Dark Doodad (2008 Dec 08)

[kjardine]

To add a bit more information, the dust cloud complex pictured here:

http://antwrp.gsfc.nasa.gov/apod/ap081208.html

is "officially" called DCld 301.0-08.6 by SIMBAD and it is catalogued in this paper here:

http://cdsads.u-strasbg.fr/cgi-bin/nph- ... ..63...27H

This paper points out that bits of this long filament are also catalogued as Sandqvist 141, Sandqvist 143 and Sandqvist 145.

You can also see the whole Musca dust cloud complex in this colour composite IRAS infrared image here:

http://galaxymap.org/iras/iras.php?cent ... _markers=1

Kevin

Kevin Jardine
Galaxy Map
http://galaxymap.org

[neufer]

http://apod.nasa.gov/apod/ap081208.html

<<The Dark Doodad Nebula can be found with strong binoculars toward the southern constellation of the Fly (Musca).>>

This paper points out that bits of this long filament are also catalogued as Sandqvist 141, Sandqvist 143 and Sandqvist 145.

You can also see the whole Musca dust cloud complex in this colour composite IRAS infrared image here:

http://galaxymap.org/iras/iras.php?cent ... _markers=1

Kevin Jardine
Galaxy Map
http://galaxymap.org

[bystander]

(Doodad is slang for a thingy or a whatchamacallit.)

A thingie is related to the whatchamacallit, the doohicky, the doodad, and Michael Stipe. It is a shorter, more formal version of the word thingie-ma-bob. Said to be the devious emanation from the unclean mind of Satan, a thingie is commonly used to ritually sacrifice unbaptized children, Coke bottles, Russian techno bands, animals named Zeke, and, again, Michael Stipe.

The whatchamacallit is one of the greatest inventions of mankind. Few things surpass its ingenuity. The main functions of a whatchamacallit include doing this, doing that, and doing this and that, as well as those, and the other.

[sfcraiger]

how do those clouds form?

[astrolabe]

Hello Bystander,

Your terminology, with or without definitions, reminded me of these ever useful items: the muffler bearing, the board stretcher and the venerable (but rarely used) finesstabreeze.

[starnut]

how do those clouds form?

By mutual gravitational attraction of the dust particles and gas molecules, assisted by the galactic magnetic fields, stellar winds, and expanding supernova remnants.

Gary

[kjardine]

how do those clouds form?

The first generation of stars were formed from hydrogen, helium and probably a bit of lithium. So I don't think there were dust clouds in the early universe. Within those stars, heaver elements, including carbon and silicon, formed. These were released as stars evolved into red giants and Wolf-Rayet stars, which have huge outflows. More was released when some stars exploded as supernovae.

In today's Milky Way, I believe the dust clouds are still mostly hydrogen and helium, but also contain a lot of fine sand particles (silicates) and soot (carbon).

So far as I can tell, the location of the Musca dust cloud complex is no accident. I believe that the Musca clouds are near similar dust clouds in Chamealeon and Lupus and form part of the inner boundary of the Orion spur.

These are to the left of the Sco OB2 association on this face-on map:

http://galaxymap.org/detail_maps/gould.html

(This shows our local part of the Milky Way as it would appear from a starship hovering far above the galactic plane.)

So far as I know, these molecular clouds have been compressed and driven in towards the inner galaxy by solar winds and supernovae created by star formation that happened tens of millions of years ago within the Gould Belt, which not only compressed the dust clouds but also created the relatively empty cavity that our Sun is currently travelling through, called the Local Bubble.

So the Dark Doodad may have a silly nickname, but it is actually a fairly significant local landmark!

Kevin Jardine
Galaxy Map
http://galaxymap.org

[neufer]

So far as I can tell, the location of the Musca dust cloud complex is no accident. I believe that the Musca clouds are near similar dust clouds in Chamealeon and Lupus and form part of the inner boundary of the Orion spur.

These are to the left of the Sco OB2 association on this face-on map:

http://galaxymap.org/detail_maps/gould.html

(This shows our local part of the Milky Way as it would appear from a starship hovering far above the galactic plane.)

