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 102552HIP 102609HIP 102680HIP 102722HIP 102953HIP 103040HIP 103061HIP 103066HIP 103189HIP 103284HIP 103322HIP 103402HIP 103452HIP 103525HIP 103593HIP 103608HIP 103798HIP 103870HIP 10391HIP 103942HIP 104021HIP 104136HIP 104297HIP 104361HIP 10443HIP 104447HIP 104448HIP 104449HIP 104454HIP 104472HIP 104483HIP 104484HIP 104485HIP 104490HIP 104491HIP 104502HIP 104508HIP 104512HIP 104516HIP 104527HIP 104537HIP 104548HIP 10456HIP 104566HIP 104567HIP 104568HIP 104571HIP 104573

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