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

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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.

[Ann]

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.

Click to view full size image

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?

Click to view full size image

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

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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:

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).

[Ann]

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:

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).

Click to view full size image

Neither of us? (reacting)

Ann

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

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Click to play embedded YouTube video.

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

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

[Ann]

Click to play embedded YouTube video.

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!

Ann

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<<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.>>

Sequence of HST SN 1987A images from 1994 to 2009

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<<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.>>

A close-up view of different components in the SN 1987A system: carbon monoxide molecular gas is shown in orange, hot hydrogen gas is shown in purple, and the dust which surrounds the neutron star is shown in cyan. Credit: Cardiff University

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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.>>

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Scheme of stardust accumulation in our solar system. (Graphic from Ek et al, Nature Astronomy, 2019)

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Stardust from red giants
ETH Zurich News | 09.12.2019
By: Barbara Vonarburg (public outreach)

<<Some of the Earth's building material was stardust from red giants, researchers from ETH Zurich have established. They can also explain why the Earth contains more of this stardust than the asteroids or the planet Mars, which are farther from the sun.

Around 4.5 billion years ago, an interstellar molecular cloud collapsed. At its centre, the Sun was formed; around that, a disc of gas and dust appeared, out of which the earth and the other planets would form. This thoroughly mixed interstellar material included exotic grains of dust: “Stardust that had formed around other suns,” explains Maria Schönbächler, a professor at the Institute of Geochemistry and Petrology at ETH Zurich. These dust grains only made up a small percentage of the entire dust mass and were distributed unevenly throughout the disc. “The stardust was like salt and pepper,” the geochemist says. As the planets formed, each one ended up with its own mix.

Thanks to extremely precise measurement techniques, researchers are nowadays able to detect the stardust that was present at the birth of our solar system. They examine specific chemical elements and measure the abundance of different isotopes – the different atomic flavours of a given element, which all share the same number of protons in their nuclei but vary in the number of neutrons. “The variable proportions of these isotopes act like a fingerprint,” Schönbächler says: “Stardust has really extreme, unique fingerprints – and because it was spread unevenly through the protoplanetary disc, each planet and each asteroid got its own fingerprint when it was formed.”

Over the past ten years, researchers studying rocks from the Earth and meteorites have been able to demonstrate these so-​called isotopic anomalies for more and more elements. Schönbächler and her group have been looking at meteorites that were originally part of asteroid cores that were destroyed a long time ago, with a focus on the element palladium.

Other teams had already investigated neighbouring elements in the periodic table, such as molybdenum and ruthenium, so Schönbächler’s team could predict what their palladium results would show. But their laboratory measurements did not confirm the predictions. “The meteorites contained far smaller palladium anomalies than expected,” says Mattias Ek, postdoc at the University of Bristol who made the isotope measurements during his doctoral research at ETH.

Now the researchers have come up with a new model to explain these results, as they report in the journal Nature Astronomy. They argue that stardust consisted mainly of material that was produced in red giant stars. These are aging stars that expand because they have exhausted the fuel in their core. Our sun, too, will become a red giant four or five billion years from now.
Scheme of stardust accumulation in our solar system. (Graphic from Ek et al, Nature Astronomy, 2019)

In these stars heavy elements such as molybdenum and palladium were produced by what is known at the slow neutron capture process. “Palladium is slightly more volatile than the other elements measured. As a result, less of it condensed into dust around these stars, and therefore there is less palladium from stardust in the meteorites we studied” Ek says.

The ETH researchers also have a plausible explanation for another stardust puzzle: the higher abundance of material from red giants on Earth compared to Mars or Vesta or other asteroids further out in the solar system. This outer region saw an accumulation of material from supernova explosions.

“When the planets formed, temperatures closer to the Sun were very high,” Schönbächler explains. This caused unstable grains of dust, for instance those with an icy crust, to evaporate. The interstellar material contained more of this kind of dust that was destroyed close to the Sun, whereas stardust from red giants was less prone to destruction and hence concentrated there. It is conceivable that dust originating in supernova explosions also evaporates more easily, since it is somewhat smaller. “This allows us to explain why the Earth has the largest enrichment of stardust from red giant stars compared to other bodies in the solar system” Schönbächler says.>>

[Ann]

Scheme of stardust accumulation in our solar system. (Graphic from Ek et al, Nature Astronomy, 2019)

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Stardust from red giants
ETH Zurich News | 09.12.2019
By: Barbara Vonarburg (public outreach)

<<Some of the Earth's building material was stardust from red giants, researchers from ETH Zurich have established. They can also explain why the Earth contains more of this stardust than the asteroids or the planet Mars, which are farther from the sun.

Around 4.5 billion years ago, an interstellar molecular cloud collapsed. At its centre, the Sun was formed; around that, a disc of gas and dust appeared, out of which the earth and the other planets would form. This thoroughly mixed interstellar material included exotic grains of dust: “Stardust that had formed around other suns,” explains Maria Schönbächler, a professor at the Institute of Geochemistry and Petrology at ETH Zurich. These dust grains only made up a small percentage of the entire dust mass and were distributed unevenly throughout the disc. “The stardust was like salt and pepper,” the geochemist says. As the planets formed, each one ended up with its own mix.

Thanks to extremely precise measurement techniques, researchers are nowadays able to detect the stardust that was present at the birth of our solar system. They examine specific chemical elements and measure the abundance of different isotopes – the different atomic flavours of a given element, which all share the same number of protons in their nuclei but vary in the number of neutrons. “The variable proportions of these isotopes act like a fingerprint,” Schönbächler says: “Stardust has really extreme, unique fingerprints – and because it was spread unevenly through the protoplanetary disc, each planet and each asteroid got its own fingerprint when it was formed.”

Over the past ten years, researchers studying rocks from the Earth and meteorites have been able to demonstrate these so-​called isotopic anomalies for more and more elements. Schönbächler and her group have been looking at meteorites that were originally part of asteroid cores that were destroyed a long time ago, with a focus on the element palladium.

Click to view full size image

Palladium. Photo: Jorchr.

Click to view full size image

Palladium. Photo: Annette.

Wow. Who'd a thunk that Palladium was so important?

Ann

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Wow. Who'd a thunk that Palladium was so important?

• Palladium is only important in SOHO:

<<William Hyde Wollaston noted the discovery of a new noble metal in July 1802 in his lab book and named it palladium after the asteroid 2 Pallas in August of the same year. Wollaston purified a quantity of the material and offered it, without naming the discoverer, in a small shop in SOHO in April 1803.>>

<<The London Palladium is a 2,286-seat theatre located in the famous area of SOHO. Walter Gibbons, an early moving-pictures manager, built the Palladium in 1910 to compete with Sir Edward Moss's London Hippodrome and Sir Oswald Stoll's London Coliseum.

<<The name SOHO first appears in the 17th century. The name may possibly derive from a former hunting cry. A significant event in the history of epidemiology and public health was Dr. John Snow's study of an 1854 outbreak of cholera in Soho. Snow mapped the addresses of the sick, and noted that they were mostly people whose nearest access to water was the Broad Street public pump. He persuaded the authorities to remove the handle of the pump, thus preventing any more of the infected water from being collected. The spring below the pump was later found to have been contaminated with sewage. This is an early example of epidemiology, public health medicine and the application of science—the germ theory of disease—in a real-life crisis.>>