Starship Asterisk*

http://apod.nasa.gov/apod/ap081019.html

In this APOD detail of the Lagoon Nebula, it appears the dust clouds are condensing and raining down… although “down” is relative and I’m uncertain how to interpret “down” in relation to the celestial sphere. I expect that "down" is simply inappropriate. The caption states that stellar winds are shaping the cloud formations so I suppose “outward” is a better word.

It is intriguing that the lower area of the dust cloud appears to be “raining” and, wow! It makes for quite a large “storm”!

Where did all that dust come from?

emc wrote:I’m uncertain how to interpret “down” in relation to the celestial sphere.

In http://antwrp.gsfc.nasa.gov/apod/ap030304.html you have the same picture, only it's raining sideways. Now we have 33 Lagoon Nebula APODs in 12.5 years. What a popular object!

emc wrote:Where did all that dust come from?

It came from previous generations of stars, which fused light elements into heavier ones and released them when the stars exploded.

Chris Peterson wrote:

emc wrote:Where did all that dust come from?

It came from previous generations of stars, which fused light elements into heavier ones and released them when the stars exploded.

So the Lagoon Nebula is the result of several star explosions…



Being that it spans a monstrous 110 by 50 light years and given that the largest known star is VY Canis Majoris and it's a mere 8 light hours in circumference… it does seem impossible that this nebula is the result of one star explosion yet it's signature gives me that impression.

Can the nebula be backtracked at all (from previous observations) to provide more detail of its formation?

apodman wrote:

emc wrote:I’m uncertain how to interpret “down” in relation to the celestial sphere.

In http://antwrp.gsfc.nasa.gov/apod/ap030304.html you have the same picture, only it's raining sideways. Now we have 33 Lagoon Nebula APODs in 12.5 years. What a popular object!

In the APOD FAQs, Q4 tells us that the editors usually repeat images on the weekends. Good thing too, repeating helps us folks that haven't been with APOD for that long.

apodman wrote:Now we have 33 Lagoon Nebula APODs in 12.5 years. What a popular object!

http://apod.nasa.gov/cgi-bin/apod/apod_ ... oon+Nebula

emc wrote:Being that it spans a monstrous 110 by 50 light years and given that the largest known star is VY Canis Majoris and it's a mere 8 light hours in circumference… it does seem impossible that this nebula is the result of one star explosion yet it's signature gives me that impression.

Can the nebula be backtracked at all (from previous observations) to provide more detail of its formation?

What do you mean by "signature"?

Nebulas fall broadly into two major categories. Planetary nebulas are the outward expanding gas and dust from a supernova explosion. Nebulas like the Lagoon are the gravitationally collapsing clouds of material from multiple past stellar explosions.

If you could trace the Lagoon backwards (which is impossible, because the local turbulence has destroyed the original velocity information), you'd see that it had collapsed from much larger, diffuse clouds. If you could keep tracing those diffuse clouds backwards, you'd eventually see them shrink down to tight planetary nebulas and then individual stars.

Chris Peterson wrote:What do you mean by "signature"?

Sorry - It would have been better to say "shape".

Thanks for the explanation... It would be interesting to see a movie or slide show of the formation if that were possible.

Wouldn't the original stars themselves have developed from condensing [dust]; or the original material from the Big Bang? Just curious; Its kind of the impression I had.

Orin

orin stepanek wrote:Wouldn't the original stars themselves have developed from condensing [dust]; or the original material from the Big Bang? Just curious; Its kind of the impression I had.:?

Exactly. There have been several generations of star formation since the Big Bang. The first stars had nothing but H and He to work with, and models show them being somewhat different from "modern" stars. With later generations, heavier elements were available to be incorporated as well.

Chris Peterson wrote:

orin stepanek wrote:Wouldn't the original stars themselves have developed from condensing [dust]; or the original material from the Big Bang? Just curious; Its kind of the impression I had.

Exactly. There have been several generations of star formation since the Big Bang. The first stars had nothing but H and He to work with, and models show them being somewhat different from "modern" stars. With later generations, heavier elements were available to be incorporated as well.

Thanks Chris! Makes sense! 8)

Orin

The thing that impresses me about this photo is how the shapes seem to be formed by currents outside themselves .. as if what we can see is suspended in something we can't see .. like dropping paint into water for instance.

By the way .. the 'Big Bang' is a theory, an idea, a possibility but not a likelihood and it bothers me the way it is thrown around as if fact.

Up and Down in space .. up and down are terms we for orientation .. 'dust raining down' in space could be attracted by an invisible thing's gravity.

Well if you think about it, part of the reason paint or dye drops in water can form the enrapturing patterns they do is because the density is approximately the same, so the dye moves through the water as though it were...weightless.

And of course, this nebula is in deep space where for all practical considerations it's weightless. You've hit right on a very apt analogy.

Sputnick wrote:The thing that impresses me about this photo is how the shapes seem to be formed by currents outside themselves .. as if what we can see is suspended in something we can't see .. like dropping paint into water for instance.

The dust is the medium but it is apparently shaped by the stellar winds... 8)

Speaking of shaped by winds... I am reminded that artists will go to great lengths to be unique and creative... take this artist for example who paints by tossing a can of paint into the jet exhaust that is blasting a canvas... http://www.jetartproductions.com/ Wild... but that and shaping half light year long funnel clouds requires more energy than using a brush.

Ed .. I meant the medium the dust is in .. the dust is the visible stuff, shapes, etc.. the medium is the invisible stuff. I could use a jet exhaust for my moped.

Sputnick wrote:Ed .. I meant the medium the dust is in .. the dust is the visible stuff, shapes, etc.. the medium is the invisible stuff. I could use a jet exhaust for my moped.

Sorry - I took artistic license with your post.

You may want to reconsider the jet exhaust for your moped as your MPG will go astro and gas prices are difficult to budget... at least here in GA USA.

Chris Peterson wrote: Planetary nebulas are the outward expanding gas and dust from a supernova explosion. Nebulas like the Lagoon are the gravitationally collapsing clouds of material from multiple past stellar explosions.

If you could trace the Lagoon backwards (which is impossible, because the local turbulence has destroyed the original velocity information), you'd see that it had collapsed from much larger, diffuse clouds. If you could keep tracing those diffuse clouds backwards, you'd eventually see them shrink down to tight planetary nebulas and then individual stars.

Um... you might want to check into the definition of "planetary nebula" some more, Chris. It is not a supernova remnant nor a dust cloud. It is the expelled outer layer of a sun-like star at the end of the star's life, with a white dwarf at the center.

Gary

starnut wrote:Um... you might want to check into the definition of "planetary nebula" some more, Chris. It is not a supernova remnant nor a dust cloud. It is the expelled outer layer of a sun-like star at the end of the star's life, with a white dwarf at the center.

I'd argue we're both being overly narrow. "Planetary nebula" usually describes a particular morphology: a nebula expanding outwards from a stellar core of some sort. That may be the product of a supernova, nova, or even certain cyclical cataclysmic events. From a material standpoint, it will consist of both dust and gas. A supernova remnant may appear as a planetary nebula, and a planetary nebula may have something other than a white dwarf at the center.

In any case, any cataclysmic star event can throw off material which eventually ends up in a new star forming region. The point being, that this material all originated in earlier generation stars.

I've split out posts from this thread that are way off-topic, into a new thread in the Café: Café posts split from Stormy Lagoon Nebula (19Oct). Please let's try to stay focussed in our "Discuss an APOD" posts ...

For anyone who hasn't noticed, the thread that split from this one has continued to grow and has gained focus.