So far as I know, these molecular clouds have been compressed and driven in towards the inner galaxy by solar winds and supernovae created by star formation that happened tens of millions of years ago within the Gould Belt, which not only compressed the dust clouds but also created the relatively empty cavity that our Sun is currently traveling through, called the Local Bubble.

So the Dark Doodad may have a silly nickname, but it is actually a fairly significant local landmark!

Kevin Jardine
Galaxy Map
http://galaxymap.org

http://galaxymap.org/detail_maps/gould.html
Nebulae are shown as red spheres.
Molecular clouds are shown as green spheres.

Hi Kevin,

We've sure come a long way since I was an astronomy grad student at Univ. of Md. in 1970
(before being drafted into the U.S. Army)
when no one was even sure whether or not the sun, itself, was a part of the Gum Nebula.

Which Gould Belt star formation do you suggest happened tens of millions of years ago to create the Local Bubble?
Could it have possibly kicked some "sand & soot" ice balls out of the Oort cloud to give us today's comets?

Galaxy Map is a wonderful site!!! Who runs it?

[kjardine]

Galaxy Map is a wonderful site!!! Who runs it?

I do, actually.



On the history of the Gould Belt ... this is all pretty controversial, and I wouldn't put this on my own site, but here's a capsule speculation:

Star formation appears to have started about 50 million years ago inside a molecular cloud shaped roughly like an American football and inclined at an angle of about 20 degrees to the galactic plane. This created what is sometimes called the Cas-Tau OB association. Stellar winds and supernovae from this association created a large bubble that eventually broke through the galactic plane (top and bottom) into the halo region, and so the denser gas formed a doughnut. Like the molecular cloud, the doughnut was tilted at an angle of about 20 degrees. Star formation was triggered inside the doughnut in several places, but especially in Orion and Scorpius to form the Ori OB1 and Sco OB2 associations (aka many of the brightest stars in those constellations).

This tilted doughnut of bright stars (within which is our Sun) is what astronomers call the Gould belt.

Eventually the Cas-Tau association dispersed, leaving only a core of stars visible around Alpha Persei (Mirfak, which is thus a sort-of mother star for our region).

One interesting question is what sparked the original Cas-Tau star formation. Some astronomers argue that the Gould Belt molecular cloud was a high velocity cloud orbiting the Milky Way and that the Cas-Tau star formation was sparked when the molecular cloud hit the galactic plane at a 20 degree angle, a little bit like a meteor hitting the moon. A little bit like because neither the cloud nor the galactic plane was solid and actually what would happen is the cloud would have gone right through the plane, and then fallen back again, oscillating up and down until it reached its current position.

Now a very few people speculate that the whole process of being attracted to the galactic plane, breaking through, oscillating, forming stars, etc, probably can be dated back a little earlier than the Cas-Tau association itself. So I suppose that you could write a science fiction novel in which the dinosaurs were wiped out by a comet dislodged from the Oort cloud as the Gould Belt cloud approached the galactic plane.

No real evidence for it, but it would be pretty cool if the same event that shaped the night sky allowed for the evolution of the human race.

That would be cosmic.

But at this point, also just science fiction.

Kevin Jardine
Galaxy Map
http://galaxymap.org

[astrolabe]

Hello all,

Does this mean that molecular clouds are only present within a galaxy? Sounds like PAHs are destroyed or cannot form at all in open space environments where perhaps purer, harsher doses of cosmic radiation like gamma and other types (tachyon maybe) go undiluted by stellar winds and billions of magnetospheres.

Molecular clouds seem to occur at certain distances within the edges of the x/y plane of a galaxy (like within the arms) and also keep within certain latitudes within the z thickness as well. PAHs and molecular clouds must, being both molecular, posses similar properties even if not the same composition.

