NGC 7009, also known as the Saturn Nebula, is a famous planetary nebula in the constellation Aquarius. It has an apparent magnitude of +8.3 and therefore bright enough to be spotted with binoculars. Because of its high surface brightness, it's relatively easy to find and observe with virtually any type of telescope. Visually the planetary appears small and compact but when seen through larger scopes it somewhat resembles the planet Saturn, hence the nickname "Saturn Nebula". The 3rd Earl of Rosse, William Parsons, came up with the name in 1840.
The planetary is best seen during the months of July, August and September.
The Saturn Nebula lies in the western corner of Aquarius, just over a degree west of Nu Aqr (ν Aqr - mag. +4.5). The curious asterism M73 is 2 degrees southwest of the Saturn Nebula, with 9th magnitude globular cluster M72 a further 1.5 degrees west of M73.
Since it spans less than an arc minute in diameter, the planetary appears as a faint "star" through binoculars. An 80mm (3.1-inch) scope reveals a small blue-green ellipse, surrounding a mag. +11.5 central star. The brighter central portion of the nebula, which can be seen through small scopes, measures 25 x 17 arc seconds. Under good conditions, a 250mm (10-inch) scope will show the ansae, which are the projecting arms of nebulosity extending out from either side of the disk. They span 41 arc seconds. These faint extensions of nebulosity are visually tricky to observe and a magnification of 250x is recommended. Like other planetary nebulae, NGC 7009 responds well to an Olll filter.
The Saturn Nebula is a beautiful complex planetary nebula. It's a superb object that's often high on the observing lists of backyard astronomers and is number 55 in the Caldwell catalogue.
NGC 7009 Data Table
|Object Type||Planetary Nebula|
|Distance (light-years)||2,000 -> 4,000|
|RA (J2000)||21h 04m 11s|
|DEC (J2000)||-11d 21m 49s|
|Apparent Size (arc secs)||41 x 35|
|Radius (light-years)||0.20 -> 0.40|
|Notable Features||Reasonably bright central star at mag. +11.5|