NGC 6302, also known as the Bug Nebula or Butterfly Nebula, is a bipolar planetary nebula in the constellation of Scorpius. It's an unusual object, complex in structure with an incredibly hot star at its core. At a temperature of 250,000 degrees Celsius, this dying star is one of the hottest known in the galaxy. However, since it radiates predominantly in UV and is shrouded by dust, it's visually challenging to observe.

The discoverer of the Bug Nebula is debatable. Edward E. Barnard observed the planetary in 1880, although some references suggest that James Dunlop may have found it in 1826. The nebula itself shines at mag. of +9.6 and therefore well within the reach of medium size backyard scopes.

Finder Chart for NGC 6302 - pdf format (credit:- freestarcharts)

The Bug Nebula is positioned towards the centre of Scorpius; close to the sting of the Scorpion and 4 degrees due west of Lambda Scorpii (λ Sco - mag. +1.6). It spans a mere 1.8 x 1.3 arc minutes and through a 150mm (6-inch) telescope appears as a dim, slender fuzzy streak. However, the planetary does have a relatively high surface brightness. A larger 250mm (10-inch) instrument reveals an extended object, with two "wings" protruding outwards from a narrow centre. It looks somewhat like an hourglass shape. As with many such nebulae, a UHC or Olll filter will assist.

NGC 6302 is estimated to be 4,000 light-years distant. The nebula contains hydrocarbons, carbonates, water ice and iron and is estimated to be about 10,000 years ago. It has a spatial diameter of 2 light-years.

The Bug Nebula is number 69 in the Caldwell catalogue and is best seen from southern and tropical locations during the months of June, July and August.

NGC 6302 Data Table