Like most comets, it is made of ice, dust, and gas. When Halley's Comet orbits close to the Sun, it has a bright and glowing appearance that can be seen from Earth. It is said that it was first noticed back in 240 BC. In 1705, an astronomer named Edmond Halley discovered that the comet appears every 75 to 76 years.
Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and the only naked-eye comet that might appear twice in a human lifetime. Halley last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.