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Objects in the Milky Way

Pleiades M45 H and Chi Persei Globular Cluster M92 Globular Cluster Palomar 5 Dumbbell Nebula M27 Ring Nebula M57 Horsehead Nebula G192.16-3.82 Veil Nebula Witch's Broom California Nebula Rosette Nebula

Pleiades
The Pleiades (M45), also called "Seven Sisters", are a 70 million years old open star cluster in Taurus with more then 1000 members. Depending on the brightness of the night sky one can see the five to eight brightest stars of this cluster with the naked eye. Between the stars several nebulous filaments are illuminated by the surrounding stars. The brightest stars are high mass stars, so they are hot and have a blue color. The so called Schmidt-Ghosts (visible as red, green or blue artificial longish structures with an extended halo) are due to starlight reflected from the correction plate of the Schmidt teleskop. This composite picture is based on images taken in the ultra-violet, yellow-green and red pass-band (Johnson UVR System). Image size: 1.4° x 1.0 °.


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H and Chi Persei
H and Chi Persei are two open star clusters (NGC869, NGC884) which are already visible with the naked eye. They are seperated by only 100 lightyears and are 7000 lightyears distant. Both are very young with an age of 11.7 and 10.8 million years for H and Chi, respectively. H is the right and Chi the left cluster in the image. The observations where carried out in the ultra-violett, blue and infrared bandpass (Johnson UB + I). Image size: 1.7° x 1.7°.


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M92
The Globular Cluster M92 has an age of about 10 billion years and belongs to the oldes objects in the Milky Way. He is situated in the Halo of our Galaxy at a distance of approximately 26000 light years. The cluster has a total luminosity of 100000 solar luminosities. At least 100000 stars belong to this cluster. M92 is visible through binoculars or a small telescope in the constellation Hercules. He is one of the best-studied globular clusters. This composite picture is based on images taken in the ultra-violet, blue and red pass-band (Johnson UBR System). Image size: 0.29° x 0.28°.


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Palomar5
Not all globular clusters look so spectacular as M92. The sparse appearance of Palomar 5 is likely due to advanced destruction by strong galactic tidal forces. The cluster is at a distance of about 70000 light years. There is evidence for a devision of the halo globular clusters into two groups: such ones formed during the collapse of the protogalaxy and those formed from the subsequent infall and dispersal of satellite-galaxy sized units. The discovery of the disrupting Sagittarius dwarf galaxy in 1994 has reinforced this view. It has been suggested that the cluster Palomar 5 has been stripped from the Sagittarius galaxy. The CCD image was taken in the R pass-band. Image size: 0.14° x 0.14°.


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Dumbbell Nebula
The Dumbbell Nebula (M27), called after its remarkable shape, was discovered in 1764 by Charles Messier in his search for comets. It is the first ever found object of the class of Planetary Nebulae. These objects form if a star has exhausted all its hydrogen reserves for nuclear fusion and undergoes the Red Giant phase in its evolution. Thereby pulsations and instabilities occur resulting in the ejection of parts of the outer shell of the star into the surrounding space. The star evolves into a hot, compact White Dwarf, visible as a bluish object in the centre of the image. It excites the surrounding gas and causes it to radiate. The image is based on Tautenburg CCD observations in the colours blue, red and infrared. Contrary to stars the gas does not radiate in the infrared, resulting in the blue-green colour of the nebula. Image size: 0.14° x 0.14°.


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Ring Nebula
The Ring Nebula (M57) in the constellation Lyra is a planetary nebula at a distance of about 2000 lightyears and a diameter of one lightyear. It was created when a sun-like star evolves to throw off its outer atmosphere and becomes a white dwarf. This composite picture is based on images taken in the blue, yellow-gree and red pass-band (Johnson BVR System). Image size: 0.1° x 0.1°.


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Ring Nebula Detail
In this four colour composite (BVR+Halpha) close-up of M57 one can infer the temperatures of different object parts by means of the colours. A high surface temperature of the white dwarf leads to his blue colour. The surrounding gas is getting cooler with the distance from the star. So we see a colour trend from green to red. This composite image also shows quite well the much more extended (three lightyears) red emission of atomic hydrogen, visualized by a contrast enhancement of the outer parts of the nebula. Image size: 0.05° x 0.05°.


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Horsehead Nebula
The Horsehead Nebula in Orion is the most famous dark cloud in the sky. Such clouds are a common place for star formation. This 1500 light years distant dust cloud is visible because it is situated in front of a bright emission nebula. In the image this emission is visible as green diffuse background. The colour image is composed of images taken in yellow-green, a narrow band and a red bandpass (V, [SII], I system). Since the dust absorbs all the visible and ultra-violet light, the stars behind the cloud appear in red colour. In contrast to the other images north is to the left here. Image size: 0.18° x 0.13°.


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G192.16-3.82
G192.16-3.82 is an ultra-compact HII (UCHII) region which shows a giant bipolar outflow known as HH 396/397. The distance to the object is about 6500 light years. Concerning the angular extension one determines a length of the outflow of more than 20 light years. Propagation of the outflow into the surrounding gas leads to shocks which excite the gas and cause the radiation. In the image the shocked gas appears blue (emission of atomic hydrogen) while its source, a protostar 20000 times more luminous than our sun, south of the reflection nebulosity (image centre), is hidden. The image was taken in the I-bandpass and the narrow band filter SII and Halpha. Spikes at the brighter stars in the image are due to overexposing of the CCD camera. Image size: 0.27° x 0.22°.


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Veil Nebula
The Veil Nebula, also called Cygnus Loop, in the constellation Cygnus is the remnant of a supernova, wich exploded more then ten thousand years ago. At that time, its apparent magnitude even exceeded the brightness of the full moon for several days. The present filamentary structure of the nebula is caused by the interaction of the expanding shock fronts with the interstellar medium. This 1400 light years distant object nowadays has an apparent diameter of 3° (six times the apparent diameter of the moon). This composite picture is based on images taken in the ultra-violet, blue and red pass-band (Johnson UBR System). Image size: 2.5° x 2.6°.


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NGC 6992
This detail (NGC 6992) of the Veil Nebula shows the filamentary structure of the emitting gas. The shock front ionizes the gas and causes it to radiate. The red colour indicates the presence of hydrogen and the blue one that of oxygen. Image size: 0.51° x 0.47°.


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NGC 6960
Blow-up of Witch's Broom (NGC 6960). The bright star is a foreground object which is not physically connected to the nebula. It can be seen with the unaided eye (4.2 magnitudes). Image size: 0.42° x 0.83°.


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California Nebula
The California Nebula (NGC 1499) in Perseus is a large gas cloud at a distance of 1500 light-years, consisting mainly of ionized hydrogen. Note the bright star in the upper part of this picture. This star is situated in the close vicinity to the nebula. Its highly energetic light ionises the gas, causing it to radiate. Image size: 2.4° x 1.6 °.


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Rosetta Nebula
The Rosette Nebula is a gas and dust nebula with an open cluster (NGC 2244) in its centre, containing several young hot stars. These stars have formed some million years ago out of the material of the nebula. They produce an intense particle flow (stellar wind) which clears up the nebula and is responsible for the characteristic hole in its centre. The intense radiation of the stars ionises the gas. Image size: 1.4° x 1.3°.


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