What is the “Unknown physics” of the new Kilonovae explosion?

[Maximum7]

TL;DR Summary

I’m trying to figure out what the perfect spherical supernovae explosion means

Scientists recently observed a kilonovae explosion. To their surprise, the explosion is completely spherical. They are saying that this is the cause of unknown physics but I don’t understand why they think unknown physics is causing this. What’s unknown about a perfect spherical explosion? My physics isn’t great but I am very curious.

 

[Ibix]

Link...?

 

[Maximum7]

https://amp.theguardian.com/science/2023/feb/15/perfect-explosion-kilonova-neutron-stars-explode

 

[Ibix]

Thank you. The first thing you do is note the authors named in the article, Sneppen and Watson, and plug their names into the search at arxiv.org. That usually gets you the actual paper: https://arxiv.org/abs/2302.06621. That's always going to be more helpful than a journalist's bad paraphrase.

I'll have a look. The abstract says that in a neutron star merger you expect the neutron stars' spins and orbit to provide directionality to the blast, but apparently not in this case. From the abstract I'm not sure they're proposing new physics, just that there's something they are missing.

 

[Ibix]

I've read the paper, and that's about it. We expect neutron star merger novae to be oblate because they come from rapidly spinning sources. Modelling of such extremely non-spherical sources suggests that the ejecta should be oblate because the material is ejected at different speeds at different angles to the spins and orbital planes of the neutron stars. Imaging of this one suggests that's not the case, and it's difficult to see how the models can be tweaked to look like it. So there's something fairly drastic going on (at least in this case) that isn't in the models.

 

[Filip Larsen]

Albert Sneppen, age 24, made local (non-science) news in Denmark with this paper being his second accepted in Nature since his single-authered one, https://www.nature.com/articles/s41598-021-93595-w (open access), got accepted when he was just 22. Always inspiring to see young brilliant scientists making new discoveries.

 

[Maximum7]

I've read the paper, and that's about it. We expect neutron star merger novae to be oblate because they come from rapidly spinning sources. Modelling of such extremely non-spherical sources suggests that the ejecta should be oblate because the material is ejected at different speeds at different angles to the spins and orbital planes of the neutron stars. Imaging of this one suggests that's not the case, and it's difficult to see how the models can be tweaked to look like it. So there's something fairly drastic going on (at least in this case) that isn't in the models.

But how is it unknown physics? The article said something about a magnetic bomb in the center.

 

[Ibix]

But how is it unknown physics? The article said something about a magnetic bomb in the center.

Well if it were known physics the models would predict the same as the observations... I don't know (and I suspect the authors don't know either) what's wrong with the models. It could be stuff we already know but didn't apply correctly, or it could be genuinely new (to us) physics in the extreme conditions of a collision between neutron stars. And as far as I understand it this is also just one data point, so it could always be some unknown interfering factor in this one case. "New physics" is a pretty wide umbrella.

I'm not sure where you are reading "magnetic bomb". Magnetic reconnection is mentioned, which is where magnetic field lines are forced to cross, which releases energy from the magnetic field. It's a known phenomenon, but I think they're saying that as we understand the phenomenon it can't do enough to explain this. But it's always possible that we don't understand magnetic fields in extreme conditions as well as we think.

 

[Vanadium 50]

This question is a little like "What is the name of the person buried in the Tomb of the Unknown Soldier".'?

If the authors say they don;t know, who are we to tell them that they do?

 

[Ibix]

It's also worth noting that "there could be new physics here" is a good way of selling your work to the scientifically interested public, which can lead to moral pressure on funding bodies to continue supporting you. I don't doubt their claims that there's stuff they don't understand there, and high energy events are certainly likely places to find genuinely new behaviour. But one should probably treat such claims in the popular press the same way you would treat "that shirt looks great on you, sir" from a clothes shop assistant - a defensible claim and certainly possible, but not from an entirely disinterested source.

 

[Maximum7]

This question is a little like "What is the name of the person buried in the Tomb of the Unknown Soldier".'?

If the authors say they don;t know, who are we to tell them that they do?

Well I was just looking for a definition of what they could mean as “unknown physics”. Is the mechanism behind the spherical explosion unknown. Is it because of a new particle or a new fundamental law. I honestly don’t have a clue. When I read “New unknown physics” I get excited and am not even remotely smart enough to imagine what that means.

 

[Vanadium 50]

The authors say they don't lmpw what is going on. Isb y6our position really that not only are they lying and have a good idea, but we also know on PF what they are thinking? Really?

 

[Maximum7]

The authors say they don't lmpw what is going on. Isb y6our position really that not only are they lying and have a good idea, but we also know on PF what they are thinking? Really?

Of course not. I was just looking for someone to weigh in with some speculation. Geez

 

[Ibix]

Well I was just looking for a definition of what they could mean as “unknown physics”.

It can be almost anything, that's the point. For example, much closer to home, we have occasionally found heavenly bodies not quite where we expect. With Mercury that turned out to be new physics (general relativity). With Uranus it turned out to be no new physics but a planet we didn't know about (Neptune). With the Pioneer probe it turned out to be a tiny thrust from radiation from its power supply bouncing off its antenna dish (well known physics that nobody had realised needed to be applied). So that's everything from "oh...duh" to rewriting physics from the ground up.

Of course not. I was just looking for someone to weigh in with some speculation. Geez

That's not really what we do here. Unless somebody has a detailed knowledge of neutron star physics their speculation isn't worth a whole lot. And people with detailed knowledge of neutron stars are more likely to publish in journals than here. You could search for papers citing the one on arxiv - that's where there'll be meaningful speculation. The abstracts will give you a clue what they're talking about, even if you don't follow the detail, and that's a topic for discussion.

 

[Maximum7]

It can be almost anything, that's the point. For example, much closer to home, we have occasionally found heavenly bodies not quite where we expect. With Mercury that turned out to be new physics (general relativity). With Uranus it turned out to be no new physics but a planet we didn't know about (Neptune). With the Pioneer probe it turned out to be a tiny thrust from radiation from its power supply bouncing off its antenna dish (well known physics that nobody had realised needed to be applied). So that's everything from "oh...duh" to rewriting physics from the ground up.

That's not really what we do here. Unless somebody has a detailed knowledge of neutron star physics their speculation isn't worth a whole lot. And people with detailed knowledge of neutron stars are more likely to publish in journals than here. You could search for papers citing the one on arxiv - that's where there'll be meaningful speculation. The abstracts will give you a clue what they're talking about, even if you don't follow the detail, and that's a topic for discussion.

Fair enough. I just read “Unknown physics” and get excited lol

 

[hmmm27]

Fair enough. I just read “Unknown physics” and get excited lol

Share the excitement ; where does the article you linked mention that phrase ?

 

[Maximum7]

Share the excitement ; where does the article you linked mention that phrase ?

https://www.independent.co.uk/space/explosion-kilonova-perfect-sphere-nature-b2282933.html?ampIt’s in the article.

 

[Nugatory]

Fair enough. I just read “Unknown physics” and get excited lol

And that is why people say "unknown physics" instead of "We don't know what we're doing wrong here"