The supermassive black hole at the center of our galaxy may be just as active as in other galaxies, it's just taking a little break. The evidence for this? The reverberations from a massive explosion that occurred 300 years ago
The black hole at the center of our galaxy is quiet - too quiet - so astronomers might say. But according to a team of Japanese astronomers, the supermassive black hole at the center of our galaxy may be just as active as in other galaxies, it's just taking a little break. The evidence for this? The reverberations from a massive explosion that occurred 300 years ago.
The astronomers found evidence of the explosion using the XMM-Newton space telescope, as well as Japanese radio satellites and NASA satellites. This helps solve the puzzle of why the black hole at the center of the Milky Way is so quiet. Although its mass is 4 million times greater than our sun, it emits a very low amount of radiation compared to black holes in the centers of other galaxies.
"We wondered why the Milky Way's black hole behaves like the old giant in its genome," says team leader Tatsuya Inyo of Kyoto University in Japan. "But now we understand that the black hole was much more active in the past. Maybe he was just resting after a huge explosion."
The team collected observations from 1994 to 2005. They saw in the X-ray images how clouds of gas in the region of the black hole's center brightened and dimmed as pulses of radiation washed over the area. These are the reverberations, which remain long after the black hole has gone silent again.
One large gas cloud is Sagittarius B2, and it is 300 light years from the center of the black hole. In other words, the source of radiation reflected from Sagittarius B2 was ejected from the black hole 300 years earlier.
Through observations of the region over 10 years, the astronomers were able to see an event that happened to the cloud. About 300 years ago, the black hole produced a massive explosion that made it a million times brighter than it is today.
It is difficult to understand why the black hole changes the amount of radiation emission so drastically. A supernova in the area may have thrown gas and dust into the vicinity of the black hole. This led to a feeder for it and caused the black hole to create a large eruption.
57 תגובות
My last tag concerns your discussion in responses 40-42
Point and Roy Tsezana
The effect according to which movement is observed as if at a speed higher than the speed of light (supperluminal motion)
It is well known and explained:
http://en.wikipedia.org/wiki/Superluminal_motion
In general, it can be shown that for a Lorentz factor g>>1 an observed velocity of up to gc is obtained for movement at an angle of 1-^g (in radians of course) in the direction of the observer.
To understand the effect, consider a distant source that moves at speed v and angle a (relative to the line of sight to the viewer) and emits two pulses at a certain time difference t (we are constantly working in the viewer system)
Suppose the first signal arrives at time 0, then the second signal arrives at time dt equal to ((t*(1-cos(a
At the same time the object traveled a distance (on the axis perpendicular to the line of sight) dx equal to ((v*(sin(a
So the observed speed is: U=dx/dt
For angle 1-^g (under the assumption g>>1) we get (using the Taylor column) that ֹU=gv~gc
To the respondent 52
Finally someone who understands that gravity is calculated with respect to our radius from the center
My argument that I have been attacked here is that this is also true of galaxies
If the Earth's distance from the center of the galaxy is 25000 light years. All stars whose distance is equal to or less than 25000 light years from the center of the galaxy affect the gravity we feel
To the point (note 50):
In your nice explanation, you certainly did not mean the radius smaller than the radius of the body on which the force acts, but the radius smaller than the distance between the center of the body on which the force acts and the center of the ball of mass that exerts the force.
For the purpose of calculating gravity, the earth exerts a force on me as if all the mass of the earth were concentrated in the center of the sphere. My radius is not important. If I am in a hole deep in the ground - then for the purpose of calculating gravity only the mass inside the small ball on the edge of which I am sitting affects me.
Point, you explained it well, point to your credit.
Meir, I meant that you did not understand what I wrote, that the things you say are nonsense from a physical point of view. I recommended that you start with a science encyclopedia for youth and that's how you progress.
A simple example, where did you get this nonsense that the gravitational force comes from the peripheral mass? It's just the opposite! The force of gravity arises only from a mass that is organized in a spherical shape with a radius smaller than the radius of the body on which the force acts. And the things you say are the exact opposite of this simple physical fact.
