Starship Asterisk*

VictorBorun wrote: ↑Sun Oct 02, 2022 3:00 pm

Chris Peterson wrote: ↑Sun Oct 02, 2022 1:43 pm

ErikTheWise wrote: ↑Sun Oct 02, 2022 12:07 pm No problem. All that is needed is to violate Conservation of Momentum. And yes, that's sarcasm.

Well, yes, that would work. But it's not hard to see momentum conserved in situations like this. The mass of the remnant is much greater, so its motion is much slower (and harder to detect). I think that lack of understanding here is in why some supernovas are so highly asymmetric in the way the explode. That an asymmetric explosion can lead to this outcome is not hard to understand.

there are 2 poles of the maximum brightness of the shell of the SNR, one directly under the 1000 km/s cannonball pulsar neutron star.
So there is a symmetry to the SN explosion.
There may be even a second cannonball, twice the mass and 500 km/s the speed, aproaching the other pole of the shell from inside and going to become visible soon. If so, the third mass may well stay in the center of the shell.
By the way, do we know any candidate remnant dwarf stars near the center of the shell?

Now if you want to wonder at a complex conservation of an impact momentum, look at Dimorphous' ejecta in radiowaves:

The impact momentum's direction is 5 o'clock, the bisector of the two longest jets

Could the SN in this APOD be caused by an impact with a cannonball, I wonder

johnnydeep wrote: ↑Mon Oct 03, 2022 1:54 pm

jamjam wrote: ↑Mon Oct 03, 2022 2:01 am Well the mechanism wasn't known back in 2019 when this first appeared, but recently it’s been proposed https://phys.org/news/2022-08-neutrino ... lsars.html that neutrino emission which is asymmetrical because such emission can violate parity causes the pulsars to jet off, and I’d bet that's right.

Wow! That's pretty cool. From the link:

It has been shown that Cooper pairs of neutrons that have been formed by neutron binding also undergo gyrator motion in the superfluid region of neutron stars. Based on calculations, the researchers discovered that these left- and right-handed neutrinos, which are emitted by neutron Cooper pairs, have high energies.

Furthermore, left-handed neutrinos and right-handed neutrinos emit in the same direction due to their non-conservation of parity. As a result of the conservation of momentum, when a neutron star emits a neutrino stream along its rotation axis, the neutron star itself acquires a recoil velocity in the forward direction along its rotation axis.

So, I wonder how long this "neutrino beam rocket" can fire, and if there is any upper limit (other than c of course) to how fast it can propel the neutron star.

Chris Peterson wrote: ↑Mon Oct 03, 2022 12:57 pm

Ann wrote: ↑Mon Oct 03, 2022 7:30 am

Rauf wrote: ↑Mon Oct 03, 2022 5:08 am So what is supernova plural form?? Is it supernovas or supernovae??

Chris will tell you it is supernovas. He has convinced me, too.

I would say that in English, being a descriptive, not prescriptive language, the plural form is determined by usage. And both forms here are common and widely used. Where there is a form that follows normal English convention alongside a historical Latin form, I generally prefer the former.

Chris Peterson wrote: ↑Mon Oct 03, 2022 2:07 pm

johnnydeep wrote: ↑Mon Oct 03, 2022 1:59 pm

VictorBorun wrote: ↑Sun Oct 02, 2022 10:27 pm

not if the impactor went at 1000 km/s, much faster than the escape velocity of a star.

A neutron star has an escape velocity about c/2 = 150,000 km/s and can merge with another neutron star (creating a kilonova).
A white dwarf has an escape velocity about 5000 km/s and can merge with a 1000 km/s cannon ball neutron star.

But our Sun has an escape velocity of just 615 km/s and so would not merge with a 1000 km/s cannon ball neutron star. If hit by such, much of our Sun will get thrown about

Yes, a neutron star colliding with the Sun at 1000 km/s would certainly wreck havoc. But I would think that a direct hit would still cause a merger. 1000 km/s is not even double the 615 km/s escape velocity of the Sun. I suspect the neutron star would oscillate around the core of the Sun until it finally sank to the center.

A neutron star colliding with the Sun at 1000 km/s would continue on its way with an altered path. It would shred the Sun and probably capture some of its material, but the two bodies (or remnants) would not be in closed orbits around each other, and most of the Sun's material would be left behind.

johnnydeep wrote: ↑Mon Oct 03, 2022 1:59 pm

VictorBorun wrote: ↑Sun Oct 02, 2022 10:27 pm

johnnydeep wrote: ↑Sun Oct 02, 2022 7:12 pm if they actually collided, they would almost certainly merge

not if the impactor went at 1000 km/s, much faster than the escape velocity of a star.

