APOD: Recycling Cassiopeia A (2023 Jun 01)

[APOD Robot]

Recycling Cassiopeia A

Explanation: Massive stars in our Milky Way Galaxy live spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant would have been first seen in planet Earth's sky about 350 years ago, although it took that light about 11,000 years to reach us. This false-color image, composed of X-ray and optical image data from the Chandra X-ray Observatory and Hubble Space Telescope, shows the still hot filaments and knots in the remnant. It spans about 30 light-years at the estimated distance of Cassiopeia A. High-energy X-ray emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help astronomers explore the recycling of our galaxy's star stuff. Still expanding, the outer blast wave is seen in blue hues. The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core.

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[AVAO]

Recycling Cassiopeia A

There is an update from JWST:
Slider: Hubble and Webb’s views of Cassiopeia A
https://esawebb.org/images/comparisons/weic2311a/

...dynamic region...

Click to view full size image

bigger: https://live.staticflickr.com/65535/529 ... e916_k.jpg

Click to view full size image

bigger:https://live.staticflickr.com/65535/529 ... 4e5b_o.jpg
Composit: SST(polarisation filters), HERSCHEL(Clouds), HST and JWST
jac berne (flickr)

Interesting article & paper:

Credit: J.Vink/astronomie.nl
https://phys.org/news/2022-03-ejection- ... venly.html
"An image of Cassiopeia A showing only two shells of nebulae. The blue arrows on the right (astronomers call this the west side) show that the inner shell is not expanding outwards at this point, but inwards. The red arrows show that the other remnants do expand outwards."

[daddyo]

That’s interesting that those elements were created so non-homogeneously, maybe each comes from different depths of the originating star when it explodes.

[orin stepanek]

Anybody notice what looks like a dog's head of sorts? Wonder if that
shows the direction of the blast?
Tis a beautiful photo though!

[johnnydeep]

So, we have "silicon in red, sulfur in yellow, calcium in green and iron in purple," and "the outer blast wave is seen in blue hues". Can anything be said from this image about what elements are in that outer blast wave? Is blue hydrogen and/or helium, or is it a combination of the other four colors? Similarly, what about the white regions?

[AVAO]

Chandrafirstlight_0_1024.jpg
Anybody notice what looks like a dog's head of sorts? Wonder if that
shows the direction of the blast?
Tis a beautiful photo though!

ThanX Orin

Your question is simple but not really easy to answer.

The following time-lapse video ( https://www.youtube.com/watch?v=VunToqmW9so )shows that, in principle, the explosion spreads outwards evenly all around. The core of the exploded star is still stable in the center in the form of a neutron star, which is not always the case. Unfortunately, there are also structures on the right side in a small area that are moving towards the inside. This leads the astronomers to assume that something from the outside has entered the expansion bubble or has crossed it from right to left. On my composite image above you can see very well that the polarized filament structures from a light echo of SPITZER (SST) on the right side are exactly in the extension of this axis and continue several 100 light years into space. To me this means that the processes behind supernovae explosions are possibly much more complex than we think we know.

Jac

[AVAO]

So, we have "silicon in red, sulfur in yellow, calcium in green and iron in purple," and "the outer blast wave is seen in blue hues". Can anything be said from this image about what elements are in that outer blast wave? Is blue hydrogen and/or helium, or is it a combination of the other four colors? Similarly, what about the white regions?

Good question? Visible in X-rays, but...

https://www.nasa.gov/feature/goddard/20 ... loded-star
https://apod.nasa.gov/apod/ap000103.html

I'm sure Chris can help.

[Chris Peterson]

So, we have "silicon in red, sulfur in yellow, calcium in green and iron in purple," and "the outer blast wave is seen in blue hues". Can anything be said from this image about what elements are in that outer blast wave? Is blue hydrogen and/or helium, or is it a combination of the other four colors? Similarly, what about the white regions?

There's a reason that science doesn't make use of colored images like this. They scramble information. In some cases, as with the Hubble palette, that information is recoverable. Because there are only three wavelengths, and they are uniquely mapped to the three physical color channels (red, green, and blue). But yellow is a mixture of red and green. So when we see yellow here, is it sulfur, or is it a mixture of silicon and calcium? Purple is a mixture of red and blue. So is purple showing us iron, or a mixture of silicon and whatever the blue channel is mapped from (which isn't stated here)?

If we were analyzing this scientifically, we'd have a full set of monochrome images, one from each filter. We would know unambiguously what was what (with some error created by the contribution of continuum sources like stars). But in an image like this? Well, we can sort of make a guess at some of what we're seeing, but it isn't very rigorous or very certain.

In general, if you have an image with no more than three source wavelengths and they are mapped to the primary colors, you may be able to determine quite a lot. More than three inputs, and mappings to combinations of primaries? Not so much.

[AVAO]

So, we have "silicon in red, sulfur in yellow, calcium in green and iron in purple," and "the outer blast wave is seen in blue hues". Can anything be said from this image about what elements are in that outer blast wave? Is blue hydrogen and/or helium, or is it a combination of the other four colors? Similarly, what about the white regions?

