Reading the book of F.D. Seward and P.A. Charles, “Exploring the X-ray Universe”, I found out some really massive and luminous O type stars that are close by and can be pointed out easily at the night sky:
| star | distance (kpc) | magnitude (V) | spectral type |
|---|---|---|---|
| ζ Pup | 0.44 | 2.3 | O4If |
| δ Ori | 0.5 | 2.2 | O9.5II |
| θ Ori C (*) | 0.5 | 5.1 | O6V |
| ζ Ori | 0.5 | 1.6 | O9.7Ib |
| η Car (*) | 2.6 | -1 to 7 | LBV |
(*): binary systems