Filaments and Prominences

Filament and prominence are different names for the same thing. They both refer to relatively cool, dense clouds of gas which hang in the hot, thin corona.

H-alpha image from Tenerife VTT/MSDP

H-alpha image from Big Bear Solar Observatory

Solar astronomers call this sort of thing a filament when they see it on the disk of the Sun, where they appear dark (see the pictures above and below to the left), and a prominence when the 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 5000-8000 K. They are easy to observe in H-alpha, a particular wavelength of light produced by the hydrogen atom. Material in filaments is in constant motion. In a H-alpha picture of the Sun you can see filaments all over the disk. In order to see the prominences off limb it is good to use an H-alpha coronagraph which blocks out the bright solar disk.

H-alpha image from the Observatory of Paris at Meudon. The long dark shapes are filaments.	This H-alpha coronagraph image from Pic du Midi Observatory shows prominences off the limb of the Sun

In this SOHO/EIT image made from light emitted by once ionized helium (produced at 60,000 degrees K) we can see three filaments which extend from the Sun's disk out over the limb.

When we observe plasma at higher temperatures (like the 1.5 million degrees K plasma shown in this image made from light from iron ionized 11 times) we often only see the filament channel, a cavity which may or may not contain the cool filament material seen in H-alpha images

Erupting Filaments

Last modification: 21 March 1999