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 35868 HIP 35869 HIP 84628 HIP 8469 HIP 8474 HIP 59279 HIP 8503 HIP 35886 HIP 35887 HIP 35893 HIP 35906 HIP 35909 HIP 56617 HIP 38999 HIP 39004 HIP 35920 HIP 35926 HIP 35933 HIP 56634 HIP 39013 HIP 39014 HIP 85022 HIP 35951 HIP 35955 HIP 35970 HIP 39063 HIP 35988 HIP 35996 HIP 35997 HIP 85094 HIP 85095 HIP 39073 HIP 39081 HIP 39084 HIP 36009 HIP 36013 HIP 36024 HIP 80606 HIP 39100 HIP 39105 HIP 39107 HIP 36038 HIP 3604 HIP 36040 HIP 36065 HIP 36066 HIP 36068 HIP 36070

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