Sunday, March 11, 2012

Horsehead nebula

B 33 and IC 434

      It's winter and you look again towards Orion and it's famous belt stands out as usually: there is no other asterism on the sky that is as conspicuous as the belt for me: Alnitak, Alnilam and Mintaka are 2nd magnitude stars quite far away at ~ 1500 light years average distance. 

     If you live in a very, very clear of light pollution spot on Earth and you have a telescope at hand, sliding south of Alnitak will bring into view one of those emission nebulae I was writing about: it's IC 434. It's a long   pinkish nebula with a bright rim, which if you can follow might seem interrupted at some point by a dark spot. Well, that dark spot is B 33, also famously called the Horsehead Nebula for some reason :). The color is given by the nearby (quite some light years away still) Sigma Orionis ionizing the hydrogen in the nebula. Especially bright, massive stars affect their environment a lot!

     It is a very difficult object to see in anything less that ideal conditions, but don't give up if you have a limiting magnitude better than +6 and a good telescope. It took me quite some patience (a couple of hours) to finally detect it with a 8" Newtonian under +6.5 skies. Totally worth it under the -10 C at the time.

    There are a few stars forming at the base of the horse (funny expression, isn't it?) but one day under the pressure of Sigma Orionis and with the help of the intense magnetic fields already in the region, the whole Horse will shine!

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