APOD: Unusual Nebula Pa 30 (2024 Apr 03)

[APOD Robot]

Unusual Nebula Pa 30

Explanation: What created this unusual celestial firework? The nebula, dubbed Pa 30, appears in the same sky direction now as a bright "guest star" did in the year 1181. Although Pa 30's filaments look similar to that created by a nova (for example GK Per), and a planetary nebula (for example NGC 6751), some astronomers now propose that it was created by a rare type of supernova: a thermonuclear Type Iax, and so is (also) named SN 1181. In this model, the supernova was not the result of the detonation of a single star, but rather a blast that occurred when two white dwarf stars spiraled together and merged. The blue dot in the center is hypothesized to be a zombie star, the remnant white dwarf that somehow survived this supernova-level explosion. The featured image combines images and data obtained with infrared (WISE), visible (MDM, Pan-STARRS), and X-ray (Chandra, XMM) telescopes. Future observations and analyses may tell us more.

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[VictorBorun]

With a temperature near 200,000 K, WD J005311 is the hottest star known. The extreme properties of the central star are being powered by the residual radioactive decay of ⁵⁶Ni, where the usual half-life of 6.0 days from electron capture is increased to many centuries due to the nickel being completely ionized.
Does "completely ionized" mean "stripped of all its 28 electrons"?
Why a super-heavy white dwarf would "completely ionize" its nickel?
How can this prolong ⁵⁶Ni existence?

[Ann]

At first I ho-hummed this APOD, because I didn't find it beautiful or immediately interesting.

Unusual Nebula Pa 30. Image Credit: NASA, ESA, USAF, NSF; Processing: G. Ferrand (U. Manitoba), J. English (U. Manitoba), R. A. Fesen (Dartmouth), C. Treyturik (U. Manitoba); Text: G. Ferrand & J. English

---

I still don't find the image beautiful, but now I think it is really interesting!

The event that created the nebula seen in the APOD was the merger of two white dwarfs. Okay, that happens. Such a merger normally leads to one out of two possible outcomes: 1) There is a supernova type Ia explosion, or, 2) the merger product is not sufficiently massive to overwhelm its own electron degeneracy pressure, and we get a very massive white dwarf, but no supernova.

Two white dwarfs spiral together, merge, and explode as a supernova. No remnant is left behind. Credit: NASA/CXC/M Weiss.

---

Massive (1.14 solar masses) and fairly old (1.3 billion years) white dwarf WDJ0551+4135 is the product of two white dwarfs merging together. The merger did not create a supernova. Credit: Sciencepics/Shutterstock.com

---

So when two white dwarfs merge, you either get a supernova, or you get a very massive white dwarf. Yes, but in the scenario of today's APOD, the merger of the two white dwarfs created a supernova and a remnant white dwarf!!!

Wikipedia wrote about Pa 30, the nebula seen in today's APOD:

Pa 30 was discovered in 2013 by American amateur astronomer Dana Patchick while searching for planetary nebula in WISE infrared data. It was the 30th nebula discovered by his searches, and as a result it is designated Pa 30. Pa 30 appeared as a nearly-round nebula roughly 171x156 arc-seconds in size, with an extremely blue central star. Pa 30 refers to both the nebula (originally catalogued as IRAS 00500+6713) and the central star (designated as WD J005311).

Okay, the Color commentator wants to know what it means that the central star of Pa 30, WD J005311, is "extremely blue". Does it mean that it is "blue", ███, or does it mean that it is very very hot, without necessarily being bright at wavelengths between 400 and 500 nm? I suspect the latter.

Pa 30. The hot blue central star appears to be invisible in this infrared image. Credit: WISE/Meli thev

---

With a temperature near 200,000 K, WD J005311 is the hottest star known.

Right! But how do we know that the nebula in today's APOD, Pa 30, was created in a supernova explosion and not in an ordinary nova explosion? Where the outer and recently acquired layers of the white dwarf blow off, but the white dwarf itself survives? As in, say, Nova Persei?

