Hot out there
A couple of years ago I posted an attempt at my nephew's question, "Which is hotter, 1000 miles from the surface of the sun, or the hottest rocks in the middle of the earth?". TL;DR - 1,000 miles from the surface of the sun is hotter.
Part of the answer included the fact that the corona - the bit above the 'surface' of the sun (the photosphere) - is actually a few million degrees, whereas the photosphere itself is only about 5,800 K. Which, in one of those fun coincidences-or-is-it, is about the temperature we think the centre of the Earth might be.
It bothered me that I knew that was the case, but had no clear idea about why. I can easily understand how the surface is cooler than the centre. (Think about a round onion bhaji that you can pick up easily, but is still searingly hot inside.) But how does the upper atmosphere get to be *hotter* than the surface? If it happened on a planet, and was orders of magnitude less extreme, it could possibly be because of heating from the sun, but that's not looking likely as an explanation here. Somehow the energy from the centre of the sun is heating the outer layers of atmosphere but not the photosphere. WTF?
And today I learned that, although there are some candidate explanations, it's a problem that bothers actual solar physicists too. Which I can't help thinking is kind of ... cool.
This entry crossposted to http://doug.dreamwidth.org/278793.html, where there are
comment(s) not shown here.
Part of the answer included the fact that the corona - the bit above the 'surface' of the sun (the photosphere) - is actually a few million degrees, whereas the photosphere itself is only about 5,800 K. Which, in one of those fun coincidences-or-is-it, is about the temperature we think the centre of the Earth might be.
It bothered me that I knew that was the case, but had no clear idea about why. I can easily understand how the surface is cooler than the centre. (Think about a round onion bhaji that you can pick up easily, but is still searingly hot inside.) But how does the upper atmosphere get to be *hotter* than the surface? If it happened on a planet, and was orders of magnitude less extreme, it could possibly be because of heating from the sun, but that's not looking likely as an explanation here. Somehow the energy from the centre of the sun is heating the outer layers of atmosphere but not the photosphere. WTF?
And today I learned that, although there are some candidate explanations, it's a problem that bothers actual solar physicists too. Which I can't help thinking is kind of ... cool.
This entry crossposted to http://doug.dreamwidth.org/278793.html, where there are
comment(s) not shown here.