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Forum » SpaceEngine » Science and Astronomy Discussions » Comets thread (Anything and everything to do with comets)
Comets thread
HarbingerDawnDate: Sunday, 31.03.2013, 21:25 | Message # 121
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What is the atm pressure on the surface of a comet

Varies depending on location and time (the jets are localized and not always in the same places) and depending on the individual comet. But it would be extremely low.





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WatsisnameDate: Monday, 01.04.2013, 04:52 | Message # 122
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Effectively zero. The surface gravity is on the order of 10-4g, so unlike planetary atmospheres the tenuous coma is not bound to the body and there's no meaningful pressure due to its own weight. Instead there is a small amount of pressure supplied by the kinetic energy of molecules that strike the surface, but the gas density is so low that this is also negligible.

I believe the effects of solar radiation pressure should actually be dominant over gas pressure here.





 
SpaceEngineerDate: Wednesday, 03.04.2013, 22:04 | Message # 123
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Epic photo of PanSTARRS from Ukrainian amateur:



http://www.astronomy.ru/forum....2368179





 
HarbingerDawnDate: Thursday, 04.04.2013, 00:53 | Message # 124
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Epic photo of PanSTARRS from Ukrainian amateur

surprised That's amazing!





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SolarisDate: Thursday, 04.04.2013, 01:26 | Message # 125
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It's absolutly splendid.

Color version :
 
HarbingerDawnDate: Thursday, 04.04.2013, 01:32 | Message # 126
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Color version from apod

Actually that picture is by a different author smile





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SolarisDate: Thursday, 04.04.2013, 01:35 | Message # 127
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Yeah I've just looked on SE link to check and found it there.. I wanted share the colors one here too smile

This Russian thread is full of pearls cool

http://www.astronomy.ru/forum....2362419
 
HarbingerDawnDate: Thursday, 04.04.2013, 01:51 | Message # 128
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So many beautiful images cry




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SpaceEngineerDate: Saturday, 06.04.2013, 23:12 | Message # 129
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From the same forum:

http://www.astronomy.ru/forum....2372743





 
HarbingerDawnDate: Sunday, 07.04.2013, 00:52 | Message # 130
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From the same forum

Obviously a composite of different images, but still cool smile





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WatsisnameDate: Monday, 08.04.2013, 23:31 | Message # 131
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Finally, I hear some quantitative and observationally-supported claim on the size of C 2012 S1's nucleus.

Quote (Spaceweather.com)
Recent measurements by NASA's Swift spacecraft shows that the comet's nucleus is spewing more than 112,000 pounds (51,000 kg) of dust, or about two-thirds the mass of an unfueled space shuttle, every minute. To produce so much dust, the comet's nucleus is probably about 5 km wide. For comparison, the nucleus of bright sungrazing Comet Lovejoy, which wowed observers in 2011, was only about one-tenth as large. Comet ISON could put on quite a show when it approaches the sun later this year.


Sounds promising! And judging from the latest light-curves it looks like the comet has undergone a slow-down event (where the rate of brightness increase with time decreases), but this is normal for comets and if it continues on this track we can still expect a peak magnitude well in the negatives. I can't wait for November to come! smile





 
NovaSiliskoDate: Tuesday, 09.04.2013, 02:17 | Message # 132
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(I hope!)

Edit: Here's hoping it's actually bigger than the estimates suggest


Edited by NovaSilisko - Tuesday, 09.04.2013, 02:22
 
Antza2Date: Tuesday, 09.04.2013, 10:12 | Message # 133
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Pics i took last night. (click for full rez)







Go to antza2.deviantart.com for cool photos!
 
MartekDate: Monday, 15.04.2013, 06:48 | Message # 134
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Comet ISON is next! What are your bets? GREAT or NOT?




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WatsisnameDate: Monday, 15.04.2013, 08:34 | Message # 135
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I dunno, I don't bet on comet brightnesses. smile

Judging by the light curves it looks like it is undergoing an SD event (makes sense given its distance -- it's undergoing a transition from CO/CO2 sublimation to H2O sublimation). Its peak brightness at perihelion will depend on how this SD event plays out, among other uncertainties. It certainly has the potential to be a great comet though, no doubt about that.





 
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