Nova Persei. The central white dwarf, GK Persei, remains. Credit: X-ray: NASA/CXC/RIKEN/D.Takei et al; Optical: NASA/STScI; Radio: NRAO/VLA

---

We know that Pa 30 must be a supernova remnant because it has certain properties that can only be produced by supernovas:

In 2019, optical spectroscopy of the central star revealed a very hot star with an intense stellar wind expanding at a very high velocity of 16,000 km/s and a composition mainly of carbon, oxygen, and neon (with no hydrogen or helium). Such a speed could only arise from a supernova or an event of similar magnitude, more specifically from a merger of two white dwarfs. X-ray spectroscopy studies of the shell also revealed a very hot nebula containing carbon-burning ashes which can only be produced in a supernova.

So what happened here? The white dwarfs exploded, but they did not explode? Did one of the white dwarfs explode to create a supernova, but the other white dwarf remained, perhaps endowed with some new properties? The white dwarfs exchanged matter, so that one of them was just pushed over its electron degeneracy brink to explode as a (faint) supernova, and the surviving white dwarf incorporated some of the supernova debris into itself to become super-heavy and really really blue-hot? Is that it?

Inquiring minds want to know!

Ann

[Ann]

With a temperature near 200,000 K, WD J005311 is the hottest star known. The extreme properties of the central star are being powered by the residual radioactive decay of ⁵⁶Ni, where the usual half-life of 6.0 days from electron capture is increased to many centuries due to the nickel being completely ionized.
Does "completely ionized" mean "stripped of all its 28 electrons"?
Why a super-heavy white dwarf would "completely ionize" its nickel?
How can this prolong ⁵⁶Ni existence?

Does "completely ionized" mean "stripped of all its 28 electrons"? I would guess so.

Why would a super-heavy white dwarf "completely ionize" its nickel? I would guess it's because this super-heavy white dwarf is so hot.

How can this prolong ⁵⁶Ni existence? Because there is so much of it? Chris, what do you think?

Ann

[pettygrew]

Beautiful. They should call it the Dandelion nebula.

[Tekija]

Dana Patchick of Pa 30.

[Chris Peterson]

With a temperature near 200,000 K, WD J005311 is the hottest star known. The extreme properties of the central star are being powered by the residual radioactive decay of ⁵⁶Ni, where the usual half-life of 6.0 days from electron capture is increased to many centuries due to the nickel being completely ionized.
Does "completely ionized" mean "stripped of all its 28 electrons"?
Why a super-heavy white dwarf would "completely ionize" its nickel?
How can this prolong ⁵⁶Ni existence?

Does "completely ionized" mean "stripped of all its 28 electrons"? I would guess so.

Why would a super-heavy white dwarf "completely ionize" its nickel? I would guess it's because this super-heavy white dwarf is so hot.

How can this prolong ⁵⁶Ni existence? Because there is so much of it? Chris, what do you think?

Ann

A nuclear physicist I am not! But at least from the basics, this would be my guess: normally, ⁵⁶Ni decays via the β⁺ process, meaning that a proton is converted to a neutron, and a positron is created and ejected. The atomic mass stays the same, but the atomic number decreases. So the ⁵⁶Ni becomes ⁵⁶Co. Beta decay is trying to balance the number of protons and neutrons in a heavy atom when there are a lot more of one than the other. A highly ionized Ni atom will have a large positive charge. Perhaps that interferes with the weak force process underlying beta decay, slowing things down? Or even converts the decay process to electron capture, where it is the capture of an external electron that converts the proton to a neutron? Of course, in a highly ionized atom there is no low shell electron available for this process, so it would require a chance interaction with an electron from the environment. I can believe that would greatly extend the half-life.

[Tekija]

Says ChatGPT:

The radioactive decay of nickel-56 (⁵⁶Ni) typically proceeds through electron capture, where one of the atom's inner shell electrons is captured by the nucleus, resulting in the transformation of a proton into a neutron. This process converts the nucleus into iron-56 (⁵⁶Fe) through the process of beta decay.

However, when nickel-56 is completely ionized, meaning that all its electrons have been stripped away, the situation changes. The process of electron capture requires an available electron to be captured by the nucleus. When the atom is completely ionized, there are no electrons available for capture. As a result, the decay of nickel-56 in its fully ionized state is significantly slowed down or even halted altogether.

