A mercury-manganese star is a type of chemically
peculiar star with a prominent spectral line
at 398.4 nm, due to absorption from ionized
mercury.
These stars are of spectral type B8, B9, or
A0, corresponding to surface temperatures
between about 10,000 and 15,000 K, with two
distinctive characteristics:
An atmospheric excess of elements like phosphorus,
manganese, gallium, strontium, yttrium, zirconium,
platinum and mercury.
A lack of a strong dipole magnetic field.Their
rotation is relatively slow, and as a consequence
their atmosphere is relatively calm.
It is thought, but has not been proven, that
some types of atoms sink under the force of
gravity, while others are lifted towards the
exterior of the star by radiation pressure,
making a heterogeneous atmosphere.
== List ==
The following table includes the brightest
stars in this group
