New Discoveries in the Outer Solar System: Ceres, Pluto and Planet X – April 12, 2016 Lecture

by Ira Polans, Program Chair

Dr. Jim Green

Dr. James Green, Director of Planetary Sciences, NASA

The April meeting of the AAAP will be held on the 12th at 7:30 PM in Peyton Hall on the Princeton University campus. The speaker will be Dr. James Green, NASA’s Director Planetary Science. Dr. Green will talk about “New Discoveries in the Outer Solar System: Ceres, Pluto, and Planet X”. The Program Committee would like to thank AAAP member Ken Kremer for arranging this talk.

Ceres was first discovered in 1801 and thought to be a planet. It was realized 50 years later that Ceres was a member of a huge number of objects in what we now know as the asteroid belt. The Dawn spacecraft was captured into orbit around the dwarf planet Ceres in March 2015. We knew almost nothing about Ceres, and the new images that are being sent back are showing a fascinating world from heavily cratered regions to large smooth plains, and a number of mysterious bright spots. Ceres has started to reveal its secrets.

Pluto was discovered in 1930 by Clyde Tombaugh and was at first thought to be the size of the Earth. Over time, observations of Pluto determined that it is considerably smaller (~2,000 km in diameter). Pluto’s orbit is moderately inclined relative to the ecliptic by over 17° and moderately elliptical with a period of 248 Earth years. Before the flyby, we knew so very little about Pluto and its moons. Beginning in 1992, planetary astronomers began to find Pluto like objects beyond the orbit of Neptune showing us that Pluto was a member of an entirely new family of objects we now call the Kuiper Belt. The Kuiper Belt is believed to have tens of thousands of similar bodies to Pluto that are left over from the formation of the Solar System. On July 14, 2015 the New Horizons spacecraft flew by the Pluto system revealing a fascinating new world and its five moons whose complexity surprised many of our planetary scientists.

Over the last several years, our ground-based telescopes have revealed a handful of Kuiper Belt Objects that have highly unusual orbits perhaps indicating they have been scattered by an unseen large planet that exists at a phenomenal distance from the sun. This is indeed a fascinating time for planetary science.

There will be a meet-the-speaker dinner at 5:45 PM at Winberie’s in Palmer Square. Since we’re hoping for a large turn-out if you’re planning to attend please contact on Monday, April 11 by 5PM. Please note that the dinner starts 15 minutes earlier than normal.

Members are encouraged to invite their friends and family to what is sure to be an interesting and informative talk! We look forward to seeing you at the April meeting.

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