Dark clouds in space

Sep 13, 2011
An infrared image of an infrared dark cloud, seen against a glowing background of warm infrared dust. This IRDC has a young star forming within (seen as green spot). Credit: NASA Spitzer

(PhysOrg.com) -- Infrared dark clouds (IRDCs) are dark patches in the sky seen against the continuous, bright infrared background produced by our galaxy. IRDCs are rich in molecules and relatively dense, cool gas, and they are natural sites for future star birth. Studies of IRDCs to date have emphasized those candidates that already have star formation underway within them, but astronomers are increasingly interested in probing younger, colder clouds to probe earlier stages in the star formation process.

One tool to use is the gas, ammonia. In 1969, astronomers discovered that ammonia (NH3) was present in large quantities in interstellar gas clouds. The species was most apparent in regions of where the density and temperature of the gas enabled it to emit bright radio-wavelength radiation. Since then, ammonia has become one of the staple diagnostic probes of the regions where are forming. One issue has been that capable of detecting ammonia have relatively poor spatial discrimination; this means many IRDCs appear as point sources, without structure.

CfA astronomer David Wilner and two colleagues teamed up to use a combined set of telescopes: one group in New Mexico and the second one in West Virginia. Operating together coherently, the combination is able to see small sub-structures in IRDCs, including regions within the clouds where new stars may be forming.

The group reports on a set of six relatively young IRDCs in the new issue of the .

They find strong signals from ammonia, and calculate from them that the gas temperatures are only about ten degrees above . Although a few of their sample of IRDCs are known to contain young stars, the ammonia gas in all cases was cold - apparently the new stars have not heated up the cloud. Of particular importance is their conclusion that the density of the gas is high (none has frozen out onto dust, for example, as can happen to molecules like carbon monoxide). The paper concludes from the overall physical conditions that these clouds are probably resistant to collapsing into new stars. New stars do form in them, they argue, largely because of pressure from the much warmer gas reservoir surrounding them in their galactic neighborhoods.

Explore further: New mass map of a distant galaxy cluster is the most precise yet

Provided by Smithsonian Astrophysical Observatory

4.7 /5 (7 votes)

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User comments : 21

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kevinrtrs
1.1 / 5 (18) Sep 13, 2011
Just how do they know that that green spot is a star forming? What previous and current observations do they have that it is in the formation stage? What are the tell-tale signals that are presented when stars form?
Right now it has to be said that it is sheer speculation on their part because the light spot is already visible from this far out in space.
kevinrtrs
1.1 / 5 (17) Sep 13, 2011
The paper concludes from the overall physical conditions that these clouds are probably resistant to collapsing into new stars. New stars do form in them, they argue, largely because of pressure from the much warmer gas reservoir surrounding them in their galactic neighborhoods.

So which way is it going to go now? To form or not to form, that is the question. Looks like the authors have a rather wishful view and are overlooking their own probability analysis in favor of what they would like to happen.
antialias_physorg
5 / 5 (12) Sep 13, 2011
Right now it has to be said that it is sheer speculation on their part because the light spot is already visible from this far out in space.

It's an infrared image.

Just how do they know that that green spot is a star forming? What previous and current observations do they have that it is in the formation stage? What are the tell-tale signals that are presented when stars form?

Would it be too much to ask for you to go to wikipedia before posting?
http://en.wikiped...ormation

Or what cause do you have to do this away as "sheer speculation"? (Other than sheer speculation on your part that this is sheer speculation, that is)
Turritopsis
4.7 / 5 (13) Sep 13, 2011
When you stand on the street and a car is coming directly for you it is speculative to say that the car will hit you (speculative means theoretical). The event itself did not happen yet so it hasn't been demonstrated. Do you:

a) get out of the street because you speculate that the car will hit you?
or/
b) stand there obliviously because you're not buying into the notion that a massive speeding body heading for you will hit you. (await demonstration)

By using our knowledge of physical laws we can speculate within an astonishing degree of certainty that gravity will cause the gas to coalesce, pressure will ultimately cause ignition and fusion.
Turritopsis
5 / 5 (2) Sep 13, 2011
pressure will ultimately cause ignition and fusion.


*If enough matter is present, and
*If the cloud doesn't get dispersed by interfering forces.
Jayded
1.3 / 5 (14) Sep 13, 2011
Turritopsis - Honestly dude, you can buy into science but not wholesale. The speculation/theory/guess work is nothing more than that. As you point out, until the car hits you everything is speculation, therefore your 'astonishing degree of certainty' is simply laughable.
Nobody...wait... NOBODY has a clue about gravity, let alone its role in the creation of pressure related fusion, IF that is even what you are viewing. I would go as far to say that until we have some craft with some toss, viewing some event seen million of lightyears away we havent even seen a car coming let alone calculated its end result.
Turritopsis
5 / 5 (9) Sep 13, 2011
NOBODY has a clue about gravity


We have practical knowledge gathered from observation to attest for gravity. Try jumping to the moon.
Jayded
1.3 / 5 (13) Sep 13, 2011
What a joke dude. Tell me oh great one, what is gravity? Try explain it without using the word force. Hahahahaha.
antialias_physorg
5 / 5 (14) Sep 13, 2011
Tell me oh great one, what is gravity?