Meir Giladi,
First, calculating the black hole lifetime is no nonsense. If its mass is known (which you don't know exists) and its Hawking radiation is known, one can calculate how long it will take for the hole to evaporate.
You claim that your idea makes more sense, but:
A) A logical idea is not necessarily true. Quantum theory, for example, makes no sense at all, but it is incredibly accurate and works well in all experiments.
b) The existence of black holes with mass concentrated at a radius smaller than the Schwarzschild radius follows directly from the equations of general relativity.
From which equations do you conclude that black holes have no mass???
Do you think general relativity is simply not true?
Remember - it is not enough to claim that your idea "makes more sense" - such reasoning does not justify any scientific theory!
Another thing: there are endless strange theories that no one has yet disproved - this does not indicate their correctness! (And see, for example, the theory about the spaghetti monster, or about the flying teapot)
point
You probably didn't catch the point. First of all, there is no arrogance here, at least on my part. And of course I'm not a preacher. I answer the questions and doubts matter-of-factly because I understand that it is almost impossible for people to change their thinking and become less fixed and believe in everything they read. I have no interest in convincing you of my rightness because it seems lost in advance. Therefore, I wish you only the best and I do not intend to reply to you anymore .
Lenaam - this field of astrophysics is not an exact science and contrary to what you think nothing is "proven" including the big bang and wormholes and string theory. Despite the interesting publications, there is nothing absolute and well-founded here. In contrast, there are certainly many laws of physics or, for example, Kepler's laws that have been proven without any doubt.
The theories that discuss black holes can indeed calculate approximately the strength of the black hole based on the acceleration and speed of the matter near it, or the size of the event horizon and the like (apart from the black hole's existence time because that is nonsense) but they tend to associate this gravitational force with a huge mass found in the black hole and I claim that This force of attraction arises from the material around it and not from a hidden mass within it. There is nothing improbable here based on the fact that even the force of gravity on the earth, for example, is calculated as if it were entirely at its center and we all know that the gravity of the earth arises from the mass surrounding the center itself. So far none of the respondents I have not contradicted this claim of mine and all in all I am simply claiming that this is also how the galaxy should be treated. As if all its gravity is in the center and comes from the mass of the stars outside the center.
The idea is legitimate and logical and more plausible than the current theory that attributes mass to black holes. Sometimes I read about a mass of 3.5 suns for a black hole and sometimes about a mass of a black hole with the power of millions of suns.
But that's okay with you because it's written in scientific terms.
Well, unlike others, I don't take anything for granted and I don't immediately believe everything I read or hear, even if it's Hawking.
The anonymous user is me…
Meir Giladi,
The theories of the respected scientists, such as Hawking and others, are backed by complex mathematical developments and rely on physical theories that have already been confirmed in the past.
These are not just interesting ideas to quantitative calculations that give a rigid framework to the theory. For example, the theories discussing black holes offer a way to calculate the radius of events, to calculate the time of existence, to calculate the strength of fields, etc., etc.
So far you have only proposed an idea that seems right and interesting to you, but that is simply not enough. There are a huge amount of interesting theories that have been proposed in the past by very smart people, the only problem with which is that they just weren't true!
Thinking and curious people do not tend to waste time on ideas that have no basis and no foundation, there are simply too many of them.
Meir, I don't understand you, after it becomes clear to you that you didn't understand what you read, you still continue to preach as if everything is normal.
Where does this arrogance come from?
Noam
The quote I gave talks about the emission of jets from the black hole
I actually agree that the jets are emitted because of the black hole and not from it. I argued that the black hole is nothing but a virtual point (without its own material) where the gravitational forces of the material around the black hole are balanced. My intention was that the black hole causes the material that is accelerated by it to be ejected perpendicularly to the plane of rotation of the galaxy.
There is no real proof for the current theory of Hawking or others about black holes and they also shoot in the dark strange theories on other topics as well such as wormholes or going back in time without proof relying on their reputation. People tend to accept the theories as Chinese teachings.
