The Milky Way Project Talk

Question about star formation

  • Monocog007 by Monocog007

    So i've been part of the project for a while, but i've been thinking about a specific question that i have.

    Does anybody know how the gravity in space affects the formation of these stars? What part does microgravity have?


  • Opsalbai by Opsalbai

    I was wondering the same thing because of the collapse a star has to go through to form. Do you know how the formation of stars effects the make-up of the galaxy?


  • skendrew by skendrew scientist, admin

    Hi there. Well, these are really excellent questions that have no simple answers - and people are spending their careers trying to figure them out. As Opsalbai says, gravity is essential and fundamental to the formation of all stars, as material has to collapse together to form the dense hot core that can ignite fusion and become a star. There's actually a fundamental mass limit called the Jeans mass, and once this threshold is crossed in a dense region of a molecular cloud, the material will collapse and is able to form stars - that's gravity. But there are opposing forces that hold the material apart, such as the internal gas pressure and turbulence in the cloud.

    The second question, how the formation of stars affects the make-up of a galaxy, is very complex. There are many ways in which stars affect their host galaxies - through chemistry or energy or radiation.

    Many of the bubbles we are looking for in these images are signposts for regions where massive stars have recently formed, often in clusters. Massive stars are rare, but they are so powerful and energetic that they sweep material away around them, destroying molecules and ionizing the hydrogen gas in their natal molecular clouds. In this way, they can break up and over time even destroy the whole cloud. In addition, we think that the material they sweep up can get compressed, leading to the formation of new stars - this is a process called triggered star formation, which is of much interest (I wrote a paper looking at triggered star formation around our bubbles recently, you can see it here).

    Chemically, stars are little factories that process the gas in a galaxy. Before there were stars, there were no "heavy" elements, like metals. In the core of each and every "main sequence" star (that is, not a newborn and not a dying star), hydrogen is being fused into helium and eventually as it ages and depending on its mass, into heavier stuff like carbon or even iron. On their death, they release all this material into the galaxy's interstellar medium, either gently by shedding their outer layers (in the case of low mass stars), or very violently in supernova explosions (high mass stars). The return of these heavy materials to the galaxy's interstellar medium is eventually what allows rocky planets like our own to form around new generations of stars.

    These are just a couple of points, and this description is highly simplistic as this is a very complex topic indeed that we're nowhere near fully understanding. Hope that helps!