What is the shell star?

Shell Star is considered surrounded by a gas disc at its equator. These stars are also known as variable gamma Cassiopeiae, because the first example was found in the constellation Cassiopeia. Shell Star is called "variable" due to irregular changes or variability in the brightness caused by the surrounding cloud of gas. This process is not fully understood, but may be related to the rapid rotation of all known stars of this type. Stars

are classified according to their spectral characteristics and assigned by the letter and the stars of Shell are divided into four groups based on this classification. The letters are O, B, A, F, G, K and M. Stars at the end of the spectrum, called blue stars, are the hottest. The stars at the other end of the spectrum are the coldest stars and are classified as red stars. Three types of shell stars fall under O and B, or blue and blue white parts of the spectrum and the fourth group belongs to the A-F series or white and yellow-white stars. Most shell stars fall within B.

letter "E" is often applied as a secondary classification to a star to indicate increased emissions, and in most cases the Shell star will be marked as such. Increased emissions come from the hydrogen part of the emission spectrum, which means that these stars show more hydrogen in a state with higher energy than other stars. Shell Star can also show an increased emission spectra for other elements such as iron, helium and calcium.

Stars

are also classified by size, which also corresponds to the overall luminosity or brightness. Most shell stars are one of the larger types of stars. Roman numerals are used to indicate this classification, the stars are the largest and the stars are the smallest. Our own sun is a star size V. Most Shell Stars Fall to the III-IV range, but some are found in class V.

Variability in luminosity and emission spectra for shell stars make it difficultTheir full understanding or precisely classify them because it may seem that at different times they fall into different categories according to the criteria received. It is assumed that extremely fast rotation plays a major role in this variability, but does not fully explain changes in brightness or emissions. In 2011, astronomers are still trying to explain the mechanism of the gas disk and its relationship to the variability of Shell stars.