Size ΓÇö 10 miles x 5 miles x 4 miles (16.5 km x 8 km x 6.7 km)
Orbital period ΓÇö 76.1 years
Surface temperature ΓÇö 80 to 160 degrees Fahrenheit (27 to 127 degrees Celsius)
HalleyΓÇÖs Comet made its last visit to the EarthΓÇÖs vicinity in 1986. When it returns in 2061, the Earth will probably be a very different place. The comet was named after Edmund Halley, who calculated its orbit. He determined that the comets seen in 1531 and 1607 were one and the same object which followed a 76-year orbit. Unfortunately, Halley died in 1742, never living to see his prediction come true when the comet returned on Christmas Eve 1758.
HalleyΓÇÖs Comet, like every other comet, loses some of its substance every time it passes the point nearest to the Sun. Some scientists suggest that HalleyΓÇÖs ejected about 300 million tonnes of material at its 1986 appearance. This still leaves more than 10 billion tonnes of nucleus material ΓÇö enough to sustain many more reappearances.
Some people are worried about what comets could do to our lives. But unless a comet physically collides with Earth, these small chunks of dirty ice pose no danger to us. One can think of comets as travelling time machines. The next time that HalleyΓÇÖs Comet visits the EarthΓÇÖs vicinity, we may be having robots to cook, clean and sweep for us.
