Three of the oldest stars in the universe found circling the Milky Way
news.mit.edu
news.mit.edu
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
The amount we measure is extremely small because of how wide the beams are by the time they reach earth.
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.
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.
Isn't the precisely what JWST is built for?
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.
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.
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.
The EHT image is taken as confirmation but the accuracy of that technique has been called into question: 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
2: 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.
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.
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.
This is, indeed, how science works. "All models are wrong", as they say. I'm not sure what you're trying to push back against.
IIUC you're basically talking about this: https://en.wikipedia.org/wiki/Nonsingular_black_hole_models which don't seem to be fully mainstream, nor supported by any observed evidence.
Somewhat related and maybe interesting to you: https://www.llnl.gov/article/40576/black-hole-loses-its-appe...
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.
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."
And, the most recent evidence we have is... that we got the composition of G2 wrong. https://arxiv.org/pdf/2112.04543
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.
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.
I bet that the milky way could only capture these ultra fast moving stars because of dark matter.
Also, “in the halo” doesn’t necessarily mean “far from the center of the galaxy”; it means “not orbiting in the disk”.[1] Some of these stars are closer to the galactic center than the Sun.
[1] And further away from the center of the galaxy than the bulge — but the bulge is much smaller than the orbit of the Sun.
That's not how we date stars. We typically date the star by it's metallic content. More non-hydrogen elements in it's spectrograph, then we know it's an older generation of stars.
It's actually the exact opposite, but yes.
In lead stars, there are so few seed nuclei (those metals) that each of the seed nuclei that are there can capture many more neutrons.
It's all time, right?
Sure, but we can measure time dilation between the peak of a mountain and the base of a mountain, due to the differing velocities. Time is relative!
So far, to my knowledge, we have not observed any. As you note, hundreds of km/s is way too small to have any appreciable effect.
https://www.space.com/fastest-star-ever-moves-8-percent-ligh...
For example, suppose the other ship is one light-second away from yours and is moving at 0.2c. You're seeing the other ship where it was one second ago, and in that time it has moved 1/5 of a light second. Plus, supposing you're firing a laser at it, the laser will take another second to get to the target, so you have to aim 2/5 of a light second away from where you're seeing the other ship. And during that time the other ship could change direction and spoil your aiming calculation. The sci-fi book series probably is making some assumptions about how fast the ships can change direction, how fast and accurately they can aim, and typical distances between ships during combat to come up with the 0.2c number.
https://en.wikipedia.org/wiki/Cosmological_horizon
"Or, more precisely, there are events that are spatially separated for a certain frame of reference happening simultaneously with the event occurring right now for which no signal will ever reach us, even though we can observe events that occurred at the same location in space that happened in the distant past.
"While we will continue to receive signals from this location in space, even if we wait an infinite amount of time, a signal that left from that location today will never reach us."
An example closer to home, our orbital velocity around the Sun is 29.8km/s. Mercury is 47.9km/s (on average, it actually varies throughout its orbit). Neptune is 5.4km/s.
https://en.wikipedia.org/wiki/Galaxy_rotation_curve
```
The rotational/orbital speeds of galaxies/stars do not follow the rules found in other orbital systems such as stars/planets and planets/moons that have most of their mass at the centre. Stars revolve around their galaxy's centre at equal or increasing speed over a large range of distances. In contrast, the orbital velocities of planets in planetary systems and moons orbiting planets decline with distance according to Kepler’s third law.
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Which tells you that the method for determining the age of stars is wrong.
We obviously don't know the age of each and every star in the entire universe, calm down dude.
There could be a quadrillion stars of a similar age and the statement could still be true.
Same thing here. Three of the oldest stars? It means literally nothing but it paints a picture.
Thus if there are old stars then they'd be ..... right here.
So on average a large portion of the oldest stars tend to have been from elsewhere, whereas the newer stars were born here.
I would suggest, instead, that we can still see their light.
They may have popped their clogs, long ago, and we would not have known, as we're seeing their old videotapes.
There's something called the "Cosmic Event Horizon," or somesuch. It's the distance from us, that we'll never be able to see, because it is more than 13.8 billion light-years away, and we'll never see anything beyond.
Every time I think about the distances and scales of the universe, I get a headache.
[EDITED TO ADD] I wasn't talking about the nearby stars, and neither were they. That quote was talking about distant, red-shifted galaxies.
The milky way is only 100,000 light years across.
Stars of a certain small size will also continue shining for a trillion years.
Not all stars are created equal. Blue giants may only live a few billion years, while red dwarfs will last practically forever.
They were talking about distant galaxies, not the relatively nearby stars.
Nearly every single star we can see in the entire Laniakea supercluster is still shining today.
The universe is big, but stars live for a really long time.
It's an interesting quirk of these discussions of events at relativistic scales that it's very hard to precisely speak about what we mean whenever we reference time.
For all of us "here", who are within non-relativistic distance of each other, "today" is a meaningful point in time. But what does our "today" mean for that far-away star? I think you are trying to articulate that, if the star is X light years away from us, after X years from "today" we will still be receiving light that has traveled from the star to "here". But you might instead mean that if a traveller were to depart from "here" "today" at near relativistic speed, when he arrives at the star he will find it still shining "there" at "that time".
But notice those are definitely not the same data point about the star. The first data point will arrive here in X years to show us the star was still shining X years previously. But the traveler will collect the second data point (almost immediately for himself, by the way) and may find the star dead. This can happen if he and the star's last light cross paths in flight.
A pole vaulter carrying a 40m pole is running at a speed such that to an observer, he appears contracted by ½. He runs through a barn of length 20m and the doors at each end of the barn are closed simultaneously.
But to the pole vaulter, the barn appears contracted by ½ and thus appears to be 10m long to him. What does he see when the doors are closed?
No it isn't. This is a stupid psued talking point.
The only stars that have never been observed to die, are red dwarfs.
I think blue giants are the shortest-lived ones.
Ours is in the middle. I think they give the Sun about four billion more years.
BTW: That was a rhetorical statement. The issue is, we don't actually know what's going on, today.