Prominences are Cool! (relatively)

As the title says, prominences are cool. Prominences are relatively cool, dense clouds of gas which just hang around in the hot, thin corona. Filaments are cool too, because a filament and a prominence are the same thing.

H-alpha image from Tenerife VTT/MSDP.

Solar astronomers call this sort of thing a filament when they see it on the disk of the Sun, where they appear dark.....

.... and a prominence when you see it off the edge (or limb of the Sun, where they appear bright (as in the pictures to the right). Most of the material in prominences is at a temperature of 5000-8000 degrees. Remember that the corona is at least 1,000,000 degrees, so prominences are very VERY cold compared to their surroundings. It's a bit of a mystery how these cold, heavy objects support themselves in a hot, thin atmosphere like the corona.

H-alpha image from Big Bear Solar Observatory

Normally when you put a COLD object next to one which is much HOTTER then the cold object gets hotter. Something must be happening to hinder the transfer of heat energy from the corona to the prominence!

Filaments are easy to observe in H-alpha, a particular wavelength of light produced by the hydrogen atom. The plasma in filaments is in constant motion. In an H-alpha picture of the Sun you can see filaments all over the disk.

H-alpha image from the Observatory of Paris at Meudon.

coronagraph image from