Astronomy unveils exotic, unexpected
By Amanda Jermyn



One of the delights of astronomy is that there are always more exotic objects out there just waiting to be discovered. Take, for instance, the recently discovered planet about the size of Neptune with the rather unassuming name of GJ 436 b. Orbiting a red dwarf star about 33 light years away, it is the second smallest planet outside the solar system ever discovered, with an unusual atmosphere, at least by our standards for Neptune-like objects. Based on its distance from its star and its orbital shape, heat-trapping gases such as methane and carbon dioxide would be expected to explain the planetís high surface temperature. Theoretical models predict an atmosphere with large amounts of methane and very little carbon dioxide because at those temperatures and pressures, carbon dioxide tends to react with hydrogen and hydrocarbons to form water and methane. However, spectroscopic analysis shows an abundance of carbon dioxide but very little methane, the exact opposite of what would be expected. It is still not known what causes this discrepancy.
Furthermore, GJ 436 b has a highly eccentric oval orbit which has been measured over a long period of time and found to remain essentially constant over time. To explain this, an additional nearby planet or other large mass should be required, though no such an object has been detected by measuring the wobbling of the planetís star.
While GJ 436 b is the second smallest extrasolar planet discovered so far, the smallest is COROT-7b. It appears to be tidally locked with its star which means the same side always faces its star. So it is always day on one side of the planet and night on the other. We have only been able to measure the surface temperature on the sunny side, which is a scorching 4000F. There is speculation that the far side may hold water or ice. This planet has a thin atmosphere of vaporized metal - thatís right, gaseous metal! It is slightly larger than Earth, very close to its star, and has a year of 20 hours, meaning it orbits its sun every 20 hours. As advances in technology allow us to detect both smaller and more distant extrasolar planets in the future, we can only wonder how these might challenge our preconceived ideas and stagger the imagination.
Join the Springfield STARS Club on Tuesday, May 25th at 7:30pm at the Springfield Science Museum for a talk by Prof. Alan Hirshfeld PhD on Starlight Detectives of the Victorian Age: How amateur astronomers helped invent modern astronomy during the late 19th- and early 20th centuries using photography and spectroscopy to explore the physical properties of celestial objects. Prof. Hirshfeld is the director of the UMass Dartmouth Observatory and an Associate of the Harvard College Observatory. He conducts research in the history of physics and astronomy. He is the author of Parallax: The Race to Measure the Cosmos, 2002, The Electric Life of Michael Faraday, 2006, Eureka Man: The Life and Legacy of Archimedes, 2009, and many other publications. Refreshments will be served, and the public is welcome free of charge.

Amanda Jermyn, of Longmeadow, has been a member of the Springfield Stars Club since 2000 and currently serves on the club's board of directors. For more information, visit the Springfield Stars Club Web site at www.reflector.org or call 1(800)336-9054.