Thursday, 17 May 2018

NGC5005: Black holes lead to star formation?

Yes, I know, it's a bit of a strange title for this post. Let's have a close look at NGC5005, a galaxy that's not in our immediate vicinity (estimates vary greatly from 45 to 113 million light-years, with an average of 65). It's a fairly bright galaxy in Canes Venatici, the hunting dogs, which can be seen quite easily with a modest telescope. 

Through the binos at 285x, it revealed a wonderful amount of detail, such as the darker arc on the left. But what we're really interested in, is its nucleus. Spectroscopic analysis revealed that the heart of this galaxy contains a lot of non or weakly ionised atoms, such as O, O+, N+, and S+. Scientists classify galaxies with such a cloud of weak ions in their core LINERs, which stands for "Low-Ionisation Nuclear Emission". This is nothing unusual and as it appears up to a third of all galaxies could fall under this category. The question however, is what causes this enormous cloud, which may swirl inward up to 750km/s! Scientists are still heavily debating on that, but significant x-ray emissions in the case of NGC5005 seem to confirm a super-massive black hole in its centre. Another observation that we make, is that this ion cloud produces some serious star formation. Usually not a lot of stars are formed in the nucleus of a galaxy, which therefore contains an older star population, and most starburst activity is generally concentrated in billowing spiral arms. 

So may we conclude that a black hole can be so powerful as to cloak itself with a cloud of ionised gas in which thousands of new stars are born? 

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