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 30452HIP 30489HIP 30493HIP 30505HIP 53588HIP 53643HIP 87242HIP 8235HIP 8239HIP 8242HIP 53701HIP 53762HIP 53772HIP 53796HIP 53806HIP 53808HIP 53874HIP 53880HIP 30518HIP 30560HIP 30563HIP 87264HIP 87266HIP 54026HIP 54079HIP 35408HIP 3541HIP 33752HIP 54122HIP 54154HIP 54168HIP 54174HIP 54179HIP 54184HIP 54185HIP 54219HIP 77187HIP 54257HIP 77195HIP 54390HIP 30576HIP 30580HIP 30591HIP 54448HIP 54461HIP 54505HIP 550HIP 30641

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