APOD: NGC 3717: A Nearly Sideways Spiral... (2019 Nov 12)

Comments and questions about the APOD on the main view screen.
User avatar
neufer
Vacationer at Tralfamadore
Posts: 16539
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: Red giants & dwarfs

Post by neufer » Thu Nov 14, 2019 2:35 am

Ann wrote:
Thu Nov 14, 2019 1:53 am

Interesting info on the red giants, Art.

But why is your text a reply to what I said about red dwarfs?
If I have to explain what I post then it isn't as funny.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 9963
Joined: Sat May 29, 2010 5:33 am

Re: Red giants & dwarfs

Post by Ann » Thu Nov 14, 2019 3:07 am

neufer wrote:
Thu Nov 14, 2019 2:35 am
Ann wrote:
Thu Nov 14, 2019 1:53 am

Interesting info on the red giants, Art.

But why is your text a reply to what I said about red dwarfs?
If I have to explain what I post then it isn't as funny.
A comparison of stellar sizes and masses.
Credit: NASA, ESA and A. Feild
If you have to explain why I should laugh, then it isn't as funny?

And if you explain what you mean, then it isn't, I guess, as intellectually stimulating and illuminating as if you don't?

Hope you took notes, because there will be a test tomorrow!
© EtiAmmos #FO21178418
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16539
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

a steady accumaliting [sic] dust process

Post by neufer » Thu Nov 14, 2019 4:19 am

Ann wrote:
Thu Nov 14, 2019 3:07 am

If you have to explain why I should laugh, then it isn't as funny?

And if you explain what you mean, then it isn't, I guess, as intellectually stimulating and illuminating as if you don't?
The fact of the matter is...
  • I really thought the "sillyworm 2" post was sort of interesting:
Image
sillyworm 2 wrote:
Wed Nov 13, 2019 1:04 pm

So much dust from so many dying stars.

Wrapping my mind around this. Is this a steady accumalitive [sic] process or could
there have been more stars dying earlier when the galaxy was just forming?
Under such sorghum-stenches, I felt that (with a little research) I could
come up with an answer to s2's question(, at least, to my own satisfaction).

Unfortunately, this turned out not to be the case.

However, I had spent too much time not to post something that was at least
as illuminating as own your post... but that had the advantage of a nice NKC video.

Unfortunately, rather than simply enjoying the nice NKC video, you had to
"make a federal case of this" (when clearly neither of us knew what we were talking about).
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 9963
Joined: Sat May 29, 2010 5:33 am

Re: a steady accumaliting [sic] dust process

Post by Ann » Thu Nov 14, 2019 5:11 am

neufer wrote:
Thu Nov 14, 2019 4:19 am
Ann wrote:
Thu Nov 14, 2019 3:07 am

If you have to explain why I should laugh, then it isn't as funny?

And if you explain what you mean, then it isn't, I guess, as intellectually stimulating and illuminating as if you don't?
The fact of the matter is...
  • I really thought the "sillyworm 2" post was sort of interesting:
Image
sillyworm 2 wrote:
Wed Nov 13, 2019 1:04 pm

So much dust from so many dying stars.

Wrapping my mind around this. Is this a steady accumalitive [sic] process or could
there have been more stars dying earlier when the galaxy was just forming?
Under such sorghum-stenches, I felt that (with a little research) I could
come up with an answer to s2's question(, at least, to my own satisfaction).

Unfortunately, this turned out not to be the case.

However, I had spent too much time not to post something that was at least
as illuminating as own your post... but that had the advantage of a nice NKC video.

Unfortunately, rather than simply enjoying the nice NKC video, you had to
"make a federal case of this" (when clearly neither of us knew what we were talking about).

Neither of us? :?: (reacting) :arrow:

Ann

P.S. Sorghum-stenches - from "Ladle Rat Rotten Hut". I remember reading "Handsel and Gristle", but this one was harder to read.
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16539
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: a steady accumaliting [sic] dust process

Post by neufer » Thu Nov 14, 2019 10:26 pm

Click to play embedded YouTube video.
Ann wrote:
Thu Nov 14, 2019 5:11 am

P.S. Sorghum-stenches - from "Ladle Rat Rotten Hut".