This phenomenon occurs because electron capture is heavily dependent on the availability of electrons, and when all the electrons have been removed through ionization, the decay process is suppressed. Therefore, the half-life of nickel-56 in its completely ionized state can be drastically increased to many centuries or longer compared to its normal half-life of 6.0 days when it is not fully ionized.

[johnnydeep]

Some random comments:

- Is it just my imagination or does the central star look like it's at the center of a cluster of stars? (Answer: probably I'm being misled by the radiating gas/dust lines).
- So, I gather that WD J005311 ("the hottest star known") is the "zombie star".
- It annoys me to no end that "Iax" is not LA International Airport, but "1ax". The use of a roman numeral for the 1 is unfortunate.
- The nickel half life stuff above is very cool! And it really looks like the ChatGPT explanation for it quoted above is regurgitating Chris' answer!
- And finally, Ann, what exactly is a "color commentator" (though I suppose that is obvious) and how did you acquire that title? (After two years here, I figure I'd ask. )

[Chris Peterson]

Says ChatGPT:

The radioactive decay of nickel-56 (⁵⁶Ni) typically proceeds through electron capture, where one of the atom's inner shell electrons is captured by the nucleus, resulting in the transformation of a proton into a neutron. This process converts the nucleus into iron-56 (⁵⁶Fe) through the process of beta decay.

However, when nickel-56 is completely ionized, meaning that all its electrons have been stripped away, the situation changes. The process of electron capture requires an available electron to be captured by the nucleus. When the atom is completely ionized, there are no electrons available for capture. As a result, the decay of nickel-56 in its fully ionized state is significantly slowed down or even halted altogether.

This phenomenon occurs because electron capture is heavily dependent on the availability of electrons, and when all the electrons have been removed through ionization, the decay process is suppressed. Therefore, the half-life of nickel-56 in its completely ionized state can be drastically increased to many centuries or longer compared to its normal half-life of 6.0 days when it is not fully ionized.

Interesting, but I think the normal decay path for ⁵⁶Ni is beta decay, not electron capture. Could be wrong about that. But if so, then the question is what about that environment suppresses normal beta decay and (possibly) replaces it with electron capture? Obviously, decay by electron capture in an atom that lacks electrons is going to be a slow process.

[Tekija]

Says ChatGPT:

The radioactive decay of nickel-56 (⁵⁶Ni) typically proceeds through electron capture, where one of the atom's inner shell electrons is captured by the nucleus, resulting in the transformation of a proton into a neutron. This process converts the nucleus into iron-56 (⁵⁶Fe) through the process of beta decay.

However, when nickel-56 is completely ionized, meaning that all its electrons have been stripped away, the situation changes. The process of electron capture requires an available electron to be captured by the nucleus. When the atom is completely ionized, there are no electrons available for capture. As a result, the decay of nickel-56 in its fully ionized state is significantly slowed down or even halted altogether.

This phenomenon occurs because electron capture is heavily dependent on the availability of electrons, and when all the electrons have been removed through ionization, the decay process is suppressed. Therefore, the half-life of nickel-56 in its completely ionized state can be drastically increased to many centuries or longer compared to its normal half-life of 6.0 days when it is not fully ionized.

Interesting, but I think the normal decay path for ⁵⁶Ni is beta decay, not electron capture. Could be wrong about that. But if so, then the question is what about that environment suppresses normal beta decay and (possibly) replaces it with electron capture? Obviously, decay by electron capture in an atom that lacks electrons is going to be a slow process.

I would agree with you as regards the normal decay path. I found a diagram that applies to the high temperature, high pressure scenario of a supernova:



Source: https://isnap.nd.edu/assets/250195/radi ... ure_10.pdf

[AVAO]

At first I ho-hummed this APOD, because I didn't find it beautiful or immediately interesting.

Unusual Nebula Pa 30. Image Credit: NASA, ESA, USAF, NSF; Processing: G. Ferrand (U. Manitoba), J. English (U. Manitoba), R. A. Fesen (Dartmouth), C. Treyturik (U. Manitoba); Text: G. Ferrand & J. English

---

...

