Science Questions

Is dark matter failed stars or black holes?

Sun, 25th Aug 2013

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Question

jon asked:

While you do a great job most of the time, sometimes questions remain unanswered.

 

For example, last week, the questioner asked whether someone would either explode or freeze when exposed to space. You said "they will not explode" but you really meant "they will not explode quickly"; but you did not really explore how long it would take to freeze. What you did was slick, but not really compliant with the

original question. It seems as if there would be a "race" between dessication and freezing.

 

With regard to Catherine Haymans (sp?), she left quite a few questions unanswered. She said if you counted the visible stars in the galaxy, the implied mass was not enough to account for the speed of the stars around the centre of the galaxy. She did not mention invisible stars (black holes and neutron stars and brown dwarfs) which might be orbiting but not visible. And she did not mention the black hole that we now understand is at the centre of our galaxy.

 

She then immediately and without explanation said there "must" be a halo of dark matter around our galaxy. While there may be a good reason for this theory, neither she nor the interviewer attempted to explain why the dark matter is not in the center of the galaxy.

 

In fact, one might imagine that enough mass outside the star disk could pull the stars away from the centre, and make the whole gravitational situation "worse" (making the stars even faster than theory would predict).

 

She then said that if there were dark matter outside the star disk, it would cause lensing, forcing stars to appear to line up. Again, no explanation. I could imagine

that if the dark matter were restricted to a torus outside the visible star disk, then galaxies above that torus might appear different than those at the toroidal boundary. But rather than being educated by you, I am now forced to create hypotheses and mutter to myself.

 

In short, this left me with many more questions than I started out with. Could you do another discussion about this, a bit more carefully?

 

Thanks! I listen (carefully!) every week!

 

Jon

 

 

 

Answer

Transcript to follow.

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