Drifting Through Interstellar Dust Clouds

[lakeside]

I once asked astronomers on Science Friday, the NPR science radio program, if the solar system were to drift into a dust cloud, would the density be great enough to cause cooling of the earth. This seems to me to offer another variable in global heating/cooling. The astronomers were quite negative on this point, stating that there seems to be nothing much in the way of our observing galaxies very far away etc. Yet as photos of distant galaxies show clearly, galaxies contain a lot of dust and since we live in one of those galaxies my point still seems valid. This is confirmed by todays wonderful wide angle picture of dust clouds near the center of our own galaxy. Who would not believe that such dust clouds could interrupt enough of the suns light and heat to change the climate here. My question is, are such dust clouds dense enough to affect our climate should we drift through one, and how likely is this to happen during the expected life of the sun?

[ubernoir]

today's pic 26/9/09 says the LMC is below and left
surely below and right
I come here to learn and I am probably wrong and apologies for my hubris in suggesting a mistake but if you don't ask then you don't learn

[orin stepanek]

http://apod.nasa.gov/apod/ap090926.html

Looks like on the right just under the Milky Way

Orin

[bystander]

http://www.gigagalaxyzoom.org/B.html

[cmflyer]

I once asked astronomers on Science Friday, the NPR science radio program, if the solar system were to drift into a dust cloud, would the density be great enough to cause cooling of the earth. This seems to me to offer another variable in global heating/cooling. The astronomers were quite negative on this point, stating that there seems to be nothing much in the way of our observing galaxies very far away etc. Yet as photos of distant galaxies show clearly, galaxies contain a lot of dust and since we live in one of those galaxies my point still seems valid. This is confirmed by todays wonderful wide angle picture of dust clouds near the center of our own galaxy. Who would not believe that such dust clouds could interrupt enough of the suns light and heat to change the climate here. My question is, are such dust clouds dense enough to affect our climate should we drift through one, and how likely is this to happen during the expected life of the sun?

Our solar system lies between two arms of the Milky Way, which is probably a factor in our mere existence. In a denser part of the galaxy there would be much more than just dust to reduce sunlight. There could be more comet bombardments and gravitational disruptions to planet orbits by nearby stars. Also I think an interstellar dust cloud would be easily detected moving in our direction. Sorry, this is not a valid reason to celebrate global warming.

[neufer]

today's pic 26/9/09 says the LMC is below and left
surely below and right
I come here to learn and I am probably wrong and apologies for my hubris in suggesting a mistake but if you don't ask then you don't learn

Looks like on the right just under the Milky Way

Below and left of center...

Maybe LMC here stands for "Left Middle Center."

[ubernoir]

today's pic 26/9/09 says the LMC is below and left
surely below and right
I come here to learn and I am probably wrong and apologies for my hubris in suggesting a mistake but if you don't ask then you don't learn

Looks like on the right just under the Milky Way

Below and left of center...

Maybe LMC here stands for "Left Middle Center."

with reference to
http://spider.ipac.caltech.edu/staff/ja ... rt-NEW.jpg surely the Large Magellanic Cloud is at approximately 4 O'clock from galactic center??

[bystander]

today's pic 26/9/09 says the LMC is below and left
surely below and right
I come here to learn and I am probably wrong and apologies for my hubris in suggesting a mistake but if you don't ask then you don't learn

with reference to http://spider.ipac.caltech.edu/staff/ja ... rt-NEW.jpg surely the Large Magellanic Cloud is at approximately 4 O'clock from galactic center??

You are correct. The Magellanic Clouds are below and right of Galactic Center. They are Zoom 1 on http://www.gigagalaxyzoom.org/B.html

[DavidLeodis]

Having just seen this APOD I was about to query the Magellanic clouds position but I see that has already been raised and answered that they are below and right.
The link in the "Also capturing bright planets and even a comet" brings up lots more information (though I found a lot of difficulty in actually accessing some) with the see the constellations link in that being very useful. Without that I would never have spotted Jupiter! Mind you I don't know where the comet is.

[DavidLeodis]

Having just seen this APOD I was about to query the Magellanic clouds position but I see that has already been raised and answered that they are below and right.
The link in the "Also capturing bright planets and even a comet" brings up lots more information (though I found a lot of difficulty in actually accessing some) with the see the constellations link in that being very useful. Without that I would never have spotted Jupiter! Mind you I don't know where the comet is.

I've now seen where the comet apparently is! The 'See the constellations' link brought up through the "Also capturing bright planets" link shows C/2007 Boattini a little below Hydra and above Vela. It is so very obvious when you know!!!!

[Chris Peterson]

I once asked astronomers on Science Friday, the NPR science radio program, if the solar system were to drift into a dust cloud, would the density be great enough to cause cooling of the earth. This seems to me to offer another variable in global heating/cooling. The astronomers were quite negative on this point, stating that there seems to be nothing much in the way of our observing galaxies very far away etc. Yet as photos of distant galaxies show clearly, galaxies contain a lot of dust and since we live in one of those galaxies my point still seems valid. This is confirmed by todays wonderful wide angle picture of dust clouds near the center of our own galaxy. Who would not believe that such dust clouds could interrupt enough of the suns light and heat to change the climate here. My question is, are such dust clouds dense enough to affect our climate should we drift through one, and how likely is this to happen during the expected life of the sun?

