diving into dust clouds

[roidspop]

I've seen depictions of the sun's orbit about the center of the galaxy and it resembles the trace you'd get from a point on a merry-go-round horse as it gallops around its circle. It seems likely that as we pass through the plane of the disc that our chances of encountering substantial concentrations of dust and gas would be pretty high. It also seems that even though an optically dense region like the Horse Head Nebula is basically empty space, there might be significant effects to a planetary system passing through such a zone.

Would anyone care to remark on the possible consequences of such a plunge? Could we detect any effects later, say in ocean sediments or the lunar reggolith? Maybe in meteorites? Is it possible that the fractional increase in density of the interstellar medium might dump some comets from the Oort cloud? Periodic extinctions solved; read all about it?

[Bob S.]

This was talked about briefly under <u>Against the Mainstream</u>, "Nemesis".
http://www.badastronomy.com/phpBB/vi...=747&forum=1&6
See if what we posted there covers something of what you are talking about.

[John Kierein]

Look here. Help!
http://www.etheric.com/GalacticCenter/Galactic.html

[roidspop]

Yikes! Thanks for that link...I think! I have read that nearby supernovas could have effects very similar to this; the point that humanity should be on the outlook for energetic outbursts (supernova, gamma ray burster or 'superwave') certainly seems to have merit. Now how do you convince politicians that they need to spend money to watch for events that might not happen until they're out of office?

[Chip]

Hi there,

Keeping in mind that this is not exactly my field, I think that our solar system is not in danger of running into a large nebula (of the Orion - "stellar nursery" type). Maybe in several billion years. As for the other dangers, such as supernovas, (or regular novas), and Gamma ray bursts, these could be dangers to us in the long term. Current thinking is that asteroids pose the greatest danger to Earthlings, as they are much much closer to us, and faster.

A much more subtle source of danger that is not much talked about are the slight perturbations (if that's the correct term), that "nearby" stars have on our solar system as they, and we revolve together in the Milky Way's spiral arm over time. These slight effects affect the Oort cloud and in the future, could increase the odds for increased comet and asteroid collisions within the inner solar system.

As per some types of nebulas, I have an interesting notion. If we could quickly travel to a planetary nebula, which is very diffuse but appears bright from a great distance, would it not fade away to nothing as we got close? The reason I ask is that the nebula is very very thin and very large, if we were in it, only our instruments would detect gases, but we might not see anything. Of course, some nebulas are very dark and dense too.

On the other hand, when galaxies collide, the stars all miss each other, but the dust gasses crash and condense, producing violent bright areas of extensive new star birth and radiation. Millions of years from now the Andromeda galaxy might merge with our own. If so, as Bette Davis said: "It's going to be a bumpy night."

Chip

<font size=-1>[ This Message was edited by: Chip on 2002-04-04 01:14 ]</font>

[John Kierein]

These nebulae contain free floating planets and the building blocks of life. If we go, we better be prepared to meet ET.
http://www.geocities.com/CapeCanaveral/Galaxy/7827/

[roidspop]

Now that is interesting speculation! I can't see any reason to imagine that clouds like that might not be thick with comets.

Can you think of any sort of detectable signature that would reveal the presence of bodies that size in such a cloud?

Living on a planet passing through such a region would be strange...a featureless, starless sky with comets passing through the system constantly. Lots of meteoritic activity. Heads up!

[Peter B]

John Brunner's "The Crucible of Time" is based on the sort of situation discussed here.

One of the most uplifting and enjoyable SF books I've read.

[Simon]

I rather doubt we have to be on guard for nearby supernovae, at least. True, we can't predict exactly when they're going to happen, but the absence of any large red-giant stars within 10 lightyears or so probably means we aren't going to encounter one anytime soon...

'Soon' meaning a couple million years, or course. [img]/phpBB/images/smiles/icon_wink.gif[/img]