Why does a solar eclipse happen

How does a solar eclipse come about?

It has something of the end of the world - when the sun darkens in the middle of the day. During solar eclipses, the moon moves between the earth and the sun and partially or completely covers them.

It is probably the most dramatic spectacle that the sky has to offer: the sunlight is pale, the crystal clear day turns to leaden twilight. Then, as if someone were turning off the light on the dimmer, everything goes very quickly. The brightest stars flare up and where the glistening bright sun could just be seen, there is now a pitch black circle in the sky, surrounded by a fiery, finely structured ring of light. A total solar eclipse!

Solar eclipses: rarely total, mostly partial

Total solar eclipse

In a total solar eclipse, the moon slides exactly between the earth and the sun, so that the sun is completely covered. The solar eclipse is only total from places that lie along a very narrow strip of the earth. This totality zone is at most a few hundred kilometers wide and many thousands of kilometers long. The fact that eclipses can be total is due to a unique coincidence in the planetary system: the sun and moon appear to be practically the same size in the earth's sky. It is true that the diameter of the sun is actually around 400 times larger than that of the moon. But since the sun is about 400 times further away from the earth than the moon, both appear to be about the same size.

Although there are up to four solar eclipses per year (of which a maximum of two are total), a certain place on earth only experiences a total solar eclipse once in a few hundred years. We saw the last one on August 11, 1999 in southern Germany. Now we have to be patient until September 3, 2081. Partial solar eclipses are much more common: With them, only part of the sun is covered by the moon. The sun is then not completely "swallowed" by the moon, but only "bitten into".

Partial solar eclipse

Danger! The observation of solar eclipses should only be done with special glasses. Never look directly at the sun with binoculars or a telescope. Serious eye damage up to blindness would be the consequences.

To be seen in darkness: the corona

During a total solar eclipse, the dark disc of the moon is surrounded by a bright, spectacular halo. That is the corona, the atmosphere of the sun. The gas, which has a temperature of millions of degrees, is normally outshone by the bright solar disk. The corona can only be seen with the naked eye when the moon obscures the solar disk.

For astronomers today, solar eclipses are largely uninteresting. The sun can always be observed very well in telescopes and with satellites - also with the help of “artificial” eclipses in the telescopes. However, some solar researchers are still investigating the areas of the corona near the solar surface during totality. These deep areas of the solar atmosphere can hardly be observed in any other way. Ancient traditions of solar eclipses are of great importance for geophysics: From the knowledge in which regions of the earth which eclipses could be seen, the gradual slowdown of the earth's rotation can be determined.