A postcard with a cosmic address needs more information than usual. Each line represents the organisation of objects in the universe, from small to large, near to far. We begin with our familiar coordinates on Earth and move out through the solar system to the most distant galaxies in the cosmos. Today scientists understand enough about the structure of the universe to know our complete address.
In the picture below you can see a card sent to the Griffiths Observatory that Baba visited recently.