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Messier 6 and the H-II region LBN
1117 |
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Description of
object:
The open star cluster
M 6 is located in the constellation Scorpius at a distance of about 1600 light
years. The diameter of the cluster is 12 light years. M 6 appears in the sky
with an apparent diameter of 25 arc minutes, almost as large as the Moon. Due
to its visual impression in the telescope, it is also called the butterfly
cluster. The age of M6 is estimated to 95 million years. The contrast between
the hot blue stars of spectral class B and the single orange star BM Scorpii
with spectral class K is striking. BM Scorpii is a semiregular variable giant
star with brightness fluctuations between 5.5 mag and 7 mag. The right part of
the image shows the large reddish HII region LBN 1117. Even though the camera
was not modified for astro use in the red spectral range, this weaker emission
nebula could be imaged. |
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With a
brightness of 4.2 mag, M 6 can be detected by the eye as a weak nebulous object
without stars. Even small binoculars show a large number of the brighter stars
and reveal the true nature of the object.
The discovery of the cluster
is attributed to the Italian astronomer Giovanni Battista Hodierna in the
middle of the 17th century. Hodierna listed the star cluster in a catalogue of
celestial objects, which received little attention in the following years.
About 100 years later, M 6 is observed by the Swiss Jean-Philippe de
Chéseaux and Charles Messier and is listed as number 6 in his famous
Messier catalogue.
The
image left shows a size comparison with the full moon.
Click here or the thumbnail image to load a large
version. |
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