Wednesday, February 5, 2014

Different density: the two sides of the asteroid Itokawa -

Canterbury / Vienna – For the first time could be analyzed by astronomers an asteroid, which consists of two very different components. During a portion of the 600-meter-long, peanut-shaped body has a density such as granite, the other part has a significantly lower density, which corresponds to approximately from densely packed sand. This was reported by an international research team currently in the journal “Astronomy & Astrophysics”.

This discovery was made possible by

accurate measurements of the speed of rotation of the asteroid. This may change in so irregularly shaped bodies over time, which allows conclusions about its structure.

solar radiation changed rotation

The mechanism of this change in torque caused carries the bumpy name Yarkovsky-O’Keefe-Radzievskii-Paddack, or in short: YORP effect. This is because the reflection and emission of solar radiation at very irregularly shaped bodies does not take place uniformly throughout.

The tiny changes in torque caused the case – the rotation period of Itokawa changes only by 45 milliseconds per year – can be measured, however long and precise series of observations are necessary to


twelve years took in this case the time-consuming hunt for the YORP effect. Eight telescopes from the U.S., Spain and the European Southern Observatory in Chile were present in use, coordinated by the international research group led by SC Lowry of the University of Kent in Canterbury.

comparison with space data allows conclusions

Similar changes in the rotation period were indeed detected already at several asteroids at Itokawa, however, is the discovery of particular importance. Since you unlike other asteroids knows its shape very well, Itokawa offers the unique potential, not only its surface, but also its internal structure to investigate.

Back in 2005, the Japanese space probe “Hayabusa” asteroid had paid a visit and delivered a detailed topographic model. This model, the researchers could now use to predict exactly which change the rotation should theoretically result from the action of the sun radiation.

your calculations based on the assumption that the body has a homogeneous density, but did not initially bring in line with the observations. Only when the researchers two components with very different density assumptions (2850 kg per cubic meter on one side, 1750 kg per cubic meter on the other), voted the two results coincide and thus led to the first proof of an inhomogeneity in an asteroid.

collision as a possible cause

The only question is how it could come to this unusual structure. The researchers write, Itokawa could be caused by the collision of two asteroids. The two celestial objects would thus be around each other circling until the system collapsed, and the asteroids melted into each other. (Guge,, 05/02/2014)

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