APOD: Supernova Discovered in Nearby M101... (2023 May 22)

[APOD Robot]

Supernova Discovered in Nearby Spiral Galaxy M101

Explanation: A nearby star has exploded and humanity's telescopes are turning to monitor it. The supernova, dubbed SN 2023ixf, was discovered by Japanese astronomer Koichi Itagaki three days ago and subsequently located on automated images from the Zwicky Transient Facility two days earlier. SN 2023ixf occurred in the photogenic Pinwheel Galaxy M101, which, being only about 21 million light years away, makes it the closest supernova seen in the past five years, the second closest in the past 10 years, and the second supernova found in M101 in the past 15 years. Rapid follow up observations already indicate that SN 2023ixf is a Type II supernova, an explosion that occurs after a massive star runs out of nuclear fuel and collapses. The featured image shows home spiral galaxy two days ago with the supernova highlighted, while the roll-over image shows the same galaxy a month before. SN 2023ixf will likely brighten and remain visible to telescopes for months. Studying such a close and young Type II supernova may yield new clues about massive stars and how they explode.

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[spednekar]

If the star is massive, will it end end as a black hole?

[RJN]

A typo has been fixed on the main NASA APOD: the name of the supernova is SN 2003ixf. The origanal APOD text had the last two letters reversed. We apologize for the oversight. - RJN for APOD

[Ann]

M101 before Supernova. Image Credit and Copyright: Craig Stocks

---

Supernova Discovered in Nearby Spiral Galaxy M101
Image Credit & Copyright: Craig Stocks

Looks like one of the supernova diffraction spikes preceded the actual supernova in the April 20 image!

Anyway. In Craig Stock's beautiful images, it is, let's admit it, somewhat hard to see the supernova "for all the galaxy" it's in. So let's look at two supernova 2023ixf images that are less "galaxy forward".

Discovery image of SN 2023ifx

---

Supernova SN 2323ixf in M101. Credit: Kheider.

What I particularly like about Kheider's image is that the supernova is clearly the bluest "stellar object" here. And since by far most Milky Way field stars are non-blue, we can confidently conclude that all the non-blue stellar objects seen in and near M101 are Milky Way field stars. There are a few somewhat fainter bluish objects in Kheider's image that are young star clusters in M101.

As for the discovery image of SN 2023ifx, for which I have failed to find an author, the supernova seems to stand out even more. But note that the nearby star cluster in M101 looks brighter than the supernova in the discovery image. In Kheider's image, which is one day older, the supernova is brighter than the cluster.

I have a few more things to say about supernovas, but... let's save that for another day, or for later today, shall we?

Ann

[javachip3]

Why did it take five days, rather than one day, to detect this supernova? Every Messier object in the night sky is viewed at least hundreds of times each night by amateur and professional astronomers around the world. Magnitude 14.9 is discernible with a 12 inch or possibly 10 inch diameter telescope. Someone's sleeping on the job!

All kidding aside, humanity's ability to rapidly detect faint events anywhere in the night sky is truly amazing. Apparently the Zwicky Transient Facility at Mount Palomar, California scans the entire northern sky every three nights (and the plane of the Milky Way twice a night) to magnitude 20.5. Pan-STARRS in Maui records the entire sky visible in Hawaii (75% of the celestial sphere) four times a month to magnitude 22. The All-Sky Automated Survey in Chile and Maui images the entire celestial sphere every 1-3 nights to magnitude 14.

[Rauf]

I'm still hopeful that during my short lifetime, a supernova goes of in our galaxy.. Though not many known stars seems like they are gonna go boom anytime soon

[Chris Peterson]

If the star is massive, will it end end as a black hole?

Depends on how massive. If it's massive enough, it will end as a black hole. Otherwise, a neutron star.

[JohnD]

So much for the Zwicky, if it didn't notice a Super Nova!

Hooray for the human eye, and Koichi Itagaki!
John

[Christian G.]

Waking up to a supernova is a great way to start the day!

[Christian G.]

If the star is massive, will it end end as a black hole?

Depends on how massive. If it's massive enough, it will end as a black hole. Otherwise, a neutron star.

Is it not already in one of those two states as we speak? I mean: Does the supernova create the black hole or neutron star the very second the collapse is complete and bounces back off?

[Chris Peterson]

If the star is massive, will it end end as a black hole?

Depends on how massive. If it's massive enough, it will end as a black hole. Otherwise, a neutron star.

Is it not already in one of those two states as we speak? I mean: Does the supernova create the black hole or neutron star the very second the collapse is complete and bounces back off?

Yes, that happens is a second or so at the very start, before we see any increase in brightness.

