A SCOTTISH scientist is among a group of astronomers who have performed the astonishing feat of predicting the orbit of Halley’s Comet for the next 300 years.
The most famous comet of them all flies by and misses – we all sincerely hope – the Earth every 75 years, and last did so in 1986. It will return in 2061, though variations in its orbital path have long been observed.
Now astronomer and mathematician Professor Douglas Heggie of Edinburgh University and a team of Dutch scientists have explained one of the great mysteries of Halley’s Comet, namely its chaotic orbit and why that orbit, if not its cycle of return, is so irregular.
Furthermore Prof Heggie and his colleagues have predicted that in 3,000 years time, the orbit of Halley’s Comet will be upset by its increasing proximity to the giant planet Jupiter rather than Earth’s neighbour
Venus.
Named after the second Astronomer Royal, Edmond Halley, who examined reports of a comet approaching Earth in 1531, 1607 and 1682. He concluded that these three comets were actually the same comet returning over and over again, and successfully predicted the comet would come again in 1758.
Sadly, he did not live to see it as he died in 1742 aged 85 but when the comet appeared in the sky, it was acclaimed as Halley’s by popular demand.
The comet is one of the few that can be seen from the surface of Earth with the naked eye. The first record of it was by ancient Chinese astronomers who saw it in 239 BC, and its passing has been noted throughout history – perhaps most famously in 1066 when William the Conqueror took it as a good omen and made sure its appearance was included in the Bayeux Tapestry.
Its orbit does take the comet near Earth in astronomical terms, but not in any way that threatens the planet – its nearest approach in recent history was in 1910 when it passed by some 14 million miles away.
It was known that the periodic orbit around the Sun was varied because of processes inside the comet itself and its chaotic interaction with the planets and minor bodies in the solar system.
During its 1986 appearance, scientists were able for the first time to view those internal processes due to the Giotto spacecraft’s historic fly-by encounter. According to Science.org “the prevailing view among astronomers is that the orbit of Halley’s comet cannot be calculated exactly because the orbit would be chaotic on a time scale of only 70 years.
“The team of astronomers has now shown that the comet’s orbit is stable for more than 300 years. That’s much longer than expected.”
Prof Heggie and his colleagues will have their research published in the latest Monthly Notices of the Royal Astronomical Society.
Led by Simon Portegies Zwart of Leiden University in The Netherlands, the team has also made remarkable findings about the long-term future of Halley’s Comet.
Researcher Tjarda Boekholt of Leiden University said: “We did the most accurate calculations of Halley and the planets ever.
“To our surprise Halley’s orbit was most strongly influenced by the planet Venus and not by Jupiter, the planet that was always pointed to as the biggest spoiler.”
In about 3,000 years Halley’s Comet will approach the planet Jupiter relatively close, so the comet will get a big push.
From then on Venus will no longer be the main perturber and Jupiter will take over this role.
There seems very little chance that Halley’s Comet will ever veer far enough off its orbit to strike the Earth, but it should be noted that Halley himself suggested that comets could batter Earth – an atheist, he was censured by the Royal Society in 1694 for suggesting that Noah’s Flood was caused by a comet hitting the Earth.
Though it will be 45 years before the comet returns, Halley’s remnants can be seen every year as the Orionid meteor shower which occurs annually in October and the Eta Aquarids meteor show in May are both caused by fragments spread from the comet.
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