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 74215HIP 74220HIP 74248HIP 33948HIP 33981HIP 33987HIP 74347HIP 74368HIP 7455HIP 7457HIP 74447HIP 74449HIP 33998HIP 34000HIP 34005HIP 34006HIP 74552HIP 92028HIP 74622HIP 74680HIP 74716HIP 74729HIP 74801HIP 74784HIP 74820HIP 74829HIP 92036HIP 92038HIP 74869HIP 74874HIP 74910HIP 92072HIP 92076HIP 94027HIP 94029HIP 94033HIP 94035HIP 94043HIP 94045HIP 92159HIP 92163HIP 94122HIP 94135HIP 94139HIP 94149HIP 92180HIP 92188HIP 92189

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