[orin stepanek]

M101 yields Supernova! Scientists are hopeful that clues may show
more about how Supernovas form!

[Ann]

Depends on how massive. If it's massive enough, it will end as a black hole. Otherwise, a neutron star.

Is it not already in one of those two states as we speak? I mean: Does the supernova create the black hole or neutron star the very second the collapse is complete and bounces back off?

Yes, that happens is a second or so at the very start, before we see any increase in brightness.

Do we know that stars that collapse into black holes give rise to supernovas?

The way I understand it, a supernova type II (a core-collapse one) happens when the core of a massive star has run through all available fusion processes and ended up with an iron core. No more energy can be extracted from an iron core, and the tremendous gravitational pressure from the many solar masses of surrounding layers makes the inert core collapse.

But the collapse itself is not what creates the supernova. No, what creates the supernova - the way I understand it - is when all those solar masses of surrounding layers come crashing down themselves onto the core in a tremendous cosmic train wreck. This unimaginably violent collision, when the layers hit the core, makes all these layers bounce. The effect of this bounce is the supernova.

But if the core has already collapsed into a black hole, then surely there is nothing there for the crashing layers of the star to bounce off of? How can there be a supernova if there is no "trampoline" sending the falling gases flying?

There could of course be an accretion disk around the newborn black hole. Would that be the light show we are seeing when the core of a massive star collapses into a black hole?

Ann

[Chris Peterson]

Is it not already in one of those two states as we speak? I mean: Does the supernova create the black hole or neutron star the very second the collapse is complete and bounces back off?

Yes, that happens is a second or so at the very start, before we see any increase in brightness.

Do we know that stars that collapse into black holes give rise to supernovas?

The way I understand it, a supernova type II (a core-collapse one) happens when the core of a massive star has run through all available fusion processes and ended up with an iron core. No more energy can be extracted from an iron core, and the tremendous gravitational pressure from the many solar masses of surrounding layers makes the inert core collapse.

But the collapse itself is not what creates the supernova. No, what creates the supernova - the way I understand it - is when all those solar masses of surrounding layers come crashing down themselves onto the core in a tremendous cosmic train wreck. This unimaginably violent collision, when the layers hit the core, makes all these layers bounce. The effect of this bounce is the supernova.

But if the core has already collapsed into a black hole, then surely there is nothing there for the crashing layers of the star to bounce off of? How can there be a supernova if there is no "trampoline" sending the falling gases flying?

There could of course be an accretion disk around the newborn black hole. Would that be the light show we are seeing when the core of a massive star collapses into a black hole?

Ann

I think it depends on how we define "core". I see no reason why there can't be a black hole at the center while there's still an extremely dense (like a neutron soup) layer above that which is what the outer layers bounce off of. These processes are limited by the speed of light. AFAIK there is not much doubt that core collapse supernovas can and do produce black holes.

[Ann]

Okay, a few more words on supernovas. Specifically, a few more words on supernovas type II.

Supernovas type II are core-collapse supernovas. They arise from the inert iron cores of massive stars that can no longer generate any energy in their cores to stop themselves from collapsing. So they collapse.

Supernovas type II are unpredictable. They can be bright, and they can be faint. The famous supernova 1987A was faint:

SN 1987A is seen near the center of the image, to the right of the Tarantula Nebula. Credit: ESO.

---

Luis A. Milone et al. wrote:

V and B light curves for supernova 1987A covering some 120 days from the outburst are here presented and discussed; they are shown to be rather atypical for a type II supernova. The absolute magnitude at maximum brightness is also analyzed, and after applying a correction for interstellar absorption we obtain M V, max, 0 =−16.1, and M B, max, 0 =−14.7; it is then concluded that 1987A is a supernova quite fainter than average. A comparison with other known supernova is made and some similarity is found with peculiar objects such as 1948B in NGC 6946, and probably, 1909 A in M 101.

But if a supernova whose absolute V magnitude was −16.1, what is then the "typical" brightness of supernovas? Well, if we describe the typical luminosities of supernovas type Ia as "normal for supernovas", then the typical absolute V magnitude for a supernova is −19.3. This means that SN 1987A was three magnitudes fainter than a typical supernova type Ia (although I stress again that SN 1987A was a type II supernova).


But other type II supernovas are bright, like SN 2006gy.

An infrared image of supernova 2006gy (top right) and the core of its host galaxy NGC 1260 (lower left). The supernova is brighter than the galaxy in infrared light. Credit: Lick/UC Berkeley/J.Bloom & C.Hansen

---

E. O. Ofek et al. wrote:

With an extinction-corrected V-band peak absolute magnitude of about -22, supernova (SN) 2006gy is probably the brightest SN ever observed...