I remember reading "Handsel and Gristle", but this one was harder to read.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 9963
Joined: Sat May 29, 2010 5:33 am

Re: a steady accumaliting [sic] dust process

Post by Ann » Fri Nov 15, 2019 6:25 am

neufer wrote:
Thu Nov 14, 2019 10:26 pm
Click to play embedded YouTube video.
Ann wrote:
Thu Nov 14, 2019 5:11 am

P.S. Sorghum-stenches - from "Ladle Rat Rotten Hut".

I remember reading "Handsel and Gristle", but this one was harder to read.
Thanks for the translation, Art! :D

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16539
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: Red giants & dwarfs

Post by neufer » Fri Nov 22, 2019 3:39 pm

neufer wrote:
Thu Nov 14, 2019 1:29 am
https://en.wikipedia.org/wiki/Cosmic_dust#Dust_grain_formation wrote:
<<The large grains in interstellar space are probably complex, with refractory cores that condensed within stellar outflows topped by layers acquired 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-giants and carbon grains condensing in the atmospheres of cool carbon stars. Red giants have evolved or altered 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. Meteoriticists who study refractory stardust (extracted from meteorites) often call it presolar grains but that within meteorites is 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, in cases only to be destroyed or split apart by radiation and sublimation into a gas component. Finally, as the Solar System formed many interstellar dust grains were further modified by coalescence and chemical reactions in the planetary accretion disk. The history of the various types of grains in the early Solar System is complicated and only partially understood.>>
https://en.wikipedia.org/wiki/SN_1987A#Condensation_of_warm_dust_in_the_ejecta wrote:
<<Although it had been thought more than 50 years ago that dust could form in the ejecta of a core-collapse supernova, which in particular could explain the origin of the dust seen in young galaxies, that was the first time that such a condensation was observed. If SN 1987A is a typical representative of its class then the derived mass of the warm dust formed in the debris of core collapse supernovae is not sufficient to account for all the dust observed in the early universe. However, a much larger reservoir of ~0.25 solar mass of colder dust (at ~26 K) in the ejecta of SN 1987A was found with the Hershel infrared space telescope in 2011 and confirmed by ALMA. Following the confirmation of a large amount of cold dust in the ejecta, ALMA has continued observing SN 1987A. Synchrotron radiation due to shock interaction in the equatorial ring has been measured. Cold (20–100K) carbon monoxide (CO) and silicate molecules (SiO) were observed. The data show that CO and SiO distributions are clumpy, and that different nucleosynthesis products (C, O and Si) are located in different places of the ejecta, indicating the footprints of the stellar interior at the time of the explosion.>>
https://phys.org/news/2019-11-scientists-evidence-neutron-star.html wrote:
Scientists find evidence of missing neutron star
phys.org , November 19, 2019


<<[Astronomers at Cardiff University] claim to have found evidence of the location of a neutron star that was left behind [from] Supernova 1987A. For more than 30 years astronomers have been unable to locate the neutron star—the collapsed leftover core of the giant star—as it has been concealed by a thick cloud of cosmic dust.

Using extremely sharp and sensitive images taken with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in the Atacama Desert of northern Chile, the team have found a particular patch of the dust cloud that is brighter than its surroundings, and which matches the suspected location of the neutron star. The findings have been published in The Astrophysical Journal. Lead author of the study Dr. Phil Cigan, from Cardiff University's School of Physics and Astronomy, said: "For the very first time we can tell that there is a neutron star inside this cloud within the supernova remnant. Its light has been veiled by a very thick cloud of dust, blocking the direct light from the neutron star at many wavelengths like fog masking a spotlight." The supernova explosion that took place at the end of this star's life resulted in huge amounts of gas with a temperature of over a million degrees, but as the gas began to cool down quickly below zero degrees centigrade, some of the gas transformed into a solid, i.e. dust.>>
Art Neuendorffer