Star BD +31 643

Image Credit: Kalas, P. and Jewitt, D. 1996, "A Candidate Dust Disk Surrounding the Binary Stellar System BD +31 643," Nature, vol. 386, pg. 52

BD +31 643 at 0.8 microns

HD 281159       SAO 56680     HIP 17465
RA (2000) = 03 44 34.1865      Dec (2000) = +32 09 46.112
SpT = B5V    V = 8.68 mag    d = 330 pc
Proper Motion (mas/yr) =1.12 -9.43

This image traces the scattered light of a disk-like structure surrounding the binary pair of main sequence stars designated BD +31 643. Unlike HR 4796, which has a disk around one star in a binary pair, this disk surrounds both stars. Each star is a massive B5 main sequence star with projected separation 200 AU (0.6"). In the image shown here both stars lie behind the occulting mask.

BD +31 643 is about 330 pc from the Sun. As seen here, the physical radius of the disk is over 6000 AU, much larger than any other known disk around a main sequence star. Measurements indicate that the dust is depleted near the center, forming a hole in the disk approximately 2300 AU in radius.

The stars seen nearby form part of the IC 348 star cluster in Perseus. BD +31 643 lies at the center of this cluster, which is composed of many pre-main sequence stars and is generally very dusty. The image below shows a much larger view of the region.

Radiation pressure should clear the dust around BD +31 643 in about 1000 years. The fact that the dust is still present around the star argues that a population of larger objects may have formed that has replenished the dust about a thousand times over. The wispy nebulosity all around BD +31 643 represents the parental dust cloud from which the disk and binary formed. Thus the entire system may represent an intermediate stage of evolution between embedded protostars and isolated, main-sequence stars such as beta Pic.

Basic facts about BD +31 643:

1) Stellar Mass = 2 x 5 Msun, Dust Mass = 0.000001 Msun

2) Radius of Disk = 6,600 AU (20")

3) Radius of central depletion of dust = 2300 AU

4) Age < 10 Myr