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The center of Halley's Comet is made out of ice, so the temperature is very cold and ranges from about -50 to -100°C. Halley's Comet is about 10 miles long and 5 miles in diameter with a mass of 2.2x10¹⁴ kg and an average density of 0.6 g/cm³. Becasue of it's small size and mass compared to the Earth, Halley's Comet does not create much gravity and it does not have an atmosphere. Halley's Comet also has a very complex rotation because it has a irregular shape (like a peanut), and it takes between 2 to 7 earth days for it to rotate completely around.
Halley's orbit is elliptical in shape. The closest the comet gets to the sun is about 85 million miles (closer to the sun than Venus), or a little more than half the distance from the Earth to the sun. The furthest Halley's Comet travels from the sun is about 5.2 billion miles, or about the distance between Pluto and the sun. The closest Halley's Comet has ever come to Earth was 15 million miles in 1910.
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| American author Mark Twain (Samuel Clemens) was born in 1835 just after Halley's Comet appeared and died at the comet's next passing in 1910. | In 1986, the European Space Administration's first deep space probe, Giotta, captured the first close-up images of a comet when it passed within 400 miles of Halley's Comet. | Halley's Comet was named after Edmund Halley who did not actually discover the comet. Halley was the first to suggest the comet had an orbit around the sun. |