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Metallic sun

freality (324306) writes | more than 2 years ago

User Journal 1

I'm posting this for follow-up commentary from @APODNereid, since the thread is now closed.

http://slashdot.org/comments.pl?sid=2967801&cid=40758811

You ask what would keep the surface metallic. Thinking about this more, I found a couple of facts:

The Sun's surface has an energy flux density ~30x that of a hot metal rod at 3,000 C (around the glow point for tungsten in a lightbulb) in the experiment described here:

I'm posting this for follow-up commentary from @APODNereid, since the thread is now closed.

http://slashdot.org/comments.pl?sid=2967801&cid=40758811

You ask what would keep the surface metallic. Thinking about this more, I found a couple of facts:

The Sun's surface has an energy flux density ~30x that of a hot metal rod at 3,000 C (around the glow point for tungsten in a lightbulb) in the experiment described here:

    http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law#Temperature_of_the_Sun

Which is hot indeed, and would surely evaporate the tungsten here on Earth.

However, the Sun also has 28 times greater surface gravity than that on the surface of the Earth (28x the surface gravity, so linearly greater pressure for the same area too):

    http://en.wikipedia.org/wiki/Sun (see sidebar for surface gravity)

The core of the Earth is thought to be about as hot as the surface of the Sun, and yet still a solid metal ball:

    http://en.wikipedia.org/wiki/Inner_core

What explains the core not evaporating into a gas or plasma? The pressure is very high.

A 1% depth crust on the SUn (similar to the Earth's proportion) would be roughly the diameter of the Earth, so the amount of material involved is at least equally astronomical :) For a start, this tells me that the pressures on the surface of the Sun could create a solid despite the temperature. Of course, the vaporization point for Hydrogen and Iron/Nickel are very far apart, but I don't know how far at these pressures (is that even the right way to phrase it?) without some more reading.

(also, whether or not it's metallic per se is beyond me; the more interesting point vis-a-vis the original article is whether the surface is solid.)

Thoughts?

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Metallic hydrogen (1)

freality (324306) | more than 2 years ago | (#40765719)

Here's an interesting article:

    http://en.wikipedia.org/wiki/Metallic_hydrogen#Metallization_of_hydrogen_in_shock-wave_compression [wikipedia.org]

Especially the discussion of the LLNL shock-wave compression. Metallic indeed :)

3000K is not too far from the temperature of the surface of the Sun, and the pressures are thought to vary from virtually nothing at the surface to Peta-pascals in the core, so somewhere there's a transition by the 140GPa needed for metallization. Whether this is within the convective layers where the temperatures remain low..?

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