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M 80

Kroglasta kopica - Globular Cluster M80 (NGC 6093), class II, in scorpius

Rektascenzija 16 : 17.0 (u:m)
Deklinacija -22 : 59 (sto:m)
Razdalja 27.4 (*1000 sv.l.)
Vizual. magnituda 7.3 (mag)
Zorni kot 8.9 (loc min)

M80 is a fine 8th mag globular. Its 9' angular diameter corresponds to roughly 95 light years linear dimension at its distance of 36,000 light years. Its appearance resembles very much that of a comet.

On May 21, 1860, a nove occurred in M80, completely changing the appearance of this globular cluster for some days. This nova, also designated T Scorpii was discovered by Auwers at Berlin, had mag 7.0 on May 21 and 22, and faded to mag 10.5 on June 16. It was independently seen by Pogson. It was reported that Pogson had seen a rebrightening in early 1864, but this appears improbable, as nobody else could confirm this notion. The maximum brighteness of this nova corresponds to an absolute magnitude of about -8.5, if it was a cluster member. At its maximum, the nova was considerably brighter than the whole cluster !

A second nova occured in globular cluster M14 in 1938 but was only photographically observed, and found years later. A further nova was V 1148 Sagittarii which appeared near NGC 6553, but in this case a physical correlation is uncertain. Other cataclysmic variable observations in globulars are occasionally reported: Early observations of dwarf novae were recorded for M5, M30 and NGC 6712, according to Cecilia Payne-Gaposhkin's book, Stars and Clusters.

Povzeto po:
Hartmut Frommert (spider@seds.org)
Christine Kronberg (smil@lrz.uni-muenchen.de)

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