Starship Asterisk*

The X-Ray Sky from eROSITA

Explanation: What if you could see X-rays? The night sky would seem a strange and unfamiliar place. X-rays are about 1,000 times more energetic than visible light photons and are produced by violent explosions and high temperature astronomical environments. Instead of the familiar steady stars, the sky would seem to be filled with exotic stars, active galaxies, and hot supernova remnants. The featured X-ray image captures in unprecedented detail the entire sky in X-rays as seen by the eROSITA telescope onboard Spektr-RG satellite, orbiting around the L2 point of the Sun-Earth system, launched last year. The image shows the plane of our Milky Way galaxy across the center, a diffuse and pervasive X-ray background, the hot interstellar bubble known as the North Polar Spur, sizzling supernova remnants such as Vela, the Cygnus Loop and Cas A, energetic binary stars including Cyg X-1 and Cyg X-2, the LMC galaxy, and the Coma, Virgo, and Fornax clusters of galaxies. This first sky scan by eROSITA located over one million X-ray sources, some of which are not understood and will surely be topics for future research.

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I wonder what's the radius of the view shown here (360deg around).. i.e. Objects from how far distance are covered in this view..

shaileshs wrote: ↑Tue Jun 23, 2020 4:37 am I wonder what's the radius of the view shown here (360deg around).. i.e. Objects from how far distance are covered in this view..

The image is a projection of an all-sky survey. It shows every direction in the sky. There is no distance limit in the image.

Fascinating!

The first thing I saw in the picture at left was the bright blue-white source just above center. This is, as you can see in the annotated image at right, Sco X-1.

Wikipedia wrote:

Scorpius X-1 is an X-ray source located roughly 9000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest apparent source of X-rays in the sky.
...
Scorpius X-1 itself is a neutron star whose intense gravity draws material off this companion into an accretion disk, where it ultimately falls onto the surface, releasing a tremendous amount of energy. As this stellar material accelerates in Scorpius X-1's gravitational field, X-rays are emitted. The measured luminosity for Scorpius X-1 is consistent with a neutron star which is accreting matter at its Eddington limit.

This system is classified as a low-mass X-ray binary; the neutron star is roughly 1.4 solar masses, while the donor star is only 0.42 solar masses. The two stars were probably not born together; recent research suggests that the binary may have been formed by a close encounter inside a globular cluster.

Wow!!!















The huge X-ray bubble north of the plane of the Milky Way, called the North Polar Spur, reminds me very much of the gamma ray bubbles, called Fermi bubbles, detected on both sides of the Milky Way by the Fermi Gamma-Ray Space Telescope. As you can see in the illustration below, the Fermi bubbles contain not only gamma rays but X-rays too.

Surely the X-ray North Polar Spur and the gamma ray Fermi bubbles must be connected?

Interesting image... it reminds me of a closed clam shell... could we be... "The Clam Shell Galaxy"?

And to our far right... India...

:---[===] *

Interesting picture! Curious hoe LMC got in but SMC didn't!

I wonder what Superman would see if he looked through a telescope? I can see a future comic book storyline where a team of astronomers utilise Superman to discover x-ray pulsars.

In looking at the x-ray view on today's APOD, does anyone think that space travel could ever be possible since the turbulence would seem to preclude it?

drbuck917@gmail.com wrote: ↑Tue Jun 23, 2020 2:12 pm In looking at the x-ray view on today's APOD, does anyone think that space travel could ever be possible since the turbulence would seem to preclude it?

Everything you're seeing is coming from material that, in the lab, would be treated as a hard vacuum. The turbulence is taking place in most tenuous of gas, over a scale of thousands of light years. It would require the most sensitive of instruments to even know you were in it.

MarkBour wrote: ↑Tue Jun 23, 2020 5:28 am

shaileshs wrote: ↑Tue Jun 23, 2020 4:37 am I wonder what's the radius of the view shown here (360deg around).. i.e. Objects from how far distance are covered in this view..

The image is a projection of an all-sky survey. It shows every direction in the sky. There is no distance limit in the image.

If you mean the view is of entire sky "visible" to the observing camera (billions of years in any/every direction) ? If so, I wonder if the objects are placed in right scale? I mean, some objects might be only 1000s of light years away and some might be millions or billions light years away.. e.g. Orion nebula shown soooooooo far away from center giving a feeling as if it's millions/billions of light years away.. ? I guess I'm missing something.

shaileshs wrote: ↑Tue Jun 23, 2020 3:19 pm

MarkBour wrote: ↑Tue Jun 23, 2020 5:28 am

shaileshs wrote: ↑Tue Jun 23, 2020 4:37 am I wonder what's the radius of the view shown here (360deg around).. i.e. Objects from how far distance are covered in this view..

The image is a projection of an all-sky survey. It shows every direction in the sky. There is no distance limit in the image.

If you mean the view is of entire sky "visible" to the observing camera (billions of years in any/every direction) ? If so, I wonder if the objects are placed in right scale? I mean, some objects might be only 1000s of light years away and some might be millions or billions light years away.. e.g. Orion nebula shown soooooooo far away from center giving a feeling as if it's millions/billions of light years away.. ? I guess I'm missing something.

No distance scale exists in this image. Every point on it corresponds with a coordinate in the sky. I believe this data is multi-channel, so the color and intensity of each pixel represents wavelength (energy) and intensity information from that point in the sky. The distance to any source cannot be determined from this data. Some sources are inside our galaxy, some are outside it.

Chris Peterson wrote: ↑Tue Jun 23, 2020 2:18 pm

drbuck917@gmail.com wrote: ↑Tue Jun 23, 2020 2:12 pm
In looking at the x-ray view on today's APOD, does anyone think that space travel could ever be possible since the turbulence would seem to preclude it?

Everything you're seeing is coming from material that, in the lab, would be treated as a hard vacuum. The turbulence is taking place in most tenuous of gas, over a scale of thousands of light years. It would require the most sensitive of instruments to even know you were in it.

Turbulence (& the stretching of trailing galactic arms by variable "RPM" rotation) stretch & narrow magnetic field bundles as well as the HII plasma regions in which it is embedded.

This distribution of X-rays follows the same lines of the magnetic field and the Gamma Rays and, as can be seen, both detected and unconfirmed bubbles emitted by the galactic center are guessed, such as the 90º disk that the galaxy has with the Solar System in its intersection with the galactic disk. -

orin stepanek wrote: ↑Tue Jun 23, 2020 12:01 pm Interesting picture! Curious hoe LMC got in but SMC didn't!

And not Andromeda, either.

Ann

shaileshs wrote: ↑Tue Jun 23, 2020 3:19 pm

MarkBour wrote: ↑Tue Jun 23, 2020 5:28 am

shaileshs wrote: ↑Tue Jun 23, 2020 4:37 am I wonder what's the radius of the view shown here (360deg around).. i.e. Objects from how far distance are covered in this view..

The image is a projection of an all-sky survey. It shows every direction in the sky. There is no distance limit in the image.

If you mean the view is of entire sky "visible" to the observing camera (billions of years in any/every direction) ?
...

Yes.
And then the rest of your question indicates that perhaps you aren't too familiar with this kind of image, so rather than answer your questions, here are a couple of starting points.

First, there's a Wikipedia page on eROSITA: https://en.wikipedia.org/wiki/EROSITA. Near the top of that article is a lovely video that shows an overview of the mission. The satellite that is carrying this instrument is slowly spinning and over a period of the last six months has looked in every direction, mapping out a sphere of data. It is looking in every direction and telling us where it sees X-rays in the sky.

Now, if we could do it (perhaps if everyone had VR equipment), then APOD could just give you a sphere of data and you would see that the data is all around you. When you're looking in the direction of the Large Magellanic Cloud (LMC), you'd see some X-rays. If you're looking in the direction of Sco X-1, you'd see a bright X-ray source. As the APOD caption has informed us, the mission has just made a high-resolution map that has located around 1.1 million X-ray sources in the sky!

Second, since we can't look at the sphere of data, this APOD has used a projection of that sphere onto a flat page. The problem of doing this is the same problem as one has in trying to map the surface of the Earth onto a flat page. And so the solutions match as well. I think many sky surveys are plotted in a manner like the Mollweide projection (Wikipedia: Mollweide projection).

So, the entire image is a map of different directions. No point on the map represents "us", and no point is closer or farther from us. Things that are far apart on the map, are far apart because they are far apart angularly, not in distance from one another. But even this is not faithful, because the edges of the projection will wrap around to the opposite side. If an X-ray source A is spread over a wider area of the sky than an X-ray source B, then A should appear larger than B in this map.

orin stepanek wrote: ↑Tue Jun 23, 2020 12:01 pm
Interesting picture! Curious [how] LMC got in but SMC didn't!

