Even from our location, there’s a great lesson to be learned: the galactic plane obscures the Universe beyond it, about 10 degrees above and below it, in visible light, as shown here. If you want to see what lies beyond our galaxy — or any dusty galaxy — just look in the infrared, and watch the Universe open up to you. (ESO/B.TAFRESHI)

This Is How Astronomers Solved The ‘Zone Of Avoidance’ Mystery

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.

This ultraviolet composite image of the Andromeda galaxy, taken by the GALEX spacecraft, showcases the youngest, bluest stars of all, which trace out the spiral arms and the galactic bulge. Andromeda was the first spiral nebula to be identified as a galaxy beyond our own. Note the extended nature of the arms, which indicates that new waves of star formation may be triggered by mild tidal disruptions.(NASA / JPL-CALTECH / GALEX)

While stars, star clusters and other nebulae were concentrated in the plane of our Milky Way, there were no spiral nebulae present.

The Milky way’s central region in visible light, with the location of the galactic center marked by E. Siegel. Billions of stars can be found there, and Pan-STARRS has collected data on more of them than ever before. Near the plane of the galaxy, however, there are no spiral nebulae to be found. At least, not in visible light. (JAIME FERNÁNDEZ)

For some reason, they eschewed our galaxy’s plane, which became known as the Zone of Avoidance.

A map of star density in the Milky Way and surrounding sky, clearly showing the Milky Way, the Large and Small Magellanic Clouds (our two largest satellite galaxies), and if you look more closely, NGC 104 to the left of the SMC, NGC 6205 slightly above and to the left of the galactic core, and NGC 7078 slightly below. There are a great many galaxies to be discovered, but within about 10 degrees above and below the galactic plane, visible light cannot reveal them. (ESA/GAIA)

Upon discovering that spiral nebulae were galaxies beyond our own, the problem made more sense.