Cosmic particle accelerators

19:07Now, before we get into that, let's just try to hypothesize what could even do this. It's of extra galactic origin that we're talking about. What kind of particle accelerator would actually do this? If you do the calculation, you actually figure out that where that ankle was, that marks where the gyro radius of a proton, meaning like how big of a circle would be needed for a magnetic field to accelerate that thing. That exceeds the galaxy. The gyro radius of a proton that is traveling that fast exceeds galactic scales. You need a particle accelerator larger than a galaxy.

19:48I don't like it. If you just do the fundamental physics. I don't like it. It's weird. That's quite, and I'm thinking in my head one thing, but let's see if it's going to go in that direction. It's ridiculous, right? One proposed accelerator is the active galactic nucleus. This is where you've got a galaxy that's super energetic in the central region, probably a supermassive black hole that is accreting matter, and it launches these powerful jets in both directions. Those jets, when they encounter their surroundings, they create shock waves, and those shock waves can start accelerating particles because the magnetic fields there are not homogenous, they're not constant everywhere, and so you get like these-- Which we've talked about.

20:31Yeah. And so you get these massive, massive particle jets, right? So in a simplified picture, the particle would repeatedly create a shock, and it would scatter off these magnetic irregularities, and the particle has to be held in this magnetic field for long enough to gain that kind of energy. Again, it's not really trivial how this would work, right? Another source could be clusters of galaxies. As cold gas accretes and falls into the hot medium on the inside, that's gonna give rise to shock waves, and those shock waves at the outskirts of this cluster could be powerful enough to give off this kind of acceleration, but the point is we don't know, and we'd like to know. We'd like to know.

21:12Where are these ghostly messengers coming from? Yeah, it's pretty insane that you can create a particle that is that energetic. It just doesn't make sense how you pack so much energy into such a tiny amount of matter, right? So if you wanna do that, you wanna figure out where these particles came from, right? Now, for the oh my god particle, right? You could figure out, oh, it came from that direction, but that's not really a good indication of where it came from because charged particles can interact with the intergalactic medium, and they can interact with the magnetic fields there to start moving around. For example, in this particular example, you've got a supernova that's at the edge of our

21:53galaxy. There's a faint blue trace that you're seeing. That's what a charged particle would do because there's so much magnetic field anomalies in the galaxy that as it's traveling towards us, it's gonna start moving around and bending. So even though the particle came from this direction, the actual source could be somewhere else. It's like a lazy river. It's like you can point and say the top of the lazy river is there, but when you're coming down it, it's not just like the line of sight. Yeah, yeah, the line of sight could be this way, right? Even though the mountain is to the right. So instead, we wouldn't like something that has a clear line of sight.