1 / 11

O B A F G K M Hottest to Coldest (Temperature sequence)

O B A F G K M Hottest to Coldest (Temperature sequence) Classification scheme due to Annie Jump Cannon (Harvard) (non-alphabetic ordering merely an historical accident)

fabian
Download Presentation

O B A F G K M Hottest to Coldest (Temperature sequence)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. O B A F G K M Hottest to Coldest (Temperature sequence) Classification scheme due to Annie Jump Cannon (Harvard) (non-alphabetic ordering merely an historical accident) Within each letter class also a numerical class 0-9 (Hot to Cold) for further refinement. Then a Roman Numeral (e.g., I, II, V) for luminosity class Sun = G2V A0 – A9 Early to late A-type

  2. Luminosity classes (LC) Second parameter (pressure-dependent) • Super-supergiants 0 0-Ia Ia-0 • Supergiants: Ia Iab Ib • Bright giants: IIa IIab IIb • Normal giants: IIIa IIIab IIIb • Subgiants IVa IVab IVb • Main Sequence V (also “dwarfs”) a,ab,b: subclasses (in decreasing luminosity order) Transition classes (Ib-II also used)

  3. Atmospheric temperature: > 33,000 K Hydrogen Balmer lines: weak Other spectral features: Ionized Helium (He+) featuressometimes in emission, strong UV continuum Parameters (in solar units) Mass 20-60 Radius 9-15 Luminosity 90,000 – 800,000 Lifetime (M.S.): 10-1 Myr O stars

  4. Atmospheric temperature: 10,500-30,000 K Hydrogen Balmer lines: medium Other spectral features: Neutral He absorption Parameters (in solar units): Mass 3-18 Radius 3.0-8.4 Luminosity 95-52,000 Lifetime (M.S.): 400-11 Myr B stars

  5. Atmospheric temperature: 7,500-10,000 K Hydrogen Balmer lines: strong Other spectral features: H features maximum at A0, some features of heavy elements, eg Ca+ Parameters (in solar units): Mass 2.0-3.0 Radius 1.7-2.7 Luminosity 8-55 Lifetime (M.S.): 3 Gyr – 440 Myr A stars

  6. Atmospheric temperature: 6,000-7,200 K Hydrogen Balmer lines: medium Other spectral features: Ca+ lines continue to increase as Balmer lines weaken thru class (from 0 to 9) Parameters (in solar units): Mass 1.1-1.6 Radius 1.2-1.6 Luminosity 2.0-6.5 Lifetime (M.S.): 7-3 Gyr F stars

  7. Atmospheric temperature: 5,500-6,000 K Hydrogen Balmer lines: weak Other spectral features: Ca+ H&K, Na "D"Sun is G2V Parameters (in solar units): Mass 0.9-1.05 Radius 0.85-1.1 Luminosity 0.66-1.5 Lifetime (M.S.): 15-8 Gyr G stars

  8. Atmospheric temperature: 4,000-5,250 K Hydrogen Balmer lines: very weak Other spectral features: Ca+, Fe,strong molecules, eg CH, CN Parameters (in solar units): Mass 0.6-0.8 Radius 0.65-0.8 Luminosity 0.10-0.42 Lifetime (M.S.): 17 Gyr K stars

  9. Atmospheric temperature: 2,600-3,850 K Hydrogen Balmer lines: very weak Other spectral features: Molecules, eg TiO ,very red continuum Parameters (in solar units): Mass 0.08-0.5 Radius 0.17-0.63 Luminosity 0.001-0.08 Lifetime (M.S.): 56 Gyr M stars

  10. W = Wolf-Rayet (WR) stars – very massive – earlier than O-type – losing mass at high rate WN = nitrogen rich WC = carbon rich L = “stars” redder than M. May not be true stars (i.e., H burning) – brown dwarfs. "R", "N", "S" stars are cool stars with particular types of molecular bands. Other stars

More Related