Astronomers Determine Trigger of Massive Star Formation

Some regions in space are especially good at creating massive stars. Astronomers know the recipe for creating a star in one of these stellar nurseries calls for hydrogen gas, dust, and some amount of heat and gravity, but they still don't know quite how all the parts come together or what triggers the event.

So several theories have been proposed. One predicts that low-mass stars accrete surrounding material. Another calls for the forceful combination of two protostars. A third, called the "collect-and-collapse" model, says that a parent massive star influences the formation of second-generation stars.

Now, a collection of images presented by astronomers at the Laboratoire d'Astrophysique de Marseille, France provides the most complete and detailed evidence supporting the collect-and-collapse model, without ruling out the other models.

Collect-and-collapse works like this: When a star reaches a mass eight times greater than the Sun, it begins to emit intense amounts of energy in the form of ultraviolet photons, triggering a series of events that lead to the formation of massive stars. These highly-energized photons react with surrounding gas molecules, and the region near the star becomes filled with ionized hydrogen gas. Once a region is acting this way, it becomes known as an HII region.

While many scientists subscribed to the collect-and-collapse model, no strong evidence existed until the release of this set of images of Galactic HII region RCW 79, about 14,000 light-years from Earth. This collection of images gives the most complete look into a "triggered" star-forming region, clearly depicting each of its characteristics.

These images were produced by Annie Zavagno and Lise Deharveng of the Laboratoire d'Astrophysique de Marseille, France using several telescopes - NASA's Spitzer Space Telescope, the SuperCOSMOS Sky Survey, the ESO Swedish Submillimetre Telescope and the ESO-New Technology Telescope.

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Bjorn Carey is the science information officer at Stanford University. He has written and edited for various news outlets, including Live Science's Life's Little Mysteries, Space.com and Popular Science. When it comes to reporting on and explaining wacky science and weird news, Bjorn is your guy. He currently lives in the San Francisco Bay Area with his beautiful son and wife.