There is a problem in bringing findings or proofs about black holes. The problem is not only mine but all the "scientists" who invent theories. You actually believe them because they are considered. That is your right but what if they are wrong? I do not need your or anyone else's approval for my theory and everyone will accept it or not and that is their right. But for thinking and curious people I give a different point of view and food for thought. If they accept, I'll be happy. If they don't, I won't be sad about it..
Meir Giladi,
You did not understand the two articles you mentioned.
As Point wrote, the jets of matter are not emitted from the black hole but are caused by it.
Hawking did not withdraw from the subject of Hawking radiation, but referred to the nature and information that he initially thought would be lost and now thinks that the information is not lost after all.
See, you can come up with endless fascinating physical theories, but the problem is that you have to base them on findings.
Claiming that we do not understand, and everyone will still recognize your righteousness, is not the foundation of a scientific theory but a simple and pure belief.
You are of course entitled to hold your belief that everyone is wrong except you, and I know a few others who think so.
In any case, the way to convince is to present a theory based on findings, mathematics and other physical theories. I would be happy to deal with and try to understand your arguments when they go beyond belief, and reach the gates of science.
At the time when I read about it there was no explanation for the phenomenon, instead it was assumed that it was somehow an optical illusion or some kind of measurement error. It was a very distant quasar, at the edge of the universe, so perhaps all kinds of things happened on the way from the distant past to us.
The assumption is that special relativity is valid at any time and place.
point,
That sounds interesting. Is there an explanation for this impossible speed?
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my new blog - Another science
Meir, a simple explanation for your confusion:
The jets are a familiar and old phenomenon of black holes, but you imagined things that are not written anywhere. The jets do not come out of the black holes but as a result of the swirling of the gas around the black hole.
The subject of jets is interesting in itself, and regardless, there are observations that show jets from far, far away black holes that seem to move at 3 times the speed of light!
In general, Meir, you write many things that are not physically correct at all, and it seems that you think they are written somewhere. No one presents you in a negative light, but your words about physical matters as the words of Abel.
The link to the news on the science website that Hawking retracted his claim
https://www.hayadan.org.il/hawking-0704/
But in any case it neither adds nor detracts nor is it relevant to me because the jets I mentioned are not at all what scientists think they are today
Dear Noam
Please read this article
https://www.hayadan.org.il/galactic-black-hole-fires-a-jet-at-a-nearby-neighbour-1912075/
In science to the end and I quote "We have seen many jets created by black holes, but this is the first time we have seen such a jet hit another galaxy like we see here." says Dan Evans, a Harvard-Smithsonian grant scientist for astrophysics and principal investigator on the project. "This jet can cause all kinds of problems in the small galaxy they hit." You can argue as much as you want that there is no emission from black holes, but you don't understand because this is exactly the error I'm talking about because black holes have no mass - if they did, no matter would be emitted from them.
Regarding Hawking, he did admit his mistake and this has also been written before in science. But it is not relevant to my argument because Hawking's opinion is different from mine.
In general, all the claims made here and in the future to present me in a negative light do not move me from my mind because you do not understand that I am talking about a completely different essence of the black holes and you justify the popular opinion and try to defend it, again making claims and proofs, so to speak, relying on a Torah that is not correct at all from my point of view.
In order to be truly open to the innovation I bring up, you have to put aside everything you knew or read about black holes, and this is indeed difficult for you, and your reaction was expected, so I am not excited about it at all.
Maybe, it's all a matter of style
Noam, sometimes it is better and even required to tell a person that he is talking nonsense.
Meir Giladi,
There are no jets emitted from a black hole!
Although you claimed that such jets have been observed, you have not yet provided proof of this - which is exactly what I asked for. Here I ask once more, and I do not expect you to defend any theory, but to defend what you yourself have claimed.
Regarding Hawking radiation, you are wrong and misleading - Hawking did not admit to a mistake, on the contrary his hypothesis is considered correct and of course has a physical and mathematical foundation.
Hawking radiation has nothing to do with jets of matter, and before you dismiss a certain theory you should understand what you are trying to dismiss.
Meir Giladi, you are completely confused.
Start with a youth encyclopedia.
Since I do not accept the model of the black hole as shown, I point out again that these jets of matter are actually matter accelerated by the black hole and emitted perpendicular to the plane of rotation of the galaxy.
