APOD: Orion: Belt, Flame, and Horsehead (2017 Jun 04)

[APOD Robot]

Orion: Belt, Flame, and Horsehead

Explanation: What surrounds the famous belt stars of Orion? A deep exposure shows everything from dark nebula to star clusters, all embedded in an extended patch of gaseous wisps in the greater Orion Molecular Cloud Complex. The brightest three stars, appearing diagonally on the left of the featured image are indeed the famous three stars that make up the belt of Orion. Just below Alnitak, the lowest of the three belt stars, is the Flame Nebula, glowing with excited hydrogen gas and immersed in filaments of dark brown dust. Just to the right of Alnitak lies the Horsehead Nebula, a dark indentation of dense dust that has perhaps the most recognized nebular shapes on the sky. The dark molecular cloud, roughly 1,500 light years distant, is cataloged as Barnard 33 and is seen primarily because it is backlit by the nearby massive star Sigma Orionis. The Horsehead Nebula will slowly shift its apparent shape over the next few million years and will eventually be destroyed by the high-energy starlight.

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[Ann]

Apart from the Orion Nebula, the Horsehead Nebula might be the most photographed deep-sky object of them all.

Because these objects have been photographed so often, many photographers try to bring their own twist to the portraits of them. Rogelio Bernal Andreo, one of the best astrophotograpers in the world, has brought out intricate and fascinating details in the dust. In the Milky Way, dust signals the presence of gas, and without gas, there can be no star formation.

Rogelio's picture is full of fantastic details. One thing I particularly like, perhaps surprisingly, is the "explosion" of little blue stars surrounding mighty Alnilam (at 9 o'clock) like firecrackers going off all at once. Much of the field of view is very dusty, but in the vicinity of Alnilam the dust seems to clear, and the stars can shine through. There is in fact an Alnilam cluster of stars, which is now quite widely scattered. But the stars seemingly surrounding Alnilam are so scattered that I doubt that they "belong" to Alnilam.

Alnilam, by the way, is either a very, very bright star or a stupendously bright star. We know how bright it is in our skies (mag.1.7), but we frankly don't know how far away it is. Hipparcos, measured the distance to it, but Hipparcos was not that very sensitive. For objects farther away than 500 light-years, the margin of error became very large.

Alnilam is certainly at least 1000 light-years away, and the original Hipparcos measurement suggested an uncertain distance of ~1,300 light-years. But new analyses of the Hipparcos measurements suggest that the distance to Alnilam is closer to 2,000 light-years. If that is the case, the visual luminosity of Alnilam may be as high as 64,000 Suns and its bolometric (total) luminosity may be as high as 863,000 L_☉, a tremendous luminosity. In any case, it seems certain that Alnilam is farther away and brighter than Alnitak and Mintaka (the other stars of Orion's Belt).

Click to view full size image

Sigma Orionis (top center), Alnitak (center left)
and the Horsehead Nebula (center). Photo: Neil Viljoen.

But another fantastic star in Rogelio's picture is certainly Sigma Orionis. Sigma Orionis is a very young multiple star system, dominated by a massive O-type component. The Sigma Orionis system has been compared with the Trapezium in the Orion Nebula. Please note that the red nebulosity in the Horsehead region is all due to the ionizing power of Sigma Orionis.

At right is Neil Viljoen's portrait of Sigma Orionis, Altnitak, the Horsehead Nebula and the Flame Nebula. I like it, because it brings out some of the power of Sigma Orionis, and of Alnitak, of course!

Alnitak, seemingly so close to the heat of the action here, nevertheless seems strangely removed from it. The fantastic nebulas in the area don't seem to care about Alnitak. The bright star looks like a foreground object to me, but what do I know?

Ann

[neufer]

---

<<The Alexamenos graffito (a.k.a. the graffito blasfemo, or blasphemous graffito) is a piece of Roman graffiti scratched in plaster on the wall of a room near the Palatine Hill in Rome, which has now been removed and is in the Palatine Hill Museum. No clear consensus has been reached on when the image was made. Dates ranging from the late 1st to the late 3rd century have been suggested, with the beginning of the 3rd century thought to be the most likely.

