Our Milky Way is a barred spiral galaxy containing 400 billion stars bound together by gravity. From Earth, the galaxy has the appearance of a faintly luminous band in the sky.
The naked eye cannot resolve the individual stars making up the band, and it was not until the invention of the telescope in the 17th century that it was proved that the Milky Way galaxy contained multitudes of stars.
In the early decades of the 20th century, astronomer Edwin Hubble photographed other galaxies and determined that they too are huge systems of many stars, and not just small structures within our own galaxy. The Milky Way is but one among multitudes of galaxies in space.
The spiral structure of the Milky Way is obscured by the fact that our Earth, sun and nearby planets are embedded in the galaxy’s disc. Observation of the shapes of other galaxies led to the realization that ours might be a spiral type.
Today, new techniques for measuring distance n deep space are helping astronomers put together a picture of the true shape of our Milky Way galaxy, although much debate remains about details such as the exact shape and location of the spiral arms and central bar.