Hawking radiation is nothing more than a guess of a person who has already admitted that he was wrong about it. These two jets were explained by Hawking in a wrong way.
You expect me to defend a theory that I falsify in the first place.
If you debunk all the theories you've heard about before and be open to new ideas without being someone else's advocate you might think there's a real possibility I'm right.
Meyer,
It seems you got confused - I asked for a link/reference to the phenomenon you mentioned about the emission of matter from a black hole, which is not Hawking radiation ("two jets from the center").
still waiting
Small correction
My response number 29 was to Noam and not to Michael
Meir
Regarding your response number 27
As I mentioned in the example regarding the Earth, its gravity can be calculated as if all the gravity is in its center. And this force comes from the material outside its center.
This is exactly how I argued that the gravitational force of the galaxy can be calculated as being entirely in its center and its gravitational force comes from the stars around it. This gravitational center point of the galaxy is the black hole.
All the arrogance in your style is out of place. And I am convinced that the knowledge I hold is the most reasonable and does not go against any law as you try to present it.
First of all my response to comment 26 above regarding jets of matter observed perpendicular to the black hole
There are thousands of testimonies to this, but for the sake of brevity I will mention links to several articles including reports from NASA
http://www.physorg.com/news79361214.html
http://www.space.com/common/media/video/player.php?videoRef=080428_blazar-coil
http://www.wired.com/wiredscience/2009/01/spectacular-new/
And one more thing - Meir Giladi:
Your idea of "policy makers" in science is also funny.
In general, the tendency of the editors of the scientific journals, like mine, is to prevent the publication (in the case of scientific journals) and the preaching (in the case of talkback sites like the scientist) of nonsense
Meir Giladi:
What can I do about the fact that this is a hallucination?
To say that this is not a hallucination?
I, at least, say true things.
There is not an iota of truth in the idea that the gravitational forces of the stars around the black hole pull the material towards it.
If you knew anything about gravity you would know this but you probably didn't bother to study the subject.
In general - both gravitation and the electric field maintain the Gauss's law The one who says (in the case of gravitation) among other things that your claim is not possible but it is clear to me that I am speaking to deaf ears.
I am sure you have never tried to do any calculation and verify your claim because if you did you would see that it is simply impossible even according to the simple description of Newton's laws.
For a demonstration of a "toy galaxy" - imagine a situation where there are only two main stars in the galaxy.
Let's assume for simplicity that it's just the same.
Although there is an equilibrium point halfway between them called the Lagrange point, but it is an unstable equilibrium point. Any body that is not in it to begin with will not fall to it but to the star closest to it.
Your claim that there is no contradiction of the law of conservation of energy here is also really funny.
The matter falls towards the black hole and thus translates potential energy into kinetic energy.
So it reaches the disk and as it spins there it emits a large part of that energy in the form of radiation.
Because of this loss of energy, there can no longer be any process that will return it to the same distance it was when it started falling into the black hole because for that it needs kinetic energy that is the same in magnitude as the potential energy of that distant point but, as mentioned, it already has less kinetic energy.
Good.
I've really put too much effort into this delusion. After all, the one who should have devoted effort in the situation we are in is you (to study the subject you are talking about) and not me (trying to force you to study)!
Meir Giladi,
You wrote that matter is ejected from the center of a black hole in the form of two jets, and "such jets have indeed been observed".
Where did you hear about that? Can you provide a link or reference to this sensational news?
To this day, the accepted opinion among scientists is that the only matter emitted from a black hole is Hawking radiation.
You will write that you don't have the strength for this hallucination or any expression that comes to your mind and I don't intend to phrase it in the same way
You are probably not really open to new ideas. I will try to explain in other words that things are quite simple to understand.
The power of the black hole does not come from the material that is drawn to the event horizon and is there for a short time until it is ejected back into space. The mass you mentioned that is in the small area of the event horizon was not there all the time (and will not stay there beyond a short time), but was pulled there by the masses of the material outside the horizon The events and the black hole is in this respect a measure of the gravitational forces of the stars outside the event horizon and my argument is that there does not have to be material inside the event horizon for the black hole to have the power it has.
