New map of the universe unveils a stunning X-ray view of the cosmos

Catastrophe

"There never was a good war, or a bad peace."
"eROSITA spotted over a million sources of X-ray radiation from all across the cosmos, with most of the sources being active galactic nuclei, or the luminous, compact region at the center of galaxies. This number of sources roughly doubles the number of known X-ray sources that have been discovered over the 60-year history of X-ray astronomy"

Really EXTRAordinary!
 
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The article stated "This all-sky image completely changes the way we look at the energetic universe," Peter Predehl, the Principal Investigator of eROSITA at MPE, said in the same statement. "We see such a wealth of detail — the beauty of the images is really stunning." Because it is not only stunning but incredibly detailed, this new X-ray map could "revolutionize" the way that we look at the cosmos, Kirpal Nandra, head of the high-energy astrophysics group at MPE, said in the same statement."

My note *the beauty of the images*, I am glad the Earth is not orbiting close to any of these high energy X-ray sources :) It does raise questions. Lifetime of such high energy X-ray sources compared to the Hubble time as an example.
 
Dec 19, 2019
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I don't see how they can promote this as a map of the universe. Even the CMB map was only a chunk of what we could picture of the observable universe, from one direction. That being said, it is interesting to see the xray dispersion from the black hole at the center of our galaxy.
 
I don't see how they can promote this as a map of the universe. Even the CMB map was only a chunk of what we could picture of the observable universe, from one direction. That being said, it is interesting to see the xray dispersion from the black hole at the center of our galaxy.
The cosmic background radiation observations cover the whole sky and is usually presented in an all-sky Mollweide projection [ https://en.wikipedia.org/wiki/Cosmic_microwave_background#Microwave_background_observations ].

The eROSITA is also all-sky and presented similarly, see the image. It is a map "of X-ray radiation from all across the cosmos, " Just Read The Instructions.

Or maybe you meant something else?
 
Apr 12, 2020
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It was just awesome. Scientists have done such an awesome job using eROSITA instrument. Hope these kind of researches go more further and give us an exceptional result which will go beyond our imagination...
 
Feb 3, 2020
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At the risk of showing my ignorance (again/still), is there a chance one of these points of "light" has been traveling since the BB? If so, is it possible one of the x-ray emissions is approaching the "edge" of the known universe?

Here's the question: What is the current thinking about what happens when x-ray radiation hits the boundry (if that's even the right word) of the universe?
 
Dec 19, 2019
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The cosmic background radiation observations cover the whole sky and is usually presented in an all-sky Mollweide projection [ https://en.wikipedia.org/wiki/Cosmic_microwave_background#Microwave_background_observations ].

The eROSITA is also all-sky and presented similarly, see the image. It is a map "of X-ray radiation from all across the cosmos, " Just Read The Instructions.

Or maybe you meant something else?
All I had to do to come up with this implied promotion was to read the title of the article.
 

AJW

Jul 9, 2020
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At the risk of showing my ignorance (again/still), is there a chance one of these points of "light" has been traveling since the BB? If so, is it possible one of the x-ray emissions is approaching the "edge" of the known universe?

Here's the question: What is the current thinking about what happens when x-ray radiation hits the boundry (if that's even the right word) of the universe?
KC, the light from any of these sources will never reach this boundary you refer to, because the expansion of the universe prevents this.
 
Dec 19, 2019
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KC, the light from any of these sources will never reach this boundary you refer to, because the expansion of the universe prevents this.
Based on the current cosmology, there universe has no boundary. The condition of the universe is evolving. Because of this universal evolution, while the energy is the consistent with the what was around since the Bg Bang, its condition of this energy in existence now includes development of planets, stars, solar systems, galaxies, nebulas, supe galaxy clusters, and so on.
 
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Thank you, gentlemen, for your replies.

I was afraid the Expanding Universe would be the answer. I struggle a bit with that concept. But, no matter, I gather that there is currently no credible alternative to the Expanding Universe that can explain our observations.

The idea that nothing is being displaced as the universe expands does not fit well with my limited observations on the planet earth. Same holds for the ultimate contraction.
 
At the risk of showing my ignorance (again/still), is there a chance one of these points of "light" has been traveling since the BB? If so, is it possible one of the x-ray emissions is approaching the "edge" of the known universe?



Here's the question: What is the current thinking about what happens when x-ray radiation hits the boundry (if that's even the right word) of the universe?
Thank you, gentlemen, for your replies.



I was afraid the Expanding Universe would be the answer. I struggle a bit with that concept. But, no matter, I gather that there is currently no credible alternative to the Expanding Universe that can explain our observations.



