The dusty Universe

[kammueller]

I saw an article on Universe Today about some recent research that suggests the Universe is a much dustier place than we thought. It was suggested that perhaps only half the light we thought was reaching us actually is getting here and the universe is much brighter than we thought.

Just wondering what effect this would have on many things Astronomical. The obvious one would be 1990 expanding universe research that blew everyone away. That research was based on the assumption that all type 1A supernovas have the same inherent brightness. Well, if there is dust out there mucking up the works could it be that the dimmer objects really aren't as far away as we thought?

I haven'e seen any fall out from that article so i am wondering if the affect is negligible and should just be ignored, or if it is going to take some time to see what effect it really has.

[Amber Robot]

Just wondering what effect this would have on many things Astronomical. The obvious one would be 1990 expanding universe research that blew everyone away. That research was based on the assumption that all type 1A supernovas have the same inherent brightness. Well, if there is dust out there mucking up the works could it be that the dimmer objects really aren't as far away as we thought?

All the early talks I heard about the accelerating universe data always had predictions for the effects on dust. I'm pretty sure it was something that was carefully considered. I don't recall, though, the arguments for why they ruled out dust extinction.

[Tim Thompson]

I saw an article on Universe Today about some recent research that suggests the Universe is a much dustier place than we thought.

That would be There's A lot of Dust Out There in the Universe. The paper Fraser refers to in the story is The Energy Output of the Universe from 0.1 to 1000 μm; Simon P. Driver, et al., Astrophysical Journal Letters 678(2): L101-L104, 10 May 2008. While the results reported are certainly interesting, I don't think they are likely to change any astronomical conclusions in a radical sense.

Just wondering what effect this would have on many things Astronomical. The obvious one would be 1990 expanding universe research that blew everyone away. That research was based on the assumption that all type 1A supernovas have the same inherent brightness. Well, if there is dust out there mucking up the works could it be that the dimmer objects really aren't as far away as we thought?

This in fact was the very first objection raised in contention to the claim of an accelerated expansion, and has already been the focus of much research (i.e., Aguirre, 1999 and the 106 citations thereto). The primary reason for rejecting dust as having a major effect on the implication of an accelerated expansion is that interstellar & intergalactic dust have well know spectral absorption. There is no indication of such a spectral effect on the type Ia SNe observations. So the dust would have to be "grey" and absorb like a neutral density filter. So far nobody has made a convincing argument that such dust is even possible. The Driver, et al. result does not add anything new to the discussion.

[loglo]

We discussed this with Simon in class recently. He basically concurs with what Tim is saying above. He pointed out that Cepheids are generally observed in the outskirts of galaxies where the affects of dust are much less than average. And interestingly he said that some higher than normal dust corrections were part of the supernova/dark energy results in the first place, they just weren't "publicised". His paper just helps confirm those corrections were valid.

[Cougar]

Well, if there is dust out there mucking up the works could it be that the dimmer objects really aren't as far away as we thought?

I believe most of the dust they're talking about is in galaxies, not out in the universe at large (although there is some out there). So this finding would not affect the Ia supernova light curve measurements. And (as far as I know) the distance to far-off galaxies is mainly estimated via redshift. Dust affects luminosity, but not redshift.

And as Tim says, the amount of dust that an object's light has had to go through before it reaches us is directly detectable by spectral analysis, noting the differential absorption of different 'colors' of light.

I haven'e seen any fall out from that article so i am wondering if the affect is negligible and should just be ignored, or if it is going to take some time to see what effect it really has.

It's not negligible. The effect is known and accounted for where applicable.

[Cougar]

We discussed this with Simon in class recently.

You mean Dr. Driver?

[loglo]

You mean Dr. Driver?

Whoops, hope that doesn't affect my grades.