|Observations of the Sun at different wavelengths can accommodate the various aspects of the surface and the atmosphere. (Image NASA / SDO / Goddard Space Flight Center.)|
If you take a picture of the sun with a normal camera, you get a yellow featureless disk. If you do, when the light is close to the horizon, it will add a bit of red (and nothing more), because between you and the star will be more of Earth's atmosphere, the scattering waves in the blue part of the spectrum. In fact, the Sun radiates in all colors, but the yellow — the most striking of those that are visible to the naked eye.
Tools of the ground-based and space telescopes, fortunately, allow the observation of light in all its glory. Different wavelengths carry information about the various components of the Sun's surface and its atmosphere, allowing to monitor the constant changes of stars — with the spacecraft Solar Dynamics Observatory (SDO), Solar Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory (SOHO).
For example, the length of the yellow light at 5800 A is based mainly on the material heated to about 5700 ° C. Extreme ultraviolet (94 A) is produced by atoms with a temperature of 6,300,000 ° C, that is, on this length for comfortable viewing by solar flares.
We see what we see, just because the sun is composed of hot gas, and the heat produces light — as in the incandescent bulb. But at the same time the star has many different atoms (helium, hydrogen, iron, etc.), and many of their species (ions) with different electrical charges, each of which emits at a certain wavelength at a certain temperature. Catalogues of these waves was the beginning of XX century, and take hundreds of pages.
Solar telescopes use this fact in two ways. First, the special tools (called spectrometers) watch different wavelengths simultaneously and can measure the presence of each wavelength. This allows you to map the temperature of the solar material, which does not look like our normal maps, as well as graphics.
Second, the tools that allow you to get more familiar images of the sun, are focused on the emission of a single length — sometimes one that is not visible to the naked eye. For example, the SDO spacecraft mounted device Atmospheric Imaging Assembly (AIA), which are ten wavelengths. Each of them is usually a sign of one of two types of ions, although a little longer or shorter wavelengths produced by other ions, always present in the picture. These lengths are chosen so as to provide a view of all parts of the solar atmosphere: 4500 A — is the surface of the sun, or photosphere, 1700 — surface and chromosphere (just above the photosphere, where the temperature starts to rise), 1600 — upper photosphere and the transition region between the chromosphere and corona (the highest layer of the solar atmosphere), where the temperature rises very quickly, 304 — the chromosphere and transition region, 171 — Crown during a lull at this wavelength are seen as coronal loops, 193 — slightly more than the hot region of the corona, and more hot stuff of solar flares, 211 — a hot, magnetically active regions of the corona, 335 — still hot and active; 94 — corona during a solar flare, 131 — the most hot stuff outbreak.
|A detailed explanation of each wavelength here. (Image NASA / SDO / Goddard Space Flight Center.)|
Prepared according to NASA.