Milky way galaxy in a furnace.

[David Levy]

In the milky way galaxy there are about 400 Billion stars.

Scientists believe that 90% of our galaxy’s mass consists of dark matter.

 

So if we could place the Milky way in a furnace, what would be the average temp in that furnace?

Edited April 22, 2016 by David Levy

[Strange]

Is the furnace gas-fired or electric?

 

(Or, to put it another way, what the heck are you blathering about now?)

In the unlikely event you are interested in the science, you could take a look at this: http://www.nasa.gov/mission_pages/chandra/multimedia/hot_gas_halo.html

 

Other studies have shown that the Milky Way and other galaxies are embedded in warm gas, with temperatures between 100,000 and one million degrees, and there have been indications that a hotter component with a temperature greater than a million degrees is also present.

[David Levy]

Is the furnace gas-fired or electric?

 

No, the furnace is only used as some sort of thermal isolation.

It can't generate any heat. Without the Milky Way its temp is 0 (zero) K.

So, if we could cover the Milky way galaxy with thermal isolation - (Let's call it furnace), what might be the average temp in that furnace?

Edited April 22, 2016 by David Levy

[Strange]

 

No, the furnace is only used as some sort of thermal isolation.

It can't generate any heat. Without the Milky Way its temp is is 0 (zero) K.

So, if we could cover the Milky way galaxy with thermal isolation - (Let's call it furnace), what might be the average temp in that furnace?

 

It depends how long you leave it there. The longer you leave a source of heat in an insulated environment, the hotter it will get.

 

Do these questions have any point? How long do we have until you start making stuff up and saying "do you agree"?

Edited April 22, 2016 by Strange

[David Levy]

It depends how long you leave it there. The longer you leave a source of heat in an insulated environment, the hotter it will get.

 

Excellent question.

Let's assume that it would be there for unlimited time (or infinite).

[Strange]

Excellent question.

 

It wasn't a question. (Demonstrating your impressive comprehension skills again.)

 

Let's assume that it would be there for unlimited time (or infinite).

 

Are you assuming an unlimited source of energy? Or that all the hydrogen will be converted by fusion in a few billion years?

 

If the former, then the temperature will rise to infinity. (BTW, this would be a variant of Olber's paradox, which is yet more evidence that the steady state model doesn't work.)

 

If the latter, then you just need to work out what the total mass of the stars is and, as an approximation, assume all the hydrogen is fused to helium. That will give you the total energy. And from that, you can work out the final temperature. For someone of your outstanding intellectual skills, that shouldn't take more than about 10 minutes. Let me know what you get.

[David Levy]

In the unlikely event you are interested in the science, you could take a look at this: http://www.nasa.gov/mission_pages/chandra/multimedia/hot_gas_halo.html

 

 

Further your reply let me update the question:

 

If we could set the whole Milky Way Hot gas Halo (The halo of gas is shown with a radius of about 300,000 light years,)

in a furnace, what might be the average temp in that Furnace?

 

 

If the latter, then you just need to work out what the total mass of the stars is and, as an approximation, assume all the hydrogen is fused to helium. That will give you the total energy. And from that, you can work out the final temperature. For someone of your outstanding intellectual skills, that shouldn't take more than about 10 minutes. Let me know what you get.

 

Thanks

I have tried to calculate the total number of stars in that halo:

In this article it is stated:

 

"Data from NASA's Chandra X-ray Observatory was used to estimate [link to press release] that the mass of the halo is comparable to the mass of all the stars in the Milky Way galaxy."

 

So, in the Milky way there are 400 Billion Stars.

Scientists believe that 90% of our galaxy’s mass consists of dark matter.

Hence, we can assume that the total mass in the Milky way (including the dark matter) is 4 Trillion stars.

Based on the article, in that halo there might be same number of stars as in the Milky way.

Therefore, the total mass in the Milky way and the halo is 8 Trillion stars.

 

So, can we assume that 8 trillion stars could set at least a few K in furnace with a radius of 1M light years (after unlimited time)?

Edited April 22, 2016 by David Levy

[Strange]

Based on the article, in that halo there might be same number of stars as in the Milky way.

 

No, that isn't what it says. Read it again and try again. Is the problem that English is not your native language?

 

Therefore, the total stars in the Milky way and the halo is 8 Trillion stars.

 

But if it did say that there were the same number of stars in the halo (it doesn't) then that would be 2 x 400 billion, or a total of 800 billion.

[David Levy]

But if it did say that there were the same number of stars in the halo (it doesn't) then that would be 2 x 400 billion, or a total of 800 billion.

 

Yes, that is correct.

But, what about the total mass of the dark matter in the Milky way?

Do you claim that the dark matter has no energy contribution?

In any case, if there are only 800 billion stars (without the dark matter), can we assume that furnace temp could be few K?

Edited April 22, 2016 by David Levy

[Strange]

Do you claim that the dark matter has no energy contribution?

 

Energy in the form of mass, yes. But not thermal energy.

