So a vaguely related question for an astronomy thread about our galaxy since smart people lurk here:
If the center of most galaxies is a super-massive black hole, including the Milky Way, and most of those SMBH have relativistic jets with lobes throwing out particles near light speed
1. Have we detected such lobes in the milky way? why not?
2. If those particles are going near the speed of light yet have no reason to slow down unless captured, unlikely outside of their original galaxy, they are still going for billions of years? (wow if so!)
3. If some of those jets from other galaxies are pointed at earth and contain physical particles with mass near the speed of light, why don't they do measurable damage?
Those lobes have been detected in our galaxy, yes. There’s a page from 2012 by NASA talking about it: https://svs.gsfc.nasa.gov/10918
As I understand it, recent research suggests the last time our SMBH consumed enough matter to erupt was millions of years ago, so the lobes have cooled down and are difficult to detect.
No, the Fermi lobes are not what is meant when talking about jetted AGNs, though they are plausibly the remnants of past episodes where Sgr A* did have jets.
>3. If some of those jets from other galaxies are pointed at earth and contain physical particles with mass near the speed of light, why don't they do measurable damage?
When they hit Earth (from these kinds of jets and other sources) they're cosmic rays. But it isn't a whole beam of them, it's individual particles way up near light speed. We can detect them, they can flip bits in computer memory, but they don't do a lot of damage because even at their speeds, a single proton, electron, or two or more protons as a bare nucleus still doesn't have a particularly large amount of energy on a human scale.
> 1. Have we detected such lobes in the milky way? why not?
Sag A* (our black hole in the center of the Milky Way) isn't considered "active" right now. We don't notice it gobbling up stars and gasses, which would be necessary for the jets to be possible. I remember back in 2020 or 2021 there was an article that we're noticing a jet from Sag A*, which we're still trying to understand why because we don't expect Sag A* to be active. It's also super difficult to monitor Sag A* since there is so much dense dust, gas, etc in the way between us and the SMBH.
> 2. If those particles are going near the speed of light yet have no reason to slow down unless captured, unlikely outside of their original galaxy, they are still going for billions of years?
Generally speaking, yeah, they are! If we're looking at photons though, they will eventually get red-shifted so much that they'll become infrared (invisible to us), until their energy is so low that it'll be near impossible to see without telescopes more powerful than anything we have right now.
> 3. If some of those jets from other galaxies are pointed at Earth and contain physical particles with mass near the speed of light, why don't they do measurable damage?
Space is a vacuum, but there are still things that can slow these particles down (loss of energy like photons, gravity wells from other massive objects, running into a spec of space dust, etc. Also, space is very empty, and statistically, it's incredibly improbable that one of these jets could be aimed directly at us, while also being close enough to us, to cause damage. We do notice them though! They're powerful enough to get picked up by scientific instruments, but are not concentrated enough or powerful enough to cause damage to us or Earth.
> Generally speaking, yeah, they are! If we're looking at photons though, they will eventually get red-shifted so much that they'll become infrared (invisible to us), until their energy is so low that it'll be near impossible to see without telescopes more powerful than anything we have right now.
Even JWST has it's limits. There are some very, very, very, very old galaxies that are so red-shifted, JWST is only able to see them thanks to gravitational lensing amplifying the energy of the light. https://www.space.com/james-webb-space-telescope-distant-gal...
When it comes to the “oldest stars” there is reason to believe that very early there were very big Population III stars that formed very quickly and burned out fast leaving nothing but black holes and there is hope JWST will see some.
In general there are multiple recent observations that things seemed to happen much more quickly in the early universe than we expected so maybe what we think was the first 1 billion years was really the first 10 billion years or there is another big secret to be discovered in cosmology.
I'm not an astronomer, and may or may not be smart.
1. I don't know; Google probably does know.
2. Those jets aren't in a complete vacuum. They're running into galactic gas, of which, on a galactic scale, there is quite a bit.
3. Several reasons. One, they aren't a perfect "beam". They spread out. If you're a few billion years away, they spread out quite a bit in that distance. Then, to get to us, they go through their galaxy's gas, intergalactic space (not totally empty), our galaxy's gas, and finally our atmosphere. Each of those reduces the amount of radiation. Oh, yeah, our magnetosphere deflects charged particles, too.