A neutron star has an escape velocity about c/2 = 150,000 km/s and can merge with another neutron star (creating a kilonova).
A white dwarf has an escape velocity about 5000 km/s and can merge with a 1000 km/s cannon ball neutron star.

But our Sun has an escape velocity of just 615 km/s and so would not merge with a 1000 km/s cannon ball neutron star. If hit by such, much of our Sun will get thrown about

Yes, a neutron star colliding with the Sun at 1000 km/s would certainly wreck havoc. But I would think that a direct hit would still cause a merger. 1000 km/s is not even double the 615 km/s escape velocity of the Sun. I suspect the neutron star would oscillate around the core of the Sun until it finally sank to the center.

VictorBorun wrote: ↑Sun Oct 02, 2022 10:27 pm

johnnydeep wrote: ↑Sun Oct 02, 2022 7:12 pm if they actually collided, they would almost certainly merge

not if the impactor went at 1000 km/s, much faster than the escape velocity of a star.

A neutron star has an escape velocity about c/2 = 150,000 km/s and can merge with another neutron star (creating a kilonova).
A white dwarf has an escape velocity about 5000 km/s and can merge with a 1000 km/s cannon ball neutron star.

But our Sun has an escape velocity of just 615 km/s and so would not merge with a 1000 km/s cannon ball neutron star. If hit by such, much of our Sun will get thrown about

jamjam wrote: ↑Mon Oct 03, 2022 2:01 am Well the mechanism wasn't known back in 2019 when this first appeared, but recently it’s been proposed https://phys.org/news/2022-08-neutrino ... lsars.html that neutrino emission which is asymmetrical because such emission can violate parity causes the pulsars to jet off, and I’d bet that's right.

It has been shown that Cooper pairs of neutrons that have been formed by neutron binding also undergo gyrator motion in the superfluid region of neutron stars. Based on calculations, the researchers discovered that these left- and right-handed neutrinos, which are emitted by neutron Cooper pairs, have high energies.

Furthermore, left-handed neutrinos and right-handed neutrinos emit in the same direction due to their non-conservation of parity. As a result of the conservation of momentum, when a neutron star emits a neutrino stream along its rotation axis, the neutron star itself acquires a recoil velocity in the forward direction along its rotation axis.

Ann wrote: ↑Mon Oct 03, 2022 7:30 am

Rauf wrote: ↑Mon Oct 03, 2022 5:08 am So what is supernova plural form?? Is it supernovas or supernovae??

Chris will tell you it is supernovas. He has convinced me, too. :wink:

Rauf wrote: ↑Mon Oct 03, 2022 5:08 am So what is supernova plural form?? Is it supernovas or supernovae??

heehaw wrote: ↑Sun Oct 02, 2022 11:22 pm I still would like to know if photos years from now will show changes. I hope so, of course.

Chris Peterson wrote: ↑Sun Oct 02, 2022 7:07 pm many if not most such systems are binary, so a companion could conceivably be ejected in some direction. And there could be cases where that companion was a neutron star.

johnnydeep wrote: ↑Sun Oct 02, 2022 7:12 pm if they actually collided, they would almost certainly merge

Chris Peterson wrote: ↑Sun Oct 02, 2022 7:07 pm

johnnydeep wrote: ↑Sun Oct 02, 2022 7:03 pm

Chris Peterson wrote: ↑Sun Oct 02, 2022 3:05 pm

There are two issues- non-spherical symmetry and any completely non-symmetric expansion. I think both are observed to exist. Which this is isn't entirely clear (you may well be right that there is a polar symmetry here, as we see with many supernovas). There are several examples of ejected progenitors; I don't know of any examples of polar pairs of them, however.

The other problem is that a supernova only produces one neutron star or pulsar. At least, I can't image (or explain how!) two being created!

Agreed... although many if not most such systems are binary, so a companion could conceivably be ejected in some direction. And there could be cases where that companion was a neutron star.

johnnydeep wrote: ↑Sun Oct 02, 2022 7:03 pm

Chris Peterson wrote: ↑Sun Oct 02, 2022 3:05 pm

VictorBorun wrote: ↑Sun Oct 02, 2022 3:00 pm

there are 2 poles of the maximum brightness of the shell of the SNR, one directly under the 1000 km/s cannonball pulsar neutron star.
So there is a symmetry to the SN explosion.
There may be even a second cannonball, twice the mass and 500 km/s the speed, aproaching the other pole of the shell from inside and going to become visible soon. If so, the third mass may well stay in the center of the shell.
By the way, do we know any candidate remnant dwarf stars near the center of the shell?