If black holes had their own mass, their power would increase in direct proportion to the "swallowed" matter - my intention in this formulation is that the matter entering the event horizon cannot remain in the event horizon and over time increase the black hole's power because the matter after entering the event horizon continues to spin and gain acceleration until which reaches the center of the black hole and is ejected back into space in the form of two jets of matter perpendicular to the plane of rotation. These jets were indeed observed and photographed. What if the power of the black hole was due to an enormous hidden mass. The material reaching the black hole would not have been ejected back into space, but added to the mass that is supposedly hidden in the center of the black hole and thus the power of the black hole would have increased in direct proportion to the incoming mass and not ejected and over time the black holes would have "swallowing" all the matter in the universe.
Regarding your proposal to write an article in a serious science journal. I believe that the change will come and in time my opinions will be accepted and then I would be happy if they would allow me to write articles. Meanwhile this is not the case because the policy makers are people like you who do not allow free expression of "abnormal" opinions
Meir Giladi, what is this: "It is therefore a mistake to think that black holes have a mass of their own. If this were the case, their power would increase in direct proportion to the matter that was "swallowed" by them, and over time they would "swallow" all the matter in the universe."
1) You did not mention that it depends on the speed of the material that may be swallowed by the black hole. 2) What is the connection between the assumption and the conclusion?
I think you are confused. A black hole is the name of the entire region that is in a radius smaller than the radius of the event horizon as it is seen from the outside with us.
Inside that area is a mass. So what exactly are you trying to say, I didn't understand.
Meir Giladi:
It is not a case that your opinion is abnormal.
It is simply not true.
You repeatedly fail even in math when you try to convince us that putting zero in the denominator of a fraction whose numerator is not zero gives zero as a result (when infinity is the correct result as anyone who understands knows).
I don't have the strength to continue dealing with this hallucination.
We'll see you put it in some serious scientific journal.
An expected and not surprising response
For the sake of entertainment I will answer you that there is no contradiction between what I gave to the law of conservation of energy and the black hole at the center of the galaxy is the sum of the gravitational forces of all the matter in the galaxy and it acts as an accelerator and the matter that reaches the event horizon of the black hole is simply thrown by two jets that have already been observed and I have not innovated anything in this. There is no contradiction here to the law of conservation of energy.
I did not claim that there are no black holes, therefore your last sentence is strange, which implies that I denied the existence of black holes
My argument was about their character. In my opinion, they are not "collapsed stars" or a concentrated mass of matter, but rather their enormous gravitational force comes from the matter around them and not from the matter supposedly existing inside them.
Regarding the gravitational force near the black hole. The closer we get, of course, it will increase squarely, but the theoretical point whose distance from the center is 0. If you put a distance of 0 in the formula, you will get a final result of 0 gravity
It is true that distance 0 is theoretical. But we are dealing with theory and at some distance and even zero from the center the gravitational force will of course be enormous although not infinite.
Regarding my understanding. With all due respect, I represent an unusual opinion and I am aware of it. Anyone who has ever invented or innovated has had an unusual opinion.
Anyone who thought like you never innovated or invented anything original.
Meir Giladi:
There is indeed a misunderstanding on the subject, but mainly with you.
Just for fun, I'll point out one of your misunderstandings. The formulas of general relativity as well as Newton's gravitation formulas predict an infinite gravitational force at zero distance.
As we know, the difference between zero and infinity is quite large.
Your entire description of what you think should happen to the material spinning in the disc also contradicts the law of conservation of energy.
Beyond the matter of the theory - there is also indirect evidence of the existence of black holes and among them also stellar orbits that would not be possible otherwise.
There is a fundamental error in understanding "black holes"
Black holes are not collapsing stars. If these were collapsing stars, the gravitational force we would feel if we were standing on the surface of the star would be equal to the gravitational force after the collapse of the star into itself if we continued to stand at the same point in space. The gravitational force of any body such as a star comes from its mass. Because the collapsing star does not contain, due to its collapse, more mass than it had before. The strength of gravity will not change even if the body collapsed. The force of gravity is always calculated as if all the mass was concentrated in the center from the beginning. Although if we collapsed together with the star "and stayed alive" we would feel a huge force of gravity because our distance from the center of the star was shortened to almost zero. Therefore the effect of collapsing stars on Their environment in space before they collapsed and the creation of black holes as a result is complete nonsense.
