Class O — O-type (Blue)

O-type stars are the hottest and most luminous main-sequence stars. With surface temperatures exceeding 30,000 K, they appear blue-white and emit strongly in the ultraviolet. They are extremely rare, comprising less than 0.00003% of main-sequence stars, but their enormous luminosity makes them visible across vast distances. O-type stars have short lifetimes of only a few million years and end their lives as supernovae, often leaving behind neutron stars or black holes. Examples include the Trapezium stars in Orion.

O-type stars are the hottest, most luminous, and rarest stars in the universe. With surface temperatures exceeding 30,000 K and luminosities up to millions of times that of the Sun, they are cosmic powerhouses that dominate the appearance of young star-forming regions despite comprising less than 0.00003% of main-sequence stars. Their intense ultraviolet radiation ionizes surrounding hydrogen gas, creating the glowing H II regions and emission nebulae that mark spiral arms in galaxies.

Characteristics

O-type stars appear blue-white and have masses ranging from 15 to over 100 solar masses. Their spectra show ionized helium (He II) absorption lines — a defining feature, as helium requires extreme temperatures to become doubly ionized. These stars burn through their hydrogen fuel at prodigious rates: while the Sun will shine for 10 billion years, an O-type star exhausts its fuel in just 1-10 million years before exploding as a core-collapse supernova, often leaving behind a neutron star or black hole. Their powerful stellar winds eject material at speeds exceeding 2,000 km/s.

Notable Examples

Famous O-type stars include Alnitak (Zeta Orionis), the leftmost star of Orion's Belt at type O9.5Ib and 250,000 times the Sun's luminosity. Naos (Zeta Puppis, O4If) is one of the hottest stars visible to the naked eye at approximately 40,000 K. Theta-1 Orionis C, the brightest member of the Trapezium Cluster illuminating the Orion Nebula, is a young O6 star responsible for sculpting one of the sky's most famous nebulae. Many O stars are found in OB associations — loose groupings of young, hot stars born from the same molecular cloud.

HIP 79172 HIP 79978 HIP 80755 HIP 81100 HIP 81305 HIP 81696 HIP 81702 HIP 81736 HIP 82121 HIP 82148 HIP 82366 HIP 82378 HIP 82436 HIP 82493 HIP 82685 HIP 82691 HIP 82767 HIP 82775 HIP 82783 HIP 82876 HIP 82936 HIP 83499 HIP 83706 HIP 83973 HIP 84401 HIP 84922 HIP 85331 HIP 86011 HIP 86605 HIP 87232 HIP 87706 HIP 87810 HIP 88040 HIP 88333 HIP 88581 HIP 88652 HIP 89218 HIP 89441 HIP 89584 HIP 89630 HIP 89681 HIP 89729 HIP 89743 HIP 89856 HIP 90204 HIP 90303 HIP 90320 HIP 90600

Häufig gestellte Fragen

What is a class O star?

Class O (O-type (Blue)) stars are blue stars. O-type stars are the hottest and most luminous main-sequence stars. With surface temperatures exceeding 30,000 K, they appear blue-white and emit strongly in the ultraviolet. They are extremely rare,

How hot are class O stars?

Class O stars have surface temperatures between 30,000 K and 50,000 K.

What color are class O stars?

Class O stars appear blue.

How many class O stars are in the StarFYI database?

StarFYI currently catalogs 264 class O stars.

How luminous are class O stars?

Extremely luminous, 30,000-1,000,000 solar luminosities