According to Wikipedia, the peak apparent magnitude of the supernova (at a distance of 238 million light-years) was +14.2. But the apparent magnitude of the entire galaxy is +14.3! The supernova was indeed brighter than the galaxy! And the galaxy is bright, probably at least as bright as the Milky Way.

And of course, SN 2006gy was some six magnitudes brighter than SN 1987A in the Large Magellanic Cloud.

More remarkable still, NGC 1260, home to one of the brightest supernovas that humanity has recorded, is a galaxy dominated by old low-mass stars.

Galaxy NGC 1260, host galaxy of brilliant type II supernova SN 2006gy. How strange that such a super-luminous supernova should be found in a galaxy strongly dominated by old low-mass stars, even though there is a dust ring around the core, containing a bright emission nebula, the birth place of massive stars. Credit: NASA/HST/Fabian RRRR

---

But nearby galaxy M65 has also hosted a supernova type !!, even if the supernova in itself was unremarkable. But like NGC 1260, M65 is strongly dominated by old low-mass stars. However, the galaxy has a dust lane with some star formation, and this is where the supernova was found. Credit: Bill Williams.

---

So, yeah. Supernovas type II are strange. They can be bright, they can be faint, and they can appear exactly in the sort of galaxies where you would expect them, like in M101, or in galaxies where they could hardly be more out of place, like in NGC 1260.

What about the new supernova in M101, SN 2023ifx? Well... it looks a bit on the faint side to me. Of course, it is still brightening.

Ann

[Ann]

Yes, that happens is a second or so at the very start, before we see any increase in brightness.

Do we know that stars that collapse into black holes give rise to supernovas?

The way I understand it, a supernova type II (a core-collapse one) happens when the core of a massive star has run through all available fusion processes and ended up with an iron core. No more energy can be extracted from an iron core, and the tremendous gravitational pressure from the many solar masses of surrounding layers makes the inert core collapse.

But the collapse itself is not what creates the supernova. No, what creates the supernova - the way I understand it - is when all those solar masses of surrounding layers come crashing down themselves onto the core in a tremendous cosmic train wreck. This unimaginably violent collision, when the layers hit the core, makes all these layers bounce. The effect of this bounce is the supernova.

But if the core has already collapsed into a black hole, then surely there is nothing there for the crashing layers of the star to bounce off of? How can there be a supernova if there is no "trampoline" sending the falling gases flying?

There could of course be an accretion disk around the newborn black hole. Would that be the light show we are seeing when the core of a massive star collapses into a black hole?

Ann

I think it depends on how we define "core". I see no reason why there can't be a black hole at the center while there's still an extremely dense (like a neutron soup) layer above that which is what the outer layers bounce off of. These processes are limited by the speed of light. AFAIK there is not much doubt that core collapse supernovas can and do produce black holes.

I don't doubt that very massive stars can create black holes. The question, to me, is whether the collapse of a black hole progenitor creates a supernova.

But I guess you may be right: The transition of the stellar core to a black hole is probably not instantaneous (because of the finite speed of light), and there may be an intermediate stage where the core is a neutron star, capable of making crashing gaseous layers bounce.

Ann

[Christian G.]

I can imagine a star collapsing so violently that gravity pulls everything straight down to near zero, crushing every layer on the way and leaving no time for anything to bounce off anything, or pulling right back any form of bounce. But I'm only imagining…
(if we were to find somehow that a given black hole's mass was roughly the same as the star's mass, I suppose we'd have a such a case) (but how?…)

[Chris Peterson]

Do we know that stars that collapse into black holes give rise to supernovas?

The way I understand it, a supernova type II (a core-collapse one) happens when the core of a massive star has run through all available fusion processes and ended up with an iron core. No more energy can be extracted from an iron core, and the tremendous gravitational pressure from the many solar masses of surrounding layers makes the inert core collapse.

But the collapse itself is not what creates the supernova. No, what creates the supernova - the way I understand it - is when all those solar masses of surrounding layers come crashing down themselves onto the core in a tremendous cosmic train wreck. This unimaginably violent collision, when the layers hit the core, makes all these layers bounce. The effect of this bounce is the supernova.

But if the core has already collapsed into a black hole, then surely there is nothing there for the crashing layers of the star to bounce off of? How can there be a supernova if there is no "trampoline" sending the falling gases flying?

There could of course be an accretion disk around the newborn black hole. Would that be the light show we are seeing when the core of a massive star collapses into a black hole?