 

In any case, if there are only 800 billion stars

 

No, there are only 400 billion, as you have read

 

 

can we assume that furnace temp could be few K?

 

That depends on the time. The temperature will rise as the stars radiate energy and there is nowhere for it to go.

[David Levy]

That depends on the time. The temperature will rise as the stars radiate energy and there is nowhere for it to go.

 

That is perfect.

 

So I can assume that even if the furnace size will be 1 or 10 Million Ly, after significant time frame, those 400 Billion stars could easily set a few K temp in this furnace?

 

Edited April 22, 2016 by David Levy

[Strange]

Here is one key bit of information you need:

• 5 × 10³⁶ W – astro: approximate luminosity of the Milky Way galaxy.

https://en.wikipedia.org/wiki/Orders_of_magnitude_%28power%29#Greater_than_one_thousand_yottawatts

 

Then you need to look up the specific heat of the gas in the galaxy. You can ignore the dark matter, for obvious reasons. And I suppose you need to decide if your "furnace" has a constant volume or a constant pressure.

[David Levy]

Here is one key bit of information you need:

• 5 × 10³⁶ W – astro: approximate luminosity of the Milky Way galaxy.

https://en.wikipedia.org/wiki/Orders_of_magnitude_%28power%29#Greater_than_one_thousand_yottawatts

 

Then you need to look up the specific heat of the gas in the galaxy. You can ignore the dark matter, for obvious reasons. And I suppose you need to decide if your "furnace" has a constant volume or a constant pressure.

 

Thanks

[Strange]

So, from here we have the mass of hydrogen in the galaxy as about 10% of the mass of the stars, or about 5x10^9 solar masses:

https://en.wikipedia.org/wiki/Milky_Way#Size_and_mass

 

And here, we have the specific heat of hydrogen as 14300 J/(kg K)

http://www.periodictable.com/Elements/001/data.html

(This is not very accurate as that is for H₂, and most of the hydrogen in the galaxy is monatomic. And the specific heat varies with temperature, and possibly pressure. But it will have to do.)

 

So putting all of that into Wolfram alpha: 5x10^36W / (10^40 kg * 14300 J/(kg K))

http://www.wolframalpha.com/input/?i=5x10^36W+%2F+%2810^40+kg+*+14300+J%2F%28kg+K%29%29

We get 3.5x10^-8 K/s (kelvins increase per second)

 

Which means that it would take a billion years for the temperature to rise by 10 degrees.

 

I suppose that is quite interesting.

Edited April 22, 2016 by Strange

[swansont]

Then you need to look up the specific heat of the gas in the galaxy. You can ignore the dark matter, for obvious reasons. And I suppose you need to decide if your "furnace" has a constant volume or a constant pressure.

Dark matter may moderate the temperature rise. Dark matter will gain energy by collision, which will take energy from the normal matter.

[ACG52]

Except that DM foes not interact with normal matter (except gravitationally) so there is no transfer of kinetic [thermal] energy.

[David Levy]

Except that DM foes not interact with normal matter (except gravitationally) so there is no transfer of kinetic [thermal] energy.

 

I had the impression that any mass/matter should have some sort of energy.

 

If the DM contribution is only gravitational power, why don't we call it "dark gravitational power" instead of dark matter?

 

In any case, if it adds gravitational power to the regular mass in the galaxy, then why this extra gravitational power can't be transformed into new energy?

 

[Mordred]

Dark matter does have energy however it's equation of state w=0 (pressureless) as well as being extremely weakly interactive, as well as slow moving means it's temperature contribution is low. DM isn't considered as having a lot of kinetic energy.

 

Radiation such as protons and neutrinos make up a far larger contribution to the blackbody temperature due to being relativistic. (Extremely high amount of kinetic energy). Though a particles kinetic energy isn't the only temperature contribution. Other factors being spin, entropy density, chemical reactivity, Etc.

 

As we don't know the precise properties of dark matter it's largely hypothetical approximation to try to estimate DMs temperature contribution.

 

If you for example treat DM as a boson ie zero spin its temperature contribution would be different than if you treat it as a sterile neutrino with spin 1/2.

 

We simply don't have enough data on DM to give anything other than possible approximations

If you look at enough articles, there have been papers trying to model DMs temperature contribution, However the value will depend on how the author chooses to model DM. Ie spin etc.

 

Here is one example paper that studies nearby galaxies to try to determine DMs temperature contribution.

 

http://www.google.ca/url?q=http://arxiv.org/abs/0910.0822&sa=U&ved=0ahUKEwiU0-jylKTMAhUO92MKHQn0AVcQFggVMAE&usg=AFQjCNH1YCLHPDmAgM1Aj8y2wBnjLdnBrg

Edited April 23, 2016 by Mordred

[David Levy]

Thanks

[Strange]

Dark matter may moderate the temperature rise. Dark matter will gain energy by collision, which will take energy from the normal matter.

 

If there is some interaction, I suspect it will be smaller than the errors in my estimates - some of which are within an order of magnitude at best. I probably should have rounded more to do a proper Fermi estimate: http://what-if.xkcd.com/84/