Other measurementsEdit

R☉           Solar Radius

M☉          Solar Mass

L☉           Solar Luminosity

AU           Astronomical Unit                =149.597.871 km

Harvard ClassificationEdit

Class IEdit

White and blue stars with broad heavy hydrogen line

This includes the modern class A and early class F. Some include early class B.

Class IIEdit

Yellow stars

Hydrogen less strong, but evident metallic lines

This includes the modern classes G and K as well as late class F.

Class IIIEdit

Orange to red stars with complex band spectra

This corresponds to the modern class M.

Class IVEdit

Red stars with significant carbon bands and lines (carbon stars.)

Class VEdit

Emission-line stars.

Secchi ClassificationEdit


Temperature          ≥ 35000  ºC
Color                      Blue
Mass                     ≥ 16 M☉
Radius                   ≥ 6.6 R☉
Luminosity             ≥ 30,000 L☉
Hydrohen Lines      Weak

B Edit

Temperature          9700- 33,000 ºC
Color                     Deep Blue/ White
Mass                     2.1–16 M☉
Radius                   1.8–6.6 R☉
Luminosity             25–30,000 L☉
Hydrohen Lines      Medium


Temperature          7200-9800 ºC
Color                      Blue White
Mass                     1.4–2.1 M☉
Radius                   1.4–1.8 R☉
Luminosity             5–25 L☉
Hydrohen Lines      Strong


Temperature          5800- 9800 ºC
Color                      Yellow White
Mass                     1.04–1.4 M☉
Radius                   1.15–1.4 R☉
Luminosity             1.5–5 L☉
Hydrohen Lines      Medium


Temperature          5000-5800 ºC
Color                     Yellowish White         
Mass                     0.8–1.04 M☉
Radius                   0.96–1.15 R☉
Luminosity             0.6–1.5 L☉
Hydrohen Lines      Weak


Temperature            3500- 5000 ºC
Color                      Pale Yellow/Orange
Mass                     0.45–0.8 M☉
Radius                   0.7–0.96 R☉
Luminosity             0.08–0.6 L☉
Hydrohen Lines      Very weak


Temperature         1700- 3500 ºC
Color                    Red, Light Orange/ Red  
Mass                   ≤ 0.45 M☉
Radius                  ≤ 0.7 R☉
Luminosity             ≤ 0.08 L☉
Hydrohen Lines      Very weak


Temperature           1000- 1700 ºC
Color                      Red Brown, Scarlet
Mass                     n/a
Radius                   n/a
Luminosity             n/a
Hydrohen Lines      Extremely Weak


Temperature           400- 1000ºC
Color                      Brown, Magenta
Mass                     n/a
Radius                   n/a
Luminosity             n/a
Hydrohen Lines      Extremely Weak


Temperature           ≤ 400 ºC

Color                      Dark Bown, Dark Purple
Mass                     n/a
Radius                   n/a
Luminosity              n/a
Hydrohen Lines      Extremely Weak