Comet Halley, new research

This video says about itself:

Giotto: Halley’s Comet Flyby Animation (1986.03.14)

1 October 2011

On March 13, 1986, ESA’s Giotto probe swept within 600 km of Comet Halley, obtaining the first close-up images of a comet. It revealed the first evidence of organic material in a comet and, still today, much of what we know about comets comes from the pioneering mission.

Launched on July 2, 1985 by Ariane 1, Giotto was ESA’s first deep-space mission, part of an ambitious international effort to solve the mysteries surrounding Comet Halley. It was also the first deep-space mission to change orbit by returning to Earth from an interplanetary trajectory for a gravity-assist.

After a cruise of eight months, Giotto arrived at its destination and revealed the size and shape of Halley’s nucleus, found that its surface is very dark (the blackest object in the Solar System) and that it emitted jets of gas and dust.

Giotto’s camera recorded many images that gave scientists a rare opportunity — the comet will not return to the inner Solar System again until 2061 — to study Halley intensively. It was particularly important to determine its composition through the readings made by Giotto as it passed through Halley’s tail.

After completing its Halley mission, Giotto went into hibernation before being woken up in the summer of 1990, and then hibernating again until early 1992.

Although a few of the instruments had been damaged during the Halley encounter, the spacecraft had survived the battering by cometary dust and was able to conduct a second flyby, this time of Comet 26P/Grigg-Skjellerup, in July 1992.

This video is a new compilation of Giotto’s historic images acquired by the Halley Multicolour Camera (HMC). It shows the comet as seen by the probe as it approached from about 900,000 km, coming to within 596 km.

The images were processed by the HMC team under the leadership of Uwe Keller at the Max Planck Institute for Solar System Research (MPS/Lindau), where this video was newly produced in 2011 together with B. Grieger from the Rosetta team at ESA/ESAC to mark the 25th anniversary of Giotto’s flyby.

credit: Max Planck Institute for Solar System Research

From Leiden University in the Netherlands:

Chaotic orbit of Comet Halley explained

Published on 30 June 2016

A team of Dutch and Scottish researchers led by Simon Portegies Zwart (Leiden University) has found an explanation for the chaotic behavior of the orbit of Halley’s Comet. The findings are accepted for publication in the Monthly Notices of the Royal Astronomical Society.

Halley’s Comet is one of the most famous comets. Halley can be seen from the Earth every 75 years. The last time was in 1986, the next time will be in 2061. Despite his regular return, the comet’s orbit cannot be predicted exactly. This is partly due to processes inside the comet and partly because the orbit of Halley is disturbed by the chaotic interaction with the planets and minor bodies in the solar system.

Stable

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 seventy years. The team of astronomers has now shown that the comet’s orbit is stable for more than three hundred years. That’s much longer than expected.

Venus

‘We did the most accurate calculations of Halley and the planets ever,’ said researcher Tjarda Boekholt (Leiden University). ‘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.’

Jupiter

In about three thousand years the comet will approach the planet Jupiter relatively close, so Halley will get a big push. From then on Venus will no longer be the main perturber and Jupiter will take over this role. ‘After that predictions of the orbit become less accurate, because the precise effect of Jupiter’s gravity introduces a relatively large error in our calculations,’ says fellow researcher Inti Pelupessy (Leiden University).