The headline was going to be 'bursting with' (not 'surrounded by') but that phrase is too sensational.
M82 is known as a starburst galaxy which suggested 'bursting.'
M82 in its X-ray image has its core and disk surrounded by many X-ray sources, which all look like stars in optical, in many directions.
There are two news stories about M82 using Chandra images but the two stories are remarkable in comparison.
The attached Chandra story (2011) has a wide angle image around M82.
This new deep Chandra image reveals hundreds of point-like X-ray sources, some of which likely contain black holes.
Supernova explosions have produced bubbles of hot gas that extend millions of light years away from the plane of the galaxy.
Valid or not, the huge 'bubbles' suggest the Fermi bubbles of our Milky Way.
I cannot recall any supernovae creating bubbles of hot gas that extend beyond their galaxy. Atoms in a gas can do only emission lines which I expect can never reach the X-ray frequency energy.
Cosmologists propose those distant sources as likely black holes but I expect they have no alternate suggestion.
This image shows M82 galaxy literally in the middle of many scattered X-ray sources. There is no explanation offered for this observation. Instead, a 'brush with M81 set off this torrent of star formation' in M82, a starburst galaxy. That 'brush' refers to only stars forming in M82 not those out in the wide space around it.
My simple summary of these X-ray sources in the image:
There are several near the core, and 3 in a line which in optical are in the galactic disk, but the rest of the hundreds are outside the halo and disk.
Most of those well outside the core have the same intensity as those near the core implying these sources are the same type of object.
Noticing 3 of them are in the disk could suggest they are just a few unusual stars intense in X-ray. That coincidence fails with similar sources found both above and below the disk and the rest are in an almost random distribution in space.
The NASA story (2010) titled 'Starburst Galaxy M82' emphasizes its Chandra X-ray image (with the story) which shows two possible black holes at the core but says nothing about the many sources surrounding the galaxy.
An excerpt from its caption:
The pullout is a Chandra image that shows the central region of the galaxy and contains two bright X-ray sources -- identified in a labeled version -- of special interest.
This pullout is a zoom into the core but this pullout hides many of those sources surrounding M82. This placement could be either accidental or intentional. With the explicit 'special interest' this placement seems intentional.
I did not select this NASA story and its image for this post because the core is not of special interest. The text offers much detail about the analysis of the black hole pair, not to be discussed here.
excerpt from Wikipedia:
In the core of M82, the active starburst region spans a diameter of 500 pc. Four high surface brightness regions or clumps (designated A, C, D, and E) are detectable in this region at visible wavelengths. These clumps correspond to known sources at X-ray, infrared, and radio frequencies.
The Chandra X-ray Observatory detected fluctuating X-ray emissions from a location approximately 600 light-years away from the center of M82. Astronomers have postulated that this fluctuating emission comes from the first known intermediate-mass black hole, of roughly 200 to 5000 solar masses.M82, like most galaxies, hosts a supermassive black hole at its center with a mass of approximately 3 x 10^7 solar masses as measured from stellar dynamics.
My summary of the pullout image:
The core consists of one very bright source (X1), 3 sources (X3) in a pyramid to its left and another bright source (X2) at a distance in the 4 o'clock direction, having another dimmer source nearly adjacent to it.
An intermediate source (X4) is below the pyramid in the active cloud.
An intermediate source (X5) is below the core in the active cloud.
There are about 11 other slightly dimmer sources scattered about the 4 in their close bunch (called X1+X3 here).
My summary might have some similarities but I could find no image identifying the A, C, D, E clumps mentioned. The set of [ A=X1 + X3, C=X4, D=X5, E = intense cloud left of X3 ] is one possibility. This galaxy has distorted arms so perhaps some of that distortion is in the line of sight with the core. The core explanation is not the main topic of this post.
The pulsar is probably X2 but the image has no scale to check 600ly.