The graffito was discovered in 1857 when a building called the domus Gelotiana was unearthed on the Palatine Hill. The emperor Caligula had acquired the house for the imperial palace, which, after Caligula died, became used as a Paedagogium (boarding school) for the imperial page boys. Later, the street on which the house sat was walled off to give support to extensions to the buildings above, and it thus remained sealed for centuries.

The image depicts a human-like figure affixed to a cross and possessing the head of a donkey. In the top right of the image is what has been interpreted as either the Greek letter upsilon or a tau cross. To the left of the image is a young man, apparently intended to represent Alexamenos, a Roman soldier/guard, raising one hand in a gesture possibly suggesting worship. Beneath the cross is a caption written in crude Greek: ΑΛΕ ξΑΜΕΝΟϹ ϹΕΒΕΤΕ θΕΟΝ. ϹΕΒΕΤΕ can be understood as a variant spelling (possibly a phonetic misspelling) of Standard Greek ϹΕΒΕΤΑΙ, which means "worships". The full inscription would then be read as Ᾰλεξᾰ́μενος σέβεται θεόν, "Alexamenos worships [his] God". Several other sources suggest "Alexamenos worshiping a god", or similar variants, as the intended translation.

It seems to have been commonly believed at the time that Christians practiced onolatry (donkey-worship). That was based on the misconception that Jews worshipped a god in the form of a donkey, a claim made by Apion (30-20 BC – c. AD 45-48): "Apion ought to have had a regard to these facts; unless he had himself had either an asse’s heart, or a dog’s impudence: of such a dog I mean as they worship. For he had no other external reason for the lies he tells of us. As for us Jews, we ascribe no honor, nor power to asses;">>

[douglas]

Really, Art? [LOL]

In almost perfect reply to that [!], perhaps this comment?!

"However, the dynamical masses are all larger than the evolutionary masses by more than their margins of error, indicating a systemic problem. This type of mass discrepancy is a common and long-standing problem found in many stars."

https://en.wikipedia.org/wiki/Sigma_Ori ... iscrepancy

You'll note during that discussion at no time did the author invoke a need to theorize IMBH's as the most likely explanation for mass discrepancies.
Yet, others, despite "surviving peer review", gallop forth with exactly such a theory:

"The resulting depletion of the high-mass end of the stellar mass function in the cluster is one of the important points where our models fit the observational data." Ladislav Šubr

http://iopscience.iop.org/article/10.10 ... 0-40-1-105

Tilting at windmills in the presence of mass discrepancies: "oh-k".

http://asterisk.apod.com/viewtopic.php? ... 06#p268006

/sarc

[neufer]

Really, Art? [LOL]

The Alexandria Virgaffito:

[steve wiggins]

I've seen the horsehead on a clear night with binoculars when I was a meteorological technician at Quillayute airport. It was a difficult sighting but once you can make out the background nebulosity it shows quite clearly.

[neufer]

Click to play embedded YouTube video.

I've seen the horsehead on a clear night with binoculars when I was a meteorological technician at Quillayute airport. It was a difficult sighting but once you can make out the background nebulosity it shows quite clearly.

"There's a slight crosswind from the right, so be ready for it."

[ta152h0]

Striking visual, like the 1951 Alfa Romeo formula 1 race car. They also had a farm implement division called Alfalfa Romeo division.

[Ann]

Really, Art? [LOL]

The Alexandria Virgaffito:

Your post evokes utter confusion on my part, although I can see one, quite farfetched, connection between the Horsehead Nebula and some 2,000-year-old donkey-head graffiti. But my response to Virgaffito is

Click to view full size image

The Flame Nebula. X-rays in purple from Chandra,
and red, green and blue infrared details from Spitzer.

I said in my previous post that Alnitak appears to be located in front of all these amazing nebulas in Orion. But apparently not, according to Wikipedia:

Wikipedia wrote:
The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 900 to 1,500 light-years away.
The bright star Alnitak (ζ Ori), the easternmost star in the Belt of Orion, shines energetic ultraviolet light into the Flame and this knocks electrons away from the great clouds of hydrogen gas that reside there. Much of the glow results when the electrons and ionized hydrogen recombine. Additional dark gas and dust lies in front of the bright part of the nebula and this is what causes the dark network that appears in the center of the glowing gas.

