A Class O star is the brightest type of star, sitting on the line between main sequence and giant. Traditionally, they are coloured blue. They are also the rarest type of main-sequence star, making up only 0.00001% of luminous stars.

A typical class O star has a mass of 50 solar masses, a radius of 10 solar radii, a luminosity of 100,000 solar luminosities, a surface temperature of 40000 K and a lifespan of 10 million years.

The habitable zone of a typical O-Class star is on the order of 500 AU. This, coupled with their short lifespans, makes them poor candidates for having solar systems , especially those that support life.

Stellar Classes
Ω · N · D · Y · T · L · M · K · G · F · A · B · O