Temperatures in space??

[Outbackmanyep]

Hey guys,
Just wanted to know i anyone had a link or something to find out the temperature range in the solar system at certain distances.
Im just putting together a map of how the chemical structure that is in a comets make-up would start to sublime at certain temperatures.
I know comets don't usually start to show themselves until they reach approx 5AU, and tails form between 1 to 2 AU.

I want to learn a bit more about temperatures from the sun to around 7 AU.

Cheers!

[higginsdj]

I don't think it is that simple. There is heat from absorption (ie dark surfaces absorb more heat that light surfaces) and radioactivity to contend with as well. Then there is photoionisation processes affecting molecular makeup and bonds.

I have a book 'Comet Science' by Jacques Crovisier and Therese Encrenaz (both professionals in the field) (ISBN 0521645913 or 0521641799) with a section titled 'sublimation of cometary ices' with some formulae and charts detailing sublimation rates of various compound for distances from the sun as well as the molecular evolution and production rates observed at various distances.

If you are interested then drop me a line and I can scan them for you (just 2 sub A4 sized pages) and post them. It is for education purposes afterall - isn't it :)

Cheers

[Outbackmanyep]

Thankyou Higginsdj!
That'd be sweet! If you would like to scan them and send to
outbackmanyep@hotmail.com

appreciate it very much! I'm after anything on this subject.:thumbsup:

Cheers and Thankyou! :)

[Suzy_A]

As David point's out, it depends on what you mean. 'Empty space' contains no heat and so has no 'temperature'. But space is far from empty...

It also depends on what you mean by 'temperature'.

Temperature is really simply the amount of random motion of atoms (or molecules). The amount of 'heat' , or energy, there is, however, is very different and is also dependent on the mass of the material and other physical properties such as the specific heat. One way of putting the difference is that a thimble-full (1 ml) of boiling water has a high temperature (100 C or 373 K), but very little heat (energy). On the other hand, a 1,000,000 tonne thundercloud has a low temperature but a lot of heat (energy). To give numbers... I hope these are right... the 1 ml of 100 C water = 0.001 kg x 373 K x 4180 J = 1560 J The thundercloud at -20 C = 1,000,000,000 kg x 253 K x 4180 = 1,057,540,000,000,000 J of heat energy.

The factors that would affect a comet nucleus are the 'temperature' of the particles around it - the solar wind has a temperature of hundreds of thousands of degrees C - but is very tenuous so the effect is small as the heat is low. Also the light energy on the comet which is converted to heat is also small. But even so, we get sublimation and a tail, although the tail is basically a vacuum better than what we can make on Earth. There are probably other factors as well such as heating caused by gravitation (tidal) effects.

[Outbackmanyep]

Thanks Suzy, its a pain when you find out there is much complexity in the answer for a question that seems relatively simple!
I guess when you look at something like methane it has to form ices under its freezing point which is...???, it starts to sublime at ???? temperature.
The temperature @ about 5 AU is...?????

Its a bit like blankety blanks!

So my question basic but as you have pointed out its not quite that simple! I was aiming to try and get information on Heliocentric distance / over temperature (K). Most comets do not start to produce a coma until its around 5 AU.....so whats the temperature (K) at which a coma starts to form??
Comets also get energy from the crystallisation of amorphous water ice, it is one mechanism to explain where a comets heat source might start at large heliocentric distances.

Hope that may help to explain what i'm trying to achieve.

Cheers!

[janoskiss]

From Sun to 7AU out I'm not sure about, but if you go far enough, the temperature of the emptiest of empty space is about 2.7 kelvin, i.e. 2.7 degrees above absolute zero (or at -270.3 degree celsius). This is the temperature associated with the cosmic microwave background radiation that pervades the entire universe.

See http://map.gsfc.nasa.gov/m_uni/uni_101bbtest3.html
or http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiati on (more detailed).

[Suzy_A]

The 2.7 K is the 'radiation temperature' in deep space. The 'atomic temperature' - the temperature (speed) of the atoms, molecules and dust, would be from 2.7 K up to a few million K.

As for the question - when does the coma form - well, that's another can of wormholes...

The coma is basically the atmosphere of the comet and there will always be something there - just most of the time it's too thin and dim to see. Some gas will always be given off, according to the Stefan-Boltzman distribution which states that, basically, the 'temperature' that we measure is really only the average and an object at ... 100 K, for example, will actually be composed of molecules at 0 K (or slightly more) up to a thousand or so - you can actually work out the number ussing the SB law. Because of this, there will always be some outgassin - just like water at 20 C will slowly gassify as the higher energy molecules (ie faster ones) break free of the surface tension and turn to vapour.

And then size does matter too - a 10 m comet will probably be fried in the sun with no one noticing it. A 500 km comet (pluto?) might be visible at 100 AUs...

Well then, maybe you could define it when you can see it - well that won't work either. If you can't see it with your 8" SCT, then maybe you can see it with the Keck or the Hubble or with the proposed 100 m 'Suzyscope' on Ceres.



Sorry to be a bore!

Probably what you need to do is define the question first - eg for a 10 km comet, at what distance from the sun will enough gas and dust be released so that it's visible in a ... 10 " f10 SCT...


"There goes that rotten Halley's Comet! It makes me sick! I want to vomet!"

[duncan]

Well done Suzy!!!:thumbsup:

[fringe_dweller]

more importantly perhaps, would the beer stay cold? :P :D

to think of comets in a homogenous predictable way is fraught with problems ;)

[duncan]

Ay Suzy ,
Just washed up me dishes and thinking about me packet of "Nice " bickies with a cuppa (coffee),LOL:lol::lol::lol:
Cheers,
Duncan

[duncan]

Kearn the beer is always cold, very cold,LOL:lol::lol::lol:

[Suzy_A]

The temperature distribution is give by Maxwell-Boltzmann Statistics, not S-B... It was too late at night.

[Outbackmanyep]

If i sent a probe into the solar system and it had a thermometer that had a probe sticking out...what readings (in K) would i get at 1 AU, 2 AU, 3 AU etc etc...just from sunlight, no comets, no asteroids........

Thankyou Suzy for putting up with this thread and giving me some informative things to think about! hehe

And Kearn, i hope your beer is cold when i come down to SA one day!

PS...you're not a bore!!! :) :thumbsup: