Question

How did scientists determine the shape of the Milky Way?

Answer 1

Due to dust clouds optical observation of milky way is difficult.

Explanation:

Molecular hydrogen in the Galaxy emit radiation in 21 centimeter wave length. This was used by radio telescopes to map the milky way..THis was the first mapping.LaterUsing the Very Long Baseline Array (VLBA), a system of 10 radio telescopes spanning the globe from Hawaii to New England to the Virgin Islands, and operated in Socorro, N.M., Reid’s team studied masers — naturally occurring sources of laser-like radio waves from clouds of gas near luminous stars — to map our galaxy in unprecedented detail.
From space .com.news.