June 2019 - Pluto from Myth or Reality
Members of the Horndean & District U3A met for their regular monthly meeting on Friday 7th June at Merchistoun Hall. They were entertained by Graham Bryant who is the Chairman of the Clanfield Observatory – the largest amateur observatory in the UK, President of the Hampshire Astronomical Group and he is a Fellow of the Royal Astronomical Society.
Graham talked about the planet Pluto (now Dwarf planet Pluto). Actually discovered over 7 centuries ago and in recent years a probe was sent there. The planets names can be traced back to mythology and characters of the underworld - Poseidon, Zeus. Hades, Persephone, Charon, Nix, Kerberos (Cerberos) and Hercules. The recent discovery of Pluto can be traced to Bath where William Herschel was looking for planets. He built his own telescope in his back garden where he discovered many objects. In 1781 he discovered a pale blue round disc which was Uranus which doubled the size of the solar system.
He started measuring its movement, how far away it was and how long it would take to go round it. He had international co-operation. He found it wasn't behaving properly. It wasn't going round the sun at a steady pace but it was erratic, sometimes it moved very fast and sometimes very slowly. It proved something was pulling on it. In 1846 it was found that the planet Neptune was the cause.
Again there were abnormalities with Neptune which again was not behaving properly. The astronomers spent a considerable amount of time searching for the cause. In 1894 a rich American, Percival Lowell, built an observatory on Mars Hill in Arizona which had a telescope with 24" optics. He placed it high up where there would be little interference. They were searching for Planet X (Pluto) They did not have precise observations and had no idea where it was, how big it was and had to make educated guesses. He and his assistants searched for ten years.
Meanwhile a young farm hand who loved astrology Clyde Tombaugh built a telescope out of farm equipment and bits and pieces. He sent his observations to the Lowell Observatory for their comments. They were extremely impressed and offered him the job of assistant to find Planet X. He spent thousands of hours looking and after just 10 months he finally found Pluto, the 9th planet in our solar system, in January 1930. Searched for a further 13 years (7,000 hours) and searched 90 million celestial objects. In 1978 the moon Charon was discovered which travels around Pluto. In the 1990's the Hubble space telescope showed that there were even more satellites out there.
Early in the 20th century they were beginning to identify objects in that part of the solar system known as trans Neptunian objects and were far larger than Pluto so it was decided to downgrade Pluto from a full planet to a dwarf planet. Caused an outrage in America!
Finances are always difficult regarding space exploration, so Dr Alan Stern decided to make a cheap probe to go to Pluto. Using bits from other obsolete craft he built what is known as New Horizons, the fastest space craft ever launched. In 2006 it was launched to Pluto and arrived after 9 years in 2015 where it conducted a 6 month flyby of Pluto and its moons. From it we have been able to see the rotation and features on the surface of Pluto and its moons. They are made up primarily of ice as hard as rock. The probe is travelling at an incredible rate and It will continue further into the Kuiper Belt.
Graham provided many more interesting facts, figures and photographs. It was a fascinating and an inspirational talk and at the end he was enthusiastically asked questions and warmly thanked by the Members.
Diane Stoner
Speaker Coordinator