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M 55

Kroglasta kopica - Globular Cluster M55 (NGC 6809), class XI, in sagittarius

Rektascenzija 19 : 40.0 (u:m)
Deklinacija -30 : 58 (sto:m)
Razdalja 16.6 (*1000 sv.l.)
Vizual. magnituda 6.3 (mag)
Zorni kot 19.0 (loc min)

M55 is a quite large globular cluster (about 19', roughly 2/3 of the Moon's apparent diameter) but has such a loose appearence, that the present author had a star cluster impression even in 7x50 binoculars, where most globulars look like round nebulae: This one appeared very grainy. As it is about 20,000 light years distant, this diameter corresponds to a linear of about 110 light years. M55 has only very few known variables, 5 or 6. The published values for M55's magnitude vary from mag 5 to 7. Its total luminosity may be near 100,000 times that of the Sun.

M55 was originally discovered by Lacaille in 1751-1752 (his Lac I.14), when he was observing in South Africa. Messier finally found it in 1778, having probably looked in vain as early as 1764: This is a consequence of this object's southern declination. The present author can confirm that M55 is most difficult from Southern Germany also, but splendid if you go a bit more southward (it was very impressive e.g. from Northern Greece).

Vec posnetkov M55

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

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