L’astéroïde Itokawa, dit aussi la cacahuète, possède une structure interne complexe.
Asteroid’s anatomy uncovered for the first time | Mail Online
▻http://www.dailymail.co.uk/sciencetech/article-2551476/Revealed-Peanut-asteroids-anatomy-uncovered-time-unlock-secrets-planets
The discovery was made by a team of astronomers at Kent University who found that different parts of a near-Earth asteroid - called Itokawa - have different densities.
Using telescope images from 2001 to 2013, Dr Stephen measured the speed peanut-shaped Itokawa spins and how its spin rate is changing over time.
They combined these delicate observations with new theoretical work on how asteroids radiate heat.
This provided the space scientists with a unique opportunity to explore its interior, revealing the complexity within its core and secrets about its formation.
(…)
This phenomenon, known as the YORP effect, occurs when absorbed photons from the sun are re-emitted from the surface of the object in the form of heat.
When the shape of the asteroid is very irregular the heat is not radiated evenly and this creates a tiny, but continuous, torque on the body and changes its spin rate.
Dr Lowry’s team measured that the YORP effect was slowly accelerating the speed at which it spins.
The change in rotation speed is tiny – only around 45 milliseconds per year - and was far from expected.
Scientists suspected Itokawa’s ‘bi-lobed’ or ‘peanut-like’ appearance is the result of two bodies of very different densities, that came together at some point in its ancient history.
La toponymie d’Itokawa après sa cartographie par la sonde Hayabusa qui a rapporté des échantillons de son sol en juin 2010.
The asteroid ITOKAWA (1998 SF36) was discovered by a project called the “Lincoln Near Earth Asteroid Research (LINEAR)” at the Lincoln Laboratory, Massachusetts Institute of Technology, on September 26, 1998. ITOKAWA looks like a sweet potato with a dimension of about 500 meters in length and 300 meters in width. Its rotation period is about 12 hours, and it is an S-type asteroid whose orbit is an elliptical orbit traveling between the Earth’s orbit and Mars’s orbit with a period of about 1.5 years.
(sur ▻http://www.jaxa.jp/press/2009/03/20090303_itokawa_e.html )