There are two bits of historical trivia that people like to cite about the 16th century Danish astronomer Tycho Brahe. The first is that he lost part of his nose when it was cut off in a duel in 1566 -- the dispute was over a mathematical formula, not a woman as was usually the case, although the argument occurred at a wedding banquet -- and had a metal fake nose made to replace it, which he wore strapped to his head in public.

The second is that he suffered a very strange death. According to a first-person account by Johannes Kepler -- then a protege of Brahe's -- Brahe was dining with the Danish emperor, and badly needed to relieve himself midway through the meal. But it would have been rude to leave the table before royalty. Back home, he found it was both difficult and painful to urinate. His bladder burst and he died a few days later – perhaps the only person in history to die from good manners.

OR DID HE? In a plot twist straight out of a classic murder mystery, there have been rumors over the last century or so that the famed astronomer was actually murdered. The suspects included Brahe's distant cousin, Erik Brahe, who supposed carried out the deed on behalf of King Christian IV of Denmark -- apparently he suspected Tycho Brahe of sleeping with his mother.

The second possible culprit was Kepler himself -- yes, the dude who went on to formulate the laws of planetary motion. Kepler, the theory goes, desired fuller access to his mentor's extensive catalog of astronomical observations, all of which he inherited upon Brahe's death. Glory! Riches! A place in the historical pantheon of the greatest astronomers of all time! Who wouldn't be tempted to slip their mentor a lethal dose of mercury for that?

Yes, it seems incredibly far-fetched, but the rumors are based on a 1901 autopsy of Brahe's exhumed remains, which found traces of mercury in hairs taken from his beard -- and no evidence of kidney stones, the ostensible cause of death recorded by the 16th century physicist who examined Brahe's body immediately after his death.

But a new analysis by Danish and Czech scientists indicates that this legend is just too good to be true, and that Brahe likely did indeed fall victim to uremia and a burst bladder. As for those toxic levels of mercury, it's possible they came from Brahe's metallic nose.

Mercury, or quicksilver, as it is commonly known, is a transition metal, one of five elements that are liquid at standard room temperatures. Frankly, it's quite lovely as elements go, its beauty belying its deadly nature -- a veritable l'element fatale.

It filled decorative pools and fountains in Islamic Spain, a practice revived by Alexander Calder when he built a mercury fountain for the Spanish Pavilion at the 1937 World's Fair in Paris. (That fountain is still on display in Barcelona.)

Mercury has historically been used to treat various ailments, before its toxic properties were fully understood. It was certainly known in ancient China; China's first emperor, Qin Shi Huang Di, is believed to have been driven insane and killed by mercury pills. Ironically, he took them in hopes of achieving eternal life, and legend holds he was buried in a tomb containing rivers of flowing mercury to represent the rivers of China.

The ancient Greeks used mercury in ointments, and it found its way into Roman cosmetics as well.

Among medieval alchemists, mercury was a required element for the transmutation of base metals into gold (something the alchemists never achieved, but hey, they kept hoping). During the 1800s, it was used to treat syphilis, (sometimes killing the intended patient), and to treat constipation, depression, and toothaches. In the early 20th century, children were administered mercury every year as a laxative and dewormer.

It was also used to refine gold and silver ores, something still practiced by gold miners in Brazil's Amazon basin. In modern times, it's been used to cool nuclear reactions, as an ingredient in dental amalgams, and before the advent of digital thermometers, the devices were filled with mercury.

You know that phrase, "mad as a hatter"? It most likely arose in the 18th and 19th centuries, when the furs used to make beaver felt hats were dipped in mercury compounds to separate the fur from the pelt ad mat it together. The solution produced toxic vapors which adversely affected workers in the felt hat trade. The poisoning caused shaking and plurred speech, symptoms which were lumped under "hatter's disease."

The most potent form of mercury is dimethyl mercury, a neurotoxin that can easily cross the blood/brain barrier and can prove lethal even in minuscule amounts (on the order of a fraction of a milliliter).

This compound damages the central nervous system, kidneys, and the endocrine system, and prolonged or heavy exposure results in brain damage and death. Mostly, its effects are cumulative; usually, by the time its effects are noticed, it is too late to save the victim.

Any way you slice it, mercury poisoning is a nasty way to go, and we wouldn't wish such a fate on one of our favorite astronomers. Back in 2010, the aforementioned Czech and Danish scientists decided to put the poison rumors to rest once and for all and exhumed Brahe's body one last time.

