Massive Star Formation

layers between the very gas, ionized by the intense starlight, and the much cooler, denser molecular cloud. As the shocks plow into the molecular cloud, needless to say, they stir things up dynamically even further, which may foment still more massive star formation. With new massive stars, the process continues until the molecular cloud is basically eaten up. This entire process is called "Sequential Star Formation."

In a later stage of this process, when most of the gas in the molecular cloud has been incorporated into stars, or blown off by the stars themselves, the result is something like the Pleaides, where one can see hundreds of bright young massive stars, with just a hint of the molecular cloud from which they came.

Stars formed in this way usually drift apart over millions of years, and result in "OB associations." "O" and "B" come from the stellar types of the most massive stars. Examples of OB associations are quite familiar. Most of the constellations of Orion and Scorpius are populated by OB association stars. These stars are still drifting away from each other as they flee from their birthplaces; however most of their stars will only live to be tens of millions to hundreds of millions of years old before exploding as supernovae.

The idea of sequential star formation seems plausible, but it still does not fully address why more dynamically active molecular clouds preferrentially produce massive stars, and there really is no theory that adequately does so. Worse still, one of the most pressing questions is cosmology right now is why there seems to have been much more star formation, in particuar, massive star formation, billions of years ago, between redshifts of one and perhaps 2, than there is today. Obviously one can simply assert that typically there were was more merging of galaxies, etc., but still, why are these active regions in merging galaxies so good at making massive stars? Once again, the question comes down to our fundamental lack of any detailed understanding of the star formation process.

Go To Page: 1 2

Articles in this Topic    Discussions in this Topic