Mercury-manganese star

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.[1] 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:

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.[2]

List

The following table includes the brightest stars in this group.

Name[3]Bayer or Flamsteed designationSpectral type[3]Apparent visual magnitude[3]
Alpheratzα AndromedaeB8IVmnp2.06
Gienah Corviγ Corvi AB8III2.59
Maia20 TauriB8III3.87
χ LupiB9IV3.96
Muliphein[4]γ Canis MajorisB8II4.10
φ Herculis[5]B9mnp4.23
π1 BootisB9p4.91
ι Coronae BorealisA0p4.98
κ Cancri AB8IIImnp5.24
14 Sagittae[5]B9p5.89
Dabih Minor[6]β Capricorni BB9.5III/IV6.10
HD 30963B9 III7.23
gollark: All machine insides are in different places inside the compact machine dimension.
gollark: For machine interiors.
gollark: No, ONE dimension.
gollark: Compact Machines probably shouldn't do much for load time, at least.
gollark: Hmm.

References
  1. Mercury-manganese star. The Internet Encyclopedia of Science, David Darling. Accessed on line August 14, 2008.
  2. Michaud, Georges (May 1970). "Diffusion Processes in Peculiar A Stars". Astrophysical Journal. 160: 641–658. Bibcode:1970ApJ...160..641M. doi:10.1086/150459.
  3. Names, spectral types and apparent magnitudes taken from SIMBAD, except as noted.
  4. Muliphein Archived 2008-05-17 at the Wayback Machine, Stars, Jim Kaler. Accessed on line August 14, 2008.
  5. Adelman, S. J. (December 1988), "Elemental Abundance Analyses with Coadded DAO Spectrograms - Part Five - the Mercury-Manganese Stars Phi-Herculis 28-HERCULIS and HR:7664", Monthly Notices of the Royal Astronomical Society, 235 (3): 763, Bibcode:1988MNRAS.235..763A, doi:10.1093/mnras/235.3.763.
  6. Dabih Archived 2006-08-24 at the Wayback Machine, Stars, Jim Kaler. Accessed on line August 14, 2008.
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