Hmmm. If the Flame Nebula is first and foremost an emission nebula, that doesn't explain the yellow color of the Flame. I would guess that yellow and orange light from the newborn stars inside penetrates the nebula. But apparently Alnitak plays a part, too.

Click to view full size image

The Pleiades.
Photo: Tom Wildoner.

At the center of the Flame Nebula is a cluster of newly formed stars,[2] 86% of which have circumstellar disks.[3] X-ray observations by the Chandra X-ray Observatory[4][5] show several hundred young stars, out of an estimated population of 800 stars.

A total number of 800 young stars in the Flame Nebula isn't bad. Of course, the estimated total number of stars in the Pleiades is more than 1,000.

Ann

[sbdeak@msn.com]

Curious how the star spikes have been eliminated in some of your pictures. Are these being removed through digital manipulation? Surely these photos are not taken with a refracting telescope.

[neufer]

Really, Art? [LOL]

The Alexandria Virgaffito:

Your post evokes utter confusion on my part, although I can see one, quite farfetched, connection between the Horsehead Nebula and some 2,000-year-old donkey-head graffiti. But my response to Virgaffito is

• I know where you live...do you know where I live?

If the Flame Nebula is first and foremost an emission nebula, that doesn't explain the yellow color of the Flame. I would guess that yellow and orange light from the newborn stars inside penetrates the nebula. But apparently Alnitak plays a part, too.

• Helium perhaps

---

<<Helium emission and absorption spectra. When electrons in an element become excited (by heating), they enter higher energy orbits. When they return to their ground state they release the extra energy as light radiation at a specific wavelength. The wavelengths emitted by an element are characteristic of that element. A matching absorption spectrum occurs when light passes through a material and is absorbed by its atoms. The 12 lines of the visible helium spectrum correspond to wavelengths of 388.8, 447.1, 471.3, 492.1, 501.5, 504.7, 587.5, 667.8, 686.7, 706.5, 728.1 and 781.3 nanometres (nm). >>

[neufer]

. http://www.deepskycolors.com/gear.html

---

Curious how the star spikes have been eliminated in some of your pictures. Are these being removed through digital manipulation?

Surely these photos are not taken with a refracting telescope.

Why not (And don't call him Shirley.)

[Ann]

The Alexandria Virgaffito:

Your post evokes utter confusion on my part, although I can see one, quite farfetched, connection between the Horsehead Nebula and some 2,000-year-old donkey-head graffiti. But my response to Virgaffito is

• I know where you live...do you know where I live?

Ohh... My bad. Sorry.

(So... do I take that to mean that you have a lot of donkey head graffiti in Alexandria, Virginia?)

The helium lines are interesting. Maybe they contribute to the yellow color of the Flame Nebula.

Ann

[neufer]

[b][color=#0000FF]by Thomas Nast. Harper's Weekly, January 19, 1870.[/color][/b]

---

(So... do I take that to mean that you have a lot of
donkey head graffiti in Alexandria, Virginia?

• We Virginia Democrats do our best (in our purple state).

<<The most common mascot symbol for the "Democrat Party" has been the donkey, or jackass. Andrew Jackson's enemies twisted his name to "jackass" as a term of ridicule regarding a stupid and stubborn animal. However, the Democrats liked the common-man implications and picked it up too, so the image persisted and evolved. Its most lasting impression came from the cartoons of Thomas Nast from 1870 in Harper's Weekly. Cartoonists followed Nast and used the donkey to represent the Democrats, and the elephant to represent the Republicans.>>

[Nitpicker]

Neufer, it was somewhat wittier when you brought up the Alexamenos graffito previously, in this 7yo topic:
http://asterisk.apod.com/viewtopic.php? ... os#p114189

But surely, Shirley, there are better avenues for your nuisance graffiti, than today's APOD discussion? Perhaps an avenue nearer to your home in Alexandria? You are wasting your not inconsiderable brilliance here on The Starship.

[douglas]

Neufer, it was somewhat wittier when you brought up the Alexamenos graffito previously, in this 7yo topic:
http://asterisk.apod.com/viewtopic.php? ... os#p114189

But surely, Shirley, there are better avenues for your nuisance graffiti, than today's APOD discussion? Perhaps an avenue nearer to your home in Alexandria? You are wasting your not inconsiderable brilliance here on The Starship.

