There is no cluster in the position indicated by Messier, which he expressed in terms of itsright ascension anddeclination with respect to the star2 Puppis. However, if the signs (+ and −) he wrote are swapped, the position matches.[4] Until this equivalency was found, M47 was considered a lost Messier Object. This identification as the same thing (ad idem) only came in 1959 with a realization by Canadian astronomer T. F. Morris.[5]
M47 is centered about 1,600light-years away and is about 78 million years old. The memberstars have been measured down to aboutred dwarfs atapparent magnitude 19. There are around 500 members,[1] the brightest being HD 60855, amagnitude 5.7Be star. The cluster is dominated by hot class Bmain sequence andgiant stars, but a noticeable colour contrast comes from its brightestred giants.[5]
It about a degree fromMessier 46, which is much older and much further away.[5]
Image of star cluster Messier 47 taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.