For #3, I think I remember reading that the Sun’s heliosphere (which contains the entirety of the familiar Solar System) also plays a role in cutting down what gets to Earth, but I may be misremembering.
Kerr's paper is quite specifically about not believing in singularities, not about not believing in black holes. It's hardly a controversial opinion in the science community to believe that singularities in black holes are an artifact of our incomplete mathematical representation of how gravity works. That is not the same as suggesting that black holes or event horizons don't exist. Kerr's solution to the field equations involves two event horizons to begin with, and his argument in the new paper is based on Kerr black holes and explicitly talks about event horizons in multiple places.
I'm very confused as to why you believe that paper provides significant argument as to why calling SgA* a black hole would be jumping the gun.
Neither of those are "very good sources". Further, they are basically mathematical modelling papers. We have a lot of experimental evidence about the nature of black holes. If you argument is just "black holes might not be a true singularity", well, nobody is strongly disagreeing with that, we just don't have evidence or good support for alternative models. People aren't being dogmatic, they just don't have any better models that explain the observations.
Laura Mersini-Houghton and Roy Kerr seem like very good sources to me. Are you familiar with their work? It seems not.
A "black hole" implies a singularity behind an event horizon not even light can escape from. There isn't any proof that such a thing exists in nature. You're correct in saying that we see the indirect gravitational effects of something that doesn't fit any model our imaginations have conjured up to date except for "black hole." That doesn't mean it's clear that black holes are a real thing.
That would be perfectly lovely for me if that was actually the attitude of most people weighing in on these discussions. But in practice, when it's insinuated that a more beloved sci-fi model may perhaps be incorrect/incoherent it's met with people being upset that it's being pointed out.
I'm not advocating for any given alternative model really. I primarily want to call out that we're not really sure what we mean when we say "black hole" and there is good reason to be at least a little skeptical-- especially of models invoking a singularity. The vast majority of people take it as a given that black holes as depicted by popular sci-fi films/TV exist in nature and we're far from being sure of that.
I read the linked news article and the related paper and it just says that they're struggling to figure out what one of the light sources that's orbiting the hole is made of. The article doesn't really say much that isn't mainstream understanding of black holes.
You sort of have to read between the lines with popular science reporting. Prior to the event, the gas cloud was spotted and it was big news in the media as this would effectively be an empirical test of black hole theory and we'd get to see it in action. But the event came and went and nothing remarkable happened. You had to look it up to find out what ended up happening because it wasn't widely reported. We're still trying to come up with answers for why the experiment didn't turn out as expected.
So we either don't understand the gas cloud or our SgA* black hole model isn't correct (or some combination of both.) In either case, we seemed quite sure prior to the event. I think anomalies like this are where the really interesting information lies and we should be more humble wrt the veracity of our current models.
You're making a lot of arguments and linking a lot of things that are only loosely related and definitely are not actually supporting evidence for your argument.This article (and event in general) also have very little to say about whether or not black holes exist.
The galactic center is one of the noisiest portions of the galaxy and most difficult for us to look at. (Relatively) high densities of gas further obscure things within them. It's a pretty huge leap to go from the fairly obvious answer - we weren't quite right about everything inside of G2 - to "Black holes as we think of them don't exist."
I think some of the apparently dogmatic attitude is from exhaustion. Usually (I'm not implying you) someone calling commonly accepted science into question are just waiting for a moment to drop something about Jesus, or Chemtrails or some other nonsense.
Or even more commonly with astronomy, are misinterpreting the material to prop up their pop science influenced preconceived notions.
I think everyone in the hard sciences has had some experience of having to deal with someone with no technical insight, arguing a point that has already been discussed in far more detail by experts and claiming that scientists are just being dogmatic because they don't care to repeat the same points over and over again.
If the center of most galaxies is a super-massive black hole, including the Milky Way, and most of those SMBH have relativistic jets with lobes throwing out particles near light speed
1. Have we detected such lobes in the milky way? why not?
2. If those particles are going near the speed of light yet have no reason to slow down unless captured, unlikely outside of their original galaxy, they are still going for billions of years? (wow if so!)
3. If some of those jets from other galaxies are pointed at earth and contain physical particles with mass near the speed of light, why don't they do measurable damage?
reference: https://www.nustar.caltech.edu/page/relativistic_jets