I was assuming he was making an oblique reference to that Rushdie fellow, but yes, he's still got me laughing with King Canute.

And his wit in this topic has FAR EXCEEDED that from 7 yrs. ago.

Alfred E. Neumann to the fore.

[Nitpicker]

One's mind can wander just about anywhere from the stuff our dear, oblique friend regurgitates from the web. Ye gods, now that a relationship between Rushdie and this APOD has been claimed, it will probably trigger another lengthy bout of obliquity from the great neufer. You may love it, but my poor scrolling finger is getting sore!

[geckzilla]

As for myself, having participated in numerous quasi-off-topic discussions spanning several pages including ones on language usage and The Great Debate on the Morphology of a Certain Sportsball, I am usually unable to provide Art any criticism these days. I remember trying when I was more ambitious and full of vigor. You're just going to have to wait for the old man to kick the bucket if you're tired of him.

[Nitpicker]

Quasi off topic is not completely off topic. Happy to discuss the shape of horse/ass heads/asses.

[geckzilla]

Quasi off topic is not completely off topic. Happy to discuss the shape of horse/ass heads/asses.

Perhaps not, but we still get people expressing the same dissatisfaction when they come to the thread and find it all about a typo or, say, Orion's dong. You missed that one, I think.

[Nitpicker]

I suppose I don't even mind off-topic discussions too much. But when there is just an off-topic pasting of another part of the internet, with no associated commentary or discussion provided in the actual words of the poster, I suppose it makes me grumpy. (To be honest, I probably lack ambition too, geck, but I haven't yet run out of vigour. I can't just sit around waiting for dear neufer to kark it, at least.)

[hamilton1]

I still don't understand if the Orion's Belt stars, M42 and the 'Orion Molecular Cloud Complex' are all part of the same stucture or not. I've seen wildly differing distance estimates for each but it seems as though Alnilam for one is maybe twice as far away as its 'companions'.

[neufer]

As for myself, having participated in numerous quasi-off-topic discussions spanning several pages including ones on language usage and The Great Debate on the Morphology of a Certain Sportsball, I am usually unable to provide Art any criticism these days. I remember trying when I was more ambitious and full of vigor. You're just going to have to wait for the old man to kick the bucket if you're tired of him.

Click to play embedded YouTube video.

The Odyssey Book XII Translated by Samuel Butler

Then Circe took me by the hand and bade me be seated away from the others, while she reclined by my side and asked me all about our adventures. "'So far so good,' said she, when I had ended my story, 'and now pay attention to what I am about to tell you- heaven itself, indeed, will recall it to your recollection. First you will come to the Sirens who enchant all who come near them. If any one unwarily draws in too close and hears the singing of the Sirens, his wife and children will never welcome him home again, for they sit in a green field and warble him to death with the sweetness of their song. There is a great heap of dead men's bones lying all around, with the flesh still rotting off them. Therefore pass these Sirens by, and stop your men's ears with wax that none of them may hear; but if you like you can listen yourself, for you may get the men to bind you as you stand upright on a cross-piece half way up the mast, and they must lash the rope's ends to the mast itself, that you may have the pleasure of listening. If you beg and pray the men to unloose you, then they must bind you faster. 'When your crew have taken you past these Sirens, I cannot give you coherent directions as to which of two courses you are to take.'"

[rstevenson]

I suppose I don't even mind off-topic discussions too much. But when there is just an off-topic pasting of another part of the internet, with no associated commentary or discussion provided in the actual words of the poster, I suppose it makes me grumpy. (To be honest, I probably lack ambition too, geck, but I haven't yet run out of vigour. I can't just sit around waiting for dear neufer to kark it, at least.)

Face it, Nit, Art is in the high of the be'older.

Rob

[neufer]

---

I suppose I don't even mind off-topic discussions too much. But when there is just an off-topic pasting of another part of the internet, with no associated commentary or discussion provided in the actual words of the poster, I suppose it makes me grumpy. (To be honest, I probably lack ambition too, geck, but I haven't yet run out of vigour. I can't just sit around waiting for dear neufer to kark it, at least.)

Face it, Nit, Art is in the high of the be'older.

Rob