Well, as in 5th year Science we're currently on the topic of the Universe, I thought you would be interested to know that they represent the seven stars which form the Ursa Major constellation, also known as the Big Dipper or Great Bear. This is visible above the Sierra de Guadarrama during most of the year.
The five points of the stars represent the five provinces that border Madrid: Toledo, Ávila, Segovia, Guadalajara and Cuenca.
Thank you to the blog Science and Fun for this information!