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 97315 HIP 97334 HIP 97339 HIP 97356 HIP 97357 HIP 97374 HIP 97376 HIP 97392 HIP 97403 HIP 97422 HIP 97442 HIP 97461 HIP 97466 HIP 97471 HIP 97472 HIP 97478 HIP 97479 HIP 97485 HIP 97498 HIP 97503 HIP 97506 HIP 97545 HIP 97563 HIP 97572 HIP 97584 HIP 97594 HIP 97597 HIP 97602 HIP 97607 HIP 97611 HIP 97618 HIP 97620 HIP 97624 HIP 97628 HIP 97634 HIP 9765 HIP 97652 HIP 97670 HIP 97673 HIP 97680 HIP 97681 HIP 97698 HIP 97707 HIP 97730 HIP 97750 HIP 97759 HIP 97774 HIP 97778

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