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Object description
The stars Acrux+Acrux B, the planetary nebula PK 299-0.2 and the open star cluster van den Bergh-Hagen 131

Object description:

« « The planetary nebula PK 299-0.2. The object appears more as a small H-II region and is also cataloged as GN and RCW 64, but is listed as a planetary nebula in the Aladin/Simbad database with an extent of 4 arcmin. More detailed information about the object is not available. GN 12.23.8 is an extremely faint H-II region.

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For the open star cluster van den Bergh-Hagen 131 no further information is available except for the apparent diameter of nearly 5 arcminutes.

« Acruxis (possibly) a quadruple star system, consisting of two blue, luminous stars of spectral classes B1 and B2 (Acrux a1 and Acrus a2) and a somewhat fainter component of spectral class B4 (Acrux B) at a very wide distance to the two main components, which are nearly equally bright (Acrux a1 is also a spectroscopic double star.

Acrux B has the same distance to the solar system and also the same proper motion and direction as Acrux a1 and a2, but whether it really belongs to the Acrux a1 and a2 system is uncertain.

Acrux a1 and a2 appear in distinct blue color in visual observation. To separate the components visually it requires a telescope aperture of 5 to 6 inches, the apparent separation is currently 4 arcseconds. The distance to the solar system is 312 light years, the orbital period of the main components is about 1500 years.

The image on the left is an old "lucky imaging" image of Acrux a1/a2 and Acrux B, taken in the primary focus of the Celestron C14 Tlescope. Further imaging information is unfortunately no longer available.

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