I was curious about that claim, so I did a bit of research and made a "back of the envelope" calculation. According to Wikipedia [1], the angular resolution of a telescope is proportional to <wavelength of light>/<diameter>. Starlink seems to operate from 10 to 40GHz, so assume the hardware has a 50% design margin so is capable of reaching 60GHz. Visible light has a frequency of 400 to 800THz, so take the middle of 600THz. Using those figures, it come out that the Starlink satellites, used as a telescope, would have the same angular resolution as a 1.3m visible light telescope. Is it enough to resolve exoplanets ? I'm not sure but I think not. Hubble is 6m and can apparently resolve some exoplanets so it's not too far off. Some launches to GEO would boost the resolution to the equivalent of 8.4m in visible. (IANAA)
60GHz has a wavelength of 5mm. Effective diameter would be ~13000km. Someone check my math but I end up with 5e-3/13e6 radians or ~.0001 arcseconds. Hubble is ~.05 arcseconds.
The Event Horizon Telescope "imaged" two black hole structures down to 10 microarcsecond resolution. The create synthetic apertures from radio telescope pairs separated as much as 8,000 miles and operating up to 450 GigaHertz. (Synthetic telescopes have been created since the 1970s, but used much lower radio frequencies with a much lower computation burden.) Each telescope pair samples a small bit of spatial frequencies. So sophisticated inversions were run to compute the image that best fit these samples.
I was curious about that claim, so I did a bit of research and made a "back of the envelope" calculation. According to Wikipedia [1], the angular resolution of a telescope is proportional to <wavelength of light>/<diameter>. Starlink seems to operate from 10 to 40GHz, so assume the hardware has a 50% design margin so is capable of reaching 60GHz. Visible light has a frequency of 400 to 800THz, so take the middle of 600THz. Using those figures, it come out that the Starlink satellites, used as a telescope, would have the same angular resolution as a 1.3m visible light telescope. Is it enough to resolve exoplanets ? I'm not sure but I think not. Hubble is 6m and can apparently resolve some exoplanets so it's not too far off. Some launches to GEO would boost the resolution to the equivalent of 8.4m in visible. (IANAA)
1: https://en.wikipedia.org/wiki/Angular_resolution