After 9 light curves in last week’s post, we have a look at an image this week 🙂
As many of our observers already know we have an extended 2-week ‘campaign’ coming up for the Sigma-Ori target field (hourly observations in B, V, R, I, and H-alpha from Nov 23 to Dec 08 incl.). Thus, we thought to show you how the field looks like with a wide-field camera. The above image is a B, V, R filter colour composite of 3x2min exposures taken with the LCO network of 0.4m telescopes. It was taken at relatively high airmass late in last years observing season, thus it is a bit noisy.
Sigma-Ori itself is obviously the bright blue star in the image centre. The young cluster of stars we are investigating is distributed around this star. Even if it is not obvious, there is a cluster. It just does not stand out that much from the field star population. Further afield, we have the Horsehead Nebula to the East of the cluster. It is about half a degree away and hence is not part of the Sigma-Ori images for most of our data, which are taken with a smaller field of view.
The red glow in the East is originating from the H-alpha emission line. The Hydrogen gas in this part is ionised by UV radiation from the bright, blue, massive star Sigma-Ori itself. The very bright star just visible in the upper left corner is Alnitak, the Eastern most of the three stars in Orions Belt. This is also a massive blue star, but is most likely slightly in the foreground, about 100 light years closer to us than Sigma-Ori.