William Herschel thought that the Sun and Earth were roughly at the center of the great grouping of stars we call the Milky Way. Today we know this is not the case. What was a key reason that Herschel did not realize our true position in the Milky Way?

William Herschel's Theory (Heliocentrism)

Explanation:

It was in 1783, when William Herschel examined the stars using his handmade telescope to figure out the shape of the galaxy. As a result of this examination, he concluded that the shape of our Milky Way was that of a 'disk' and that the sun was positioned in the center of this disk.

The reason he came to such a conclusion was that to him the Earth appeared to be 'amidst of several other stars' and when he worked out for the magnitudes of these stars the resulted figures were same in every direction. Therefore, based on these findings he concluded that the Earth is positioned somewhat near to the 'center' of the Milky Way.

Later on it was revealed that there were two errors in his findings;

The magnitude is not considered as a reliable means to measure the distance of the stars. He was unable to keep in consideration the dark areas containing nebulae which blocked the view to the center of the galaxy and he thought of them as the vacant spaces.

Nebulae: Plural of Nebula (Latin for cloud or fog). A nebula is initially referred to any dispersed astronomical object, including galaxies beyond Milky Way.

Explained

Explanation:

William Herschel thought that the Sun and Earth were roughly at the center of the great grouping of stars we call the Milky Way. He could say so because he was only able to see a small part of the galaxy. This was because of the fact that dust extended throughout the disk of the galaxy, making visibility very low.