The researchers took samples from Brahe's beard, bones and teeth and used three different chemical methods to measure the mercury concentrations. They concluded that the levels of mercury in the beard and bones just weren't high enough to have caused the astronomer's death. (The analysis of the teeth is not yet complete.)

As for Brahe's prosthetic nose, it has usually been described as being made of gold and silver silver, but the researchers found that in fact, it was made of brass, based on traces of copper and zinc revealed by this latest analysis.

Now that scientists have cleared up the mystery of Brahe's death, perhaps they can take a look at the demise of the astronomer's pet moose. Yes, Brahe kept an elk as a pet, but the creature apparently drank too much beer one night at dinner, fell down some stairs and died. That has to be a cover story, right?

Science has developed all kinds of tools and techniques for what I shall call historical forensics: the alkaloid poison test (for detecting quinine, morphine, strychnine, atropine and opium); spectrum analysis using spectroscopes; and ultracentrifuges to separate particles by mass, making it possible to precisely measure the molecular weights of complex proteins. In the 1950s, ultraviolet and infrared spectrometry, along with x-ray diffraction and gas chromatography, found forensic applications, and in 1966, scientists introduced Fourier-transformed infrared spectroscopy and atomic absorption spectroscopy.

Last year, researchers used the intense x-ray beams at Brookhaven National Laboratory's Synchrotron Light Source to analyze hair samples collected from the decomposed bodies of 15th century royalty: Ferdinand II of Aragon (a medieval kingdom that is now part of modern Spain) and Isabella (princess of Naples and Duchess of Milan).

There is circumstantial evidence that mercury poisoning may have caused or contributed to their deaths. Ferdinand's death was marked by fever, fatigue, and bloody diarrhea. Isabella, too, suffered from recurrent fevers, and died of dropsy, a general swelling of the body. At the time, mercury was used as a remedy for skin disease, and both Ferdinand and Isabella had been treated accordingly -- Ferdinand for syphilis, most likely. The international team who used Brookhaven's facility found elevated levels of mercury in Isabella’s hair, within 20 days of her death, while Ferdinand's hair had very high mercuty levels in the 15 days preceding his death.

Science is still giving us new ways to test chemical substances like poison and solve all kinds of unsolved mysteries -- or just to clear up some lingering rumors, like the one about how Napoleon Bonaparte was poisoned by prison guards (rather than dying of stomach cancer) during his imprisonment at Saint Helena.

Samples of Napoleon's hair did show high levels of arsenic, but, like the poison from soil leaching into exhumed bodies, it need not be the result of deliberate poisoning.

Arsenic was used in lots of things, including as a pigment in some wallpapers at the time of Napoleon's death. Put that wallpaper in a damp environment, and a toxic mold will form, which converts the copper arsenite pigment into a poisonous vapor.

Physicists used x-ray fluoroscent spectroscopy in 1982 to measure the amount of copper and arsenic in the wallpaper in Napoleon's residence at Longwood House on St. Helena, and found there was sufficient arsenic to at least hasten the exiled emperor's death by exacerbating existing conditions, although it was unlikely to have caused his death outright.

Prolonged exposure to that wallpaper could account for the high levels of arsenic found in Napoleon's remains, along with the fact that his body was buried for 20 years on the island before being exhumed and moved to its final resting place.

In the spring of 2008, another group of physicists came to the rescue to resolve the issue once and for all. They used a small nuclear reactor at the Italian National Institute of Nuclear Physics (INFN), built to detect neutrinos for the Cryogenic Underground Observatory for Rare Events. Except instead of testing neutrinos, this time the scientists used the machine to study particles in Napoleon's preserved hair samples.

They checked out hair samples taken from four periods during Bonaparte's life -- when he was a boy, during his exile to Elba, the day he died, and the day after his death -- as well as hairs from his son and wife, the Empress Josephine. Neutron activation established that all of the hair samples -- including the control samples -- contained traces of arsenic.

While the levels were pretty high, apparently they weren't unusually so for the time: all the hair samples taken from 200 years ago had levels some 100 times higher than those taken from folks today. And there was no significant increase in those arsenic shortly before Napoleon's death, as there would have been if he'd been administered a fatal dose.

So Napoleon's guards have been exonerated by science, along with Johannes Kepler. Still, at least one historical case of suspected arsenic poisoning turned out to be true, when forensic scientists determined that famed racehorse Phar Lap died after ingesting a massive dose of arsenic. Next they'll be telling us someone poisoned Seabiscuit, or perhaps Brahe's drunken pet moose.