The idea that nothing is being displaced as the universe expands does not fit well with my limited observations on the planet earth. Same holds for the ultimate contraction.
The linked press release from Max Planck mentions seeing "active galactic nuclei, accreting supermassive black holes at cosmological distances," but does not give redshift (the astronomer way to give distances). I dunno about the X ray observatory technology but at a guess they will need to compare the active galactic nuclei sources with optical astronomy maps in order to get redshift. I also think that X-rays are easily occluded by dust, so they won't see as far as say infrared astronomy which may penetrate dust [the technology of the upcoming far seeing James Webb telescope].

On the question of geometry, since you mention "the known universe", this can be understood several complementary ways. The universe has a geometry that may or may not have a boundary and that universe may be "known" in many ways, and at the same time the light that reaches an observer has traveled in a geometry that may have a boundary - the observable universe.

The distance that the oldest light reaches us makes a vast, expanding shell, and oddly enough expansion will maximize its radius eventually [ https://en.wikipedia.org/wiki/Observable_universe ].

The "known" universe is largest in the models that explain the observations we see - the data and physics we know about - and is right now ~ 10 million times larger in volume than the volume that is spanned by the light reaching us today. If observations improve, we will know more - since space seems to be average perfectly flat the universe may be infinite.

So, having already mentioned that distant light reaching us travels in expanding space we should recognize that it isn't easy to keep track of the many ways we can define cosmological distance and expansion [ http://www.astro.ucla.edu/~wright/cosmo_02.htm#DH ]. But here is the nut: space expands and it is all what it does in the terms of the general relativity that describes space (and time) [ https://en.wikipedia.org/wiki/Expansion_of_the_universe#Scale_factor ].

TL;DR: One reason that "that nothing is being displaced as the universe expands" may not fit well is that such a thing does not happen - if you think space expands in something preexisting that somehow is and isn't space. * Or you are literary understanding that nothing is displaced since space doesn't occupy something outside itself** - after all, the universe is all there is, literary.

* You often see this misunderstanding, even after a century of big bang cosmology, in that some think the universe started out from some 'location' and/or 'exploded'. The better way to state it is that the hot big bang happened everywhere, however large a volume that was, at the same time. "Big Bang was a place in time, not in space" is a modern meme describing that.

** This is expressed in general relativistic models of the universe, they are self contained.
 
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All I had to do to come up with this implied promotion was to read the title of the article.
"New map of the universe unveils a stunning X-ray view of the cosmos". Obviously we agree on that, I referred to it as "a map "of X-ray radiation from all across the cosmos," excerpted from the article.

I was questioning why you don't "see how" that is, and why you think an all-sky map is a picture "from one direction". In the answer to KC you seem to recognize at least some of the geometry of the universe, so I'm even more at a loss trying to grok your questioning and your stated rationale.
 
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Our understanding of [this] universe keeps growing as our ability to see the environment of space continues to develop. Our views of the universe is severally curtailed by our technological prowess. It has been a scant 60 years since the beginning of modern astronomy, but what would be like when it turns 120 years young? What will astronomy look like then and what will the images of [this] universe look like. Three D? Holographic ? Will we see the BB itself. Will we have a radio telescope on Luna? Will we have an observatory on Mars? In the Star Wars movie, the Clone Wars, Master Yoda uses a holographic map of the quadrant n order to find a lost planet. Will we have a 6000, 100,000, or a 1million mega pixel camera for astronomy?
 
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Thank all of you for your thoughtful commentary. I was about to ask the semi-serious question: Is the universe expanding to make room for the radiation emanating from the BB or does the radiation keep traveling because the universe is expanding?

But, I've thought better of it. Instead I ask the following:


The "known" universe is largest in the models that explain the observations we see - the data and physics we know about - and is right now ~ 10 million times larger in volume than the volume that is spanned by the light reaching us today. If observations improve, we will know more - since space seems to be average perfectly flat the universe may be infinite.
If the universe is at least the size described above, wouldn't the expansion have to be faster than the speed of light?

Our understanding of [this] universe keeps growing as our ability to see the environment of space continues to develop. Our views of the universe is severally curtailed by our technological prowess. It has been a scant 60 years since the beginning of modern astronomy, but what would be like when it turns 120 years young? What will astronomy look like then and what will the images of [this] universe look like. Three D? Holographic ? Will we see the BB itself. Will we have a radio telescope on Luna? Will we have an observatory on Mars? In the Star Wars movie, the Clone Wars, Master Yoda uses a holographic map of the quadrant n order to find a lost planet. Will we have a 6000, 100,000, or a 1million mega pixel camera for astronomy?