When you look at these dust clouds in the Milky Way, or dust lanes in other galaxies, you are seeing structures on a scale of kiloparsecs. Typical visible-band extinction values in these dust clouds are on the order of a few magnitudes/kpc. In terms of astronomical units, you are looking at nanomagnitudes. In other words, if our solar system were in the midst of a galactic dust lane, we'd see a drop in solar radiation on the order of microwatts per square meter (on the normal value of around 1 kw/m^2). I don't think our current technology is good enough to even detect such a small change. The reduction in energy we'd receive from the Sun if we were in a dust cloud is smaller than the reduction caused by a single small sunspot. Indeed, I wouldn't be surprised if the dust density within the Solar System right now is much greater than the dust density in galactic clouds.

Furthermore, while we were in a dust cloud, it seems likely that it would locally be made even more tenuous by the effects of solar wind and solar radiation, both of which would probably create a bubble of lower density around the Sun.

We undoubtedly pass through dust in the course of orbiting within the Milky Way, probably with a period of a few tens of million years.

[neufer]

When you look at these dust clouds in the Milky Way, or dust lanes in other galaxies, you are seeing structures on a scale of kiloparsecs.

Typical visible-band extinction values in these dust clouds are on the order of a few magnitudes/kpc.

In terms of astronomical units, you are looking at nanomagnitudes. In other words, if our solar system were in the midst of a galactic dust lane, we'd see a drop in solar radiation on the order of microwatts per square meter (on the normal value of around 1 kw/m^2). I don't think our current technology is good enough to even detect such a small change. The reduction in energy we'd receive from the Sun if we were in a dust cloud is smaller than the reduction caused by a single small sunspot.

Indeed, I wouldn't be surprised if the dust density within the Solar System right now is much greater than the dust density in galactic clouds.

<<The zodiacal light is produced by sunlight reflecting off dust particles in the solar system known as cosmic dust. Consequently, its spectrum is the same as the solar spectrum. The material producing the zodiacal light is located in a lens-shaped volume of space centered on the sun and extending well out beyond the orbit of Earth. This material is known as the interplanetary dust cloud. Since most of the material is located near the plane of the solar system, the zodiacal light is seen along the ecliptic. The amount of material needed to produce the observed zodiacal light is amazingly small. If it were in the form of 1 mm particles, each with the same albedo (reflecting power) as Earth's moon, each particle would be 8 km from its neighbors. The gegenschein may be because particles directly opposite the sun as seen from Earth would be in full phase.

1 optical depth of zodiacal dust ~ [(8 × 10^6)^3 mm]/ (30.857 × 10^18 mm/parsec)
1 optical depth of zodiacal dust ~ 16.6 parsecs.
60 optical depths of zodiacal dust ~ 1 kiloparsec

Zodiacal dust visible-band extinction ~ 65 magnitudes / kpc

<<Ancient Egyptian cosmology talks about a bird known as the Great Cackler, a cosmic goose, who brings the universe into manifestation by letting out a divine honk or call. It lays the sun-egg from which the creator god emerges, his name altering depending on which cult centre the myth is attached. On the famous round zodiac of Denderah, created as late as c. 50 BC, there appears a cosmic goose, and careful analysis of its position in the night sky shows that it formed part of a constellation composed of the stars of Cygnus and the bright star Altair in Aquila, the celestial eagle, an area of the Milky Way dominated by the dark nebulous region known as the Great Rift. This indicates that the Ancient Egyptians saw the point of creation as located in the vicinity of Cygnus. In addition to this, the Great Cackler was a totem of Geb, the earth god, whose wife/lover was Nut, the sky-goddess. Occasionally, the Great Cackler is shown at the feet of Nut as she is prised apart from Geb in order to form the sky and earth.>>

[lakeside]

I want to thank you all for the definitive answers to drifting through dust clouds.!

Jack White
Albany OR

[DavidLeodis]

I've noticed that the explanation has been altered so that it now states the Magellanic Clouds are "Below and right of center".

[NoelC]

I should think that dust on a galactic scale is still pretty thin and while it might block radiation from other stars it wouldn't significantly affect the insanely more powerful radiation we get from our own sun.

For my own nit, I noticed the use of the word "imbedded". I have always thought that it should be more correctly spelled "embedded".

-Noel

[bystander]

Axel Mellinger, of Central Michigan University, created this panorama of the Milky Way from 3,000 individual photographs that he melded together with mathematical models. Credit: Dr. Axel Mellinger

3,000 Images Combine for Stunning Milky Way Portrait
Space.com - 2009 Oct 30

A new panoramic image of the full night sky — with the Milky Way as its centerpiece — has been made by piecing together 3,000 individual photographs.

The panorama's creator, Axel Mellinger of Central Michigan University, spent 22 months and traveled over 26,000 miles to take digital photographs at dark sky locations in South Africa, Texas and Michigan.

"This panorama image shows stars 1,000 times fainter than the human eye can see, as well as hundreds of galaxies, star clusters and nebulae," Mellinger said.
...
The result is an image of our home galaxy that no star-gazer could ever see from a single spot on earth. Mellinger plans to make the giant 648 megapixel image available to planetariums around the world.

I think gigagalaxy zoom and Serge Brunier stole his thunder. Nice picture, but I reserve judgement until I see the hi-res version.

It's here!