Spectral Classification 光谱型 表面温度(K) 颜色 特征谱线 30,000 蓝 强电离He线，重元素多次电离线 B 20,000 蓝白 中性He线，重元素一次电离线，H线 A 10,000 白 H线，重元素一次电离线 F 7,000 黄白 重元素一次电离线，中性金属线，H线较 明显 G 6,000 黄 重元素一次电离线，中性金属线，弱H线 K 4,000 红橙 中性金属线，重元素一次电离线，无H线 M 3,000 红 中性金属线，分子带 the spectral class sequence is really a temperature sequence
光谱型 表面温度(K) 颜色 特征谱线 O 30,000 蓝 强电离He线，重元素多次电离线 B 20,000 蓝白 中性He线，重元素一次电离线，H线 A 10,000 白 H线，重元素一次电离线 F 7,000 黄白 重元素一次电离线，中性金属线，H线较 明显 G 6,000 黄 重元素一次电离线，中性金属线，弱H线 K 4,000 红橙 中性金属线，重元素一次电离线，无H线 M 3,000 红 中性金属线，分子带 the spectral class sequence is really a temperature sequence. Spectral Classification
←Surface temperature(K) 50,000 25,000 10,000 8000 6000 5000 4000 3000 H ↑ CaⅡ HeⅡ HeI TiO suans aurT Ca I MgⅡ FeⅡ FeI Si III Si 05 BO A0 FO GO KO MO M7 Spectral type G:Hydrogen lines very weak;Ca Il H and K lines reach maximum strength near G2;neutral metal (Fe 1,Mn 1,Ca I)lines strengthening while ionised metal lines diminish
G：Hydrogen lines very weak; Ca II H and K lines reach maximum strength near G2; neutral metal (Fe I, Mn I, Ca I) lines strengthening while ionised metal lines diminish
A star's spectrum also gives information BOV (HD237007) about the pressure in the star's atmosphere. That pressure is related to the star's luminosity;high-pressure atmosphere stars 400O 50 6000 7000 are low luminosity dwarfs,low-pressure Wavelength (A) (A) atmosphere stars are high luminosity giants or even supergiants FU HD10032) In addition to the temperature classification,there is the following luminosity classification: 4000 5000 6000 7000 V -dwarf Wavelength(A) IV sub-giant Ill giant COV (HD2809分 Il (bright)giant,or also just giant 一 supergiant The Sun is a G2V star! 4000 500U 60U0 7000
A star’s spectrum also gives information about the pressure in the star’s atmosphere. That pressure is related to the star’s luminosity; high-pressure atmosphere stars are low luminosity dwarfs, low-pressure atmosphere stars are high luminosity giants or even supergiants In addition to the temperature classification, there is the following luminosity classification: • V – dwarf • IV – sub-giant • III – giant • II – (bright) giant, or also just giant • I – supergiant The Sun is a G2V star!
Surface temperature (K) 25,00010,00080006000500040003000 106 -10 Luminosity Class Luminous supergiants V-dwarf(包括主序) IV-subgiant 104 Less luminous supergiants Ib lll giant Bright giants 1 Il bright giant 102 Giants 0 。1- supergiant Subgiants Main sequence IV Same Teff,maybe same M*, +5 but different R*,causes Sun different surface pressure and strengths of spectral lines. 10-2 +10 2-D Classification,Teff and g 104 +15 Morgan-Keenan(MK)system The Sun is a G2V star! O5 BO A0 FO GO KO MO M8 Spectral type
• V – dwarf (包括主序） • IV – subgiant • III – giant • II – bright giant • I – supergiant Same Teff, maybe same M*, but different R*, causes different surface pressure and strengths of spectral lines. 2-D Classification, Teff and g Morgan-Keenan (MK) system The Sun is a G2V star! Luminosity Class
10,000 Stellar Demographics 5000 Red B A F G K M dwarfs Supergiants Giants -10 Main sequence White 0 M dwarfs K N G A 5<6
Stellar Demographics