The cause of Tycho Brahe's death on 24 October 1601 (New Style) has been disputed for over four centuries. He fell suddenly ill eleven days before his death following a banquet hosted by Baron Peter Vok Rožmberk in Prague, and died after a rapid physical decline. Three broad explanations have attracted sustained attention: natural urological failure, accidental heavy-metal exposure through alchemical or medical practice, and deliberate poisoning. The question is contested across forensic chemistry, historical biography, and the history of science, and no account has achieved universal acceptance among researchers despite significant forensic investment, including a second exhumation of Brahe's remains in 2010.

The oldest and most widely held account holds that Brahe died of uremia following a bladder rupture or severe urinary retention. Contemporary accounts recorded that he was unable to urinate after the banquet and suffered escalating pain and confusion over the following days before dying. Brahe is known to have suffered from what paleopathological analysis of his skeleton identifies as diffuse idiopathic skeletal hyperostosis (DISH), a condition associated with metabolic syndrome - including obesity, elevated blood pressure, and type II diabetes. Proponents of this account argue that his known lifestyle, dietary habits, and physical condition made urological crisis a plausible and expected cause of death without recourse to toxicological explanation, and that the rapidity of his illness is consistent with acute kidney failure rather than poisoning.

The 2012 report by the Danish-Czech research team led by Jens Vellev and Kaare Lund Rasmussen, following analysis of bone, beard, and hair samples from the 2010 exhumation, concluded that mercury concentrations in Brahe's remains were not elevated beyond normal population ranges and declined to the low end of normal in the weeks preceding death. Researchers in this tradition argue that these findings remove the principal forensic basis for a poisoning hypothesis, and that uremia - whether from bladder rupture or from complications of metabolic disease - remains the most parsimonious explanation consistent with the physical and documentary evidence.

A second account holds that Brahe's death was hastened by mercury he ingested inadvertently as part of contemporary medical practice or alchemical work, without deliberate intent by any party. Mercury-based compounds were widely prescribed in the late sixteenth century as treatments for urinary and renal conditions, and Brahe maintained an active alchemical laboratory at both Uraniborg and his Prague residence. Under this reading, mercury found in early analyses of his hair and beard reflects routine occupational and medicinal exposure rather than poisoning, and the acceleration of his illness during his final days may have been a consequence of mercury compounds administered in an attempt to treat his worsening condition.

Some researchers have specifically noted that mercury's nephrotoxic properties could have compounded an existing renal crisis, making the accidental-exposure account compatible with the urological hypothesis rather than in competition with it. This interpretation has the advantage of explaining detectable mercury in the historical samples while remaining consistent with the 2012 finding that mercury concentrations never reached acutely toxic levels.

A third account, developed most fully by Joshua and Anne-Lee Gilder in their 2004 book Heavenly Intrigue: Johannes Kepler, Tycho Brahe, and the Murder Behind One of History's Greatest Scientific Discoveries, holds that Brahe was systematically poisoned - most likely by Kepler. The circumstantial case rests on several elements: Kepler's documented desire to obtain Brahe's closely guarded planetary observations, which Kepler needed to complete his own theoretical work; Kepler's physical proximity to Brahe during his final illness; anomalies in Kepler's account of the circumstances of Brahe's death; and Kepler's rapid acquisition of Brahe's data and position at the imperial court after his employer died.

The forensic foundation of the Gilder argument rested on 1990s analyses of hair samples taken during the 1901 exhumation, in which Swedish physicist Jan Pallon and Danish forensic scientist Bent Kæmpe detected mercury concentrations they considered elevated. The Gilders argued that these levels indicated deliberate administration rather than occupational exposure, and that Kepler had both the laboratory access and the technical knowledge to have administered mercury compounds covertly. The Gilders also proposed that a second, larger dose was administered in Brahe's final days to produce the acute crisis.

Defenders of this account have argued that the 2012 findings do not fully close the question, as mercury analysis cannot rule out other poisons, and that circumstantial historical evidence concerning Kepler's motives and opportunity retains independent weight. A 2016 re-examination of Brahe's remains by a separate research group reported that his body contained concentrations of gold significantly above normal levels - some estimates placing the anomaly at 20 to 100 times normal - a finding that has not been fully explained and which some researchers regard as warranting further forensic inquiry into possible toxic exposure from sources other than mercury.

Researchers across all three positions agree on the following: that Brahe died rapidly following a dinner party on 13 October 1601 (New Style); that his illness involved acute urinary retention and probable renal compromise; that mercury was present in his remains in detectable quantities; that he operated an alchemical laboratory and that mercury exposure through occupational or medicinal means was common in his milieu; and that the 2010 exhumation and subsequent analysis substantially weakened the specific hypothesis of acute mercury poisoning advanced by the Gilders. Most researchers also agree that the historical and forensic record is unlikely to yield a conclusive resolution.

• Tycho Brahe
• Tycho Brahe - History
• Tycho Brahe - Astronomical Consensus
• Tycho Brahe - Historical Role Viewpoint
• Johannes Kepler

1. Dreyer, J.L.E. Tycho Brahe: A Picture of Scientific Life and Work in the Sixteenth Century. Edinburgh: Adam and Charles Black, 1890. Repr. New York: Dover, 1963. Primary account of Brahe's final days, drawing on contemporary testimony.
2. Thoren, Victor E. The Lord of Uraniborg: A Biography of Tycho Brahe. Cambridge: Cambridge University Press, 1990. ISBN 0-521-35158-8. Standard scholarly biography; treats the circumstances of Brahe's death in detail.
3. Gilder, Joshua, and Anne-Lee Gilder. Heavenly Intrigue: Johannes Kepler, Tycho Brahe, and the Murder Behind One of History's Greatest Scientific Discoveries. New York: Doubleday, 2004. ISBN 0-385-50844-1. Principal popular exposition of the deliberate-poisoning hypothesis; identifies Kepler as the likely perpetrator.
4. Pallon, Jan, and Bent Kæmpe. Forensic analyses of hair samples from the 1901 exhumation detecting elevated mercury, conducted in 1992 and 1996 respectively; Kæmpe's 1996 analysis published in a Danish forensic journal; both summarized in Gilder and Gilder (2004) and subsequent literature.
5. Vellev, Jens, et al. Report on the 2010 re-exhumation of Brahe's remains from the Church of Our Lady before Týn, Prague. Aarhus University, 2012.
6. Rasmussen, Kaare Lund, et al. “Was He Murdered Or Was He Not? - Part I: Analyses of Mercury in the Remains of Tycho Brahe.” Archaeometry 55 (2013): 168-195. Primary forensic report on mercury concentrations from the 2010 exhumation; concludes that toxic mercury exposure is excluded as cause of death.
7. Rasmussen, Kaare Lund, et al. Paleopathological analysis of skeletal remains, 2012-2013. Identifies DISH and metabolic syndrome as background conditions consistent with urological death.
8. Jivkova, Kat. “Mercury Murder Mystery: An Analysis of the Demise of Tycho Brahe.” Retrospect Journal, February 2021. Survey of the forensic debate including the 2016 gold anomaly finding.