Mississauga Centre RASC

73rd Meeting

                                          Speakers’ Night

 

 

 

 

Day:                Friday November 3, 2006

 

Speaker:  Scott Young

 

Randy Attwood introduced Scott Young, the National President of the Royal Astronomical Society of Canada. It is a tradition since the 1980’s for the President to visit other centre during his tenure as did Randy during his presidency. 

 

 

Pluto vs. the Ice Dwarfs, or conflict at the edge of the solar system

 

Scott Young became interested on astronomy in 1979 when he sneaked a peek out of the window at the total eclipse of the sun in February if that year while in grade 2. For his day job he works in the planetarium in Winnipeg and is greatly involved in astronomy education. He stated that most children’s favourite planet in Pluto, now designated dwarf planet 134340Pluto after its planetary status was withdrawn by the International Astronomical Union (IAU). Due to confusion, the status may change again in the near future.

 

Scott showed images of what Pluto might look like with its diffuse atmosphere present for 40 years of each orbit.  The largest moon, Charon would appear 7 times as large in Pluto’s sky than the Moon does in ours. Pluto also has two other recently discovered moons: Nix and Hydra.

 

In 1930 Clyde Tombaugh discovered Pluto at Lowell Observatory in Arizona. His job was to look for planet X as the perturbing object on the motion of Neptune. A blinking instrument showed the motion of the dot on two separate photographic plates. Even now with the Hubble Space Telescope we can only see Pluto as a slightly larger “dot” with a few vague markings. 

 

So, is Pluto a planet? After its discovery, it was found that Pluto was much smaller than the expected planet X, the press release had already gone out announcing a new planet and so the planetary designation remained until now. However, up until now no one had defined what is a planet. Certainly school children in Grade 4 learned that Pluto is a planet.

 

Scott then discussed solar system discoveries. In ancient times, the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn were recognized as different from the fixed stars. In 1781 William Herschel, not looking for anything in particular, found an object with a disc, and, after an orbit was calculated, it was announced as a planet. The next “planet” discovered, Ceres, was by G. Piazzi on Jan. 1, 1801 between Mars and Jupiter. Soon Juno, Vesta and more were discovered until by 1901 there were over 100 objects that were not planets but “minor planets”. Thus a precedent was made for losing planets. Then in 1846 Johannes Galle and Heinrich d’Arrest found Neptune after John Adams and LeVerrier predicted where it should be by its perturbation of Uranus’ orbit. It was the first planet discovered by calculating where it should be. Arguments ensued between the French and British over credit for the discovery; there was great prestige to the country which discovered a planet.  On February 18, 1930 Clyde Tombaugh discovered Pluto. It was announced as a planet and the USA had the prestige of discovery.  Solar system diagrams then showed 9 planets with Pluto as prominent in importance as the others, and asteroids located in a belt between Mars and Jupiter.

 

 The largest of the many asteroids is Ceres at 950 km in diameter, and a planet if roundness is used as the criterion. The Kuiper belt at the edge of the solar system was calculated theoretically in the 1950’s. The first object, Quaoar with a diameter of 800 miles, was found in 1990. Thousands of Kuiper belt objects are predicted, some larger than Pluto, and Pluto looks just like one of them when its orbit is shown. Thus it is hard to justify Pluto as a planet.  Then an object even larger was found, 2003UB313. Now called Eris after the goddess of discord, it has a moon named Dysnomia from the goddess of lawlessness. The oval shaped orbit takes Eris to 96A.U. from the Sun.  The object Sedna goes even farther – to 800 A.U. 

 

The New Horizons spacecraft, launched in January 2006 is the fastest man-made object moving at 22 ˝ km per sec. It should reach Jupiter in February 2007, and Pluto in 2015.  During the rapid flyby Pluto’s size will grow from 1 pixel and then shrink again back to 1 pixel in 4 hours. In this brief time, the nuclear powered spacecraft is to map Pluto, Charon, maybe Nix and Hydra, and then it will be re-directed to another Kuiper belt object that has not even been discovered yet.

 

 

Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to Miss Centre. meeting reports page
Mississauga Centre RASC