APOD: SN 1006: A Supernova Ribbon from Hubble (2023 Aug 06)

[APOD Robot]

SN 1006: A Supernova Ribbon from Hubble

Explanation: What created this unusual space ribbon? The answer: one of the most violent explosions ever witnessed by ancient humans. Back in the year 1006 AD, light reached Earth from a stellar explosion in the constellation of the Wolf (Lupus), creating a "guest star" in the sky that appeared brighter than Venus and lasted for over two years. The supernova, now cataloged at SN 1006, occurred about 7,000 light years away and has left a large remnant that continues to expand and fade today. Pictured here is a small part of that expanding supernova remnant dominated by a thin and outwardly moving shock front that heats and ionizes surrounding ambient gas. The supernova remnant SN 1006 now has a diameter of nearly 60 light years.

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[Ann]

SN 1006: A Supernova Ribbon from Hubble. Credit: NASA, ESA, Hubble Heritage (STScI/AURA); Acknowledgement: W. Blair et al. (JHU)

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APOD Robot wrote:

What created this unusual space ribbon? The answer: one of the most violent explosions ever witnessed by ancient humans. Back in the year 1006 AD, light reached Earth from a stellar explosion in the constellation of the Wolf (Lupus), creating a "guest star" in the sky that appeared brighter than Venus and lasted for over two years...

Pictured here is a small part of that expanding supernova remnant dominated by a thin and outwardly moving shock front that heats and ionizes surrounding ambient gas.

Wow. It looks positively unreal.

I'm a bit surprised at the color of shock front in the APOD, but I'm more surprised at the shock front's razor-sharp edges and perfectly uniform width.

Let's compare the APOD with two pictures of the Vela supernova remnant, one wide-angle picture of much of the supernova remnant, and one closeup of the part of the Vela supernova remnant known as the Pencil Nebula:

The Vela supernova remnant. The yellow rectangle marks the approximate position of the Vela Pulsar. Credit: Harel Boren.

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The Pencil Nebula, which is a part of the Vela supernova remnant. Credit: ESO.

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You can see that the Vela supernova remnant shock fronts tend to be rounded and "arc-shaped", not perfectly straight and narrow. Well, the Pencil Nebula is fairly straight, but parts of it flair out like a broom.

Also note the red/blue color dichotomy in the Vela supernova remnant. Much of the ionized gas is red-glowing hydrogen alpha, but the outermost edges of the shock fronts are blue-green from doubly ionized oxygen.

In today's APOD, we can see an undulating line of white bordering the shock front. Why is it white? Should it really be blue-green from OIII?

I found something interesting and confusing on the Hubblesite page where you can read about the picture that is today's APOD:

Compass image with filter information.

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Hubblesite wrote:

This image combines several exposures in both ACS and WFPC2. The ACS images were exposed through a filter transmitting the light of hydrogen, and the WFPC2 images were made through three filters transmitting wide bands of color in the red and near infrared, yellow- green, and blue portions of the spectrum. In the color composite, the ACS image is shown in red, the WFPC2 red/IR filter images are shown in red-orange, yellow-green filter images in green, and blue filter images in blue-violet. Blue: F439W (B) Green: F555W (V) (Green=F555W) Red: F658 N (H-alpha+[N II]) + F814W (I)

So according to the caption, the yellow-green filter used for today's APOD was a wideband filter centered on 555 nm, which is indeed a shade of yellow-green, ███.
But in the annotated image you can see that another filter was used, namely F606W. 606 nm is this color: ███. That's a big difference to me.

The "W" in the filter names means "wide", so these filters are sensitive to a wide range of wavelengths. Still, if you want to photograph an OIII ionization front, which is this color, ███, it seems like a better idea to use filters centered on ███ and ███ than on filters centered on ███ and ███.

So what I'm asking is this. Could there really be a cyan-colored OIII shock front in today's APOD, but the filters used for the image didn't do a good job of picking up the cyan hue of doubly ionized oxygen?

Ann

[De58te]

Cool. A shock wave that actually looks like a wave. I wonder do we know which direction it is moving? Is it moving from right to left or vice versa like a wave on the ocean, or is it moving in one mass from top to bottom or vice versa.

[Chris Peterson]

I'm a bit surprised at the color of shock front in the APOD, but I'm more surprised at the shock front's razor-sharp edges and perfectly uniform width.

Let's compare the APOD with two pictures of the Vela supernova remnant, one wide-angle picture of much of the supernova remnant, and one closeup of the part of the Vela supernova remnant known as the Pencil Nebula:

Got to be careful with such comparisons, however. The remnant in today's APOD is less than a tenth of the age of the Vela remnants. It is hardly surprising that a recent SN would have finer structure surrounding it. Material is denser, speeds are higher, and the time for stuff to diffuse much less.

[Ann]

I'm a bit surprised at the color of shock front in the APOD, but I'm more surprised at the shock front's razor-sharp edges and perfectly uniform width.

