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This page contains recent press releases concerning discoveries and information about minor planets (asteroids) and related issues. The page will be updated as and when time permits.
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Observers in South America catch Eris occultation
Asteroid (136199) Eris is one of the main outer solar system objects which a few years ago forced astronomers to consider the question of where exactly the dividing line between planets and asteroids should be drawn. Now this dwarf planet has yielded one of its key secrets when on the night of 6th November 2010 three telescopes in South America observed Eris pass in front of a 17th magnitude star in Cetus. Emmanuël Jehin observing using the 60-cm TRAPPIST telescope at La Silla Observatory, a team of 3 observers using a 50 cm telescope at the SPACE observatory and Jose-Luis Ortiz using a 40-cm instrument at the same observatory all recorded the event. The maximum separation between the observers was some 740km providing a good baseline for a very accurate measurement of the dwarf planet's diameter which is now believed to be significantly smaller than earlier estimates. Infrared studies made shortly after its discovery suggested that Eris was significantly larger than Pluto, but those esimates were based on the assumption that Eris rotates in such a way that the feeble heat from the Sun is roughly evenly distributed over the dwarf planet's surface. The new occultation observations suggest a value of about 2300km subject to a more detailed analysis. This measurement means that the surface is warmer than had been assumed, probably because Eris' axis is currently pointing towards the Earth (and the Sun) and one hemisphere gets warmer as it faces the Sun for an extended period of time. The new value would make Eris and Pluto nearly identical in size but with Eris known to be significantly more massive than Pluto it is thus much denser, with much more rocky material and a thinner ice crust over the top.
References:
SPACE observatory report
Sky and Telescope article
Universe Today article
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