Thursday, 9 July 2015

The littlest nebula

One last item piqued my interest on the way back. NGC 6153 is a curiosity, of that there's no doubt.

The star charts report it as a "planetary nebula" - one that is only around one light year across - and the expanding remnants of an old red star. Viewed from the nearest system the size of the nebula is quite apparent and, despite the name, there is no connection with planetary objects here. The composition is highly unusual and very nitrogen rich, suggesting that the star originated in another part of this galaxy.

There are enough explorers out there now to make a search for the origin of this star will happen, at least in breadth of the galaxy if not in depth.

Easily missed on the map, it has a characteristic emission profile that draws attention. The chemical spectra are coming back with neon, argon, oxygen, chlorine and carbon at far higher levels than expected from the local neighbourhood.

The Wolf-Rayet at the centre of the planetary nebula is also a common feature of this kind of phenomenon. With most of the outer core gone the inner body carries the remaining heavier elements. Incredibly hot, and emitting much of its light into the ultra-violet.