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NGC 5617 and Trumpler 22 - a double star cluster in the
southern sky, Pismis 19 and the small bipolar planetary nebula He
2-111 |
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Description of object:
NGC 5617 is a galactic open star
cluster in the constellation Centaurus. According to Trumpler it is classified
as Type I 3 m. Our image shows about 80 stars, in
total about 175 stars are assigned to the cluster. It is located about 5000
light-years from the solar system and with an apparent diameter of about 10
arcminutes its real diameter is 15 light-years. NGC 5617 was discovered on May
8, 1826 by the Scottish astronomer James Dunlop.
NGC 5617 forms together
with Trumpler 22 a double star cluster.
Trumpler 22 lies 0.6 degrees southeast of NGC 5617. Both clusters have the same
distance to the solar system and have the same radial velocity. The stars in
both clusters are the same age, about 70 million years, and have similar
metallicity (the relative abundance of iron compared to hydrogen), suggesting
that they formed together from a cloud of interstellar dust. The distance
between NGC 5617 and Trumpler 22 is about 60 light-years.
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Henize 2-111 - - also cataloged
as PK 315.0-00.3 - is a small, bipolar planetary nebula, near Alpha Centauri.
Its apparent diameter is only about 20 arcseconds and its apparent magnitude is
given as 16.7 mag. In its morphology it resembles
NGC 6302 in the constellation Scorpio. The intensity
maximum of the radiation is at 658.4 nm (N-II), therefore it appears in deep
red color in the image.
He 2-111 is embedded in an elongated oval halo
of reddish nebulae, probably gas masses ejected from the central star long ago.
The planetary nebula is about 11.500 light years away from the solar
system.
It was discovered in 1967 by Karl Gordon Henize. Karl Gordon
Henize was an astronomer and NASA science astronaut. In 1985, Henize launched
as a mission specialist on the space shuttle Challenger for the Spacelab-2
mission (STS-51-F). He died tragically in 1993 while attempting to climb Mount
Everest.
Click here or on the thumbnail to load a larger
image » |
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Only
little information is available about Pismis
19. The cluster has an apparent diameter of only 2 arcminutes and
the brightest stars are about 12th magnitude. The yellowish-reddish color of
the stars is striking. It is due to a high interstellar absorption by dust
lying in front of it.
Pismis 19 has a distance of about 8000 light-years to
the solar system. Its age is given as about 800 million years, so the cluster
is about 100 times older than NGC 5617 and Trumpler 22.
Paris Maria
Pismis was an astronomer of Armenian origin who worked on open star clusters in
Mexico and published a corresponding catalog.
« Click here or the thumbna.l to load a large annoted
image
The bluish
brightening on the left side is scattered light from the bright star alpha
Cenrauri. |
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All Images and all Content are ©
by Franz Hofmann + Wolfgang Paech |