Menu
Physical Characteristics
A typical planetary nebula is the average length of one light year, and consists of a highly rarefied gas density of about 1000 particles per cm, which is negligibly small compared with, for example, the density of the Earth's atmosphere, but in approximately 10-100 times greater than the density of interplanetary space on the distance of the Earth's orbit from the Sun. Young planetary nebulae have the greatest density, sometimes reaching to 106 particles per cm. As aging nebulae expansion leads to a reduction in density.
Radiation of the central star heats the gas to temperatures of about 10 000 K. ironic that sometimes the gas temperature increases with increasing distance from the central star. This happens because as more energy is the photon, the less likely that it will be absorbed. Therefore, in the interior areas of the nebula maloenergeticheskie absorbed photons, and the rest with high-energy absorbed by the external fields, leading to an increase of temperature.
Nebula can be divided into the poor material and poor radiation. According to this terminology in the first case, the nebula does not have enough material to absorb all the ultraviolet photons emitted by a star. Therefore, visible nebula is fully ionized. In the second case, the central star emits insufficient ultraviolet photons to ionize all the surrounding gas, and the ionization front moves into the neutral interstellar space.
Since most of the planetary nebula ionized gas (ie a plasma), a significant effect on its structure provides to the magnetic field, causing phenomena such as fiber and plasma instability.