Astronomers look to neighboring galaxy for star formation insight

Nov 30, 2011
A color image of the Large Magellanic Cloud galaxy combining maps of neutral atomic hydrogen gas (red), hydrogen ionized by nearby young stars (blue), and new data from Wong’s team which roughly trace dense clouds of molecular hydrogen (green). Credit: Tony Wong, University of Illinois

An international team of astronomers has mapped in detail the star-birthing regions of the nearest star-forming galaxy to our own, a step toward understanding the conditions surrounding star creation.

Led by University of Illinois astronomy professor Tony Wong, the researchers published their findings in the December issue of the Supplement Series.

The (LMC) is a popular galaxy among both for its nearness to our and for the spectacular view it provides, a big-picture vista impossible to capture of our own galaxy.

"If you imagine a galaxy being a disc, the LMC is tilted almost face-on so we can look down on it, which gives us a very clear view of what's going on inside," Wong said.

Although astronomers have a working theory of how individual form, they know very little about what triggers the process or the that are optimal for . Wong's team focused on areas called , which are dense patches of gas – primarily molecular hydrogen – where stars are born. By studying these molecular clouds and their relationship to new stars in the galaxy, the team hopes to learn more about the metamorphosis of gas clouds into stars.

"When we study , an important question is, what is the environment doing? How does the location of star formation reflect the conditions of that environment? There's no better place to study the wider environment than the LMC."

Using a 22-meter-diameter radio telescope in Australia, the astronomers mapped more than 100 molecular clouds in the LMC and estimated their sizes and masses, identifying regions with ample material for making stars. This seemingly simple task engendered a surprising find.

Conventional wisdom states that most of the molecular gas mass in a galaxy is apportioned to a few large clouds. However, Wong's team found many more low-mass clouds than they expected – so many, in fact, that a majority of the dense gas may be sprinkled across the galaxy in these small molecular clouds, rather than clumped together in a few large blobs.

"We thought that the big clouds hog most of the mass," Wong said, "but we found that in this galaxy, it appears that the playing field is more level. The low-mass clouds are quite numerous and they actually contribute a significant amount of the mass. This provides the first evidence that the common wisdom about molecular clouds may not apply here."

The large numbers of these relatively low-mass clouds means that star-forming conditions in the LMC may be relatively widespread and easy to achieve. The findings raise some interesting questions about why some stopped their star formation while others have continued it.

To better understand the connection between molecular clouds and star formation, the team compared their molecular cloud maps to maps of infrared radiation, which reveal where young stars are heating cosmic dust.

For the comparison, they exploited a carefully selected sample of newborn heavy stars compiled by U. of I. astronomy professor You-Hua Chu and resident scientist Robert Gruendl, who also were co-authors of the paper. These stars are so young that they are still deeply embedded in cocoons of gas and dust.

"It turns out that there's actually very nice correspondence between these young massive stars and molecular clouds," Wong said. "That's not entirely surprising, but it's reassuring. We assume that these stars have to form in molecular clouds, and it tells us that the molecular clouds do hang around long enough for us to see them associated with these massive young stars."

Wong hopes to continue to study the relationship between molecular clouds and star formation in greater detail. If researchers can determine the relative ages of young stars, they can correlate these against molecular clouds to figure out which clouds have star formation, how long the clouds live and what eventually leads to their destruction. They also plan to use a newly constructed array of telescopes in Chile to see the cloud environment in higher resolution, pinpointing exactly where inside the molecular cloud star formation will occur.

"This study provides us with our most detailed view of an entire population of clouds in another galaxy," Wong said. "We can say with great confidence that these clouds are where the stars form, but we are still trying to figure out why they have the properties they do."

Explore further: Astronomer confirms a new "Super-Earth" planet

More information: The paper, "The Magellanic Mopra Assessment (MAGMA). I. The Molecular Cloud Population of the Large Magellanic Cloud," is available online at iopscience.iop.org/0067-0049/197/2/16

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omatumr
1 / 5 (5) Nov 30, 2011
Wong's team focused on areas called molecular clouds, which are dense patches of gas primarily molecular hydrogen where stars are born.


Stars form by:

a.) Collapse of interstellar clouds and then fuse Hydrogen into heavier elements and then into compact, neutron-rich objects, and perhaps into black holes - - - as the Big Bang Model of the universe predicts, OR

b.) Fragmentation of massive, compact neutron-rich objects into galaxies of stars that continue to emit neutrons because of neutron repulsion [1] and generate the Hydrogen that fills interstellar space and causes the universe to expand [2].

1. "Neutron Repulsion", The APEIRON Journal, in press (2011)

http://arxiv.org/...2.1499v1

2. "Is the universe expanding?" The Journal of Cosmology 13, 4187-4190 (2011)

http://journalofc...102.html

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
http://myprofile....anuelo09
kevinrtrs
1 / 5 (5) Dec 01, 2011
astronomers have a working theory of how individual stars form, they know very little about what triggers the process

If the theory actually worked, it would be able to show how stars formed from scratch - how did the FIRST stars form?

Right now there is no explanation for the formation of the first stars, hence there is no explanation for the formation of subsequent stars either. Scientists know this conundrum very well but are not going to shout it from the rooftop. Even given a so-called working theory, like they say - the actual mechanism that initiates star formation is a totally unknown mystery - it just cannot be fathomed at this stage. To their credit, at least they are willing to acknowledge this.
jsdarkdestruction
3 / 5 (2) Dec 01, 2011
Oliver Manuel's recent efforts to plaster Physorg.com and other public news sites with his theories and personal URLs are a bit puzzling, as scientists have a variety of publications available to communicate directly to each other in. My best guess is that he is desperately trying to prop up his legacy in light of his arrest in his university office on 7 charges of rape and sodomy based on allegations by 4 of his own children. The charges have been reduced to one count of felony attempted sodomy, not necessarily because of his innocence, but because of the statute of limitations. One can only guess how the recent charges and decades of family strife have affected his ability to reason rationally and to remain objective while defending his unpopular theories.

http://www.homefa...uel.html

http://mominer.ms...hildren/

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