Recent star formation in the SMC has led to a large population of massive stars and high-mass X-ray binaries (HMXBs) similar to Cygnus X-1 which are the brightest persistent sources of hard X-rays—those with energies from about 30 up to several hundred keV but which are relatively faint in eROSITA soft X-rays (0.3 - 10 keV).

https://en.wikipedia.org/wiki/Cygnus_X-1 wrote:
<<Though highly and erratically variable, Cygnus X-1 is typically the brightest persistent source of hard X-rays—those with energies from about 30 up to several hundred keV—in the sky. The X-rays are produced as lower-energy photons in the thin inner accretion disk, then given more energy through Compton scattering with very high-temperature electrons in a geometrically thicker, but nearly transparent corona enveloping it, as well as by some further reflection from the surface of the thin disk. An alternative possibility is that the X-rays may be Compton scattered by the base of a jet instead of a disk corona.>>

https://en.wikipedia.org/wiki/Small_Magellanic_Cloud#X-ray_sources wrote:
<<No hard X-rays above background were picked up from either Magellanic Cloud during the September 20, 1966, Nike-Tomahawk rocket flight nor that of two days later. The LMC was not detected in the X-ray range 8–80 keV. Another rocket flight was launched from same atoll at 11:32 UTC on October 29, 1968, to scan the LMC for soft X-rays. The first discrete X-ray source in Dorado was at RA 05h 20m Dec −69°, and it was the Large Magellanic Cloud. This X-ray source extended over about 12° and is consistent with the Cloud. Its emission rate between 1.5–10.5 keV for a distance of 50 kpc is 4 x 10³¹W.

An X-ray astronomy instrument was carried aboard a Thor missile launched from the same atoll on September 24, 1970, at 12:54 UTC and altitudes above 300 km, to search for the Small Magellanic Cloud and to extend observation of the LMC. The source in the LMC appeared extended and contained star ε Dor. The X-ray luminosity (Lx) over the range 1.5–12 keV was 6 × 10³¹W. The SMC was detected with an X-ray luminosity of 5×10³¹W in the range 1.5–12 keV, and 25×10³¹W in the range 5–50 keV for an apparently extended source.

The Small Magellanic Cloud contains a large and active population of X-ray binaries. Recent star formation has led to a large population of massive stars and high-mass X-ray binaries (HMXBs) which are the relics of the short-lived upper end of the initial mass function. The young stellar population and the majority of the known X-ray binaries are concentrated in the SMC's Bar. HMXB pulsars are rotating neutron stars in binary systems with Be-type (spectral type 09-B2, luminosity classes V–III) or supergiant stellar companions. Most HMXBs are of the Be type which account for 70% in the Milky Way and 98% in the SMC. The Be-star equatorial disk provides a reservoir of matter that can be accreted onto the neutron star during periastron passage (most known systems have large orbital eccentricity) or during large-scale disk ejection episodes. This scenario leads to strings of X-ray outbursts with typical X-ray luminosities Lx = 0.1-1.0 ×10³¹W, spaced at the orbital period, plus infrequent giant outbursts of greater duration and luminosity.>>

shaileshs wrote: ↑Tue Jun 23, 2020 3:19 pm

MarkBour wrote: ↑Tue Jun 23, 2020 5:28 am

shaileshs wrote: ↑Tue Jun 23, 2020 4:37 am I wonder what's the radius of the view shown here (360deg around).. i.e. Objects from how far distance are covered in this view..

The image is a projection of an all-sky survey. It shows every direction in the sky. There is no distance limit in the image.

If you mean the view is of entire sky "visible" to the observing camera (billions of years in any/every direction) ? If so, I wonder if the objects are placed in right scale? I mean, some objects might be only 1000s of light years away and some might be millions or billions light years away.. e.g. Orion nebula shown soooooooo far away from center giving a feeling as if it's millions/billions of light years away.. ? I guess I'm missing something.

Thank you Mark and Chris for your explanation. It helped.

Less than a year ago the Fermi Bubble were big news. I was amazed to see them here prominently, but wholly uncommented, without noting!