Smoking galaxy revealed

telfrow · Mar 17, 2006

Where there's smoke, there's fire - even in outer space. A new infrared image from NASA's Spitzer Space Telescope shows a burning hot galaxy whose fiery stars appear to be blowing out giant billows of smoky dust. The galaxy, called Messier 82, or the "Cigar galaxy," was previously known to host a hotbed of young, massive stars. The new Spitzer image reveals, for the first time, the "smoke" surrounding those stellar fires. "We've never seen anything like this," said Dr. Charles Engelbracht of the University of Arizona, Tucson. "This unusual galaxy has ejected an enormous amount of dust to cover itself with a cloud brighter than any we've seen around other galaxies." The false-colored view shows Messier 82, an irregular-shaped galaxy positioned on its side, as a diffuse bar of blue light. Fanning out from its top and bottom like the wings of a butterfly are huge red clouds of dust believed to contain a compound similar to car exhaust. The smelly material, called polycyclic aromatic hydrocarbon, can be found on Earth in tailpipes, barbecue pits and other places where combustion reactions have occurred. In galaxies, the stuff is created by stars, whose winds and radiation blow the material out into space. "Usually you see smoke before a fire, but we knew about the fire in this galaxy before Spitzer's infrared eyes saw the smoke," said Dr. David Leisawitz, Spitzer program scientist at NASA Headquarters in Washington. These hazy clouds are some of the biggest ever seen around a galaxy. They stretch out 20,000 light-years away from the galactic plane in both directions, far beyond where stars are found. Previous observations of Messier 82 had revealed two cone-shaped clouds of very hot gas projecting outward below and above the center of galaxy. Spitzer's sensitive infrared vision allowed astronomers to see the galaxy's dust. L <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

siriusmre · Mar 17, 2006

The false-colored view shows Messier 82, an irregular-shaped galaxy positioned on its side, as a diffuse bar of blue light. Fanning out from its top and bottom like the wings of a butterfly are huge red clouds of dust believed to contain a compound similar to car exhaust. Again, more assertions based on a "belief." The smelly material, called polycyclic aromatic hydrocarbon, can be found on Earth in tailpipes, barbecue pits and other places where combustion reactions have occurred. In galaxies, the stuff is created by stars, whose winds and radiation blow the material out into space. [Emphasis added.] Even though Engelbracht says, "We still don't understand why the dust is all over the place and not cone-shaped," the "stars, whose winds and radiation blow the material out into space," clearly show that they have a preference for the areas above and below the galactic center, not "all over the place." Why is that? Indeed, this characterization is contradicted in the article itself: "Fanning out from its top and bottom like the wings of a butterfly are huge red clouds of dust..." It says nothing about "all over the place," nor is that suggested by the image. <div class="Discussion_UserSignature"> </div>

cosmictalk · Mar 17, 2006

I've read up on polycyclic aromatic hydrocarbon but I do not understand exactly the difference between that and black carbon which is known to absorb radiation.

telfrow · Mar 17, 2006

Aren't PAHs a by-product/component of carbon black? <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

cosmictalk · Mar 17, 2006

I don't know I'm still reading up and trying to find answers. Got lost in this..... The compositional patterns of polycyclic aromatic hydrocarbon (PAH) and aliphatic hydrocarbon (AH) assemblages have been used to discern the origins of hydrocarbon compounds found in the aquatic environment (Sporstøl et al. 1983, Colombo et al. 1989, and references therein). PAHs are sensitive indicators of petrogenic and pyrogenic inputs of hydrocarbons while n-alkanes are useful in identifying biogenic- or petrogenic-products. In general, PAHs from petrogenic-related sources are abundant in alkylated homologues relative to their parent compounds, while combustion of fossil fuels yields PAHs generally devoid of alkylated homologues. These observations prompted the introduction of two useful indicators: 1) alkyl homologue distributions (AHDs) of naphthalene, phenanthrene/anthracene, and fluoranthene/pyrene, etc.; and 2) parent compound distributions (PCDs) (Lake et al. 1979). Other individual ratios generally involving two PAH compounds (e.g., phenanthrene/anthracene (P/A), methylphenanthrene/phenanthrene (MP/P), fluoranthene/pyrene (FL/PYR), and benz[a]anthracene/chrysene (BZ[a]A/CHR)) have also been applied to source recognition. Similarly, several molecular indices derived from n-alkane components have been shown to be sensitive in differentiating biogenic and petrogenic inputs of hydrocarbons (Colombo et al. 1989, and references therein). http://www.sccwrp.org/pubs/annrpt/94-95/art-04.htm Started to think they were the same thing! I'll keep searching.....

telfrow · Mar 17, 2006

Found this... On Earth these compounds are quite common, being formed during incomplete combustion of almost any kind of organic material hence they are continually being released into the environment [1]. They are present in coal extracts, internal combustion engine exhaust fumes, cigarette smoke, soil, marine sediments, soot, smoke from wood burning, and even fried or grilled food! Since some of the PAHs are known carcinogens [2] their presence in the environment (particularly in food) is a cause of concern to health authorities. ------ Two main mechanisms have been proposed to account for the possible formation of PAHs in the ISM. First, collisions between dust grains (thought to consist of graphite and/or silicates) could fracture the graphite planes thus releasing free PAHs [7]. Secondly, PAHs could Îgrowâ from reactions between smaller unsaturated hydrocarbon molecules and radicals in the remnants of carbon rich stars [8]. Once formed the PAHs would be remarkably stable, and would resist dissociation from UV absorption (unlike most other polyatomic molecules in the ISM) since they are extremely efficient at rapidly re-emitting the absorbed energy at infra-red wavelengths. From this site <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

telfrow · Mar 17, 2006

And not to get too far off track from the subject of the thread, but there is significant mention of PAHs in the article Young Galaxies Were Hostile To Life. <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

cosmictalk · Mar 17, 2006

most helpful <img src="/images/icons/smile.gif" />

heatherjk · Apr 10, 2006

Hey New user here. Just radomly came across this post. Anyways, to those of you still interested: I have just finished my thesis and the topic is precisely this. When I started in Spetemeber my supervisor was just publishing the first observations of PAH emission in the halo of a galaxy. I have found similar results with a different galaxy!!! Very exciting! Anyways, to read more about what I have found, and to see some pictures check out my msn space, click on physics/astronomy in the blog list, http://spaces.msn.com/krazykennedy/ Hopefully you'll find this interesting <img src="/images/icons/smile.gif" />

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