W49A might be one of the best-kept secrets in our  galaxy. This star-forming region shines 100 times brighter than the  Orion nebula, but is so obscured by dust that very little visible or  infrared light escapes. The Smithsonian's Submillimeter Array (SMA) has  peered through the dusty fog to provide the first clear view of this  stellar nursery. The SMA revealed an active site of star formation being  fed by streamers of infalling gas. "We were amazed by all the features  we saw in the SMA images," says lead author Roberto Galván-Madrid, who  conducted this research at the Harvard-Smithsonian Center for  Astrophysics (CfA) and the European Southern Observatory (ESO).

  W49A is located about 36,000 light-years from  Earth, on the opposite side of the Milky Way. It represents a nearby  example of the sort of vigorous star formation seen in so-called  "starburst" galaxies, where stars form 100 times faster than in our  galaxy. The heart of W49A holds a giant yet surprisingly compact star  cluster. About 100,000 stars already exist within a space only 10  light-years on a side. In contrast, fewer than 10 stars lie within 10  light-years of our Sun. In a few million years, the giant star cluster  in W49A will be almost as crowded as a globular cluster.

  The SMA also revealed an intricate network of  filaments feeding gas into the center, much like tributaries feed water  into mighty rivers on Earth. The gaseous filaments in W49A form three  big streamers, which funnel star-building material inward at speeds of  about 4,500 miles per hour (2 km/sec). "Move over, Mississippi!" quips  co-author Qizhou Zhang of the CfA. Being denser than average will help  the W49A star cluster to survive. Most star clusters in the galactic  disk dissolve rapidly, their stars migrating away from each other under  the influence of gravitational tides. This is why none of the Sun's  sibling stars remain nearby. Since it is so compact, the cluster in W49A  might remain intact for billions of years. The Submillimeter Array  mapped the molecular gas within W49A in exquisite detail. It showed that  central 30 light-years of W49A is several hundred times denser than the  average molecular cloud in the Milky Way. In total, the nebula contains  about 1 million suns' worth of gas, mostly molecular hydrogen.

This image from the Smithsonian's  Submillimeter Array maps the projected density of molecular gas in the  central 30 light years of W49A. Brighter colors mark denser regions. The  brightest region at the image center is less than three light-years  across, yet it contains about 50,000 suns' worth of molecular gas.  Credit: Roberto Galván-Madrid (ESO), Hauyu Baobab Liu (ASIAA, Taiwan),  Tzu-Cheng Peng (ESO)  

For a little more insight into the project see this：http://phys.org/print306424187.html