Wednesday 25 January 2017

Appearances may deceive

When I was observing the remote open cluster NGC1193, I turned my telescope to this nearby couple of galaxies, which listen to the names NGC1160 (on the left) and NGC1161 (on the right). Not that they are that extraordinary to look at. NGC1160 definitely looked fainter than it's bigger sister, although I was able to make out a dark lane near its southwestern border (top left on my sketch). NGC1161 showed a bright and compact nucleus and a faint, regular spiral structure. It's obvious that the latter is the dominant galaxy of the two and its smaller companion looked a bit irregular and even distorted to me, as if it's being cannibalised by the other. 

Now here comes the surprise: they're no couple at all. In fact, they're nowhere near to each other and the brighter galaxy actually lies much further away from us! NGC1160 lies at a distance of 78 million lightyears, whereas big NGC1161's 102 million lightyears away. In other words, the distance between the two's ten times the distance between Earth and the Andromeda galaxy! 

Both galaxies are receding from us at incredible speeds, but nearby NGC1160's surprisingly faster. "Hey! Wait for me!" It's moving away from us at a speed of 2.500km per second (!) whereas big NGC1161 is doing only 1.950km per second. So perhaps... some time the little one may catch up with the bigger one after all. 

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