Jonckheere 900 - Planetary Nebula
The planetary nebula "Jonckheere 900" can be found with a brightness of 12.4mag and an apparent size of only 8" (arcseconds) in the constellation
Gemini at the border to Orion. The PN was discovered by Robert Jonckheere in 1912 and as a result was named after him.
The nebula is located at a distance of 16,000 light-years and moves away from us by another 47 kilometers every second. The dusty envelope has a
true diameter of 0.70 light-years. Assuming an expansion velocity of 25km/s an age of 4,200 years could be expected.
The central star has a brightness of 17.8mag and is therefore not visually visible in the bright nebula.
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This Planetary appears very small in my 20" telescope even at a magnification of 270x and is not much bigger than Uranus. But it is quite bright and
greenish in color. The brightness of the roundish disk increases towards the center. You can also see a brighter knot, but it doesn't seem to be directly
in the center, but is shifted a bit to the west.
The surrounding area is rich in stars and directly south of the PN there is a brighter 13mag star.
