sentences:  The filaments are the remnants of the progenitor star's atmosphere, and consist largely of ionised helium and hydrogen, along with carbon, oxygen, nitrogen, iron, neon and sulfur.The filaments' temperatures are typically between 11,000 and 18,000 K, and their densities are about 1,300 particles per cm3.In 1953, Iosif Shklovsky proposed that the diffuse blue region is predominantly produced by synchrotron radiation, which is radiation given off by the curving motion of electrons in a magnetic field.