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 31934 HIP 31939 HIP 63 HIP 38518 HIP 38520 HIP 38523 HIP 38536 HIP 38540 HIP 31945 HIP 31951 HIP 31955 HIP 31959 HIP 31962 HIP 31969 HIP 3197 HIP 81281 HIP 6311 HIP 62894 HIP 96228 HIP 62949 HIP 62953 HIP 62982 HIP 63045 HIP 63049 HIP 99164 HIP 99166 HIP 99167 HIP 99168 HIP 99172 HIP 99179 HIP 31975 HIP 31976 HIP 31992 HIP 31993 HIP 32 HIP 63166 HIP 63167 HIP 63170 HIP 63194 HIP 63206 HIP 63210 HIP 63225 HIP 63250 HIP 63256 HIP 63299 HIP 63275 HIP 63277 HIP 635

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