bladder, prostatic hypertrophy, acute prostatitis, or prostate cancer, which lead to urinary retention, overflow incontinence, and uremia. Investigations in the 1990s suggested that Tycho may not have died from urinary problems, but instead from mercury poisoning. It was speculated that he had been intentionally poisoned. The two main suspects were his assistant, Johannes Kepler, whose motives would be to gain access to Tycho's laboratory and chemicals, and his cousin, Erik Brahe, at the order of friend-turned-enemy Christian IV, because of rumors that Tycho had had an affair with Christian's mother. In February 2010, the Prague city authorities approved a request by Danish scientists to exhume the remains, and in November 2010 a group of Czech and Danish scientists from Aarhus University collected bone, hair and clothing samples for analysis. The scientists, led by Dr Jens Vellev, analyzed Tycho's beard hair once again. The team reported in November 2012 that not only was there not enough mercury present to substantiate murder, but that there were no lethal levels of any poisons present. The team's conclusion was that "it is impossible that Tycho Brahe could have been murdered". The findings were confirmed by scientists from the University of Rostock, who examined a sample of Tycho's beard hairs that had been taken in 1901. Although traces of mercury were found, these were present only in the outer scales. Therefore, mercury poisoning as the cause of death was ruled out, while the study suggests that the accumulation of mercury may have come from the "precipitation of mercury dust from the air during [Tycho's] long-term alchemistic activities". Tycho is buried in the Church of Our Lady before Týn, in Old Town Square near the Prague Astronomical Clock. Career: observing the heavens Observational astronomy Tycho's view of science was driven by his passion for accurate observations, and the quest for improved instruments of measurement drove his life's work. Tycho was the last major astronomer to work without the aid of a telescope, soon to be turned skyward by Galileo Galilei and others. Given the limitations of the naked eye for making accurate observations, he devoted many of his efforts to improving the accuracy of the existing types of instrument—the sextant and the quadrant. He designed larger versions of these instruments, which allowed him to achieve much higher accuracy. Because of the accuracy of his instruments, he quickly realized the influence of wind and the movement of