The gravitational force of the Earth, for example, is calculated as if all its mass were concentrated in the center. The gravitational force we feel is affected by our distance from the center of the Earth, therefore there is a small change in the strength of the gravitational force on the surface of the Earth because it is not a perfect sphere but an ellipse. Therefore, satellites are launched from the equator at a lower cost than at the poles.
The gravitational force of the entire Milky Way galaxy is also calculated as if it were all concentrated in the center. Or rather, in the center of the sum of the gravitational forces. This center is actually the "black hole" and its power is derived from the mass of the stars and the material around it without its own material.
If our distance from the center of the Milky Way is about 25 thousand light years. There will be the force of gravity in which we will be pulled together with the Earth to the center equal to the force of gravity resulting from the mass of the stars and matter in a radius of 25 thousand light years from the center. The stars outside this radius affect us in a different way. Some pull us together with the black hole and some pull us against this force (these are stars we are between and the black hole).
It is therefore a mistake to think that black holes have their own mass. If this were the case, their power would increase in direct proportion to the matter "swallowed" by them and over time they would "swallow" all the matter in the universe.
Because black holes do not have their own mass and in fact at the virtual point in the center of the black hole there will be no gravitational force at all because the distance from the center is 0 and according to the gravitational force formula at a distance of 0 the force is also 0.
The material that is accelerated towards the black hole and falls into its event horizon and swirls with acceleration and is finally thrown back into space in the form of two jets perpendicular to the plane of rotation. Why perpendicular? Because only perpendicular to the plane of rotation of the stars is the force of gravity the smallest, because the stars rotate in the plane of a disk around the center, therefore only perpendicular to the disk is the force of gravity weaker and the material can escape.
True, changing the photon's movement under a gravitational field does not require any mass for the body, which changes its trajectory.
I just now noticed claim number 2 in your response.
This claim is not true.
There has not yet been found a single result of quantum entanglement that contradicts the theory of relativity and the fact that you can fantasize about such results does not make them happen in reality.
The photon is not bent in a gravitational field. Its trajectory is bent due to the warping of space. Einstein predicted this even though he did not attribute any mass to the photon.
A laser beam is light.
You probably mean to say that there is a medium where light travels faster than vacuum. I think I also once came across an article about such a discovery.
In principle, it doesn't change anything.
1. They managed to accelerate a laser beam in the laboratory above the speed of light for a short distance through a medium of cesium, if I'm not mistaken it was even in the science that I saw about it for the first time.
2. It is still unknown whether it is possible or impossible to transfer information through quantum entangled particles, in any case the theory of relativity states that any reaction cannot operate faster than the speed of light and the phenomenon of quantum entanglement completely contradicts this.
3. I believe that there may be a certain rest mass for the photon mainly due to the fact that it is "bent" under a gravitational field.
The theory of relativity says that you cannot exceed the speed of light in a vacuum.
This is something they have never been able to do anywhere.
The mutual influence of quantum entangled particles does not even allow the transfer of information.
Transmitting information at a speed that exceeds the speed of light will allow the order of cause and effect to be reversed.
You, personally, are welcome to continue believing, but to me (personally) it seems improbable.
I have a comment about the speed of light, according to the theory of relativity nothing can exceed the speed of light (if I'm not mistaken there is an asymptote exactly at the speed of light), they have already managed to exceed the speed of light in the laboratories - which is something that raises a great deal of confusion regarding the matter.
Experiments in quantum mechanics have already shown that with quantum entanglement the effect is much higher than the speed of light and is instantaneous - something that raises even more questions because they completely contradict the theory of relativity.
One day quantum theory and relativity will straighten the generations between them, personally I believe that the speed of light can be exceeded and that photons have a certain mass that has not yet been measured.
