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Thursday, 12 July 2012

The Sun still has secrets.....

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From mysteries on the edge of the solar system, to a mystery in its heart:: How the Sun transports heat between it's core and surface.

Image above: The structure of the Sun. Or, at least, what we thought the structure of the Sun was. Image courtesy of the University of Alberta.

The theory goes that the Sun gets heat from its fusing core to the surface by convection currents [1]. Boil some frozen veg in a pan - you see how the veg churns around and around? Convection currents.

Video above: A demonstration of convection currents, moving heat from a hot spot, on the left, to a cold spot, on the right. The same principle applies to any fluid, even ultra hot plasma. Video courtesy of teacherAJH via youtube

Our understanding of convection currents in the Sun is based almost entirely upon theory, and our best guess of how they should work under conditions beneath the solar surface. There's very little actual data on these massive solar convection flows, because the Suns surface is a maelstrom of super hot plasma, twisted magnetic fields, flares, sunspots..... it's impossible to see through,basically.

Image above: The Solar Dynamics Observatory sees the Moon partly obscure the Sun. It's not relevant, it's just very cool. Image courtesy of NASA.

Using the Helioseismic and Magnetic Imager (HMI) on board NASA’s Solar Dynamics Observatory [2], researchers have measured [3] how these convection currents actually move -  the process is a lot like watching the veg move on the surface of a stew*: We can't see beneath the surface but we can see how things move on the surface, and build up a picture from that.

Video above: An explanation of the Heliosismic and Magnetic Imager, a sixteen million pixel camera for finding out how the Sun works. Video courtesy of NASA

The results show that the currents move about a hundred times slower than expected. Which means we may have the Suns system of transporting heat all wrong. We may need to re-think our ideas on how the Sun moves heat about, how it generates magnetic fields at the surface.... it's brilliant. The universe has surprised us again, and now we have the chance to discover a whole bunch of new things, as we work out what's actually going on......

* I was hungry when I wrote this post.

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