Class B — B-type (Blue-White)

B-type stars are very hot and luminous blue-white stars with surface temperatures between 10,000 and 30,000 K. They are relatively rare, making up about 0.13% of main-sequence stars. B-type stars are prominent members of young open clusters and OB associations. Many of the brightest stars visible to the naked eye are B-type, including Rigel (B8Ia), Spica (B1V), and Regulus (B8IVn). They live for tens to hundreds of millions of years.

B-type stars are among the most visually striking objects in the night sky, combining high luminosity with a distinctive blue-white color. With surface temperatures between 10,000 and 30,000 K and masses from 2 to 16 solar masses, they are far more common than O-types while still being rare compared to cooler stars — roughly 0.13% of main-sequence stars. Many of the brightest stars visible to the naked eye are B-type, making them disproportionately important in defining constellation patterns.

Characteristics

B-type spectra are characterized by neutral helium (He I) absorption lines, which reach maximum strength at B2. Hydrogen Balmer lines are also prominent. B stars have lifetimes of 10-500 million years — long enough to drift from their birthplace but short enough that they still trace spiral arm structure. Many B stars are rapid rotators, with equatorial velocities exceeding 200 km/s. The Be stars (B-emission) are a fascinating subclass that eject matter into circumstellar disks, producing emission lines that can appear and disappear over years.

Notable Examples

Rigel (Beta Orionis, B8Ia) is the quintessential blue supergiant — the seventh-brightest star in the sky, shining at 120,000 solar luminosities from 860 light-years away. Spica (Alpha Virginis, B1III) is a close binary whose components nearly touch. The Pleiades (Seven Sisters) are dominated by hot B-type stars wrapped in reflection nebulosity. Achernar (Alpha Eridani, B6Vep) is one of the flattest stars known — its rapid rotation distorts it into an oblate shape 56% wider at the equator.

HIP 111429 HIP 111457 HIP 111458 HIP 11146 HIP 111491 HIP 1115 HIP 111525 HIP 111546 HIP 111550 HIP 111554 HIP 111563 HIP 111576 HIP 111589 HIP 111625 HIP 111636 HIP 11166 HIP 11168 HIP 111683 HIP 111702 HIP 111743 HIP 111773 HIP 111785 HIP 111828 HIP 111848 HIP 11188 HIP 11189 HIP 111925 HIP 111939 HIP 11195 HIP 111950 HIP 111964 HIP 111966 HIP 11201 HIP 112014 HIP 112022 HIP 112038 HIP 112105 HIP 112107 HIP 112111 HIP 11213 HIP 112144 HIP 112148 HIP 112149 HIP 112152 HIP 112167 HIP 112169 HIP 112172 HIP 112173

Frequently Asked Questions

What is a class B star?

Class B (B-type (Blue-White)) stars are blue-white stars. B-type stars are very hot and luminous blue-white stars with surface temperatures between 10,000 and 30,000 K. They are relatively rare, making up about 0.13% of main-sequence stars. B-type stars are

How hot are class B stars?

Class B stars have surface temperatures between 10,000 K and 30,000 K.

What color are class B stars?

Class B stars appear blue-white.

How many class B stars are in the StarFYI database?

StarFYI currently catalogs 10,413 class B stars.

How luminous are class B stars?

Very luminous, 25-30,000 solar luminosities