Well, maybe one more addition to the answer from Chris. As far as I know, a large number of elements can in principle be ionized more strongly by the interaction of shock waves with the surrounding interstellar medium, so that they also emit radiation in the X-ray range. However, lighter elements such as hydrogen or helium cannot usually be ionized as strongly and emit only little X-ray radiation. If you look at the outer blast wave, based on the previous investigations using the elimination process, you can actually only say that they contain very little iron. https://chandra.si.edu/photo/2017/casa_life/more.html

[Ann]

So, we have "silicon in red, sulfur in yellow, calcium in green and iron in purple," and "the outer blast wave is seen in blue hues". Can anything be said from this image about what elements are in that outer blast wave? Is blue hydrogen and/or helium, or is it a combination of the other four colors? Similarly, what about the white regions?

There's a reason that science doesn't make use of colored images like this. They scramble information. In some cases, as with the Hubble palette, that information is recoverable. Because there are only three wavelengths, and they are uniquely mapped to the three physical color channels (red, green, and blue). But yellow is a mixture of red and green. So when we see yellow here, is it sulfur, or is it a mixture of silicon and calcium? Purple is a mixture of red and blue. So is purple showing us iron, or a mixture of silicon and whatever the blue channel is mapped from (which isn't stated here)?

If we were analyzing this scientifically, we'd have a full set of monochrome images, one from each filter. We would know unambiguously what was what (with some error created by the contribution of continuum sources like stars). But in an image like this? Well, we can sort of make a guess at some of what we're seeing, but it isn't very rigorous or very certain.

In general, if you have an image with no more than three source wavelengths and they are mapped to the primary colors, you may be able to determine quite a lot. More than three inputs, and mappings to combinations of primaries? Not so much.

Thanks, Chris.

I'm not so fond of this picture because it doesn't appeal very much to my sense of aesthetics. But more than that, as you say, the choice of mapped colors here makes the image hard or impossible to "read" for scientific purposes.

Ann

[Ann]

So, we have "silicon in red, sulfur in yellow, calcium in green and iron in purple," and "the outer blast wave is seen in blue hues". Can anything be said from this image about what elements are in that outer blast wave? Is blue hydrogen and/or helium, or is it a combination of the other four colors? Similarly, what about the white regions?

Good question? Visible in X-rays, but...

https://www.nasa.gov/feature/goddard/20 ... loded-star
https://apod.nasa.gov/apod/ap000103.html

I'm sure Chris can help.

I think the images you posted here explains it. The blue shell is high-energy X-rays, which are created when the supernova shell blasts into the surrounding medium at high speeds. My guess is that this shell may be visible at other wavelengths as well, although this is not certain.

Other supernova remnants are also surrounded by glowing outer shells:

The Vela Supernova remnant. The bluish glow is ionized oxygen, OIII. Credit: Marco Lorenzi.

---

Supernova remnant SNR 0509-67.5 in the Large Magellanic Cloud. Green and blue colors are X-rays. I'm not sure what the red shell is made of, but I think it is optically visible. Image Credit: NASA, ESA, CXC, SAO, the Hubble Heritage Team (STScI/AURA), and J. Hughes (Rutgers University)

---

[johnnydeep]

Thanks guys for the answers to my question about the other colors!

[beryllium732]

How big is the explosion or the size of the nebula? If there's were a neighbouring starsystem with a earth like planet what would happen to it?

[Rauf]

How big is the explosion or the size of the nebula? If there's were a neighbouring starsystem with a earth like planet what would happen to it?

The expanding cloud of material left over from the supernova now appears approximately 10 light-years (3 pc) across from Earth's perspective.

That's the current size of course. Back when it happened in 17th century the size was way smaller. According to Wikipedia it's expanding at an approximate rate of 4000-6000 km/s.
And It depends on how neighboring you are talking about. If the planets were orbiting the star system that caused the supernova, they probably crumbled at the result of the shockwave. If they were farther than that, they would be still effected, maybe blowing out their atmosphere or sth?
I once heard somewhere that a supernova must be around 30 light years or closer to affect life on Earth. Luckily, there are no supernova candidates discovered at this distance.. yet.

[beryllium732]

How big is the explosion or the size of the nebula? If there's were a neighbouring starsystem with a earth like planet what would happen to it?

The expanding cloud of material left over from the supernova now appears approximately 10 light-years (3 pc) across from Earth's perspective.

That's the current size of course. Back when it happened in 17th century the size was way smaller. According to Wikipedia it's expanding at an approximate rate of 4000-6000 km/s.
And It depends on how neighboring you are talking about. If the planets were orbiting the star system that caused the supernova, they probably crumbled at the result of the shockwave. If they were farther than that, they would be still effected, maybe blowing out their atmosphere or sth?
I once heard somewhere that a supernova must be around 30 light years or closer to affect life on Earth. Luckily, there are no supernova candidates discovered at this distance.. yet.

What's the nearest star to Cassiopeia? Isn't 30 light years a bit to close still not affecting any neighbouring starsystem?