Source: https://www.nature.com/articles/d41586-022-01320-y Black hole at the centre of our Galaxy imaged for the first time The Event Horizon Telescope network has captured the second-ever direct image of a black hole — called Sagittarius A* — at the centre of the Milky Way. . . . It would be hubris to the max for anyone, species, planet, or solar system to claim a black hole is theirs. Bob Wilson
At least this article didn't photo-chop in some fake background stars, as did one of the network TV news shows I saw last night. Some also did this back when the M87 black hole image was released. If they don't want to be called 'fake news', they really need to stop displaying some blatant fakes just to make things look more pretty.
Will Webb even be able to see it? We can't see it in optical bands due to intervening dust and gas clouds. IR sees through some of that, but not all. EHT is a radio telescope consortium, not optical or IR. I'm seeing Webb's sensors as observing various infrared wavelengths from 0.6 to 27 μm. EHT is working at 1.3 mm, and planning to move up (in frequency) to 0.87 mm. That is quite a big gap between them.
Three orders of wave length and the exponential energy as a function of wavelength… darn! Guess we might have a clue about ‘dark matter.’ I am not sure but S. Hawkins might have postulated about black holes and dark matter effects. Bob Wilson ps. Pure speculation but photons barely escaping a black hole may achieve a virtual acceleration. As their distance from the gravitational attraction increases, shorter wavelength. PURE SOPHISTICATION !!!
Don't give up yet. I don't know the answer either. One subsequent 'news' item says Webb will look at it, but comes from an unfamiliar source and provides scanty detail. Less than two orders from MIRI's long end. Photon energy is directly proportional to frequency, or inversely proportional to wavelength. See one of Planck's equations: E = hc/λ But we are looking for transparent vs opaque band windows, not raw photon energy. No, it doesn't work that way. The photons emitted near the BH are starting very deep in a gravitational well. They experience gravitational red-shift to longer wavelengths as they climb out of that well. The surfaces of neutron stars are also deep down in a gravitational well, just not as deep as the event horizon of a BH. I seem to remember reading, some years back, that astronomers had been able to get some information about the atmosphere of a neutron star, by studying the atomic absorption lines in the gravitationally redshifted light emitted by thermonuclear flares on the surface and passing through that atmosphere. After a bunch of infalling hydrogen (obtained by devouring the outer envelope of a companion star) collects on the surface of these stars, it can ignite into nuclear fusion. These events are flares, not momentary flashes like our hydrogen bomb weapons, but sustained hydrogen burning like we have long been working on for fusion power, though at bomb-level power outputs. What blew my mind was that the 'atmospheres' being studied, illuminated from below by these thermonuclear-burning flares, are limited by the intense gravity about just 1 cm thick. Yet this was enough to cover and contain those flares.
Webb will not have the resolution of Event Horizon Telescope, the latter being absurdly good. Technology | Event Horizon Telescope
I hope readers have seen videos of stars circling Sgr A*. I don't know where those can be accessed just now. Also don't know of Webb would be very good for looking at galactic center(s) which seems to be more of a vis/UV activity.
This lists EHT's resolution, over the longest listed baseline, as 23 and 15 μas (micro-arc-seconds), depending on radio band. For comparison, I'm seeing Hubble listed as 0.04 as (arc-seconds), and Webb listed as 0.1 as. For direct comparison to EHT, these translate to 40,000 and 100,000 μas, respectively. So neither Hubble nor Webb would have any chance of getting an optical or IR image of these black holes of similar resolution as EHT, even if they were not obscured by opaque dust and gas clouds. I noticed that the EHT black hole images seem to have better resolution than the normal Rayleigh criterion, without the usual diffraction effects. It turns out that these radio astronomy programs do apply deconvolution, removing much of the diffraction smearing (mathematically, this smearing is a convolution of an ideal image with the diffraction point spread function) and making the images sharper. I don't believe deconvolution algorithms were used in optical astronomy until the Hubble Space Telescope was found to have a flawed mirror. Digital image processing with deconvolution then helped improve its images until the first servicing mission could install corrective 'glasses'. I'm hoping to see some of this applied to Webb's images, though success will be limited by the signal-to-noise ratios. That means such processing would be limited to nearer brighter objects, not the distant faint stuff that Webb is most meant for. Despite Webb's larger mirror, its resolution is less than Hubble's because of its imaging bands are at longer wavelengths. This is because a telescope's analog resolution (before digital post-processing) is limited by the ratio of photon wavelength to telescope aperture (in this case, mirror diameter). While Hubble senses at optical and shorter wavelength ultraviolet light, Webb sense longer wavelength infrared. Hubble did look at some near-IR, but Webb goes much farther into the IR band. Though thanks to its larger mirror and better sensors, Webb should see significantly fainter objects, apparently (by one claim) to 34th magnitude, vs Hubble's 31.5, a brightness ratio of about 25. I can't answer much about digital image processing, as it is beyond the more basic one-dimensional digital signal processing that surrounded me during my work career.
