Starship Asterisk*

DesertNative wrote:What is / are the chemical composition(s) of nebular dust? Where did the dust originate?

Chris Peterson wrote:

DesertNative wrote:What is / are the chemical composition(s) of nebular dust? Where did the dust originate?

Mostly silicates, with some carbonates. It originated inside stars, scattered when they shed their outer layers or when they exploded in supernovas.

Chris Peterson wrote:

DesertNative wrote:
What is / are the chemical composition(s) of nebular dust? Where did the dust originate?

Mostly silicates, with some carbonates. It originated inside stars, scattered when they shed their outer layers or when they exploded in supernovas.

https://en.wikipedia.org/wiki/Cosmic_dust wrote:
<<In circumstellar dust, astronomers have found molecular signatures of CO, silicon carbide [SiC], amorphous silicate, polycyclic aromatic hydrocarbons, water ice, and polyformaldehyde, among others (in the diffuse interstellar medium, there is evidence for silicate and carbon grains).

The large grains in interstellar space are probably complex, with refractory cores that condensed within stellar outflows topped by layers acquired subsequently during incursions into cold dense interstellar clouds. That cyclic process of growth and destruction outside of the clouds has been modeled to demonstrate that the cores live much longer than the average lifetime of dust mass. Those cores mostly start with silicate particles condensing in the atmospheres of cool oxygen rich red-giant stars and carbon grains condensing in the atmospheres of cool carbon stars. The red-giant stars have evolved off the main sequence and have entered the giant phase of their evolution and are the major source of refractory dust grain cores in galaxies. Those refractory cores are also called Stardust, which is a scientific term for the small fraction of cosmic dust that condensed thermally within stellar gases as they were ejected from the stars. Several percent of refractory grain cores have condensed within expanding interiors of supernovae, a type of cosmic decompression chamber. And meteoriticists that study this refractory stardust extracted from meteorites often call it presolar grains, although the refractory stardust that they study is actually only a small fraction of all presolar dust. Stardust condenses within the stars via considerably different condensation chemistry than that of the bulk of cosmic dust, which accretes cold onto preexisting dust in dark molecular clouds of the galaxy. Those molecular clouds are very cold, typically less than 50K, so that ices of many kinds may accrete onto grains, perhaps to be destroyed later. Finally, when the Solar System formed, interstellar dust grains were further modified by chemical reactions within the planetary accretion disk. So the history of the complex grains in the early Solar System is complicated and only partially understood.>>

https://en.wikipedia.org/wiki/Silicon_carbide#Natural_occurrence wrote:
<<While rare on Earth, silicon carbide [SiC] is remarkably common in space. It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites. The silicon carbide found in space and in meteorites is almost exclusively the beta-polymorph. Analysis of SiC grains found in the Murchison meteorite, a carbonaceous chondrite meteorite, has revealed anomalous isotopic ratios of carbon and silicon, indicating an origin from outside the solar system; 99% of these SiC grains originate around carbon-rich asymptotic giant branch stars. SiC is commonly found around these stars as deduced from their infrared spectra.>>

alcarreño wrote:I am very happy that this image was selected and annotated by you.
I wish you all a happy 2016.
Cheers
Raul Villaverde Fraile

DavidLeodis wrote:

alcarreño wrote:I am very happy that this image was selected and annotated by you.
I wish you all a happy 2016.
Cheers
Raul Villaverde Fraile

I don't seem able to get the annotated version so I would be grateful if someone could please let me know where it can be found. Thanks.

alcarreño wrote:

DavidLeodis wrote:

alcarreño wrote:I am very happy that this image was selected and annotated by you.
I wish you all a happy 2016.
Cheers
Raul Villaverde Fraile

I don't seem able to get the annotated version so I would be grateful if someone could please let me know where it can be found. Thanks.

You mean this ??

http://apod.nasa.gov/apod/ap151229.html

DavidLeodis wrote:

alcarreño wrote:I am very happy that this image was selected and annotated by you.
I wish you all a happy 2016.
Cheers
Raul Villaverde Fraile

I don't seem able to get the annotated version so I would be grateful if someone could please let me know where it can be found. Thanks.

Chris Peterson wrote:

DavidLeodis wrote:

alcarreño wrote:I am very happy that this image was selected and annotated by you.
I wish you all a happy 2016.
Cheers
Raul Villaverde Fraile

I don't seem able to get the annotated version so I would be grateful if someone could please let me know where it can be found. Thanks.

I don't believe this image has been annotated in the way we usually mean here, with an overlay identifying objects. I suspect that the term "annotate" was used instead of "notate", in reference to the caption.