what is the comet made up of?
Ethane, methane, deuterium, hydrogen, water
Comet Hyakutake
ethane and methane 
what is comet hyakutake? It is a comet. who discovered it? Yuji Hyakutake what is its orbit? It passes just 0.1 AU from Earth. when was it discovered? 30 January 1996 do you know how close to the sun does it orbit? Approximately 2 astronomical units (AU) is there is a term for it? UNANSWERABLE did a spacecraft pass through its tail? Ulysses spacecraft when? 1 May 1996 was it manned or unmanned? UNANSWERABLE
wiki:1220043
Comet Hyakutake [SEP] Composition
Terrestrial observers found ethane and methane in the comet, the first time either of these gases had been detected in a comet. Chemical analysis showed that the abundances of ethane and methane were roughly equal, which may imply that its ices formed in interstellar space, away from the Sun, which would have evaporated these volatile molecules. Hyakutake's ices must have formed at temperatures of 20 K or less, indicating that it probably formed in a denser-than-average interstellar cloud. The amount of deuterium in the comet's water ices was determined through spectroscopic observations. It was found that the ratio of deuterium to hydrogen (known as the D/H ratio) was about 3, which compares to a value in Earth's oceans of about 1.5.