Orion is a large & fascinating constellation; it graces our northern skies through the winter months. This is a brief guide and journey through some of its sights, please click on various of the images in this article, to see a larger more detailed version of that picture. Much viewing and imaging time can be spent on this subject, so I’ll start with the view that you might see with the naked eye & progress through to close-ups of some of the more striking nebulae.

The image below left (Celestial Spring) illustrates what might be seen with the naked eye whilst out walking in a rural area. Orion was “The Hunter” in Greek mythology, there are various tales about him, the most common explanation for his place in the sky is as follows:

Orion, son of Poseidon, loved Merope, one of Atlas’ daughters, as immortalised in M45 Pleiades. Merope did not love Orion and so he wandered the countryside, hunting animals. One day he was fatally injured after stepping on Scorpius, the Scorpion. In his memory, the Gods placed him in the sky, as far from Scorpius as possible. As company, they put his 2 hunting dogs Canis Major & Canis Minor with him. As quarries in the hunt, Lepus the hare & Taurus the bull are also within his region. They all stand by the river, Eridanus. An alternative story has similar details but suggests that the goddess Artemis was tricked into killing him and so created his constellation in her grief. Whichever story one goes by, Orion still chases Merope & the other Pleiades across the night sky – an eternal love story.

If you view the 2nd image, below right, you will see the outline of Orion. He is classically posed, half kneeling to aim his bow, which he holds in front of himself with his left arm. His right arm swings a weapon up above his head. Meanwhile from his belt hangs his sword, dominated by the beautiful nebula M42. The star name Betelgeuse comes from the Arabic for “The armpit”.

Following on from the above 2 images, we’ll now close in upon Orion’s body specifically the stunning region around Orion’s Belt (below) …

Celestial Spring

Our Moon, Jupiter, Orion - a beautiful springtime dusk

Note how many stars appear as we increase the total exposure time (Left image 0.33 second f2.8 ISO6400 - Right Image 2 minutes f4 ISO1600).

One of these stars, HR1988, located about 1/3 of the way from Alnitak (leftmost of Orion's Belt) to Betelgeuse, has at least one, possibly two planets in orbit around it. HR1988 is a magnitude 5.95 star with a spectral class of G4V.

Other stars of note are Saiph & Rigel (knee & toe), Betelgeuse & Bellatrix (shoulders), Meissa (head) and Alnitak, Alnilam, Mintaka (belt). Details as in the table below:

Star Magnitude Type / Info
Saiph 2.01 NSV
Rigel 0.12 Spectral Class B8Ia
Betelgeuse 0 – 1.3 (variable) SRC
Bellatrix 1.6 NSV
Meissa 3.5 Cat ID HR1879
Alnitak 1.7 NSV
Alnilam 1.7 ACYG
Mintaka 2.2 EADM

So, time to take a look at some of the nebulae within Orion. There are 3 Messier objects within Orion – M42 the Orion Nebula, M43 De Marian’s Nebula and M78. The image below shows M42 & M43 along with their immediate neighbours.

M42 The Great Orion Nebula is the large pale blue and red nebula just right of centre. The small circular red nebula with a dust column rising in front of it, that is M43. To the left is NGC1977, the Running Man and fully to the left is NGC1981 an open cluster of stars. Deep within the base of M42 lies the Trapezium cluster, click on the image below to view the larger version and pick out some of the Trapezium stars. The M42 nebula is the closest known place of star birth to our solar system. Hubble Space Telescope has not only identified star birth there but also the formation of proto-planetary discs – that from which planets of solar systems are born.

Orion's Sword M42/43

Canon 40D 500mm ISO1250 f4.5
Total Exp 1hr 20mins

In the photo above: For those of you interested in taking your own photographs, note the four different exposure times that I have used when collecting sub-exposures for stacking. This is to allow for the large dynamic range of this subject, capturing data from the bright Trapezium area, through to the duller surrounding dust clouds.

The M78 image below shows the blue star light from the reflection nebula, also appearing are the clouds of interstellar dust that lie across the region. These become more evident in images with a longer exposure. Messier 78 is another area of young hot blue stars. The second slightly smaller pale blue area is NGC2071 a similar & related object.

Messier 78 Region

Canon 40D 500mm ISO1250 f4.5 62x4mins Total Exp 4hrs 8mins

All the above nebula objects are part of the Orion Molecular Cloud Complex. This huge cloud is about 1600 light years away. The entire complex comprises dark, reflection & emission nebulae and is the birthplace of many stars. Also included in this cloud are Barnard’s Loop and my current favourite region of the night sky – The Horsehead & Flame Nebulas.

Below is my recent image of the Horsehead region …

Horsehead & Flame Nebulae

Canon 300Da 1hr 35mins ISO800 500mm f4 (17 x 5 min subs) UHC filter and 4.25hrs exposure with unmodified 20D.

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).

A question of scale: 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.

Below is an earlier image that I took of this stunning nebula group - I have labelled the different structures for easier identification:

Useful Coordinates:

ID                Name              RA              Dec

NGC2024  Flame Nebula 05:41:42  -01:51:00

M78           NGC2068         05:46:45  +00:04:48

M42  Great Orion Nebula  05:35:16  -05:23:25

M43   De Marian’s Nebula 05:35:31 -05:16:03

B33    Horsehead Nebula  05:40:54  -02:28:00

Nebulae in Orion

A widefield view of the central belt in the constellation of Orion. On the left one can see the Flame & Horsehead nebulae whilst top right the running man and Messier 42 / 43 are shown. The background shows the great clouds of dust that are present in this region.

Barnard’s Loop is a large nebulous shell of dust & ionised hydrogen gas; it is also known as Sh 2- 276. The loop partially surrounds the central region of Orion, it is some 1,600 light years from Earth and has a diameter of some 200 to 300 light years. It is currently thought that one or several significant supernova events, about 2 million years ago, blasted this matter out from the core regions of Orion. Then the strong solar winds from the bright OB1 stars of the vicinity, added to the effect and radiation from the same stars now ionises the hydrogen gas, which then emits light in the Ha band. 

The diagram & image below identifies the positioning of Barnard's Loop relative to some of the more notable features within the region (as above):

Barnards Loop Nebulae

Key nebulae of Orion framed by the H-alpha emissions of Barnards Loop - illustrated astronomy poster.

Further Info:

Betelgeuse is a huge red super giant.

Rigel is a Blue super giant and whilst much smaller than Betelgeuse it is still almost 100 times the size of our Sun.

Orion has been known as a constellation since ancient times though by different names in diverse cultures. It was Osiris to the ancient Egyptians, Al Jabbar to the ancient Arabs, a Shepherd & Sheep to the Sumerians and part of the White Tiger to the Chinese.

I hope this article has been useful & interesting to you, it’s certainly been fun in the making. As a bonus for reaching the end of this article may I invite you to join me on my spaceship for a short excursion. We'll be travelling at up to ~80 light years per second, allowing us to reach the Horsehead in under one minute. (I created the following animated journey in Vladimir Romanyuk's brilliant program, Space Engine). May I recommend viewing it in full-screen; enjoy..

I find programs like Space Engine and Universe Sandbox not just fun, but also a useful reminder of the 3-dimensional nature of the views that we represent in 2-dimensional astrophotography. Remember, the stars & DSOs in this animation are mapped representations of actual celestial objects - to travel past the Flame Nebula & on to the Horsehead gives me a better appreciation of their physicality - viewing through VR goggles, that takes it one step further again :)

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