The Milky Way

A Martian, who is in any case at home in the Milky Way, could just leave the last two address lines blank.

In addition to the Sun, the Milky Way is home to around 100 billion other stars which all rotate together around the centre of the galaxy. The Milky Way resembles a flat disc and has a spiral structure. More precisely, it corresponds to an SBc type, consisting of a spiral with a central bar.

The Sun is located in the outer area of a spiral arm. From this position, we can see the disc of the Milky Way from the side as a milky band in the sky on dark nights. Our perspective is equivalent to that of a small beetle on the edge of a plate. It also sees the plate more or less from the side and, therefore, not as a round disc, but as a flat strip.

The dimensions of the Milky Way are immense. We can only see the few thousand stars in our immediate neighbourhood with the naked eye. These stars form the night sky familiar to us with its constellations. But the journey to the centre of the Milky Way is much farther. The radio news received this evening would not be broadcast there for another 20,000 years. It takes this long for the radio waves to arrive. Anybody there interested in what is happening on Earth would find it very difficult to keep up to date.