach to the Sun. These molecules were produced by the evaporation of the dust grains released by the fragmentation of the comet’s nucleus.

In order to better understand the fragmentation process, strong lines of hydrogen cyanide (HCN) were monitored at the IRAM 30-m telescope and CSO until November 4. The signals which were measured in the field of view of the telescopes (corresponding to a projected distance of 12000 km on the comet’s surface) decreased rapidly until October 30, and then faded more slowly.*

Nucleus composition: only dust and H2O (water) in solid (ice).


Observations of hydrogen isocyanide (HNC), an isomer of HCN, were conducted at the CSO. The origin of this molecule in cometary atmospheres is matter of debate. Its abundance relative to HCN varies among comets.

Measurements in a dozen comets showed that the abundance of HNC relative to HCN increases with decreasing distance to the Sun, suggesting that HNC is released by the thermal degradation of grains as the grains become hotter when the comets are closer to the Sun (Lis et al. 2007).

The huge outburst of comet Holmes provided a unique opportunity to measure the HNC/HCN ratio for a comet far from the Sun (2.4 AU).



With this data, can I do an aproximation of 10% of my work? What data need I?

Thank you very much!

antoniseb
2010-Dec-07, 11:50 PM
... With this data, can I do an aproximation of 10% of my work? What data need I?

Probably the first major thing you need to estimate is how much the volatile layers of the comet get heated at/near perihelion.
Can you do that with the information you have so far? How deep does that heating go? You need to estimate that too.

nubeoort
2010-Dec-08, 08:57 AM
But I don't know this. I only know the temperature of the dust grains in the core, blob and shell. Internet don't show this, and without this, it's impossible to calculate...

I am winned.

nubeoort
2010-Dec-08, 11:52 AM
http://www.astrosurf.com/comets/cometas/17p/qdust.html

Production of water and dust in outburst and post-outburst.

antoniseb
2010-Dec-08, 05:12 PM
http://www.astrosurf.com/comets/cometas/17p/qdust.html

Production of water and dust in outburst and post-outburst.

You could look at this paper (http://arxiv.org/PS_cache/arxiv/pdf/1012/1012.1570v1.pdf) about Comet Holmes 17P. It doesn't answer your question fully, but it does provide some additional science about the object, and identify other people researching the matter.

BTW, I think you need to look at how much of the comet is volatiles that turn to gas-phase at lower temperatures than water-ice. This property is hard to know, but without it, you can't get to any precise guess of mass loss. Water-ice itself will probably not ever turn to steam inside such a distant comet. It only sublimates once ice particles are ejected with the other granules.

Just as a side note: your professor offered this because it is new science. You aren't going to find an easy answer.

nubeoort
2010-Dec-08, 05:23 PM
Ok, thank you very much.

tusenfem
2010-Dec-08, 05:56 PM
Also, you might have a read of the book "the physics of comets" by Krishna Swamy (http://www.amazon.com/Physics-Comets-Scientific-Astronomy-Astrophysics/dp/9814291110/ref=sr_1_1?ie=UTF8&s=books&qid=1291830922&sr=8-1) recently published in a 3rd edition. This gives lots of (general) information about outgassing, coma building etc. etc.