Wikipedia wrote about Pa 30, the nebula seen in today's APOD:

Pa 30 was discovered in 2013 by American amateur astronomer Dana Patchick while searching for planetary nebula in WISE infrared data. It was the 30th nebula discovered by his searches, and as a result it is designated Pa 30. Pa 30 appeared as a nearly-round nebula roughly 171x156 arc-seconds in size, with an extremely blue central star. Pa 30 refers to both the nebula (originally catalogued as IRAS 00500+6713) and the central star (designated as WD J005311).

Okay, the Color commentator wants to know what it means that the central star of Pa 30, WD J005311, is "extremely blue". Does it mean that it is "blue", ███, or does it mean that it is very very hot, without necessarily being bright at wavelengths between 400 and 500 nm? I suspect the latter.

Pa 30. The hot blue central star appears to be invisible in this infrared image. Credit: WISE/Meli thev

---

With a temperature near 200,000 K, WD J005311 is the hottest star known.

Right! But how do we know that the nebula in today's APOD, Pa 30, was created in a supernova explosion and not in an ordinary nova explosion? Where the outer and recently acquired layers of the white dwarf blow off, but the white dwarf itself survives? As in, say, Nova Persei?

Nova Persei. The central white dwarf, GK Persei, remains. Credit: X-ray: NASA/CXC/RIKEN/D.Takei et al; Optical: NASA/STScI; Radio: NRAO/VLA

---

We know that Pa 30 must be a supernova remnant because it has certain properties that can only be produced by supernovas:

In 2019, optical spectroscopy of the central star revealed a very hot star with an intense stellar wind expanding at a very high velocity of 16,000 km/s and a composition mainly of carbon, oxygen, and neon (with no hydrogen or helium). Such a speed could only arise from a supernova or an event of similar magnitude, more specifically from a merger of two white dwarfs. X-ray spectroscopy studies of the shell also revealed a very hot nebula containing carbon-burning ashes which can only be produced in a supernova.

So what happened here? The white dwarfs exploded, but they did not explode? Did one of the white dwarfs explode to create a supernova, but the other white dwarf remained, perhaps endowed with some new properties? The white dwarfs exchanged matter, so that one of them was just pushed over its electron degeneracy brink to explode as a (faint) supernova, and the surviving white dwarf incorporated some of the supernova debris into itself to become super-heavy and really really blue-hot? Is that it?

Inquiring minds want to know!

Ann

ThanX Ann and everyone else for the exciting discussion.

I think PA30 and GK Persei are very similar.
What is no longer visible with PA30 is the "outflow channel" like with GK Persei, Crab Nebula or all the others.

I would just like to know over time how these outflow channels really come about...


PA30

Click to view full size image

GK Persei

Click to view full size image

Crab Nebula

Click to view full size image

Jac berne (flickr)

[Ann]

Some random comments:
....
- And finally, Ann, what exactly is a "color commentator" (though I suppose that is obvious) and how did you acquire that title? (After two years here, I figure I'd ask. )

Well, the title was given to me soon after I joined Starship Asterisk* in 2010 (before we were Commodores and Captains and stuff). I loved the title, because there are, after all, three things that attract me to astronomy: 1) the actual blue (Chris would say blue-white) color of O, B, and A-type stars, which I had carefully checked out for myself by specifically observing stars to determine their color, 2) the beauty of so many things in the Universe, like blue and pink nebulas (the Trifid Nebula!) and many-colored nebula complexes (the Antares-Rho Ophiuchi complex!), long-tailed comets (some of them with obvious blue tails), gorgeous star clusters (what can beat the Pleiades?) and graceful galaxies, and 3) the incomprehensible, unbelievable, knock your socks off majesty of the Universe.

Anyway. I got the title Color Commentator because I talked and talked and talked so much about the colors of things. But when I was a newbie, I would give unfavorable comments on APODs and also on images posted in the Recent Submissions thread, and say flat out that I found their colors ugly or wrong. That irritated the moderators or those bestowing titles on members (I think it was Neufer?) so much that my Color Commentator title was taken away from me. I was heartbroken. Instead, after a while, I was given the title 4725 Å. If you look at the top right corner of every one of my posts, there is a little icon showing the Pleiades (picked by me), and below it, it says Ann and 4725 Å. 4725 Å is my current title, I guess.

