How astronomers solved the “Zone of Avoidance” puzzle – Big Think
Credit: G. Hüdepohl / atacamaphoto.com / ESO
From their earliest discovery, grand cosmic spirals have posed a tremendous puzzle.Credit: Vicent Peris/c.c.-by-2.0Most nebulae — dark nebulae, star clusters, planetary nebulae — are found everywhere: omnidirectionally.Credit: Stephanh/Wikimedia CommonsSome prefer the Milky Way’s plane: where stars, gas, and dust are most concentrated.But not spiral nebulae; they’re found everywhere except in or near the galactic plane.Credit: ESO/P. GrosbølWe called the Milky Way’s plane the “Zone of Avoidance” for lacking these objects.Credit: Samara Nagle/NRAOSpiral nebula IC 342, found in 1892, was the closest one known.Credit: ESA/Euclid/Euclid Consortium/NASA, Bildbearbeitung durch J.-C. Cuillandre, G. Anselmi; CC BY-SA 3.0 IGOElliptical nebulae “avoided” the galactic plane, too, but the reason remained obscure.Then, in 1923, we discovered that these spirals and ellipticals were galaxies beyond our own.Could dust, gas, and foreground matter block the light from these distant, extragalactic objects?Certainly, light-blocking material exists.Small matter grains, preferentially, would obscure shorter-wavelength photons.Dust grain size is location independent, allowing infrared telescopes to peer “through” the galactic plane.Credit: Planck Collaboration/ESA, HFI and LFI ConsortiumOnly with the development of infrared astronomy did galaxies finally “appear” within this zone.The first were Maffei 1 and 2, named after infrared astronomy pioneer Paolo Maffei.Over 99.5% of their visible light is blocked.With infrared astronomy, however, galaxies appear just as rich in the “Zone of Avoidance” as anywhere else.Credit: T. Jarrett (IPAC/Caltech)Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.
Source: https://bigthink.com/starts-with-a-bang/astronomers-zone-of-avoidance/
