Star-forming region RCW49 from Spitzer

Guide to star formation from the University of Arizona.

Stars have formed in the core of a molecular cloud and they have blown a hole in the cloud. You can see them glowing blue inside the hole. The remains of the cloud are heated by the new stars and glow pink. The image was obtained with the IRAC instrument on Spitzer, and ranges from 3.6 microns (blue) to 8 microns (red). Because it is an infrared image, we can see through the foreground dust that blocks our view in the visible region.

Stars normally form in the well-known regions such as Orion but occasionally in an isolated manner, as illustrated by the Bok globules (left). I have discovered an interesting piece which appeared in the New York Times, reproduced here, which perfectly describes the star forming process:


The apparent inside-out collapse has been a source of confusion for theorists and observers alike. More than a decade ago, astronomers began finding that nearly all newborn stars go through a phase in which they seem to be rejecting mass at the same time they were also presumably drawing in mass from the cloud collapse. This was a common occurrence. Astronomers repeatedly observed two jets of gas shooting out at opposite sides and perpendicular to the disk of rotating matter around the protostar. The rotational forces were apparently twisting the magnetic field lines, producing winds carrying gas out in powerful jets.


The outflow phenomenon was as frustrating as it was fascinating. The jets were easily detected by radio telescopes and tended to obscure the view of other star-formation processes, like the inflow of material. So astronomers naturally devoted most of their time and thought to the jets they could see but could not explain, rather than on the inflowing material they hoped to see but could not. The new research promises to draw new attention to questions related to the intermediate stage of star formation, the time after the initial collapse of the gas sphere into a protostar and before the fall of material ceases and planetary formation becomes possible.

The source research concerns the dark cloud Barnard 335 (right). Unusually, it makes use of the capabilities of large, single radio dishes able to observe objects with relatively large angular sizes (~30 arcsec).


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