Horsehead Nebula (B33) & local region

The Horsehead Nebula is located in the constellation of Orion, close to the supergiant binary Alnitak or Zeta Orionis. Orion & its molecular cloud is one of my favourite parts of the sky; so I am currently enjoying imaging this region. The second half of last week proved quite suitable to long imaging projects. The midweek nights had been misty but the early hours of 5th & 6th October allowed me to capture some subs of the Horsehead. Currently Alnitak rises above my horizon in the SE at 3-30am and the sky becomes too light for DSO imaging around 6am, so that limits imaging time. Over these 2 mornings I did manage to collect 4.25 hours of decent exposures – here’s the result:

  hhead-starc-1d-ndn-web Click image for larger view …

The subs were shot using a Canon 20D & 100-400L lens @ 400mm f5.6 ISO1600. The best 170 sub exposures were used to create the total exposure time as above. 23 Darks, 7 Flats & 2 Flat Darks were used to preprocess the lights; meaning that it took over 200 exposures to create this image, the most I’ve used so far. This equated to problems. I run Windows Vista which I have found to be better at memory management then previous Windows versions and my PC is a reasonable spec as follows: AMD dual core processor, 2GB Ram, 2Gb ReadyBoost Memory, 2GB DiskCache, 2/3 Tb Drive Space. Yet despite this there were issues with using adaptive stacking techniques in Iris; admittedly this did involve over 6Gb of data but it still caught me by surprise – result was that I had to use simpler additive stacking techniques in Iris, oh well!

Anyway back to the Astronomy. This region of Orion has several interesting named structures, the version of the image below is annotated to name the most prominent ones:

hhead-starc-1d-label Click image for larger view …

The Horsehead (Barnard 33) is an amazing structure of dusty clouds & stellar birth, it was voted in 2000 as the object that people most wished Hubble Space Telescope to be targeted at. We can only see B33 because it is illuminated by the bright nebula IC434 which lies immediately beyond it; both are about 1600 light years from Earth but still located within the Orion arm of our own galaxy, the Milky Way. At the base of B33 lies NGC 2023, this is an emission nebula. The star at its centre is very young & hot it is pushing a space for itself & ionising gas in its locality, hence the classic pale blue emission colour. IC 431 432 & 435 are similar nebulae wrapped around their respective star sources. All the remaining labeled items, save one, are key stars of the region.

NGC 2024, the Flame Nebula, is the remaining object. The Flame Nebula is also some 1500 – 1600 light years distant and part of the Orion Molecular Cloud Complex. Conventional wisdom was that the source of ionising radiation that illuminates the hydrogen gas of the nebula was Alnitak. However recent measurements of Alnitak put it at only 800 light years distant, therefore not the source. Most likely there is another young super hot star hidden behind the thick black dust lanes that are in front of the Flame Nebula (see link for evidence).

Horsehead CloseUp  Here’s a closer look at B33 from my imaging.

From nose to mane is a region just  over 2 light years in width; this is one enormous horsey dust cloud.

This whole region is a mass of star formation, dusts & gases; the red nebulosity above IC 434 is mainly due to high energy ionised particles being flung out into space like some grand cosmic fountain. It is a truly fantastic sight. I plan to continue imaging in & around Orion during the next few weeks / months and to post an overview of this constellation. As ever I shall be limited by the weather and my depleted sleep schedule,  zzz zzz zzz …

 You can read / view more about Hubble’s image of the Horsehead at the HubbleSite. The image was a 4.6 hour exposure for Hubble.



  • Ed

    October 9, 2007 at 4:35 am Reply

    Wow. That is absolutely beautiful – a fantastic photo.


    October 14, 2007 at 6:43 am Reply

    my name is Kamal . I live in Iran . I am astronomys teacher .
    your site is very interesting and useful . I often study your subjects.
    I will become glad to exchange our links .

    with my best regards

  • […] For more details on this image and the region, please see my previous Horsehead article. […]

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