Let's compare the APOD with two pictures of the Vela supernova remnant, one wide-angle picture of much of the supernova remnant, and one closeup of the part of the Vela supernova remnant known as the Pencil Nebula:

Got to be careful with such comparisons, however. The remnant in today's APOD is less than a tenth of the age of the Vela remnants. It is hardly surprising that a recent SN would have finer structure surrounding it. Material is denser, speeds are higher, and the time for stuff to diffuse much less.

Good point, Chris. Thanks.

Doesn't explain the lack of cyan, though. But maybe, for some reason, there is no OIII here.

Ann

[Chris Peterson]

I'm a bit surprised at the color of shock front in the APOD, but I'm more surprised at the shock front's razor-sharp edges and perfectly uniform width.

Let's compare the APOD with two pictures of the Vela supernova remnant, one wide-angle picture of much of the supernova remnant, and one closeup of the part of the Vela supernova remnant known as the Pencil Nebula:

Got to be careful with such comparisons, however. The remnant in today's APOD is less than a tenth of the age of the Vela remnants. It is hardly surprising that a recent SN would have finer structure surrounding it. Material is denser, speeds are higher, and the time for stuff to diffuse much less.

Good point, Chris. Thanks.

Doesn't explain the lack of cyan, though. But maybe, for some reason, there is no OIII here.

Ann

The 606W filter is a conventional red filter. The 505W filter is a conventional green filter. Neither will produce the colors you've represented given a white light source. While the green filter certainly captures [O III], it also captures a lot around it. Green filters do a pretty good job imaging [O III] in the absence of continuum light sources mixed with it, but if you have a lot of white light, not so much. So the question here is whether there is little oxygen, or whether its color is just being washed out. To know for sure, you'd need some narrowband data. But it's possible that a lot more could be learned from looking at the individual channels. As I've noted before, color images like this aren't very useful scientifically. They just throw away or hide too much information.

[johnnydeep]

For those wondering, this is where this fragment is situated in the larger nebula:

From https://www.eso.org/public/images/eso1308a/

Credit: ESO, Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell, X-ray: Chandra X-ray Observatory; NASA/CXC/Rutgers/G. Cassam-Chenaï, J. Hughes et al., Visible light: 0.9-metre Curtis Schmidt optical telescope; NOAO/AURA/NSF/CTIO/Middlebury College/F. Winkler and Digitized Sky Survey.

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Very detailed new observations with ESO’s Very Large Telescope (VLT) of the remains of a thousand-year-old supernova have revealed clues to the origins of cosmic rays.

The image on the left shows the entire SN 1006 supernova remnant, as seen in radio (red), X-ray (blue) and visible light (yellow). The second panel, corresponding to the small square region marked at the left, is a NASA/ESA Hubble Space Telescope close up view of the remarkably narrow region of the shock front, where the material from the supernova is colliding with interstellar medium. The third panel shows how the integral field unit of the VIMOS instrument splits up the image into many small regions, the light from each of which is spread out into a spectrum of its component colours. When these spectra are analysed, maps of the properties of the underlying object can be derived. The example shown here at the right is a map of one property of the gas (the width a spectral line), which is surprisingly variable, and implies, along with other indicators, the presence of very high-speed protons.

[Ann]

Got to be careful with such comparisons, however. The remnant in today's APOD is less than a tenth of the age of the Vela remnants. It is hardly surprising that a recent SN would have finer structure surrounding it. Material is denser, speeds are higher, and the time for stuff to diffuse much less.

Good point, Chris. Thanks.

Doesn't explain the lack of cyan, though. But maybe, for some reason, there is no OIII here.

Ann

The 606W filter is a conventional red filter. The 505W filter is a conventional green filter. Neither will produce the colors you've represented given a white light source. While the green filter certainly captures [O III], it also captures a lot around it. Green filters do a pretty good job imaging [O III] in the absence of continuum light sources mixed with it, but if you have a lot of white light, not so much. So the question here is whether there is little oxygen, or whether its color is just being washed out. To know for sure, you'd need some narrowband data. But it's possible that a lot more could be learned from looking at the individual channels. As I've noted before, color images like this aren't very useful scientifically. They just throw away or hide too much information.

Agreed, Chris. I remember the old Hubble Heritage images. They always showed you the individual filter images as well as the finished color image. Sometimes they would even show you various versions of suggested color images derived from the individual filter images. That was just so interesting!

NGC 4650A. Credits: Hubble Heritage Team (AURA/STScI/NASA)

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I'm pretty sure that the old Hubble Heritage site showed us two other "color versions" of NGC 4650A, before they settled on this one. I wish they would do things like that now, too.

Ann

[Chris Peterson]

Good point, Chris. Thanks.

Doesn't explain the lack of cyan, though. But maybe, for some reason, there is no OIII here.

