Monday, 15 January 2018

Jonckheere 320: Off the beaten path again

Most amateur astronomers prefer to stick to the well-known Messier and NGC catalogues when preparing their observation night as the more exotic ones like Minkowski, Kohoutek, Berkeley and the likes have the reputation of being too difficult for basic, amateur instruments. Nothing, however, could be further from the truth. Yes, there are some pretty invisible objects in those catalogues which even in my big binoscope refuse to reveal themselves. On the other hand, some of these more exotic objects turn out to be surprisingly easy.

Take Jonckheere 320 (J320), for example. It's a small planetary nebula in Orion, almost halfway between Bellatrix and Aldebaran. Actually, it's so small that it was originally mistaken for a double star and it takes as much magnification as circumstances allow you to bring out the details. But searching with an OIII filter will surely make it stand out against the background and I didn't have any difficulties at all finding it. When you then push telescope power to the max, you'll notice that this little gem has a lot of interesting detail on offer. 

Its bright central area boasts a lot of filaments and structures, as is typical for a young planetary nebula in full expansion. I even managed to get a glimpse of its "ansae", puffs of hot gas that are ejected from the central star's poles at the incredible speed of 43km/s. The central area itself rotates at 13km/s which is surprisingly fast. Usually stars tend to rotate slower as they grow older, but in this case the dying star's still driving the surrounding nebula into a fast spin. 

Unfortunately, the central star itself was invisible to me, but this has probably everything to do with its great distance. Measurements differ greatly, as is usually the case with nebulous objects, but 15.000 light-years seems to be the more popular value. This obviously also explains why it appears so small to us. And yet... being so far away and still shining so (reasonably) brightly in our sky... this planetary must really be something extraordinary.

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