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Messier 27 - the Dumbbell Nebula

Object description:

M 27, also called Dumbbell Nebula, is a typical planetary nebula in the constellation Vulpecula. It was first described by the French astronomer Charles Messier, who entered him as number 27 on his list on 12 July 1764. It is the second brightest of this object class after the Helix Nebula (NGC 7293) in the constellation Aquarius.

The term "planetary nebula" goes back to Friedrich Wilhelm Herschel, because in his observations of such objects the telescope view appeared to him similar to that of the planet disk of Uranus. The name Dumbbell comes from the English astronomer John Herschel, who observed the nebula in 1828 and compared its shape with that of a dumbbell.

« Click here or the thumbnail image for a comparison with the size of the Moon
Planetary nebulae represent the final stage of an average star like our sun. If the nuclear energy supply runs out in the core area of the star, nuclear fusion stops and the outer gas shell is repelled; the star "expands". The gas shell becomes visible as a planetary nebula.
The hot, exposed core area is then called a white dwarf star, which ionizes the surrounding gas shell of rejected material with intense ultraviolet light and makes it glow. With a temperature of about 100,000 degrees and a size of 0,055 solar radii (almost 40,000 km in diameter), the central star of the dumbbell nebula is one of the hottest and largest. White dwarf stars are extremely small, dense, compact objects, but still contain about 90% of the mass of the original star. One cubic centimeter of a white dwarf would also weigh the earth several tons. The most famous of all white dwarf stars is Sirius B.

Typical planetary nebulae consist of about 70% hydrogen and 28% helium. The remainder consists mainly of carbon, nitrogen and oxygen. In our galaxy about 1,500 such objects are known, diverse in form and color.

An approximate age can be determined using the expansion rates of the gas shell that spreads further. In the core area, the speed is just under 7 arc seconds per century and in the outer areas at 2.5 arc seconds per century. The average speed is 31 km/second, which results in an age of almost 10,000 years. The diameter of M 27 is about 3 light years and the distance to the solar system is about 1,400 light years.

Planetary nebulae are very short-lived objects in astronomical time scales. In a few tens of thousands of years there won't be much left of the Dumbbell Nebula. The gas particles of the expanding shell are distributed extensively in space and thus form raw material for the formation of new stars.
« The central area of M27 contains comet-like nodes, as first observed in 1996 with the Hubble Space Telescope in the Helix Nebula. Its origin is still largely unknown. Close-up of nodes in the Planetary Nebula Messier 27. Image credit: NASA, C.R. O'Dell (Vanderbilt University).

Messier 27 was the first planetary nebula to be discovered. Charles Messier found him on 12 July 1764 and described him as a "nebula without a star" that "appears oval". In the first Messier catalogue (1771) he wrote about it:

On July 12, 1764 I worked on the exploration of the nebulae, and I discovered one in the constellation of Vulpecula ...
   ... you can see it well in an ordinary refractor of 3.5 feet focal length (1,100 mm). I examined it with a Gregorian telescope that magnified 104 times. It appears in oval form; it contains no star; its diameter is about 4 arc minutes.

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