What is Halley's comet?
Halley's Comet also referred to as Comet Halley, is arguably the most popular comet. It is a periodic comet and returns to Earth's proximity about every 75-76 years. It is the only naked-eye comet that can appear twice in a human lifetime. Halley last appeared in 1986, and it is projected to return in mid-2061.
The comet is named after English astronomer Edmond Halley as he is the one who determined its periodicity in 1705. Halley's calculations showed that at least some comets orbit the sun.
The surface of Halley is largely composed of dusty, non-volatile materials, and that only a small portion of it is icy.
Why Comet Halley is so famous?
Halley's comet is the most famous and known comet. It is so because it was the first comet to be observed in detail by a spacecraft, providing the first observational data on the structure of a comet nucleus and the mechanism of coma and tail formation.
As mentioned above, Edmond Halley was the original one to discover that few comets orbit the sun. His calculations also provided a powerful model for how objects move around the solar system and the universe. This discoveries by him inspired others to name the comet after him.
The orbit and structure of Halley's Comet
Halley orbital period has varied between 74-79 years. Its orbit around the Sun is elliptical. The perihelion, the point in the comet's orbit when it is nearest to the Sun, is just 0.6 AU. Its aphelion, farthest distance from the Sun, is 35 AU.
Halley is a short-period comet and has an orbit lasting for 200 years or less. The orbit of Halley suggests that it was originally along-period comet whose orbit was perturbed by the gravity of the giant planets and directed into the inner Solar System. If Halley was once a long-period comet, it is likely to have originated in the Oort Cloud.
Like all comets, as Halley is near the Sun, its volatile compounds, such as water and other ices, begin to sublimate from the surface of its nucleus. Its shape resembles that of a peanut shell.
Halley has a very large coma and long tail. But it has a relatively small barely 15 km long and 8 km wide. Its mass is relatively low, 2.2 x 10 ^ 14 kg, and its average density is about 106g/cm3, indicating that it is made of a large number of small pieces, held together very loosely, forming a structure known as a rubber pile.
Halley is the most active of all the periodic comets. Its day side is far more active than the night side.
Hail Halley
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