Ann

I think it depends on how we define "core". I see no reason why there can't be a black hole at the center while there's still an extremely dense (like a neutron soup) layer above that which is what the outer layers bounce off of. These processes are limited by the speed of light. AFAIK there is not much doubt that core collapse supernovas can and do produce black holes.

I don't doubt that very massive stars can create black holes. The question, to me, is whether the collapse of a black hole progenitor creates a supernova.

But I guess you may be right: The transition of the stellar core to a black hole is probably not instantaneous (because of the finite speed of light), and there may be an intermediate stage where the core is a neutron star, capable of making crashing gaseous layers bounce.

Ann

I was thinking of a "core" that consisted of a black hole with a dense neutron shell around that. A sort of compound core. The neutron layer wouldn't be long for the world, but it could only be consumed at a finite rate, so might exist long enough to be the thing that the other material bounced from. Just speculating, though.

[Igwasborn]

M101 before Supernova. Image Credit and Copyright: Craig Stocks

---

M101Sn_Stocks_after_2560[1].jpg

Supernova Discovered in Nearby Spiral Galaxy M101
Image Credit & Copyright: Craig Stocks

Looks like one of the supernova diffraction spikes preceded the actual supernova in the April 20 image!

Anyway. In Craig Stock's beautiful images, it is, let's admit it, somewhat hard to see the supernova "for all the galaxy" it's in. So let's look at two supernova 2023ixf images that are less "galaxy forward".

Discovery image of SN 2023ifx

---

SN 2023ixf in M101 Kheider annotated.png

Supernova SN 2323ixf in M101. Credit: Kheider.

What I particularly like about Kheider's image is that the supernova is clearly the bluest "stellar object" here. And since by far most Milky Way field stars are non-blue, we can confidently conclude that all the non-blue stellar objects seen in and near M101 are Milky Way field stars. There are a few somewhat fainter bluish objects in Kheider's image that are young star clusters in M101.

As for the discovery image of SN 2023ifx, for which I have failed to find an author, the supernova seems to stand out even more. But note that the nearby star cluster in M101 looks brighter than the supernova in the discovery image. In Kheider's image, which is one day older, the supernova is brighter than the cluster.

I have a few more things to say about supernovas, but... let's save that for another day, or for later today, shall we?

Ann

Thank you for the images. It seems that the roll-over image option doesn't work properly in tablets, phones... Maybe only in computers.

[Chris Peterson]

What about the new supernova in M101, SN 2023ifx? Well... it looks a bit on the faint side to me. Of course, it is still brightening.

Indeed. Just imaging it right now. It's currently 20 times brighter than the core of M101!
_

[Ann]

What about the new supernova in M101, SN 2023ifx? Well... it looks a bit on the faint side to me. Of course, it is still brightening.

Indeed. Just imaging it right now. It's currently 20 times brighter than the core of M101!
_

Click to view full size image

Seriously! Wow!

Ann

[Rauf]

Okay, a few more words on supernovas. Specifically, a few more words on supernovas type II.

Supernovas type II are core-collapse supernovas. They arise from the inert iron cores of massive stars that can no longer generate any energy in their cores to stop themselves from collapsing. So they collapse.

Supernovas type II are unpredictable. They can be bright, and they can be faint. The famous supernova 1987A was faint:

SN 1987A is seen near the center of the image, to the right of the Tarantula Nebula. Credit: ESO.

---

Luis A. Milone et al. wrote:

V and B light curves for supernova 1987A covering some 120 days from the outburst are here presented and discussed; they are shown to be rather atypical for a type II supernova. The absolute magnitude at maximum brightness is also analyzed, and after applying a correction for interstellar absorption we obtain M V, max, 0 =−16.1, and M B, max, 0 =−14.7; it is then concluded that 1987A is a supernova quite fainter than average. A comparison with other known supernova is made and some similarity is found with peculiar objects such as 1948B in NGC 6946, and probably, 1909 A in M 101.

But if a supernova whose absolute V magnitude was −16.1, what is then the "typical" brightness of supernovas? Well, if we describe the typical luminosities of supernovas type Ia as "normal for supernovas", then the typical absolute V magnitude for a supernova is −19.3. This means that SN 1987A was three magnitudes fainter than a typical supernova type Ia (although I stress again that SN 1987A was a type II supernova).


But other type II supernovas are bright, like SN 2006gy.

An infrared image of supernova 2006gy (top right) and the core of its host galaxy NGC 1260 (lower left). The supernova is brighter than the galaxy in infrared light. Credit: Lick/UC Berkeley/J.Bloom & C.Hansen

---

E. O. Ofek et al. wrote:

With an extinction-corrected V-band peak absolute magnitude of about -22, supernova (SN) 2006gy is probably the brightest SN ever observed...

