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Am star
Also known as a metallic-line star, a type of A star whose spectrum has strong and often variable absorption lines of some metals (hence the "m"), such as zinc, strontium, zirconium, and barium, more typical of an F star, and deficiencies of others, such as calcium and/or scandium. These abundance anomalies are due to some elements being pushed to the surface because they are better light-absorbers, while other elements sink to lower levels under gravity – an effect that requires slow stellar rotation.
Normal A stars spin quickly, but most Am stars are known to be members of close binary systems in which the two stars slow each other down by tidal action. Familiar examples include Sirius and Acubens.
Related entries
• Ap star
• mercury-manganese star
• variable stars
Related category
• TYPES OF STAR
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