What is the speed of Halley's comet?  .

This razzle dazzle comet visits our skies for a few weeks at intervals of about 76 years. As it loops around the sun it travels at about 300 miles a second, or roughly one million miles an hour. At this speed, the famous comet could travel to the nearest star and back in time for its next visit to our sun. But we know that it does not travel even to the limits of the Solar System.

The orbit of a planet or comet is rarely if ever a perfect circle, Its perihelion is the point where it comes closest to the sun, its aphelion is the point which takes it farthest from the sun. find there is a law which says that an orbiting body must travel faster around its perihelion. Our orbital speed around the sun is a little faster in January, for that is when the earth is about three million miles closer to the sun than it is in July.

The earth’s orbit is also circular, but the orbit of Halley's comet is a long, narrow oval. One end loops close around the sun and the other end makes a U turn out beyond the orbit of Neptune. This great variation in the comets perihelion and aphelion causes a great variation in its orbital speed.

In about 76 years, the comet travels an orbit about 6,000 million miles long. We can get an idea of the variation of its orbital speed by dividing this distance roughly into six parts. One of these sections is completed in a few weeks, two similar sections each take five years and two more sections each take about 15 years. The slowest section, which takes the comet around its aphelion, takes 38 years   about half the comets year.

Right now, Halley's comet is making its pokey U turn beyond the orbit of Neptune.

It reached its aphelion in 1948 and is now creeping back towards the sun. In about 15 years it will cross the orbit of Uranus, gradually putting on speed. In five years it will cross the orbit of Saturn and be almost as close as Jupiter.

Now the comet is swinging into the perihelion section of its orbit and its speed increases at a great rate. In a few weeks, it will have crossed the orbits of Mars, the earth, Venus and Mercury, looped around the sun and started the return ,journey to its aphelion. The next 1,000 million miles will take five years, the next will take 15 years and the aphelion U turn will take 38 years.

We see the great comet soon after it crosses inside the orbit of Mars. Then its head blossoms with hazy light brighter than the brightest star and its long golden tail streams 100 million miles over the sky. For a few weeks we watch it approach and loop close around the sun. Its razzle dazzle glory lasts only a few weeks, and for most of its long journey the comet is a dead, dark bundle of stones and perhaps frozen gases.