So 4724 Å is the same as 472.5 nm, and it is this color, ███. It's a nice color, but I still sorely missed my Color Commentator title, and I decided to give it back to me. I was allowed to add a certain something at the end of each of my posts, and I chose Color Commentator. I picked the colors of the letters myself.

My Mom told me that I was crazy about colors even as a toddler. At two years old, I kept pointing at all kinds of objects around me and asking her what color they were. Even then, I vastly preferred blue things. Of course.

Ann

[Ann]

Says ChatGPT:

The radioactive decay of nickel-56 (⁵⁶Ni) typically proceeds through electron capture, where one of the atom's inner shell electrons is captured by the nucleus, resulting in the transformation of a proton into a neutron. This process converts the nucleus into iron-56 (⁵⁶Fe) through the process of beta decay.

However, when nickel-56 is completely ionized, meaning that all its electrons have been stripped away, the situation changes. The process of electron capture requires an available electron to be captured by the nucleus. When the atom is completely ionized, there are no electrons available for capture. As a result, the decay of nickel-56 in its fully ionized state is significantly slowed down or even halted altogether.

This phenomenon occurs because electron capture is heavily dependent on the availability of electrons, and when all the electrons have been removed through ionization, the decay process is suppressed. Therefore, the half-life of nickel-56 in its completely ionized state can be drastically increased to many centuries or longer compared to its normal half-life of 6.0 days when it is not fully ionized.

Thanks! Even I could understand that explanation. Nickel-56 decays through electron capture, but when nickel-56 is completely ionized, so that there are no electrons in the vicinity of the nucleus, the electron capture is slowed down so much that the decay of ⁵⁶Ni is slowed down from a matter of days to a matter of many centuries.

Thanks again!

Ann

[johnnydeep]

Some random comments:
....
- And finally, Ann, what exactly is a "color commentator" (though I suppose that is obvious) and how did you acquire that title? (After two years here, I figure I'd ask. )

Well, the title was given to me soon after I joined Starship Asterisk* in 2010 (before we were Commodores and Captains and stuff). I loved the title, because there are, after all, three things that attract me to astronomy: 1) the actual blue (Chris would say blue-white) color of O, B, and A-type stars, which I had carefully checked out for myself by specifically observing stars to determine their color, 2) the beauty of so many things in the Universe, like blue and pink nebulas (the Trifid Nebula!) and many-colored nebula complexes (the Antares-Rho Ophiuchi complex!), long-tailed comets (some of them with obvious blue tails), gorgeous star clusters (what can beat the Pleiades?) and graceful galaxies, and 3) the incomprehensible, unbelievable, knock your socks off majesty of the Universe.

Anyway. I got the title Color Commentator because I talked and talked and talked so much about the colors of things. But when I was a newbie, I would give unfavorable comments on APODs and also on images posted in the Recent Submissions thread, and say flat out that I found their colors ugly or wrong. That irritated the moderators or those bestowing titles on members (I think it was Neufer?) so much that my Color Commentator title was taken away from me. I was heartbroken. Instead, after a while, I was given the title 4725 Å. If you look at the top right corner of every one of my posts, there is a little icon showing the Pleiades (picked by me), and below it, it says Ann and 4725 Å. 4725 Å is my current title, I guess.

So 4724 Å is the same as 472.5 nm, and it is this color, ███. It's a nice color, but I still sorely missed my Color Commentator title, and I decided to give it back to me. I was allowed to add a certain something at the end of each of my posts, and I chose Color Commentator. I picked the colors of the letters myself.

My Mom told me that I was crazy about colors even as a toddler. At two years old, I kept pointing at all kinds of objects around me and asking her what color they were. Even then, I vastly preferred blue things. Of course.

Ann

Thanks for the explanation and that bit of Asterisk history. "Now I know" as they say. Perhaps someday I'll be impudent enough to dub myself the Querying Commentator.

[VictorBorun]

I found a diagram that applies to the high temperature, high pressure scenario of a supernova:

Source: https://isnap.nd.edu/assets/250195/radi ... ure_10.pdf

I think I get it… still, why would not a naked ⁵⁶Ni nucleus catch a free electron from the plasma? To be kept fully ionized it has to be bombarded by high energy electrons all the time; those have to be more point-like wave packet functions than a base orbit electron, do not they?