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Pi Puppis Cluster

Collinder 135, Cr 135

Proper NamePi Puppis Cluster
Messier NumberNone
NGC/IC NumberNone
Other DesignationsCollinder 135
ConstellationPuppis
Right Ascension7h 17m 27s
Declination-37° 2' 38"
Distance995 light years
305 parsecs
MagnitudeApparent: +2.1
Absolute: -5.4
DiameterApparent: 1° 50'
Actual: 15 light years
Number of Starsc. 4,000
Optimum VisibilityJanuary / February

Around the orange supergiant Ahadi (or Pi Puppis), directly southward from Canis Major are a swarm of fainter stars that together make up the Pi Puppis Cluster. With a visual magnitude of +2.7, Ahadi is by far the most prominent menber of the cluster, but three other stars are also visible to the naked eye. These three blue stars form an approximate line, with v2 Puppis and NV Puppis lying close together, and HR 2770 falling more distantly from the others in the sky. The cluster also contains many other less luminous stars.

Imagery provided by Aladin sky atlas

There is some question about the distance of this cluster from the Solar System, as current parallax data varies for the members, placing the cluster between eight hundred and a thousand light years from the Sun. This wide range can be expected to resolve as more precise data becomes available. Nearby to the southwest (as seen from Earth) lies a fainter and sparser cluster designated UBC 7, and there is reason to believe that this was associated with the stars of the Pi Puppis Cluster at some point in the past.

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