Explanation of techniques

I just thought I would include some small explanation of the way the various images are created. This is certainly not all of the ways scientists are currently looking at the sun, but it is the ones I have used on this page! To see examples of the images, just look on the page itself (I'm not repeating the images!)

Hydrogen-alpha line.

This is the most common image I have used in making the page. It is a good way of looking at the surface of the sun, and gives more detail than from looking at a standard white light picture. The technique used here is to study one small part of the electromagnetic spectrum. Within sun light, the continuous spectrum visible in white light is interrupted by a series of black absorption lines. One particular wavelength, at 6563 angstroms (a scale used to measure wavelength. 1 angstrom = .0000000001m) corresponds to the absorption by hydrogen atoms in the sun's atmosphere. This is near the red end of the visible spectrum, and is a particularly large line (due to the sun being mostly composed of hydrogen!). So the image produced basically shows the sun's emmissions at this one wavelength. Thus, in areas where there is a concentration of hydrogen atoms more of the light is absorbed and the area appears darker. Thus, filaments, being areas of much higher density than the surroundings, show up dark in these images.

Helium-1 line.

A different line in the spectrum, surprisingly enough connected to helium ions, rather than hydrogen. It gives rise to similar looking pictures that tell us the helium levels in the sun.

MDI magnetogram.

From the SOHO satellite, this instrument picks up the motions within the sun, and forms an image of the magnetic field on the sun. It works by measuring the polarization of electrons in the sun, which are affected by the strength and direction of the magnetic field in the locality. Thus an image can be built up of the strength of the magntetic field, and whether it is positive or negative. In these images, negative is represented by black and positive by white. Grey is the neutral field.

Yohkoh SXT pictures.

From the Yohkoh satellite, this instrument takes pictures in the soft x-ray part of the electromagnetic spectrum, and converts them into something we can look at, giving us a picture of the million degree solar corona.

EIT pictures.

Also from SOHO, this instrument takes pictures of the sun in the ultra-violet part of the spectrum.