Ann

The 606W filter is a conventional red filter. The 505W filter is a conventional green filter. Neither will produce the colors you've represented given a white light source. While the green filter certainly captures [O III], it also captures a lot around it. Green filters do a pretty good job imaging [O III] in the absence of continuum light sources mixed with it, but if you have a lot of white light, not so much. So the question here is whether there is little oxygen, or whether its color is just being washed out. To know for sure, you'd need some narrowband data. But it's possible that a lot more could be learned from looking at the individual channels. As I've noted before, color images like this aren't very useful scientifically. They just throw away or hide too much information.

Agreed, Chris. I remember the old Hubble Heritage images. They always showed you the individual filter images as well as the finished color image. Sometimes they would even show you various versions of suggested color images derived from the individual filter images. That was just so interesting!

NGC 4650A. Credits: Hubble Heritage Team (AURA/STScI/NASA)

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I'm pretty sure that the old Hubble Heritage site showed us two other "color versions" of NGC 4650A, before they settled on this one. I wish they would do things like that now, too.

Ann

I think the "scientific" way of looking at most of these things would be to process the individual channels, and then combine them into color images, experimenting with different palettes (which will emphasize different structures). We can get a lot more out of a color image than a B&W one when it comes to quickly identifying interesting things. Then using that information, we can go back to the individual channels to more fully understand what underlies those features that are easier to initially identify in color.

[Rauf]

For those wondering, this is where this fragment is situated in the larger nebula:

From https://www.eso.org/public/images/eso1308a/

Credit: ESO, Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell, X-ray: Chandra X-ray Observatory; NASA/CXC/Rutgers/G. Cassam-Chenaï, J. Hughes et al., Visible light: 0.9-metre Curtis Schmidt optical telescope; NOAO/AURA/NSF/CTIO/Middlebury College/F. Winkler and Digitized Sky Survey.

---

Very detailed new observations with ESO’s Very Large Telescope (VLT) of the remains of a thousand-year-old supernova have revealed clues to the origins of cosmic rays.

The image on the left shows the entire SN 1006 supernova remnant, as seen in radio (red), X-ray (blue) and visible light (yellow). The second panel, corresponding to the small square region marked at the left, is a NASA/ESA Hubble Space Telescope close up view of the remarkably narrow region of the shock front, where the material from the supernova is colliding with interstellar medium. The third panel shows how the integral field unit of the VIMOS instrument splits up the image into many small regions, the light from each of which is spread out into a spectrum of its component colours. When these spectra are analysed, maps of the properties of the underlying object can be derived. The example shown here at the right is a map of one property of the gas (the width a spectral line), which is surprisingly variable, and implies, along with other indicators, the presence of very high-speed protons.

I was trying to figure that out with no success, so Thanks!

[Roy]

Cool. A shock wave that actually looks like a wave. I wonder do we know which direction it is moving? Is it moving from right to left or vice versa like a wave on the ocean, or is it moving in one mass from top to bottom or vice versa.

As can be seen from the picture of the whole SN remnant, this is looking through the edge of a spherical bubble. Which is expanding its radius at an average velocity of almost 10,000 km/sec., 30ly in 1020 years. Material from the original star? Spectra should tell the tale.

[orin stepanek]

An oldie, but a goodie!

[Ann]

For those wondering, this is where this fragment is situated in the larger nebula:

From https://www.eso.org/public/images/eso1308a/

Credit: ESO, Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell, X-ray: Chandra X-ray Observatory; NASA/CXC/Rutgers/G. Cassam-Chenaï, J. Hughes et al., Visible light: 0.9-metre Curtis Schmidt optical telescope; NOAO/AURA/NSF/CTIO/Middlebury College/F. Winkler and Digitized Sky Survey.

---

Very detailed new observations with ESO’s Very Large Telescope (VLT) of the remains of a thousand-year-old supernova have revealed clues to the origins of cosmic rays.

The image on the left shows the entire SN 1006 supernova remnant, as seen in radio (red), X-ray (blue) and visible light (yellow)███. The second panel, corresponding to the small square region marked at the left, is a NASA/ESA Hubble Space Telescope close up view of the remarkably narrow region of the shock front, where the material from the supernova is colliding with interstellar medium.

Thanks, Johnny. No wonder I couldn't make head or tails of the color of the supernova remnant.

The images you posted suggest that the very narrow filament in the APOD is the only visible part of the supernova remnant. We have no idea whether it is Hα-red or OIII-green, only that at least some of the energy emitted from this part of the remnant is in the visible part of the electromagnetic spectrum.

It's mapped color through and through. I guess that the Hubble people also didn't try to figure out what kinds of visible-light ionization can be found in the remarkable filament. They just wanted to show us the amazing shape of this thing, not its actual visible colors.

And the shape of it is remarkable, but it is only a small part of the supernova remnant that is straight and narrow, The rest of it is not.

Ann