Now if you want to wonder at a complex conservation of an impact momentum, look at Dimorphous' ejecta in radiowaves:

The impact momentum's direction is 5 o'clock, the bisector of the two longest jets

There are two issues- non-spherical symmetry and any completely non-symmetric expansion. I think both are observed to exist. Which this is isn't entirely clear (you may well be right that there is a polar symmetry here, as we see with many supernovas). There are several examples of ejected progenitors; I don't know of any examples of polar pairs of them, however.

The other problem is that a supernova only produces one neutron star or pulsar. At least, I can't image (or explain how!) two being created!

Chris Peterson wrote: ↑Sun Oct 02, 2022 3:05 pm

VictorBorun wrote: ↑Sun Oct 02, 2022 3:00 pm

Chris Peterson wrote: ↑Sun Oct 02, 2022 1:43 pm
Well, yes, that would work. But it's not hard to see momentum conserved in situations like this. The mass of the remnant is much greater, so its motion is much slower (and harder to detect). I think that lack of understanding here is in why some supernovas are so highly asymmetric in the way the explode. That an asymmetric explosion can lead to this outcome is not hard to understand.

there are 2 poles of the maximum brightness of the shell of the SNR, one directly under the 1000 km/s cannonball pulsar neutron star.
So there is a symmetry to the SN explosion.
There may be even a second cannonball, twice the mass and 500 km/s the speed, aproaching the other pole of the shell from inside and going to become visible soon. If so, the third mass may well stay in the center of the shell.
By the way, do we know any candidate remnant dwarf stars near the center of the shell?

Now if you want to wonder at a complex conservation of an impact momentum, look at Dimorphous' ejecta in radiowaves:

The impact momentum's direction is 5 o'clock, the bisector of the two longest jets

There are two issues- non-spherical symmetry and any completely non-symmetric expansion. I think both are observed to exist. Which this is isn't entirely clear (you may well be right that there is a polar symmetry here, as we see with many supernovas). There are several examples of ejected progenitors; I don't know of any examples of polar pairs of them, however.

VictorBorun wrote: ↑Sun Oct 02, 2022 3:00 pm

Chris Peterson wrote: ↑Sun Oct 02, 2022 1:43 pm

ErikTheWise wrote: ↑Sun Oct 02, 2022 12:07 pm No problem. All that is needed is to violate Conservation of Momentum. And yes, that's sarcasm.

Well, yes, that would work. But it's not hard to see momentum conserved in situations like this. The mass of the remnant is much greater, so its motion is much slower (and harder to detect). I think that lack of understanding here is in why some supernovas are so highly asymmetric in the way the explode. That an asymmetric explosion can lead to this outcome is not hard to understand.

there are 2 poles of the maximum brightness of the shell of the SNR, one directly under the 1000 km/s cannonball pulsar neutron star.
So there is a symmetry to the SN explosion.
There may be even a second cannonball, twice the mass and 500 km/s the speed, aproaching the other pole of the shell from inside and going to become visible soon. If so, the third mass may well stay in the center of the shell.
By the way, do we know any candidate remnant dwarf stars near the center of the shell?

Now if you want to wonder at a complex conservation of an impact momentum, look at Dimorphous' ejecta in radiowaves:

The impact momentum's direction is 5 o'clock, the bisector of the two longest jets

Chris Peterson wrote: ↑Sun Oct 02, 2022 1:43 pm

ErikTheWise wrote: ↑Sun Oct 02, 2022 12:07 pm No problem. All that is needed is to violate Conservation of Momentum. And yes, that's sarcasm.

Well, yes, that would work. But it's not hard to see momentum conserved in situations like this. The mass of the remnant is much greater, so its motion is much slower (and harder to detect). I think that lack of understanding here is in why some supernovas are so highly asymmetric in the way the explode. That an asymmetric explosion can lead to this outcome is not hard to understand.

Ann wrote: ↑Sun Oct 02, 2022 5:17 am What an amazing image!

I hope I'm allowed to say it, but I am somehow reminded of a sperm fertilizing an egg. Of course, it is the other way round here - the "egg" is empty, except for huge amounts of radiation (which doesn't make it empty, certainly not from a general relativity or quantum mechanics point of view, as Sabine Hossenfelder would say) and the "sperm" is "cannonballing" its way out of it.

Remarkable. As sister Monica Joan of Call the Midwife said, when handyman Fred Buckle had fixed an old telescope for her and she could see the Double Cluster of Perseus.

Remarkable indeed! Both the Double Cluster of Perseus and the supernova pulsar cannonball leaving its egg-shaped shell!

Ann

ErikTheWise wrote: ↑Sun Oct 02, 2022 12:07 pm No problem. All that is needed is to violate Conservation of Momentum. And yes, that's sarcasm.