Your points are well taken. I look forward to the technological improvements. The universe is quite a complex thing to try and understand with limited tools. I applaud the great work do so far.
 
Thank all of you for your thoughtful commentary. I was about to ask the semi-serious question: Is the universe expanding to make room for the radiation emanating from the BB or does the radiation keep traveling because the universe is expanding?

But, I've thought better of it. Instead I ask the following:

Torbjorn Larsson said:
The "known" universe is largest in the models that explain the observations we see - the data and physics we know about - and is right now ~ 10 million times larger in volume than the volume that is spanned by the light reaching us today. If observations improve, we will know more - since space seems to be average perfectly flat the universe may be infinite.
If the universe is at least the size described above, wouldn't the expansion have to be faster than the speed of light?
The first question is cool, partly because it is conceptually easier to respond to and partly here because it helps set the scene for the second question.

What effectively starts - dominates the start of - the expansion is the slow roll inflation field [Planck collaboration, 2018]. "Inflation puts the bang in big bang." But, as say Susskind's MOOC on cosmology tell us, the rate of expansion will depend on the inner state of the universe [ https://en.wikipedia.org/wiki/Scale_factor_(cosmology) ]. Since it is a gravitational controlled process Susskind illustrates it with a thrown ball parabola during the eras when mass dominated, which gets modified depending on the inner physics: the radiation dominated era at the start of the hot big bang was "super parabolic" since the expansion stretch photons (but not the model gas during the subsequent matter domination). Now of course dark energy dominates, so expansion goes like an exponential, same as during inflation but much slower.

TL;DR: Primarily it is the ongoing expansion that makes radiation stretch (cosmic background radiation cool) while it travels. But due to it dominating at one time the radiation had through its properties some say at one brief time (up until some 10 kyrs after hot big bang, IIRC) on how fast the expansion goes.

On to the 2nd question: The universal speed limit - the speed of light in vacuum - is a property that local observers can measure. Say, when a photon passes an observer. It doesn't apply to objects that are moved long distances away. So a global expansion between distant galaxies that is 10^-10 parts per year, 0.1 nm per meter and year, can add up to expansion rates that surpass an average speed at the universal speed limit and go on to increase indefinitely high indefinitely far away and/or indefinitely far into the future. None of that breaks relativity, which is why we can have a general relativistic cosmology [ https://en.wikipedia.org/wiki/Lambda-CDM_model ].

But there is a caveat: An inflationary big bang cosmology gives us a homogeneous, isotropic universe (to 10^-5 parts fluctuations, according to the cosmic background radiation) which a hot big bang universe would not (it would be messy) - inflation was a perfectly empty and cold universe (with quantum fluctuations that later gave the 10^-5 part fluctuations during hot big bang). To be such the expansion had to be what in thermodynamics is called adiabatic, a cooling one, and that meant that the expansion messed with causal signals or at least the fluctuations, also called perturbations, in the inflation field in a complicated manner [ https://en.wikipedia.org/wiki/Inflation_(cosmology) ]*. We see cosmic background radiation which is the same when we look at opposite directions despite that these volumes no longer is in what in relativity is called causal contact - they don't communicate with light radiation to even temperatures (say) out - but they had to be in such contact at one time.


The physical size of the Hubble radius (solid line) as a function of the linear expansion (scale factor) of the universe. During cosmological inflation, the Hubble radius is constant. The physical wavelength of a perturbation mode (dashed line) is also shown. The plot illustrates how the perturbation mode grows larger than the horizon during cosmological inflation before coming back inside the horizon, which grows rapidly during radiation domination. If cosmological inflation had never happened, and radiation domination continued back until a gravitational singularity, then the mode would never have been inside the horizon in the very early universe, and no causal mechanism could have ensured that the universe was homogeneous on the scale of the perturbation mode.

TL;DR: Universe expansion does not break relativity, it is in fact a consequence of relativity in the sense that it is a possibility that can be made explicit in general relativity modeling space. And despite that there was a time when expansion messed with perturbations and their causal "reach" since that is why the universe is smooth.

*I'm simplifying a *lot* here, and I'm no expert. For instance, perturbations are not particles of a causal signal, and since inflation was a scalar field like Higgs it gave its particles mass - massive particles don't travel at universal speed limit - but OTOH they were not there - "cold and empty space" - and so on, and so on. It is here that quantified models comes in and makes things easier to grok. But the result is clearer.
 
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