21. It has a spectral class of F81bv, meaning that it is an F-type supergiant star. 22. This is a hot, core hydrogen-fusing B-type main sequence star of spectral class B2 Vp. 23. The red supergiant is in the constellation Carina and has a spectral class of M3. 24. It belongs to the spectral class L5; its surface temperature is 1300 to 2000 Kelvin. 25. The luminosity is also lower than predicted by models for a star of this spectral class . 26. The secondary star has an O5 spectral class . 27. No massive star remains with spectral class O for more than about 5 6 million years. 28. In 1933, Bengt Str�mgren introduced the term Hertzsprung Russell diagram to denote a luminosity-spectral class diagram. 29. The brightest member of this constellation is Aldebaran, an orange-hued, spectral class K5 III giant star. 30. In the MK system, a luminosity class is added to the spectral class using Roman numerals.
