Munich. Cosmic peanut with double structure: the first time, astronomers have succeeded is a closer look into the interior of an asteroid. Itokawa, about 600 meters long and a regular guest at perigee, therefore, could be the result of a collision between two chunks – one of them hard as granite, the other more of a pile of sand. Then let the accelerated rotation of the asteroid close, an international research team reported on Wednesday. Previously, only the average density was possible to determine from asteroids.
The measured effect is very small: At about 45 milliseconds, the time for one complete rotation of Itokawa shortened within a year. To track him, were ten records from the years 2001 to 2013 have been necessary, the participating Max Planck Institute for Solar System Research said in Göttingen.
at a total of eight telescopes in the U.S., Spain and Chile were recorded during this period changes in brightness of the asteroid. The data is combined with the theoretical work on the heat radiation of asteroids. The study published in the journal “Astronomy & Astrophysics”, the European Southern Observatory ESO in Munich and other institutions were involved.
For small, irregularly shaped bodies can be changed by the influence of the sun’s rotation, the researchers explain. They absorbed light particles, called photons, which would be released as heat back into the environment. Because of the irregular shape of this passing to different degrees in different places, result was a tiny but persistent torque.
The derived data available suggest that the smaller nub of Itokawa has a density of 2850 kilograms per cubic meter – which corresponds to about granite. However, the larger part has a density of only 1750 kg per cubic meter. This is comparable with densely packed sand, the Göttingen researchers explained.
“For the first time we have been able to find out what is inside of an asteroid,” said Stephen Lowry of the University of Kent. The Fund is an important step for the understanding of rock bodies in the solar system. In addition, the results could help to reduce risks of asteroid impacts on Earth.
The asteroid Itokawa penetrates approximately every 556 days in orbit before he thus belongs to the group of near-Earth asteroids.