« Pathogenic gut microbes induce horizontal gene transfer | Main | NADPH Oxidase: Kills microbes and now causing Lupus? »
Thursday
Jan192012

Magnetism versus Materialism: Which quality is more important for star formation?

 

by Sarah Scoles

Out in space, there are lots of stars. Chances are, you've noticed this by now.
But the stars we see have been there so long that it's easy never to stop and wonder how they got there in the first place. While babies appear all the time and kids ask awkward questions, the same is not true for stars in our night sky.

 

But whether or not you've been sitting around asking yourself, "So what does cause stars to form, anyway?" people are actively investigating that question, and are finding some answers.

This here is the birds and bees of star formation.
Source.
What do we know about star formation?

Where:
 There are clouds in interstellar space, or things that are called clouds but that are just places where the density of stuff (gas, dust, plasma) is higher than it is in "empty" space. Like in Earth's atmosphere, some clouds are more dense than others. In clouds that are the dense and hot enough, hydrogen atoms combine to become hydrogen molecules; these molecular clouds are baby star-cribs.

 

How:
The molecular cloud will remain relatively diffuse and cloudlike as long as its forces are in balance. The inward forces of gravity and external pressure must be balanced by the outward pressure from the molecules' kinetic energy. But if stars are going to be formed, that balance must be upset somehow. Once the balance is upset, the cloud begins to collapse, and the molecules get closer and closer together, eventually close enough (and hotly enough), that they start to fuse hydrogen and put out light. Here's an analogy: Imagine, if you will, walls closing in on a crowd of people, those people sticking together, the together-people becoming spherical (for the same reason that Tang squirted into the air of an Apollo rocket becomes spherical), and then, eventually, radiating.

But those are some pretty broad brush strokes, and there are many other factors at play during the time between cloud equilibrium and star equilibrium.

Molecular clouds are pretty and maybe kind of angry at you.
Source.
So what affects the cloud's evolution?
There are competing ideas, which is good, because we all love a good fight.Here we have magnetism-driven star formation in a battle to the death with turbulence-driven star formation (which I must say would sound a bit more intimidating in the arena).

 

Before we can investigate their relative merits, we should talk about why we're talking about magnetism.

 

What we talk about when we talk about magnetism in molecular clouds:
Ions, or charged atoms/molecules, interact with magnetic fields. The lines of a magnetic field affect the paths the ions take. The atoms/molecules and the magnetic field are thus coupled, and this coupling is called "flux freezing."

 

In a molecular cloud, even though many of the molecules are neutral, some of the gas in the cloud can be coupled to the cloud's magnetic field. It makes sense, then, that the path from cloudy gas to plasmid protostar might be affected by the magnetic field, since some particles that make up the cloud and which will go on to make up the protostar may be coupled with the magnetic field.

How does flux freezing affect the lifepath of molecular clouds? The question, essentially, is "Is the magnetic field an important player in star formation, or is it just a regular player?"

The idea that a cloud's magnetism might be critically important came from the way a coupled magnetic field would behave in the event of a cloud's collapsing: If the cloud collapsed, and the cloud's magnetic field were inherently linked to the cloud's molecules, the magnetic field would contract with the cloud. The magnetic field lines would be drawn more closely together, and the closer field lines are, the stronger the field is. So as the cloud becomes denser, and it becomes closer to birthing stars, the magnetic field gets stronger.

In a magnetism-driven star formation model, a molecular cloud is supported by its magnetic field. The ions hang out, but the neutral atoms, which aren't really affected by the field, migrate toward a central area--the core, which is where the star will form. This is called ambipolar diffusion, a term which I plan to teach my dog to respond to.

Gravity dominates inside the core, where the molecules are densely packed, and so they pack themselves even closer and eventually become a star. Outside the core, though, the magnetic field still dominates.

So what's this other model?
Turbulence, or "This is your brain on drugs."
Source.
Turbulence-driven star formation is of the mind that the cloud's dynamics--or how the molecules move and arrange themselves (ideally, into a core)--is driven not by the magnetic field's diffusive effects but by regular old things like stellar winds and internal stirring.

 

In this model, the magnetic field is too weak to fight gravity and prevent the collapse that leads to a star. Gravity dominates everywhere.

 

How do we test this?
The idea behind the testing is pretty straightforward, since the battle is really just gravitational energy versus magnetic energy.

 

To determine which model fits reality best, we need to know how the gravitational energy compares to the magnetic energy, also phrased as the "mass to flux ratio." The ratio of a cloud's mass to its flux can be compared to the critical value of this ratio, or the turning point between gravity's domination and magnetism's domination.

There are two possibilities:

  1. The Weak Field case, where gravity wins (supercritical).
  2. The Strong Field case, where magnetism win (subcritical).
Lucky for us, both mass and magnetism can be measured (not without complication, of course, but what kind of a narrative would science make without a few stumbling blocks?). By comparing those measurements and their ratio to the critical value, we can determine whether the cloud is a Weak Field case or a Strong Field case, and thus whether the stars being formed are magnetism- or turbulence-driven.

 

 

Verdict?
No Strong Field clouds have been found, whereas Weak Field clouds have been found.

 

This is how you become an effective driver of star formation.
Source.

Turbulence wins this round. At this time, there is no evidence that ambipolar diffusion drives star formation, and there is evidence that turbulence does.

 

Who cares?
The question of how some gas in interstellar space goes from being gas in interstellar space to being a star gets really close to being a "Why?" question. And while we tend to think of "why?" questions as philosophical or spiritual (Why do stars form? Why do galaxies form? Why is there something instead of nothing? Why are we here?), science is at the point where it has a shot at answering some of these questions.

 

 

ResearchBlogging.orgCrutcher, R., Hakobian, N., & Troland, T. (2009). TESTING MAGNETIC STAR FORMATION THEORY The Astrophysical Journal, 692 (1), 844-855 DOI: 10.1088/0004-637X/692/1/844

 

EmailEmail Article to Friend

References (48)

References allow you to track sources for this article, as well as articles that were written in response to this article.
  • Response
    Nice Web page, Keep up the fantastic work. Thank you so much!
  • Response
  • Response
    Response: internet marketers
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: acai berry
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: milfs
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: suarabakrie
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: webcammer worden
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: gw2buy.com
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Cambogia Ultra
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: vps coupon
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: l oreal skin care
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response:  juvalife review
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Air Scrubber Plus
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: {rhode island seo
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: facebook.com
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Ultimate Flush
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: ketolysis
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: testo xl Reviews
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: KW here
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Regal Ecig
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Regal Ecig Review
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Power Precision
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Review
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Magnetism versus Materialism: Which quality is more important for star formation? - Blog - Smaller Questions
  • Response
    Response: Harga Lampu Led
  • Response
    Response: Harga Lampu Led
  • Response
    For Excellent corporate catering services, our extensive database of corporate caterers will deliver superb quality Business Catering up and down the country from Edinburgh to Southampton
  • Response
    Response: Digital Signage
    High Impact Digital Signage Software
  • Response
    The Best Buffet Caterers in Oldham, Manchester
  • Response
    The Best Corporate Buffet Caterers in Oldham, Manchester
  • Response
    Some really marvellous work on behalf of the owner of this internet site , perfectly great content .

Reader Comments

There are no comments for this journal entry. To create a new comment, use the form below.

PostPost a New Comment

Enter your information below to add a new comment.

My response is on my own website »
Author Email (optional):
Author URL (optional):
Post:
 
Some HTML allowed: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <code> <em> <i> <strike> <strong>