The distortion of spacetime.

(Or to be more precise: The difference of spacetime to an abstract Euklidian space)
Noumenon
4.2 / 5 (71) Sep 13, 2011
What a joke dude. Tell me oh great one, what is gravity? Try explain it without using the word force. Hahahahaha.


As mentioned by antialias, Einstein gave a geometrical non-force formulation, that has such an 'astonishing degree of certainty', that the GPS system you use, wouldn't work without using it.
SpiffyKavu
5 / 5 (6) Sep 13, 2011
And the green in the image at the top is a radio image, which consists of contour lines (of constant radio flux). The radio image was then put on top of an infrared image of the same region.

These clouds are ~10 K, and can only be seen in the radio.
yyz
5 / 5 (3) Sep 13, 2011
"And the green in the image at the top is a radio image, which consists of contour lines (of constant radio flux). The radio image was then put on top of an infrared image of the same region."

Unfortunately at this scale, the "green" ammonia clouds appear nearly stellar (at under a minute of arc across, they're below the resolution limit of the Spitzer telescope).

Fig 2 of the paper has closeups of the six regions with (as with the image above) the radio contours plotted over a Spitzer IR image: http://arxiv.org/...82v2.pdf

[There are a number of Young Stellar Objects(YSOs) also plotted that are found in and around these clouds]
DiverseByDesign
not rated yet Sep 13, 2011
the distortion of spacetime. nice.
Jayded
1 / 5 (7) Sep 13, 2011
antialias /Noumenon - joining the drive of arguing the impossible. throws in a little einstein and believes all is good. please lets note the word theory or dare i say postulation at the end of both concepts.
Pete1983
4.9 / 5 (7) Sep 14, 2011
antialias /Noumenon - joining the drive of arguing the impossible. throws in a little einstein and believes all is good. please lets note the word theory or dare i say postulation at the end of both concepts.


So you're saying that people should just go with their gut feeling on things and not attempt to work things out through experiment and observation?

Also what do you mean note the word theory? The theory of evolution is a "theory", and it's about as concretely "correct" as anything in this world can be.
jsdarkdestruction
5 / 5 (6) Sep 14, 2011
Turritopsis - Honestly dude, you can buy into science but not wholesale. The speculation/theory/guess work is nothing more than that. As you point out, until the car hits you everything is speculation, therefore your 'astonishing degree of certainty' is simply laughable.
Nobody...wait... NOBODY has a clue about gravity, let alone its role in the creation of pressure related fusion, IF that is even what you are viewing. I would go as far to say that until we have some craft with some toss, viewing some event seen million of lightyears away we havent even seen a car coming let alone calculated its end result.

no, just because you dont have a clue doesnt mean everyone else doesnt have a clue too.
nizzim
1 / 5 (2) Sep 14, 2011
Shouldn't we have detected gravitational waves by now if they did distort space? Or succeeded in one of the many multi billion dollar fusion attempts to extract more energy than is expended.? Maybe even detected the higgs?
nizzim
5 / 5 (1) Sep 14, 2011
Kind of surprised what's his name hasn't linked his many articles of neutron repulsion yet lol
Deesky
5 / 5 (1) Sep 14, 2011
Shouldn't we have detected gravitational waves by now if they did distort space?

Their effects are so slight that direct detection requires exquisite precision and noise isolation. However, gravitational waves have been detected through indirect means.
antialias_physorg
5 / 5 (2) Sep 14, 2011
Shouldn't we have detected gravitational waves by now if they did distort space?

LIGO is working on that. but as noted: gravitational waves from close-by sources (Earth-Sun, Earth-Moon) are very small (E.g. the Earth-Sun system radiates gravity waves on the order of 200Watt). And those that are large (Black hole mergers, binary neutron stars) are usually so far away that the signal is severly attenuated (and also is in superposition with all the other sources of graviational waves - which makes for a lot of 'noise')

[q9Or succeeded in one of the many multi billion dollar fusion attempts to extract more energy than is expended.? Maybe even detected the higgs?
The thing about science is: You can't really plan when you will discover something or when the breakthrough will occur. You can only ever try to follow the path which seems most promising - and that is occasionally wrong.
Noumenon
4.1 / 5 (59) Sep 14, 2011
antialias /Noumenon - joining the drive of arguing the impossible. throws in a little einstein and believes all is good. please lets note the word theory or dare i say postulation at the end of both concepts.


I'm not sure what , if anything, your point is. You wouldn't have been able to make those posts if it were not for "theories".