
Our deepest view of the X-ray sky - xioxox
http://www.mpe.mpg.de/7461761/news20200619
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gattr
"But wait, how can you perform telescopic observations in X-rays? They tend to
penetrate matter (including telescopes), right?"

Correct, normal optics would not work. X-ray telescopes use grazing incidence
mirror arrangement (Wolter telescope [1] [2]).

[1]
[https://en.wikipedia.org/wiki/Wolter_telescope](https://en.wikipedia.org/wiki/Wolter_telescope)

[2]
[https://en.wikipedia.org/wiki/EROSITA](https://en.wikipedia.org/wiki/EROSITA)

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xioxox
I'm a scientist on the team who did this (I actually helped put this picture
together), so I can try to answer questions...

~~~
spodek
I helped build and calibrate XMM, earning my PhD
[https://www.researchgate.net/publication/252418991_The_X-
ray...](https://www.researchgate.net/publication/252418991_The_X-
ray_observational_satellite_XMM_its_spectrometer_and_observations_of_supernova_remnants)
in the 90s, before leaving academia to start my first company.

I haven't kept track of the field. Has eROSITA reproduced most of XMM's data?
I expect XMM will keep collecting data, but how useful/obsolete has it become?

~~~
xioxox
XMM is still extremely useful. There was a recent report that using clever
techniques ESA are going to keep it going for another 10 years:
[https://www.esa.int/Enabling_Support/Operations/Teaching_an_...](https://www.esa.int/Enabling_Support/Operations/Teaching_an_old_satellite_new_tricks)

XMM has a smaller field of view than eROSITA, but more light gathering
capability (effective area), particularly at higher energies. It also has
different types of instruments, such as the X-ray gratings.

eROSITA is really designed for doing surveys with its wide unobstructed field
of view, and it will be doing just that for the next 3.5 yrs. We really need
XMM to follow up in detail the most interesting sources we discover during the
survey.

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xioxox
The eROSITA telescope onboard the SRG observatory has completed its first
survey of the sky in X-rays, producing the deepest ever map in X-rays and
finding over a million sources. Most of these sources are active black holes,
clusters of galaxies, supernova remnants and stars.

Annotated and high res images can be found here:
[http://www.mpe.mpg.de/7461950/erass1-presskit](http://www.mpe.mpg.de/7461950/erass1-presskit)

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staycoolboy
This just blew my mind, from the fifth image:

"Vela Junior was discovered just 20 years ago, although this object is so
close to Earth that remains of this explosion were found in polar ice cores."

Aside from being some serious Hurcule Poirot meets Kip Thorne crossover stuff,
I want to ask "How do we know?" but I'm pretty sure I wouldn't understand the
answer.

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ncmncm
Imagine a whole article about high-energy astronomy never even mentioning
plasma or synchrotron radiation.

Trotted out "hot gas", though.

~~~
ncmncm
I am mistaken: "plasma" appears once in a hidden caption I missed first time
through.

~~~
xioxox
I'm not sure why you're bringing up synchrotron radiation in particular.
Although it's important for some sources, it's not driving the majority of
what is being seen here. Comptonization is important for active black holes.
The radiation from the milky way has strong emission lines - it's not a
synchrotron spectrum. Mostly thermal emission is emitted from clusters of
galaxies. There are a lot of different emission processes to consider in
astrophysics.

~~~
ncmncm
If, as you say, there are a lot of different emission processes, why only ever
mention the, by far, least interesting? Elsewhere in science exceptions are
interesting. The unexplained is interesting.

Lev Landau is reputed to have said, "Cosmologists are often in error, never in
doubt." Doubt is productive.

