- Mercury-manganese star
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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 or B9, with two distinctive characteristics:
- An atmospheric excess of elements like phosphorus, manganese, gallium, strontium, yttrium, zirconium, platinum and mercury.
- A lack of a strong magnetic field.
Their rotation is relatively slow, and as a consequence their atmosphere is relatively calm. Some types of atoms sink under the force of gravity, while others are lifted towards the exterior of the star by radiation pressure, making an inhomogeneous atmosphere.
The following table includes the brightest stars in this group.
Name[2] Bayer or Flamsteed designation Spectral type[2] Apparent visual magnitude[2] Alpheratz α Andromedae B8IVmnp 2.06 Gienah Corvi γ Corvi B8III 2.59 Maia 20 Tauri B8III 3.87 χ Lupi B9IV 3.96 Muliphein[3] γ Canis Majoris B8II 4.10 φ Herculis B9mnp 4.23 π1 Bootis B9p 4.91 ι Coronae Borealis A0p 4.98 κ Cancri A B8IIImnp 5.24 Dabih Minor[4] β Capricorni B B9.5III/IV 6.10 References
- ^ Mercury-manganese star. The Internet Encyclopedia of Science, David Darling. Accessed on line August 14, 2008.
- ^ a b c Names, spectral types and apparent magnitudes taken from SIMBAD, except as noted.
- ^ Muliphein, Stars, Jim Kaler. Accessed on line August 14, 2008.
- ^ Dabih, Stars, Jim Kaler. Accessed on line August 14, 2008.
Categories:- Star types
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