The Crab's Nebula.
In the year 1054 suddenly appeared a star in constellation of bull, which was so bright, that it could have been seen by the free sight even by the daylight. Chinese have noticed it, but in Europe this phenomenon remained unnoticed.
In the year 1731 an English astronomer has found by the telescope near the star Zeta Tauri misty constellation, which in his fantasy appeared to crab for him. That˘s why he called it Crab˘s Nebula.
Nebula M1 is clear enough to be studied by us. Its seemingly star˘s size is 8,4 and it equals to the flame of candle from the distance of 31 kilometres. The nebula appeared as a elliptical formation with dimension 3x4 arched minute.
In the year 1942 W.Baade published new photographs of this nebula that he took with 2,5 metres long telescope. He used also optical filters. The first famous photo with the reddest filter, which human eye can see: we can see, that the whole nebula is covered by abundant net of shining and soft fibbers. In the second photo with higher undulate length we can˘t see these fibbers.
Photographs rose attention of astrophysics. How it is possible, that internal unstructured nebula sends so much light in continuos part of spectrum and doesn˘t give any lines ? Further, why spectural lines come only from bright fibbers and they aren˘t in main body of nebula.
The spectral lines are splited, so the nebula has to expand. The speed of expanding can be measured. It was found out, that the speed is 2000 kilometres per one second !!! For one year the nebula is 0,2 times arched second bigger. This number is equal 60 billion kilometres. Distance from Earth is 6,2.1014 kilometres, so 2 kiloparsecs. For the way to Earth the light from this nebula needs 7520 years.
So there rises a question, when it expands 0,2 arched second per year. How much time did it need to grow up to 3 arched second ? It works for 900 years. So it was time, when Chinese had seen some object in the sky. So Crab˘s nebula is the rest of the explosion of Supernova from the year 1054.
When Supernova explodes, the most of the material flies out to the space and at the place, where was supernova remains only nucleus, which will change to neutron star or black hole.
The reason can be, that with the help of chemical reaction the pressure of the upper layers of the star warms the nucleus and nucleus will get so warm, that the ash of helium will ascend and helium will dissociate to heavier elements and the last product is iron (Fe).