The picture feels especially surprising because of the fuzzy contours and transparency that do not fit the sharp stars. Keep in mind that the image is a superposition of an image in some radiowave frequency range (fuzzy either because of different sensor/tech/frequency range), superimposed to a normal image in visible spectrum with very different actual resolution.
> The ghostly ORC1 (blue/green fuzz) on a backdrop of the galaxies at optical wavelengths.
Astronomical radio images are naturally overwhelmingly sharper than optical images, because radio telescopes today can have much larger apertures than optical telescopes.
The best-resolution optical images are made with two large telescopes and a temperature-controlled optical fiber from each one, arranged to interfere optically, yielding an image resolution equivalent to a mirror the size of the distance between the telescopes as the visual field is scanned on each simultaneously to sample pixels of the image, in sequence.
The electromagnetic interference operation must be conducted purely optically because we are not equipped to sample and record time-registered electromagnetic signals at 1 trillion samples per second. (Yet. It is possible in principle, it just hasn't been achieved.)
In contrast, output from radio telescopes can be sampled and recorded with careful time registration, and the samples interfered numerically, so signals from radio telescopes thousands of miles apart can be treated together, yielding images of overwhelmingly finer detail. Even when using just a single radio telescope, a reflector dish can be made much larger than any practical earthbound optical mirror.
So, if a radio-telescope image is indistinct, it is likely that the object imaged is itself indistinct.
The recent image of a black-hole accretion disc was composed from radio-telescope traces. No optical treatment could produce an image of such resolution.
>Astronomical radio images are naturally overwhelmingly sharper than optical images, because radio telescopes today can have much larger apertures than optical telescopes.
They can be higher resolution with very long baseline interferometry but I wouldn't say they are naturally higher. If I'm reading the article correctly these were collected by the ASKAP telescope array in Australia which has a resolution of 30 arcseconds at 1.4GHz [1], which is only about twice as good as the human eye.
To your point, though, when VLBI is used they can get ridiculous levels of resolution. M87 was imaged at tens of microarcseconds of resolution, which is 4-5 orders of magnitude better than any optical telescope in operation today.
Wanted to follow up to say how ridiculous a microarcsecond is. It's approximately equal to 5e^-12 in radians, which at this level is approximately the ratio of width to distance.
So, for example, it's like seeing a hydrogen atom from 7 meters away. Or a red blood cell from 400km away.
> The ghostly ORC1 (blue/green fuzz) on a backdrop of the galaxies at optical wavelengths.