Researchers have developed some pretty good models of how material collects to form stars, and they have observed numerous stars in the later stages of gravitational collapse and ignition. But tracking the early stages of the process is a real challenge. In the earlier stages of star formation, before things heat up, there's nothing hot enough to emit much by way of light. And the process takes place deep within gas clouds that typically obscure their internal structure.

Now, researchers report that they've used a variety of telescopes, some of them space-based, to get a clear look inside one of these gas clouds. In it, they find a series of filaments that are feeding gas into a pair of compact regions that will eventually form stars, one of which could be up to 100-times the mass of our Sun.

The area in question is known by the catchy name SDC335.579-0.292 (the researchers shorten that to SDC335); the SDC stands for Spitzer Dark Cloud, named after the space-based observatory that first spotted it. (Any reference to Elliot Spitzer's political career is purely coincidental.) SDC335 is a large cloud of gas that is a bit over 10,000 light-years away from Earth, and it contains enough material to form 5500 Suns. As the image above shows, the cloud clearly has some internal structure (it's not just a uniform sphere), but the nature and significance of the structure isn't obvious.

The new work relies on observations from a variety of instruments, including the Spitzer and Herschel space telescopes and the Atacama Large Millimeter Array. These allowed observations at a variety of different wavelengths, some of which allowed them to image the emissions from specific molecules found in the cloud. These include ions of carbonate and ammonia, along with methanol, which naturally forms the microwave equivalent of a laser (called a maser). Collectively, these observations allowed the researchers to reconstruct not only the distribution of material within SDC335 but also its relative motion.

What they found was that the cloud has a number of filaments, some of which you can make out to the upper right and right of this picture. These are drawing in gas from the surrounding cloud and funneling it toward a pair of star-forming regions within it. Overall, the gas is moving at just under a kilometer every second; it takes about 400 years for an amount of material sufficient to form the Sun to free-fall its way into the center of the cloud.

The analysis detected two areas of elevated density within the gas cloud itself. One of these was smaller and off on the periphery. But the second is right at the center, and it's a monster. Already, about 545 solar masses—about 10 percent of the total material in the gas cloud—have gathered there, all within the space of 0.16 light years. (That's much larger than the orbit of Neptune but smaller than the Oort cloud.) Despite the potential for this to coalesce into a star, the process doesn't seem to have started yet, given that there's little evidence for ionized gasses, or even temperatures above 100K.

What will happen when star formation does begin? The larger of the two objects is likely to be the biggest star-forming core we've yet observed, and models suggest that up to half of the gas in these cores ultimately goes into star formation. The actual process will often divide the material among a number of actual stars, creating binary and higher-complexity systems. But the authors predict that the larger core will ultimately form at least one star that is, at minimum, 50 times the Sun's mass—possibly over 100 times that size.

Over all, the cluster has enough material to form as many as 320 stars that are Sun-sized or larger. Combine that with the number of dwarf stars that are likely to form, and it's likely that the cloud will ultimately produce an entire open cluster.

Astronomy & Astrophysics, 2013. DOI: 10.1051/0004-6361/201321318 (About DOIs).