Galaxies are found uniformly everywhere in the Universe, except in the Milky Way’s plane. Here’s why.
From the time of their very first discovery, the Universe’s grand spirals have puzzled astronomers.
While stars, star clusters and other nebulae were concentrated in the plane of our Milky Way, there were no spiral nebulae present.
For some reason, they eschewed our galaxy’s plane, which became known as the Zone of Avoidance.
Upon discovering that spiral nebulae were galaxies beyond our own, the problem made more sense.
Dust, gas, and concentrated matter blocks the light from more distant objects, obscuring them.
The dust itself is composed of matter grains of specific sizes, preferentially blocking shorter-wavelength photons.
Even modern 3D dust maps show this; dust grain size is independent of its location in the galaxy.
As a result, infrared telescopes can see through the dust, revealing the material behind it.
Not only can we reveal the structure of our own galaxy from within, but we at last found galaxies behind it.
The first galaxies found in the Zone of Avoidance are named Maffei 1 and 2, after Paolo Maffei, who pioneered infrared astronomy.
Galaxies are just as rich in the Zone of Avoidance as anyplace else.
Thanks to viewing the Universe with infrared eyes, the mystery is now solved.
Mostly Mute Monday tells the scientific story of an astronomical phenomenon, object, or problem in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.