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 36244HIP 36246HIP 36250HIP 36251HIP 36252HIP 91369HIP 91380HIP 99954HIP 96962HIP 9144HIP 8951HIP 96963HIP 91460HIP 91462HIP 91466HIP 91468HIP 91508HIP 91514HIP 91522HIP 96969HIP 9697HIP 96990HIP 96992HIP 91620HIP 91623HIP 91624HIP 91625HIP 89705HIP 89708HIP 89714HIP 38650HIP 38652HIP 36420HIP 36421HIP 36427HIP 33330HIP 33331HIP 33336HIP 33339HIP 33343HIP 89831HIP 89832HIP 91790HIP 91798HIP 89898HIP 89933HIP 38667HIP 89963

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