Starship Asterisk*

What exactly is cosmic dust? Does it have a specific chemical composition? Or is it not "exactly" anything, but more of a generic term for "mostly this, but could be some of that"? In the textbook, "The Cosmos" (Pasachoff, Filippenko, 3rd ed., p. 360), Figure 15-27 has the following note: "Hydrogen molecules are formed in space with the aid of dust grains at an intermediate stage. Terrestrial laboratory research reported in 2005 showed that irregularities on the dust grains appear to be needed to form the molecules." The illustration depicts the dust grain as something with a ragged edged, a somewhat elliptical shape, and quite large relative to the size of individual hydrogen atoms. But what is it?

charlieo3 wrote:What exactly is cosmic dust? Does it have a specific chemical composition? Or is it not "exactly" anything, but more of a generic term for "mostly this, but could be some of that"?

Something like the last. It consists of particles made from clumped molecules. Its composition depends on its source, but frequently contains carbon, oxygen, silicon, iron, nickel and other refractory elements. The material may be primary, formed inside stars, or secondary, broken off of other bodies. That's kind of the same way we use "dust" when talking about the stuff that lands on your coffee table. Many sources, many sizes, many compositions.

In Swedish, "dust" translates as "damm" and "damm" is what you can see in this picture. When I first told my mother about cosmic "damm", she asked me, 'How did the "damm" get into space?'










Fighting "damm" the old-fashioned way. But how did it get into space?

Ann

Ann, where did you get that picture of my sister and me sitting on the couch with our feet up? Notice how Mama cheerily incorporates dancing into her housework, impeccably outfitted in her hand-pressed flowery print dress and color-coordinated high-heeled shoes. Ah, the "happy days" of my childhood. And, yes, you caught me out... I was really trying to determine if my dust collection from the 50's could be mined for something I can sell on eBay.

At this house ( where i also grew up ) My mother wasted absolutely nothing, i mean nothing and i'm certain that somewhere around here " the attic, the garage or somewhere " there is a giant bag of drier lint i just haven't found it yet

Dust is a good word for planetary detritus, but it seems far too lowly for material forged in stars. I like the word “stardust” for this interstellar material, because it accurately includes where this stuff comes from as well as its form.

Bruce

Maybe dust is a fine word and rather it is you who thinks too lowly of it. Assigning caste to dust seems rather silly to me.

BDanielMayfield wrote:Dust is a good word for planetary detritus, but it seems far too lowly for material forged in stars. I like the word “stardust” for this interstellar material, because it accurately includes where this stuff comes from as well as its form.

Cosmic dust contains a subcategory of interstellar dust, which is different from stardust. Only some interstellar dust is stardust, meaning it formed inside stars and is substantially unaltered. In practice, we only observe stardust trapped in meteorites or recovered by special collectors in space.

Chris Peterson wrote: Only some interstellar dust is stardust, meaning it formed inside stars and is substantially unaltered.

I'm thinking that only the elements, not the dust, were formed inside the stars, and that it is in the clumping together of some of those elements in the aftermath of a nova or supernova explosion that it becomes "dust." Is this correct or incorrect thinking?

Also, does anybody remember whether Carl Sagan said we are made of "Star Dust," or did he say "Star Stuff"?

charlieo3 wrote:I'm thinking that only the elements, not the dust, were formed inside the stars, and that it is in the clumping together of some of those elements in the aftermath of a nova or supernova explosion that it becomes "dust." Is this correct or incorrect thinking?

I believe rather large dust particles can come together in the outer layers of some stars before they explode, and that can include molecules consisting of more than a single element. Many late stage stars are cool enough in their outer layers to support unmelted, un-ionized refractory materials.

Also, does anybody remember whether Carl Sagan said we are made of "Star Dust," or did he say "Star Stuff"?

I believe he said we were made of "starstuff". But he did not come up with either the term or the concept. It was used numerous times from at least the early 20th century.

Chris Peterson wrote:

charlieo3 wrote:
Does anybody remember whether Carl Sagan said we are made of "Star Dust," or did he say "Star Stuff"?

I believe he said we were made of "starstuff". But he did not come up with either the term or the concept.
It was used numerous times from at least the early 20th century.

• King Henry VIII Act 3, Scene 2

KING HENRY VIII: You are full of heavenly stuff.

• Julius Caesar Act 3, Scene 2

ANTONY: Ambition should be made of sterner stuff.

• The Tempest Act 4, Scene 1

PROSPERO: We are such stuff as dreams are made on.

• Timon of Athens Act 5, Scene 1

TIMON: And, for thy fiction,

• Why, thy verse swells with stuff so fine and smooth
  That thou art even natural in thine Art.
  
  A Midsummer Night's Dream Act 5, Scene 1

HIPPOLYTA: This is the silliest stuff that EVER I heard.