According to Wikipedia, the peak apparent magnitude of the supernova (at a distance of 238 million light-years) was +14.2. But the apparent magnitude of the entire galaxy is +14.3! The supernova was indeed brighter than the galaxy! And the galaxy is bright, probably at least as bright as the Milky Way.

And of course, SN 2006gy was some six magnitudes brighter than SN 1987A in the Large Magellanic Cloud.

More remarkable still, NGC 1260, home to one of the brightest supernovas that humanity has recorded, is a galaxy dominated by old low-mass stars.

Galaxy NGC 1260, host galaxy of brilliant type II supernova SN 2006gy. How strange that such a super-luminous supernova should be found in a galaxy strongly dominated by old low-mass stars, even though there is a dust ring around the core, containing a bright emission nebula, the birth place of massive stars. Credit: NASA/HST/Fabian RRRR

---

But nearby galaxy M65 has also hosted a supernova type !!, even if the supernova in itself was unremarkable. But like NGC 1260, M65 is strongly dominated by old low-mass stars. However, the galaxy has a dust lane with some star formation, and this is where the supernova was found. Credit: Bill Williams.

---

So, yeah. Supernovas type II are strange. They can be bright, they can be faint, and they can appear exactly in the sort of galaxies where you would expect them, like in M101, or in galaxies where they could hardly be more out of place, like in NGC 1260.

What about the new supernova in M101, SN 2023ifx? Well... it looks a bit on the faint side to me. Of course, it is still brightening.

Ann

If I remember correctly, supernovae are used as candles to determine the distance of very far galaxies, because their absolute magnitude is predictable, and depending on the apparent magnitude that we observe, we can find out how far the host galaxy is. Is my information incorrect or is it just a certain type of supernova (Type Ia for example) used for distance measuring?

[Ann]

If I remember correctly, supernovae are used as candles to determine the distance of very far galaxies, because their absolute magnitude is predictable, and depending on the apparent magnitude that we observe, we can find out how far the host galaxy is. Is my information incorrect or is it just a certain type of supernova (Type Ia for example) used for distance measuring?

Exactly. It is the type Ia supernovas that are used as standard candles. They always explode at a given mass, 1.4 solar masses, which is the Chandrasekhar limit for electron degenerate pressure. (The electron degeneracy is what keeps a white dwarf from collapsing further in on itself, when the energy production has ceased in the core.)

Or in other words, the SN Ia progenitors are (massive) white dwarfs close to the Chandrasekhar limit of 1.4 solar masses. They then gain mass, typically from an orbiting companion, until they get so massive that the electron degeneracy is overwhelmed. And since the entire white dwarf is made of "prime fuel" - well, semi-prime fuel since the "primest" of fuels, hydrogen, is absent - all of it starts an out-of-control runaway fusion when the electron degeneracy is overwhelmed.

This leads to an explosion whose absolute V magnitude is believed to be —19.3. Supernovas type Ia can be recognized from very far away because they are so intrinsically bright, and they all show a very characteristic light curve.

Typical light curve of a supernova type Ia. Source: https://www.researchgate.net/figure/Light-curve-for-a-typical-Supernova-Ia_fig3_1745683

---

Ann

[Christian G.]

What about the new supernova in M101, SN 2023ifx? Well... it looks a bit on the faint side to me. Of course, it is still brightening.

Indeed. Just imaging it right now. It's currently 20 times brighter than the core of M101!
_
m101_2023.05.23.jpg

I second Ann's "wow!" Thanks for sharing this picture! (I also like how it brings out how thick and massive M101 is) - I wonder: what is the size of the area covered by the supernova? If that bright spot were instead, say, a star cluster, what would its dimension approximately be?

[Chris Peterson]

What about the new supernova in M101, SN 2023ifx? Well... it looks a bit on the faint side to me. Of course, it is still brightening.

Indeed. Just imaging it right now. It's currently 20 times brighter than the core of M101!
_
m101_2023.05.23.jpg

I second Ann's "wow!" Thanks for sharing this picture! (I also like how it brings out how thick and massive M101 is) - I wonder: what is the size of the area covered by the supernova? If that bright spot were instead, say, a star cluster, what would its dimension approximately be?

Well, the supernova is a point source. It only appears big because of the nature of diffractive optics and because it is saturated. FWIW, the above image was stacked from 68 60-second subs, which were themselves overexposed on the supernova. I had to go down to a 10-second exposure to avoid saturating the supernova so I could accurately measure its brightness compared with the core. This image is a completely raw 10-second image, linearly stretched so we can see anything, but with no clipping at either end, so it gives a better sense of the true brightness of the supernova compared with the galaxy core.
_