Yehuda:
No one gets involved and in describing the connection between the times you repeated what almost all the commenters have already said.
Regarding your question about the arrival speed of the neutrino particles - the answer is given in the link I provided above. The neutrino particles are launched at a more intense stage of the supernova formation process, long before the light comes out of it.
They do not move at the speed of light but their speed is close to this speed.
Hello, what are you doing?
The sun is about 30,000 light-years away from the center of the Milky Way, so the reference is of course not to an event that occurred three hundred years ago in the black hole in the center of the galaxy, which we will only see in 29,700 years, but rather to an event that occurred 30,300 years ago. We saw them 300 years ago (or Newton if he had the Hubble telescope.}
The event of Super Nova 1987A took place in the Large Magellanic Cloud about 170.000 years ago, which is the distance in light years to the aforementioned cloud.
The really difficult question is how to explain the flux of neutrino particles reaching the earth at the speed of light. Mass should not move at the speed of light. The neutrinos arrived three hours before they saw the super nova explosion in 1987!
According to the theory of relativity, no matter or information that happens can move faster than the speed of light.
For your convenience, uncertainties regarding the distances to the center of the Milky Way and the Large Magellanic Cloud can be expressed in thousands of light years.
So have a good day
Sabdarmish Yehuda
Avi:
I think you're wrong.
When talking about 1987A we refer to the year it was discovered and not the year it happened.
When talking about the year in which some cosmic event happened, it is customary to talk about the actual time it happened and not the time it was discovered.
Here there is a kind of hybrid formulation. If you want to discuss the time when it was discovered, then it is today and not 300 years ago.
See, for example, how 1987A and other supernovae are expressed in Wikipedia:
http://en.wikipedia.org/wiki/SN_1987A
The question of when something happened is irrelevant, otherwise we would have to compare today a supernova of 2543 BC that was in one direction with a supernova of 500 AD in another place. For us, the relevant time is the time when they reached us.
As for nearby stars, there may be a problem, but even 4 light years is not relevant. That's how it is at least for astronomers, only a certain type of event is important for distance and that is the determination of distance - pulsating stars used as standard candles make it possible to estimate the distance between us and the galaxy in which they are located.
To your answer - they do not mention an event 400 light years away from us that it happened 400 years ago.
Response to my father:
Why is it irrelevant when it really happened?
If you want to talk about a supernova of a star 400 light years away from us, don't you mention that the event happened 400 years ago?
For Amiram and Nimrod, it is certain that the distance in light years should be added to each event to estimate when it really happened, but that is irrelevant, otherwise there would be no talk of the Cancer Nebula - a supernova that happened in 1054, nor of the powerful supernova 1987A.
Since each distant star is a different distance away from us, the relevant scientific meaning for the matter (whether the center is quiet or not) is the time when we see the event. We also have no other way to measure.
Well, I only just came across this article and I agree, of course, with the opinion of the commenters regarding the length of time since the event in question.
Regarding Rami's question - a black hole does not emit energy (with the exception of Hawking radiation, the existence of which has not been proven and is in any case uniform and does not erupt).
A black hole is, however, responsible for energetic events in its vicinity (when more stars occasionally fall into it). I assume that the radiation in question is the one that is emitted from the disk that orbits the black hole.
Nimrod, you are absolutely right! The events in the black hole were 300 years before the light rays came out of the gas cloud to us, in total we need to add another 30,000 years (our distance from the center of the galaxy). No one knows what a mistake is - only a hundredfold.
Such a mistake must not be on such a site!
Obviously, and perhaps it would have been worthwhile to emphasize this in the article, all the events mentioned were several tens of thousands of years ago - we are light years away from the black hole in the heart of the galaxy.
A black hole emits radiation in the X-ray range.
For the 300 year issue, the gaseous cloud erupted from the black hole X time ago, if the eruption spread at the speed of light (plus or minus) and now the distance is 300 light years between the bodies - that means 300 years have passed since the eruption that we were predicting on Earth.
As far as I understand, the event did not happen 300 years ago, but 300 years + the distance in light years from the center of the galaxy to us. I'm wrong ?
Small question: how can a black hole emit energy?