Mississauga Centre RASC

71st Meeting

Speaker’s’ Night

Day:                October 6, 2006

Speaker:     Paul Delaney

Our Own Backyard: The Changing Solar System

Paul Delaney is a Professor of physics and astronomy at York University.  His main interest is in variable stars. He often speaks on TV trying to get the facts straight on astronomical topics.

The solar system is not stable. Astronomers are changing things such as the status of Pluto. In fact, astronomy is changing a great deal before our very eyes. In the Earth-Moon system, obvious differences are visible in a Galileo spacecraft image of the two bodies with Moon being dark, and Earth blue with clouds.  35 years ago, 12 men were on the Moon in the Apollo program. Surveyor had showed that the dust is at most a few cm. deep and that landing would be safe. We still, however know little of the Moon. Apollo 11 to 17 should have been the beginning of exploration, but it was the end. If all goes well, we may return to the Moon by 2020 using the Orion capsule.

The two broad categories of planets are Earthlike and Jupiterlike. All the planets move about the Sun in near circular orbits in the same direction, in almost the same plane. Pluto is different with its orbit and in its small size. Its density is less than the terrestrial planets suggesting a composition of ice and rock. Although much information can be gotten from the Earth’s surface, solar system missions are necessary to glean more information from the planets.

Mars captivates people with 150 years of stories, 100 years of observations and 40 years of space exploration. Currently, the Spirit and Opportunity Rovers having landed in 2004 are still mobile and exploring the planet even though they had only a 90 day guarantee.. Is Earth the only planet that has ever had life, or is there or was there ever life on Mars? The rovers are following the trail of water on Mars There is no doubt that Mars used to have a wet environment. Currently Opportunity has reached Victoria Crater and there is thought of sending the rover into that crater. The next mission to Mars is slated to be Phoenix for 2007-08. Phoenix, which has involvement from York University, will use LIDAR measurements to analyze the permafrost in the North polar Cap. The Canadian Northern Light Mission will use a lander and rovers to explore Mars’ environment, depositing many small packages on the planet.

Saturn and its large moon Titan with its thick hydrocarbon atmosphere are now being scrutinized by the Cassini spacecraft. Cassini’s orbit is unusual and it uses gravity assists from the satellites to change its target with each passage. Titan is thought to contain many methane lakes with a surface temperature of -180 deg C. We do not understand why there is so much methane. The Huygens probe landed in a river system on Titan.  

The “small stuff”, or “vagabonds” of the solar system can be dangerous with respect to collision with the Earth (e.g. Meteor Crater in Arizona). Objects of 500 meters or more are a concern and we need more insight in what they are. Professor Delaney described the Japanese spacecraft Hayabusa and its complicated mission to the asteroid Itokawa. Something went wrong during the touchdown on November 25, 2005. The spacecraft is in a desperate state with loss of fuel and gyroscopes. It may return in 2010 with a sample of the asteroid. Nonetheless, it has provided us with spectacular images of Itokawa.

The best known inner solar system objects are the comets especially with their nice tails. However, we want to know more about the rocky nuclei and their volatile materials because this helps us understand the origins of the solar system. The Giotto spacecraft imaged Comet Halley and noted cometary jets from the nucleus. Prof. Delaney them showed a video of Deep Impact on Comet temple 1 after it blew a hole in the nucleus helping us to understand the integrity and composition of the comet. The comet is held together very loosely with a density of 0.6 gm/cc. The Stardust probe returned to Earth in January 2006, bringing home cometary material and interstellar dust trapped in aerogel. The particles are now being extracted for study.

In 1930, Clyde Tombaugh, searching for the ninth planet, found an object that everyone took to be the planet. It eventually turned out to be smaller than expected, not a gas giant, and was found to have a large moon Charon. NASA decided to investigate the Pluto Charon system and launched the New Horizons spacecraft on January 14, 2006. With a gravity assist from Jupiter in march 2007, it is expected to arrive at Pluto in 2015, and then go on to explore other trans-Neptunian objects.

UB₃₁₃ Eris, being larger that Pluto focused the debate about Pluto and its planetary status. Most members of the astronomical community agreed that we needed to define a planet because of the many objects as large as Pluto. In the definition of a planet, mass is the determining characteristic. The object pulls itself into a spherical shape, orbits a star, is not large enough to undergo nuclear fusion, and is the dominant object in its region sweeping clear objects around it. Pluto dose not clear out its orbit and has now been called a dwarf planet as has been Eris. There was much debate about the planetary definition with a “Friends of Pluto” demonstration in New Mexico. Prof. Delaney told us to expect more debate from dynamicists in the near future.

NASA Video

Randy Attwood showed a video of the press conference from NASA about the achievement of the Opportunity Rover to reach Victoria Crater and the spectacular images that have been taken

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