Size and Shape of our Galaxy

The Milky Way galaxy, which is our home galaxy, is comparatively large in size among other galaxies.
It spans about 100,000 light-years in diameter, which is roughly 946 trillion kilometres.
The thickness of the galaxy’s disk is around 1,000 light-years.
In terms of mass, the Milky Way contains about 400 billion stars, making it one of the massive galaxies.
Furthermore, evidence suggests there is a great amount of dark matter in the Milky Way, which adds significantly to its overall mass.

The Milky Way galaxy possesses a barred spiral shape, which is characterized by a central bar-shaped structure composed of stars extending outwards.
Radiating from this bar structure are two major spiral arms and several smaller arm segments or spurs.
Moreover, our galaxy also has a spherical halo surrounding the spiralling disk, filled with ancient stars and globular clusters.
The galactic bulge at the centre of the Milky Way is spherical to oblong in shape and consists of mostly old stars, gas and dust.
The far-reaching galactic disk, where our Solar System resides, is where the majority of the Milky Way’s young and old stars, as well as interstellar medium, are located.
Despite its barred spiral shape, the Milky Way’s disc is not flat; it’s slightly warped, similar to the brim of a wide-brimmed hat.

Observations from Earth are complicated due to our position inside the galactic disk.
This means we view the galaxy’s structure edge-on rather than face-on, making it challenging to discern its full shape and size.
However, advancements in technology and techniques, including infrared astronomy, radio astronomy, and star mapping missions, have enabled us to perceive our galaxy’s barred spiral shape.
Particularly, the glowing band of light we see in the sky - the ‘Milky Way’ - is our view of the galaxy’s densely packed star-filled disk seen edge-on.