Astrology and the Archduke: Two unpublished letters by Tycho Brahe on the horoscope of Albert VII of Austria

By 1600 Holy Roman Emperor Rudolf II was still unmarried and therefore without an heir apparent. Rudolf was pressured to name a successor, who could take over as long as there was no direct heir. The obvious choice would have been one of this brothers, Archduke Albert VII of Austria among them. Through the meddling of Wolf Dietrich von Raitenau, Archbishop of Salzburg, Tycho Brahe became a pawn in a power play between the brothers of Rudolf II. Two letters of Tycho Brahe to Albert reveal how deeply he was involved.