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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 ho

by ck2 2y ago

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? reference: https://www.nustar.caltech.edu/page/relativistic_jets https://www.nustar.caltech.edu/page/relativistic_jets

Dylan16807 2y ago
They do do measurable damage! The amount we measure is extremely small because of how wide the beams are by the time they reach earth.
- SiempreViernes 2y ago
  Hey! Making extragalactic gamma-ray astronomy possible is not damage!
AnimalMuppet 2y ago
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.
- jwells89 2y ago
  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.
notaustinpowers 2y ago
> 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.
- dylan604 2y ago
  > 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. Isn't the precisely what JWST is built for?
  - notaustinpowers 2y ago
    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-galaxies https://www.space.com/james-webb-space-telescope-distant-gal...
hannasanarion 2y ago
> and most of those SMBH have relativistic jets with lobes throwing out particles near light speed This is not correct. Most SMBH do not have relativistic jets. The jets only form when the black hole is actively consuming a large quantity of matter. The Milky Way's SMBH Saggitarius A* is not actively eating anything, so it is not producing a jet.
Conasg 2y ago
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 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.
- SiempreViernes 2y ago
  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.
TheBlight 2y ago
FWIW, it's not clear that SgA* is actually a canonical black hole (nor that even such a thing truly exists in nature.) The EHT image is taken as confirmation but the accuracy of that technique has been called into question: https://arxiv.org/abs/2205.04623 https://arxiv.org/abs/2205.04623 Edit: In response to the downvotes, here are 2 very good sources who at least argue against the existence of singularities and their event horizons. 1: https://arxiv.org/pdf/2312.00841 https://arxiv.org/pdf/2312.00841 2: https://uncnewsarchive.unc.edu/2014/09/23/carolinas-laura-mersini-houghton-shows-black-holes-exist/ https://uncnewsarchive.unc.edu/2014/09/23/carolinas-laura-me... I don't know exactly when science discussion turned into rigid dogma enforcement but we are certainly in that era presently.
- sergent_moon 2y ago
  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.
  - dotnet00 2y ago
    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.
- dekhn 2y ago
  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.
colechristensen 2y ago
>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. https://en.wikipedia.org/wiki/Cosmic_ray https://en.wikipedia.org/wiki/Cosmic_ray
readams 2y ago
Some very recent evidence suggests that such jets may exist for Sagittarius A*: https://www.livescience.com/space/black-holes/milky-ways-monster-black-hole-may-be-shooting-superheated-jets-into-our-galaxy-groundbreaking-images-reveal https://www.livescience.com/space/black-holes/milky-ways-mon...

by ck2 2y ago

Dylan16807 2y ago

They do do measurable damage! The amount we measure is extremely small because of how wide the beams are by the time they reach earth.

SiempreViernes 2y ago
Hey! Making extragalactic gamma-ray astronomy possible is not damage!

AnimalMuppet 2y ago

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.

jwells89 2y ago
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.

notaustinpowers 2y ago

> 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.

dylan604 2y ago
> 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. Isn't the precisely what JWST is built for?
- notaustinpowers 2y ago
  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-galaxies https://www.space.com/james-webb-space-telescope-distant-gal...

hannasanarion 2y ago

> and most of those SMBH have relativistic jets with lobes throwing out particles near light speed This is not correct. Most SMBH do not have relativistic jets. The jets only form when the black hole is actively consuming a large quantity of matter. The Milky Way's SMBH Saggitarius A* is not actively eating anything, so it is not producing a jet.

Conasg 2y ago

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 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.

SiempreViernes 2y ago
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.

TheBlight 2y ago

FWIW, it's not clear that SgA* is actually a canonical black hole (nor that even such a thing truly exists in nature.) The EHT image is taken as confirmation but the accuracy of that technique has been called into question: https://arxiv.org/abs/2205.04623 https://arxiv.org/abs/2205.04623 Edit: In response to the downvotes, here are 2 very good sources who at least argue against the existence of singularities and their event horizons. 1: https://arxiv.org/pdf/2312.00841 https://arxiv.org/pdf/2312.00841 2: https://uncnewsarchive.unc.edu/2014/09/23/carolinas-laura-mersini-houghton-shows-black-holes-exist/ https://uncnewsarchive.unc.edu/2014/09/23/carolinas-laura-me... I don't know exactly when science discussion turned into rigid dogma enforcement but we are certainly in that era presently.

sergent_moon 2y ago
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.
- dotnet00 2y ago
  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.
dekhn 2y ago
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.

colechristensen 2y ago

>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. https://en.wikipedia.org/wiki/Cosmic_ray https://en.wikipedia.org/wiki/Cosmic_ray

readams 2y ago

Some very recent evidence suggests that such jets may exist for Sagittarius A*: https://www.livescience.com/space/black-holes/milky-ways-monster-black-hole-may-be-shooting-superheated-jets-into-our-galaxy-groundbreaking-images-reveal https://www.livescience.com/space/black-holes/milky-ways-mon...