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 104599 HIP 104605 HIP 104608 HIP 104609 HIP 10463 HIP 104642 HIP 104643 HIP 104647 HIP 104667 HIP 104669 HIP 104671 HIP 104674 HIP 104676 HIP 104694 HIP 104699 HIP 104703 HIP 104709 HIP 104714 HIP 104742 HIP 104745 HIP 104747 HIP 10475 HIP 104754 HIP 104787 HIP 104814 HIP 104839 HIP 104843 HIP 104846 HIP 10486 HIP 104862 HIP 104883 HIP 104921 HIP 104928 HIP 104931 HIP 104952 HIP 104962 HIP 104966 HIP 104989 HIP 105001 HIP 105009 HIP 105010 HIP 105037 HIP 105042 HIP 105043 HIP 105047 HIP 105054 HIP 105057 HIP 105073

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