Late in the evening of October 5, 1923. Edwin Hubble sat at the eyepiece of the Hooker telescope at the Mount Wilson Observatory. A top the mountains overlooking the Los Angeles basin. He was observing an object in the northern sky. To the unaided eye, it was visible as a faint smudge. But through a telescope it sharpened into a brilliant ellipse called the Andromeda Nebula. To settle a debate about the size of the Milky. Way — which was then thought to be the entire universe — Hubble needed to determine Andromeda’s distance from us. In the telescope’s field of view, Andromeda was a giant. Hubble patiently captured several exposures covering many glass photographic plates
Our Island Universe
From the Earth’s surface — if you are Phone Number List somewhere very dark — you can only see the bright stripe of the Milky Way’s galactic disk. Edge-on. But the galaxy we live in is so much more complicated. A supermassive black hole churns at its center. Surrounded by the “bulge,” a knot of stars containing some of the galaxy’s oldest stellar denizens. Next comes the “thin disk” — the structure we can see — where most of the Milky. Way’s stars, including the sun. Are partitioned into gargantuan spiraling arms. The thin disk is encased in a wider “thick disk,” which contains older stars that are more spread out.
A New Map of the Milky Way
Three years after CXB Directory Edwin Hubble realized. Andromeda was a galaxy unto itself. He and other astronomers were busy imaging .And classifying hundreds of island universes. Those galaxies seemed to exist in a few prevailing shapes and sizes. So Hubble developed a basic classification scheme known as the tuning fork diagram: It divides galaxies into two categories, ellipticals and spirals. Astronomers still use this scheme to categorize galaxies, including ours.