Comment on Order of magnitude is a hell of a drug
conditional_soup@lemm.ee 2 days agoIsn’t this functionally true for objects on the infinite focal plane? I.e. a star? Betelgeuse might actually be huge in absolute terms, but from earth, and even in a large telescope, it’s still a pinpoint whose circumference is not meaningfully distinct from its diameter.
oce@jlai.lu 2 days ago
It would be the size of the telescope’s diffraction artifacts probably. Meaning the shape you see on the picture is not related to the size of the star but only to the physical limits of the optical instrument. This diffraction pattern is proportional to the color your looking at and inversely proportional to the size of the telescope primary mirror. The bigger the telescope primary mirror, the smaller the diffraction pattern and the more chance you have that this artifact will not completely hide the object you are looking at. I didn’t do the math, but I guess to image the actual disk of Betelgeuse, the size of the telescope you need is probably still science fiction, even with interferometry.
conditional_soup@lemm.ee 2 days ago
I want you to know that you nerd sniped me with this comment and I started doing the math. To raise the apparent size of Betelgeuse to the apparent size of Jupiter (at its largest to the naked eye), you’d need a minimum 20 inch diameter telescope to pull the required 1000x magnification. Mind you:
20 inches is not a mass produced telescope size, but there ARE custom makers who produce reflectors at and well beyond this size. There are certainly terrestrial telescopes that can achieve what we need.
you’re still not resolving any details at that size, it’s just raising Betelgeuse to the same apparent size as Jupiter at its naked eye largest.
most places on earth are not conducive to magnifications over 300x. You can certainly do it, and sometimes the atmospheric conditions are ridiculously clear and you can pull off stupid levels of magnification, but there’s a reason why observatories get built up on mountains a lot. 1000x is… Well, good luck. Especially since Orion and Betelgeuse never get too close to the zenith, meaning there’s always a substantial amount of atmosphere to deal with.
oce@jlai.lu 2 days ago
I was surprised so I did the computation just to resolve the disk of Betelgeuse at 550 nm, and I found a telescope of 2.8 m, that’s definitely already doable. We already have 8 m in one piece and 10 m segmented, JWST is 6.5 m segmented. The ELT is planned to be 39 m for 2028. So this star is closer and bigger than I thought.