Determining the form of the Milky Way, our own galaxy, has been a challenging task due to a few reasons:
Our position within the galaxy: We are located inside the Milky Way, which makes it difficult to observe its overall structure from an external viewpoint. Imagine trying to understand the shape and structure of a building while being inside it. Our vantage point within the galaxy limits our ability to observe its full extent and shape.
Interstellar dust and gas: The Milky Way contains vast amounts of interstellar dust and gas that can obscure our view of distant stars and objects. This dust scatters and absorbs light, making it difficult to observe objects located on the other side of the galaxy or in regions heavily obscured by dust.
Obstacles in observing the galactic plane: The majority of stars, gas, and dust in the Milky Way are concentrated in a flattened, disk-like structure called the galactic plane. Observing the galactic plane poses challenges because it is densely populated with stars, and the light from distant objects can be easily absorbed or scattered by the interstellar medium.
Three-dimensional structure: Determining the three-dimensional structure of the Milky Way is particularly challenging. Since we are confined to observing the galaxy from within, it is challenging to measure distances accurately to objects spread across the galaxy. Estimating distances in astronomy is often a complex task, and obtaining precise distance measurements to various regions within the Milky Way has been a significant challenge.
Over time, astronomers have employed various techniques and observations to gain a better understanding of the Milky Way's structure. These include studying the distribution and motion of stars, observing radio waves, using infrared and X-ray observations to penetrate interstellar dust, and employing sophisticated computer models and simulations. These efforts have gradually provided insights into the overall shape and structure of our galaxy, but understanding its precise details remains an ongoing scientific endeavor.