The Ring Nebula in Lyra

M57 The Ring Nebula (my photo)

Had "une belle nuit de l'astronomie dans le jardin". I photographed a number of astro treats through my refractor. The "seeing" was not brilliant as high level cloud was an intermittent problem.  The lack of light pollution thanks to Suffolk County Council turning off the street lights at midnight was a great help. Thank you SCC!

 

M57 The Ring Nebula ( Hubble photo)

M57 The Ring Nebula (my photo enlargement)

Planetary nebula nucleus (PNN)

The central PNN was discovered by Hungarian astronomer Jenő Gothard on September 1, 1886 from images taken at his observatory in Herény, near Szombathely (now part of Szombathely). Within the last two thousand years, the central star of the Ring Nebula has left the asymptotic giant branch after exhausting its supply of hydrogen fuel. Thus it no longer produces its energy through nuclear fusion and, in evolutionary terms, it is now becoming a compact white dwarf star.

The PNN now consists primarily of carbon and oxygen with a thin outer envelope composed of lighter elements. Its mass is about 0.61–0.62 solar mass, with a surface temperature of 125,000±5,000 K. Currently it is 200 times more luminous than the Sun, but its apparent magnitude is only +15.75.

M 57 is 0.7 kpc (2,300 light-years) from Earth. It has a visual magnitude of 8.8v and photographic magnitude of 9.7p. Photographically, over a period of 50 years, the rate of nebula expansion is roughly 1 arcsecond per century, which corresponds from spectroscopic observations to 20–30 km⁻¹). M 57 is illuminated by a central white dwarf or planetary nebula nucleus (PNN) of 15.75v visual magnitude, whose mass is approximately 1.2 MΘ (in solar masses.)

All the interior parts of this nebula have a blue-green tinge that is caused by the doubly ionized oxygen emission lines at 495.7 and 500.7 nm. These observed so-called "forbidden lines" occur only in conditions of very low density containing a few atoms per cubic centimetre. In the outer region of the ring, part of the reddish hue is caused by hydrogen emission at 656.3 nm, forming part of the Balmer series of lines. Forbidden lines of ionized nitrogen or [N II] contributes to the reddishness at 654.8 and 658.3 nm.