Planetary Nebulae

Planetary  nebulae are  the remains of  expanding gas shells  ejected from dying red giant stars.  They are emission nebulae in that their gas clouds are ionized  by the compact  stellar core or white dwarf star that remains in the centre of the cloud. They  have a ring or hourglass shaped structure and generally look like "planetary" disks  in a small telescope - hence the name. Thay are fairly young objects and normally less than 50,000 years old. The most  well known object of this class is the Ring Nebula in Lyra (M57).  Many of these  are colourful objects appearing as shades of green  as a result of light emitted by doubly ionized oxygen. It is for this reason that I decided to image a few with the SXF Single Shot  Colour CCD camera. Here are a few examples:

 M57   The famous Ring Nebula in Lyra. This is a short twenty second exposure. Lying at a distance of 1500 light years this explosion  occurred about 20,000 years ago. The diameter of the ring is about 1 light year .

NGC 2371/2This galactic butterfly appears as a bilobed object when viewed visually. The colour image reveals a range of blue and red emissions, and is a 4x40 sec exposure  with 50 cm f/4 . This object is well placed for winter viewing in Gemini and glows at only 13th mag.

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M76                  The Little Dumbell in Perseus. Mag. 11. 1750 light years distance with a probable diameter of  1 light year.

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NGC 2438 This small nebulous spot glows in the northern part of the open star cluster M46. It is however a foreground object the cluster itself is over 5,000 light years distant.

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NGC 2440 The white dwarf star that resides at the centre of this nebula has one of the hottest surface temperatures known - approx 200,000 deg C about 30x hotter than the sun.

The image below was taken a few days later with the colour CCD showing a red colour to the expanding gas shell.