Wednesday, 8 March 2017

The baby boom galaxy

In my previous post I told you about the close encounter of the M81 and M82 galaxies which happened a few hundred million years ago. As you could see on the sketch, M81 remained fairly intact after the M82 fly-by. Now have a look at the latter. Although evidence of a spiral structure has been found recently, it's obvious that this small galaxy has been deformed dramatically by the tidal forces that the encounter generated. Gas and dust have been stirred up severely and the main dark structures can already be observed through a small telescope. 

Now, what would be the consequence of all this, you might ask? Is this galaxy headed for destruction? Will it blow up? Fall apart?... Nothing of the kind! Actually, this galaxy's become a baby boomer! In another post I explained that galaxies are a bit like a cup of coffee. Older galaxies are like a cup in which the milk has been mixed completely. It's cooling down and the coffee has a plain, unattractive light-brown colour. Not much activity going on in that. Young and active galaxies, such as our own, are like coffee to which the milk's only just been added and which you're giving a good stir. The white trails of milk form a spiral pattern in the coffee and there's a lot of activity going on... clouds of gas and matter that are swirling, contracting and... forming stars. Now consider this little bugger. Here the milk's not simply been added and stirred. Oh no! In this case a whole can of milk was poured in at once and the coffee and milk are splashing everywhere! How about that for activity! The Hubble space telescope's discovered 197 starburst clusters in the core of this galaxy with an average mass of 200.000 Suns. This means that every single one of them is like a supermassive globular cluster of stars, all within the galaxy's central region! Stars in the core of this galaxy are being born ten times faster than they are in our entire Milky Way and consequently there are also much more supernova explosions when the biggest of those stars reach the end of their very short lives. Exactly three years ago one of these supernovae happened and could even be observed through ordinary binoculars. Here you can see the sketch that I made at the time with my former 18" telescope. The high supernova rate (about one every ten years) generates incredible superwinds that blow out matter from the galaxy's core as you can clearly see on my sketch. Most of this matter will eventually fall back into the galaxy (remember the splashing coffee) or form small and active satellite galaxies such as UGC5336 near M81.   

The universe never ceases to amaze us...


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