P.S. This is actually an older post of mine from back in July, '08

[neufer]

On the history of the Gould Belt ... this is all pretty controversial, and I wouldn't put this on my own site, but here's a capsule speculation:

Star formation appears to have started about 50 million years ago inside a molecular cloud shaped roughly like an American football and inclined at an angle of about 20 degrees to the galactic plane. This created what is sometimes called the Cas-Tau OB association. Stellar winds and supernovae from this association created a large bubble that eventually broke through the galactic plane (top and bottom) into the halo region, and so the denser gas formed a doughnut. Like the molecular cloud, the doughnut was tilted at an angle of about 20 degrees. Star formation was triggered inside the doughnut in several places, but especially in Orion and Scorpius to form the Ori OB1 and Sco OB2 associations (aka many of the brightest stars in those constellations).

This tilted doughnut of bright stars (within which is our Sun) is what astronomers call the Gould belt.

Eventually the Cas-Tau association dispersed, leaving only a core of stars visible around Alpha Persei (Mirfak, which is thus a sort-of mother star for our region).

One interesting question is what sparked the original Cas-Tau star formation. Some astronomers argue that the Gould Belt molecular cloud was a high velocity cloud orbiting the Milky Way and that the Cas-Tau star formation was sparked when the molecular cloud hit the galactic plane at a 20 degree angle, a little bit like a meteor hitting the moon. A little bit like because neither the cloud nor the galactic plane was solid and actually what would happen is the cloud would have gone right through the plane, and then fallen back again, oscillating up and down until it reached its current position.

Now a very few people speculate that the whole process of being attracted to the galactic plane, breaking through, oscillating, forming stars, etc, probably can be dated back a little earlier than the Cas-Tau association itself. So I suppose that you could write a science fiction novel in which the dinosaurs were wiped out by a comet dislodged from the Oort cloud as the Gould Belt cloud approached the galactic plane.

No real evidence for it, but it would be pretty cool if the same event that shaped the night sky allowed for the evolution of the human race.

That would be cosmic.

But at this point, also just science fiction.

Well.... some sorta fiction.
-----------------------------------------------------
http://en.wikipedia.org/wiki/Whale

<<All cetaceans, including whales, dolphins and porpoises, are descendants of land-living mammals of the Artiodactyl order (even-toed ungulate animals). Whales are the closest living relatives of hippos; they evolved from a common ancestor at around 54 million years ago. Whales entered the water roughly 50 million years ago>>
-----------------------------------------------------
http://www.coldwater.k12.mi.us/lms/plan ... cetus.html

<<Cetus, in the form of a monstrous whale, set upon his mission of destruction and began the slaughter, working his way up and down the coast. The frightened people gathered and pleaded to their king to save them. Cepheus consulted an oracle--one with magical powers who could communicate with the gods when men sought their advice. The oracle told Cepheus that there was only one way to stop the slaughter: "You must offer your daughter Andromeda as a sacrifice." She was to be chained to the rocks on the coast and left for Cetus to devour. He made the bitter choice of sacrificing Andromeda, whereupon she was chained to the rocks and abandoned to await Cetus.
When Cetus discovered the prize awaiting him, he left off his wholesale destruction of the land and began swimming toward the ledge where Andromeda was chained. But then a distant figure appeared in the sky. It was Perseus, the brave son of Zeus and Danae, just returning from a journey during which he had succeeded in killing the dreaded Medusa.
It was when Perseus was flow over the coast of Æthiopia that he noticed Andromeda chained to the rocks by the sea, and not far away he could see Cetus rapidly nearing her. Down he swept to the girl's side. "Why are you thus bound?" he asked, overwhelmed by Andromeda's beauty. Andromeda told him the story of her boastful mother and the advice the oracle had given her father.
Perseus quickly turned to Cepheus and said: "I can save your daughter from the sea-monster, but for my reward I demand Andromeda's hand in marriage, and a kingdom." Cepheus promised Perseus that he would have what he asked for, whereupon Perseus unsheathed his sword and leapt into the air to the attack. One thrust of his sword found a soft spot between the armored scales of the monster. Wounded, it twisted over on its side. Perseus then inflicted another deep cut, and another. Blood now colored the water red and soaked Perseus' winged shoes. Fearful of losing his ability to fly, he settled on a rock near the shore and waited for the sea-monster to attack again. As it did, Perseus' sword plunged deeply into the monster's evil heart.>>
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Artiodactyl Neuendorffer

[sfcraiger]

thanks starnut and kjardine for answering my question