Astronomers Get A Good Look Inside Asteroid Itokawa

[ Watch the Video: Artist's Impression of Asteroid Itokawa ]

Lee Rannals for redOrbit.com – Your Universe Online

Astronomers, using the European Southern Observatory’s (ESO) New Technology Telescope (NTT), have discovered that asteroids have a highly varied internal structure.

The astronomers used the instrument to look at different parts of the asteroid Itokawa, which was the target of the Japanese spacecraft Hayabusa in 2005. This spacecraft took samples of an asteroid for the first time and delivered them back to Earth.

According to the latest observations published in the journal Astronomy & Astrophysics, different parts of Itokawa have different densities. Learning more about the secrets beneath the asteroid’s surface could reveal mysteries about what happens when these bodies collide in the Solar System.

The team made precise measurements during the observations, measuring the speed at which the near-Earth asteroid spins and how that spin rate is changing over time. They also combined these measurements with new theoretical work on how asteroids radiate heat.

The Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect occurs when absorbed light from the Sun is re-emitted from the surface of the object in the form of heat. When the shape of the asteroid is irregular the heat is not radiated evenly, creating tiny torque on the body and changing its spin rate.

Astronomers found that the YORP effect was slowly accelerating the rate at which Itokawa spins. The change in rotation period is small, but was different from what was expected and can only be explained if the two parts of the asteroid’s shape have different densities.

“This is the first time we have ever been able to determine what it is like inside an asteroid,” Stephen Lowry, from the University of Kent, said in a statement. “We can see that Itokawa has a highly varied structure — this finding is a significant step forward in our understanding of rocky bodies in the Solar System.”

Before this study, the properties of asteroid interiors could only be determined by using rough overall density measurements. The Itokawa observations have led to speculation regarding its formation.

“Finding that asteroids don’t have homogeneous interiors has far-reaching implications, particularly for models of binary asteroid formation. It could also help with work on reducing the danger of asteroid collisions with Earth, or with plans for future trips to these rocky bodies,” Lowry said in a statement.