M 57 The Ring Nebula
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M 57 The Ring Nebula


M 57 The Ring Nebula
Description: M 57 The Ring Nebula

Right Ascension 18 : 53.6 (h:m)
Declination +33 : 02 (deg:m)
Distance 2.3 (kly)
Visual Brightness 8.8 (mag)
Apparent Dimension 1.4x1.0 (arc min)

Discovered by Antoine Darquier de Pellepoix in 1779.

The famous ring nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky. Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell, thus coinciding with an early assumption by John Herschel. Viewed from this equatorial plane, it would thus more resemble the Dumbbell Nebula M27 or the Little Dumbbell Nebula M76 than its appearance we know from here: We happen to view it from near one pole.

The central star was discovered in 1800 by the German astronomer Friedrich von Hahn (1742-1805), with a 20-foot FL reflector. This object is a planet-sized white dwarf star, which shines at about 15th magnitude. It is the remainder of a sunlike star, probably once of more mass than our sun, which has blown away its outer envelopes at the end of its Mira-like phase of evolution. Now over 100,000 K hot, it will soon start to cool down, shine as a white dwarf star for a while of several billions of years, and then eventually end as a cold Black Dwarf.

From the expansion rate of one arc second per century given above, the age of the nebula can be roughly estimated under the assumption of constant expansion. For its extension of 60x80 arc seconds, this yields a time of expansion of about 6,000 to 8,000 years.

The mass of the nebular matter has been estimated at about 0.2 solar masses, the density at about 10,000 ions per ccm (cm^3). Its chemical composition has been determined as follows: On each Fluor (Fl) atom, the Ring Nebula contains 4.25 million atoms of Hydrogene (H), 337,500 Helium (He), 2,500 Oxygene (O), 1,250 Nitrogene (N), 375 Neon (Ne), 225 Sulfur (S), 30 Argon (Ar) and 9 Chlorine (Cl) atoms. It is expanding at 20 to 30 km/s, and approaching us at 21 km/s. (Source SEDS)
Date: 02.11.2006 13:38
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Added by: karcher

Caption: Processed with MaxIm DL

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