From the messier-objects-com site: 'The pulsar in M82 was given the designation M82 X-2. Its luminosity is 100 times greater than its mass should be able to produce, in theory. The pulsar is classified as an ultraluminous X-ray source (ULX).'
In this post I will ignore the M82 pulsar. Thornhill has a video about neutron stars and pulsars.
One possible quest for the M82 core: Could it resemble that of a spiral galaxy?
excerpt from Wikpedia:
M82 was previously believed to be an irregular galaxy. In 2005, however, two symmetric spiral arms were discovered in near-infrared (NIR) images of M82.
If the galaxy is rotating then it should have a magnetic field around the electric current through its axis, like in the Milky Way.
If there is a Z pinch with a birkelund filament pair in M82, there is no evidence in the images. However there is not a good X-ray image of the Milky Way core. There are images of its pairs of 'bubbles' or 'chimneys' but the Z pinch with its pair of electric currents is not an actual object. Images of the Milky Way core reveal many stars in chaotic motion among clouds of gas and dust. The distribution in the M82 core looks chaotic.
The M82 core shows many lobes not just two.
Back to the attached image with its own special interest ...
The big unknown is what are these many X-ray sources? They look like stars but are far brighter than the normal stars in M82 and its normal stars not bright in X-ray.
The other known X-ray point sources (not a fictional black hole ) are either
1) synchrotron radiation from electrons changing direction in a magnetic field, but this combination is unlikely at a great distance from a galaxy, or
2) a plasmoid.
A plasmoid could be the better selection because one was observed in M87 while stars which are very strong X-ray sources while at a remote distance from a galaxy are not observed with the unique exception of hundreds somewhat near M82 and no other galaxy.
The obvious mystery for both a black hole or a plasmoid is:
why do they have the observed random distribution?
For both, their formation out in intergalactic space is unlikely, so they must have moved there from wherever they formed. An undefined 'brush by' is not an adequate explanation.
An ejection requires an undefined mechanism but modern cosmologist have readily proposed the random interactions among a small number of bodies held loosely by gravity can result in an ejection just by the small system's chaos.
I am not suggesting that here. I am only pointing out ejecting a body out of a system is a well known scenario for many contexts including our solar system when checking the limits for its long term stability after a perturbation.
Candidates for ejections from the core, using the color image in the attached,are possibly found:
at 12 o'clock is a separated pair, 1 solitary bright source above the cloud while at 6 o'clock is a bright source in the red cloud.
at 1 o'clock there are 2 in line with the first at the edge of the red cloud.
at 2 o'clock there are 3 with a pair at the edge and the third distant.
at 4 o'clock there are 3 in line, in the disk, with the last as the brightest.
at 5 o'clock there are 3 in line, with the first in the cloud.
at 6 o'clock there are 2 in line with the core, with the closer part of a pair.
at 10 o'clock there are 3 in line with the core, with the first as the brightest and the middle as red.
These 18 could be just coincidences among what seems a random pattern.
The other coincidence is all of the most distant sources have another source between them and the core.
I find the coincidences, contrived or not, worth noting. Randomness is not a good start.
Astronomers are obsessed with black holes in general but are unconcerned about many spread across a wide area surrounding M82.
The observation of hundreds of sources around M82 is significant and needs a viable explanation.
The big question, after discovering these images of M82 is: how common are strong X-ray point sources in the space far between galaxies??
I suspect the number is extremely low.
M82 is sometimes considered relatively close to M81 but their distance is very roughly 300 kly
M82 and its vicinity presents a fascinating mystery.
Before I conclude, another observation is necessary.
The Wikipedia topic for M82 provides a high resolution image.
In my opinion, there is material from the core in an 11 o'clock direction. There is also material in the opposite direction from the core. For both, the material has structure and is not an amorphous cloud. The red is probably hydrogen gas clouds found through atoms with their specific emission line while the brown is probably dust clouds.The image suggests these closer gas and dust clouds rotate with the stellar disk behind them.
M82 is a very interesting galaxy (an irregular type). Its periphery is as well.