Am star

An On - Star or metal lines - star is a type of chemical pekuliären stars of spectral A whose spectrum has strong and often variable absorption lines of metals such as zinc, strontium, barium and zirconium, as well as a deficit in others, such as calcium or scandium. The thickness of the potassium is too early as compared to the hydrogen lines, while the metal lines are too late compared to the hydrogen lines. The fine classification of these stars would be, for example, AmkA8hA9mF3, according to the spectral type derived from the potassium line k, the hydrogen lines h and metal lines h Am- stars represent up to 50 % of all stars of Spktraltyps A8 and achieve frequency deviations up to a factor of ten compared with normal A- stars. These anomalies are caused by elements that absorb more electromagnetic radiation (eg light) and ascend by the radiation pressure in the surface layers of the star. Other elements are depleted because they fall by gravity of the star in deeper layers. These effects occur only in slow rotating stars into effect, where rapid rotation does not prevent the gravitational separation.

Normally, star of type A have high rotation speeds. Most Am stars are therefore also present in binary stars, where they give some of their rotational energy via tidal forces to the partner.

Representative

The most famous of the metal lines star is Sirius ( α Canis Majoris ).

The following table contains some more well-known of these stars in descending apparent visual magnitude: