I’ve read a lot of astronomy, and it’s always been emphasized how hot the Sun’s core is, 15 million C.
But HOW did we get to that number? Why specifically 15 million and not scientists ballparking it as ‘more than a million’?
I’ve studied transport phenomena in university, so I guessed that maybe they constructed an equation of temperature as a function of radius, and substituted r=0 to get 15 million. But it can’t possibly be that simple, as the Sun has different layers of unknown size (and if known, how do we know?) that we aren’t even about the properties.
If possible, explain this to me as simple as possible, while still describing simply the math that caused the scientist to arrive at the 15 million number
In: Planetary Science
We sort-of know what the sun is made of, partly because we’ve measured its “size”, “mass” and “spectral lines”, which gave us density which we can compare to materials we have on earth.
We also know the “temperature” of the sun’s surface due to black body radiation math and the colour of the light it produces.
Then, we know how much energy leaves the sun every second because we can measure it on earth and its result on other planets.
We can use all of this information to formulate a rate at which heat has to leave the core to sustain the size, density, colour and heat of the sun.
And lastly, we know from modelling and experimentation how quickly heat can flow from hydrogen to other hydrogen – thermal conductivity, which depends on a temperature gradient.
If the core is colder than that, the rate at which heat could leave would be too low to sustain the colour and size of the sun.
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