| Protuberances – beautiful phenomena on the Sun |
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The most magnificent and perhaps most beautiful phenomena on the Sun are perhaps the protuberances.
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They lie in the corona and appear most clearly over the rim of the Sun during an eclipse or on coronagraph images. With modern instruments in space the protuberances are followed all the time. |
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| Photo: NASA |
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Protuberances look like gigantic curves of warm gas. The temperature is 10 000 – 20 000 ºC.
So-called stationary protuberances may survive several rotations of the Sun (i.e. several months) before they disappear. In such protuberances the gas moves downwards from the corona towards the photosphere.
Protuberances are only seen as curves when lying on the brim of the Sun. In other cases we see them against the surface of the Sun. They are then far less conspicuous and are seen as shining filaments – curved, thin structures against the somewhat less luminous background.
Another type of protuberances may occur near the sunspots. These are called eruptive protuberances, may stretch 300 000 kilometres above the photosphere, and may eject material.
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| Photo: SOHO/ESA/NASA |
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A particularly beautiful example of this took place 4th January 2002. Then the Sun had one of the most spectacular eruptions that have ever been observed. A gigantic cloud of extremely hot gas was ejected from the brim of the Sun at speeds of a few million km/h.
The eruption was observed by means of the space observatory SOHO, which supervises the Sun 24 hours a day.
The image to the left shows a large shining protuberance about to be launched into space. |
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Below images of the eruption taken by 3 different instruments on SOHO at three different points of time. |
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| Click on the image in order to get a larger version. Photo: SOHO/ESA/NASA. |
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As seen from the left we can see:
- 1. image taken by the EIT instrument at 10.24: remote UV radiation shows the conditions at very high temperatures.
- 2. image taken by the LASCO C2 at 11.57: the Sun’s disc is covered in such a way that the camera is not blinded. The inner white circle shows where the Sun is. One gets a certain idea of the size when the Sun (the circle) is 109 times wider than the Earth.
- 3. image taken by the LASCO C3 instrument at 15.18: the eruption at the above left throws a huge cloud of gas out into space. |
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| Animation: SOHO/ESA/NASA |
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Click on the image to the left in order to start the animation showing the eruption from the large, shining protuberance being lifted outwards until it is to be launched into space.
The eruption was observed by means of the LASCO C2 instrument on board the space observatory SOHO supervising the Sun 24 hours a day. |
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