Minimalist frame acquisition with inferred G.
From Wikipedia:
The
Saturn Nebula (also known as
NGC 7009 or
Caldwell 55) is a
planetary nebula in the
constellationAquarius. It appears as a greenish-yellowish hue in a small
amateur telescope. It was discovered by
William Herschel on September 7, 1782, using a telescope of his own design in the garden at his home in
Datchet,
England, and was one of his earliest discoveries in his sky survey. The nebula was originally a
low-mass star that ejected its layers into space, forming the nebula. The central star is now a bright
white dwarf star of
apparent magnitude 11.5.
The Saturn Nebula gets its name from its superficial resemblance to the
planet Saturn with its rings nearly edge-on to the observer. It was so named by
Lord Rosse in the 1840s, when telescopes had improved to the point that its Saturn-like shape could be discerned.
William Henry Smyth said that the Saturn Nebula was one of
Struve's nine "Rare Celestial Objects".
[4]The Saturn Nebula is a complex planetary nebula and contains many morphological and kinematic sub-systems in three dimensions. It includes a halo, jet-like streams, multiple shells, ansae ("handles"), and small-scale filaments and knots. The ansae are expanding non-radially from the central star.
[5] Although the ansae are most prominent in the Saturn Nebula, they are also visible in other planetary nebulae, including
NGC 3242,
NGC 6543 and
NGC 2371-2.
The distance of the Saturn Nebula is not known precisely.
Sabbadin et al. 2004 estimates the distance to be 5,200
light-years (1.6
kpc). In 1963 O'Dell estimated it to be 3,900 light-years (1.2 kpc), which gives an approximate diameter of 0.5 light years for the object as a whole.The central star, a very hot bluish dwarf with a temperature of 55,000 K, from which the nebula is believed to originate, has an absolute magnitude of +1.5, which equates to a luminosity of about 20
solar luminosities and a visual magnitude of 11.5. This strong ultraviolet irradiation from the central star creates the characteristic fluorescent green tint of the nebula via the radiation of doubly ionized oxygen.
The object overall has a visual magnitude of 8 and a radial velocity of 28 miles per second towards the
Earth.The nebula is 1 degree west of the star
Nu Aquarii. The central portion measures 25″ × 17″, while the outer shell extends to 41″ × 35″. The object is on many "best of" observing lists.
[6][7]
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