Babe Among the Stars: Jupiter- friend or foe?
Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth - Ptolemy
Jupiter - Friend or Foe?
I'm lucky enough to be a member of the Cleethorpes and District Astronomy Society which has a meeting at the local observatory once a month when an eminent speaker is invited to give us a talk of around an hour's duration. Recent visiting experts have been a retired Astronomer Royal and the current professional astronomer who gives talks aboard plane flights to (attempt to) see the aurora borealis. July's speaker was Dr Jonti Horner of the University of Durham who gave a fascinating talk (with slide-show) about Jupiter, the largest planet of our solar system. In July 1994 Comet Shoemaker-Levy 9 had a date with disaster with the giant gas planet, which occurred after a previous fly-by when Jupiter's massive gravity had torn the comet apart, but not enough to drag it to its doom. Next time around, its orbital trajectory had changed sufficiently to put it on a direct collision course, and the impacts, punching holes the size of the Earth in Jupiter's atmosphere, were the first ever witnessed by human eyes. We no longer have to worry about that particular comet being harmful to the Earth but there are very many other space rocks which have the potential to become NEOs (Near-Earth Objects). I had always thought that Jupiter was the 'guardian' of the smaller inner worlds — hoovering up the stray asteroids and comets which might otherwise cause potential disaster for the Earth. However, during his talk Dr Horner explained that Jupiter is just as capable of altering the orbit of a passing lump of rock and sending it hurtling in our direction like an interplanetary game of snooker.
A team of astronomers at Sheffield University have discovered the most massive star ever detected, 165,000 light years away in the Large Magellanic Cloud, a dwarf galaxy which orbits the Milky Way. The blue hypergiant Wolf-Rayet1 star, known as R136a1, is estimated to be between 320 and 265 times the mass of our own Sun (an insignificant yellow dwarf) and possibly 30 times the size. Put simply, it would take 300 stars the size of our Sun to fill R136a1. That's one heck of big 'un, according to Prof Animal Chaos who informed me of the discovery in my journal!
August Diary Dates
The Perseids appear between 23 July and 20 August, so there's enough chances to spot some as you'll usually get a few clear nights within that time range. They are the most consistent meteor shower, providing the best annual show. The peak is on the glorious 12th; amateur astronomers are known to arrange a barbecue before the event with a 'shooting star party' following the food and drink. Head out for a dark-sky viewing area and take something comfortable to sit or lie on, also remember to take along a flask and some warm outer clothing. Not all spectacular meteors appear during meteor showers; take for example the stunning meteor procession of 1860, which occurred on the evening of 20 July. Luckily for us there was a skilled artist named Frederic Church who witnessed the phenomenon, and he was able to recreate what he had seen in a painting called The Meteor of 1860, thus preserving the awesome event for posterity and allowing us to enjoy the sight a century and a half later via Astronomy Picture of the Day.
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