Composition of Comet Halley

1910 Halley's Comet


What is Halley's Comet made of?

For millennia our ancestors wondered about the nature of Halley's Comet? What was this bright "hairy star" speeding through the sky? Where did it come from? What chemicals was Comet Halley made of?


On July 2, 1985, European robotic spacecraft named Giotto was sent into space. Its mission was to study Comet Halley.


On March 14, 1986, Giotto flew through the tail of the comet and within 8,889 km of the nucleus. Its cameras sent back the first images of the comets nulceus. Giotto's sensors discovered that the surface of Halley's Comet only reflected about 4% of the available light. This meant the surface of the comet is virtually black.


Due to this blackness a comet remains invisible, even to the world's most powerful telescopes for the vast majority of its life. It spends most of its time in the Oort Cloud or Kuiper Belt in a stable orbit. A passing star disturbs this orbit and sends it into the inner solar system. As it approaches the Sun the ice and frozen chemicals begin to melt and separate from the nucleus. They form the coma and tails. The "brilliance" of the comet is only in illusion creating by the light reflecting off the shed material. Otherwise, the nucleus flies through space as black as coal.


Giotto helped determine that the temperature of Comet Halley ranges from -53°C to -103°C. It is made up of mostly non-volatile materials.