light between the galaxies

Chipper Q
Chipper Q
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RE: more new light It's

Message 17210 in response to message 17209


It's looking to be fairly commonplace – Andromeda also appears to be about 3 times larger (in diameter) than previous estimates. It's neighbor, M33, still looks like its outer regions are clearly truncated, though...

barkster
barkster
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Would be interesting to see

Would be interesting to see if (and how much) these discoveries will account for the missing mass attributed to the "elusive dark matter".

"No, I'm not a scientist... but I did stay at a Holiday Inn Express."

MarkF
MarkF
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barkster: I have been

barkster:
I have been interested in such a possibility since I read about low surface brightness galaxies several year ago. Such galaxies have very few youg bright stars so are hard to see even though they are as large or larger than our own galaxy. So far such discoveries are adding a few decimal points to the known mormal mass without reducing the need for dark matter. The authors of my most recent post seem to imply that more dark matter is required rather than less.

barkster
barkster
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Hmmm... Increase a galaxy in

Hmmm... Increase a galaxy in size by three times and only get a few decimals increase in mass? I understand the geometry, but still.... Wow.

What's the general density of these darks stars in the outer edges compared to, let's say, the density at the edge of the bright region? Are these dark stars really just a few "stragglers" out there? If density is relatively low, I think I understand all below...

... but, if they are in large numbers, then...

... Is some "rule of thumb" ratio of star density to distance from galactic center being assumed (in spite of this new revelation)?

Can it be presumed that these darker stars have a distibution throughout the entire galaxy, and not just at the low brightness edges? Might this distibution be similar (in terms of a ratio from galactic center) to the bright stars?

Or, I guess I could have simply asked, in regards to explaining the need for dark matter, if the denisty of the dark stars is such that the mass they add to the galaxies is countered by their dispersion over a greater area.

"No, I'm not a scientist... but I did stay at a Holiday Inn Express."

MarkF
MarkF
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Barkster: My "few percent"

Barkster:
My "few percent" comment was based on several different lines of thought. Mainly that if the extra stars detected substantially altered the amount of normal matter present I think the authors would have said so. I doubt that they would have skipped over the possibility if they had a valid claim.
If amount of dark matter is to be reduced I think it is that more likely to come from evidence of many sub-stellar mass object such as brown dwarfs, planets etc. If stars can form in regions where it was previously thought none are then it is not unreasonable to assume smaller mass concentrations could also form. The count of stars sorted by mass increases at low mass enough that (according to what I have read) that majority of the stellar mass is mainly in the smallest stars. So far as I know it is equally likely that observational difficulties are as likely to explain the absence of direct observation of sub-stellar mass bodies as the absence of such bodies.

Chipper Q
Chipper Q
Joined: 20 Feb 05
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Does this count as more new

Does this count as more new light? Similar to the 'Pillars of Creation' in the Eagle Nebula, just imaged by NASA's Spitzer Telescope, are the 'Mountains of Creation', but the mountains are more than 10 times larger than the pillars, and are in the region known as "W5" in the constellation "Cassiopeia", about 7000 light-years distant...

MarkF
MarkF
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I probably wouldn't have

I probably wouldn't have thought to call this new light because it comes from a previously known star forming region. But hey, new stars - new light - why not.

Chipper Q
Chipper Q
Joined: 20 Feb 05
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RE: I probably wouldn't

Message 17217 in response to message 17216

Quote:
I probably wouldn't have thought to call this new light because it comes from a previously known star forming region. But hey, new stars - new light - why not.


Thanks, Mark. I didn't realize that. Also it's not exactly light between galaxies (ICL), either. Oops... I Should have said it's good to be able to peer through the clouds of gas and dust and see the protostars. Your kind allowance of the 'new light' aspect is more than I deserve. :)

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