***Temperature thermometer here, from zero to 10,000,000 - showing cartoons at sample temperatures ***
Use the slider under the thermometer to move the bar up and down to highlight different temperature regimes.
The solar corona has a temperature of about one million degrees. Very hot material gives out light in the ultraviolet part of the spectrum.
Here's a picture of the Sun in ultraviolet light. It was taken by EIT one of the instruments on board the SOHO spacecraft. At these ultraviolet wavelengths all we see is the very hot gas in the Sun's atmosphere - very different from the images of the Sun we are used to.
Do you see the regions that are very bright? We call these active regions. They are are hotter and denser than the surrounding regions.
Pictures like this are beautiful and they give us a lot of information about the Sun. We can get even more details about the Sun from its spectrum.
Here is a spectrum of the solar atmosphere using CDS, another of SOHO's instruments.
The spectra we get from the Sun are filled with fingerprints from different elements. The brightest line at 58.4 nm is produced by helium. To produce this line, the helium needs to be at 10,000 degrees. Helium was found first in the Sun by Sir Norman Lockyer , a very famous British astronomer.
The line at 63.0 nm, on the right, is produced by oxygen atoms that have lost 4 electrons. To be in that sorry state, the atoms have to be heated to about 250,000 degrees - getting warm.
Now you can begin to see how we measure the temperature of the Sun. Each layer of the solar atmosphere is at a different temperature.
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