Halley's Comet
JIVITHA KALETAMA EKA PARAI . .
JIVITHA KALETAMA EKA PARAI . .
The best known comet of all is Halley, which has returned with a 74-79 year period since 240 B.C. The following image shows a famous view of the full tail of Halley recorded from the Mount Wilson Observatory.
Edmund Halley and His Comet
The English astronomer Edmund Halley was a good friend of Isaac Newton. In 1705 he used Newton's new theory of gravitation to determine the orbits of comets from their recorded positions in the sky as a function of time. He found that the bright comets of 1531, 1607, and 1682 had almost the same orbits, and when he accounted for the gravitational perturbation on the cometary orbits from Jupiter and Saturn, he concluded that these were different appearances of the same comet. He then used his gravitational calculations to predict the return of this comet in 1758.
Halley did not live to see his prediction tested because he died in 1742. But on Christmas night, 1758, the comet destined everafter to bear Halley's name reappeared in a spectacular vindication of his bold conjecture and of Newton's gravitational theory. Tracing back in the historical records for recordings of bright comets and their positions in the sky, it was concluded that Halley had been observed periodically as far back as 240 B.C. The most recent return was in 1986, and the predicted next appearance of Halley in the inner Solar System will be in 2061.
The following figure shows the orbit of Halley's Comet and its predicted location in 2024 relative to the orbits of the planets.
Blue is above the plane of the ecliptic and green is below. Almost the entire Halley orbit is below the plane of the ecliptic. Further, Halley revolves around its orbit in retrograde motion (the opposite sense from planet revolution). In the preceding view the planets revolve counter-clockwise and Halley revolves clockwise. The following image shows the same thing, but from a top view.
Notice that Halley's orbit extends essentially to the distance of Pluto, but when Halley is at its greatest distance from the Sun (aphelion) it is below the plane of the ecliptic (green color) while that portion of Pluto's orbit is above the plane of the ecliptic (blue color). The following image illustrates this more clearly. It is a view of the orbit of Halley and its 1996 position from the vantage of the ecliptic plane:
Southern Arizona in 1986
