Asteroids live in own ‘little worlds’ that spilt to give birth to smaller ones

While it is believed that asteroids are giant rocks lumbering about in orbit, a new study has shown that they actually are constantly changing "little worlds" that can give birth to smaller asteroids that split off to start their own lives as they circle around the sun.

 

Astronomers have known that small asteroids get "spun up" to fast rotation rates by sunlight falling on them, much like propellers in the wind.

 

The new results show when asteroids spin fast enough, they can undergo "rotational fission," splitting into two pieces which then begin orbiting each other. Such "binary asteroids" are fairly common in the solar system.

 

The new study, led by Petr Pravec of the Astronomical Institute in the Czech Republic and involving the University of Colorado at Boulder and 15 other institutions around the world, shows that many of these binary asteroids do not remain bound to each other but escape, forming two asteroids in orbit around the sun when there previously was just one.

 

The researchers studied 35 so-called "asteroid pairs," separate asteroids in orbit around the sun that have come close to each other at some point in the past million years -- usually within a few miles, or kilometers -- at very low relative speeds.

 

They measured the relative brightness of each asteroid pair, which correlates to its size, and determined the spin rates of the asteroid pairs using a technique known as photometry.

 

"It was clear to us then that just computing orbits of the paired asteroids was not sufficient to understand their origin. We had to study the properties of the bodies. We used photometric techniques that allowed us to determine their rotation rates and study their relative sizes," Nature quoted Pravec as saying.

 

The research team showed that all of the asteroid pairs in the study had a specific relationship between the larger and smaller members, with the smallest one always less than 60% of the size of its companion asteroid.

 

While asteroid pairs were first discovered in 2008 by paper co-author David Vokrouhlicky of Charles University in Prague, their formation process remained a mystery prior to the new study.

 

Several telescopes around the world were used for the study, with the most thorough observations made with the 1-meter telescope at Wise Observatory in the Negev Desert in Israel and the Danish 1.54-meter telescope at La Silla, Chile.

 

"This study makes the clear connection between asteroids spinning up and breaking into pieces, showing that asteroids are not static, monolithic bodies," said Vokrouhlicky.

 

The study appears in the latest issue of Nature.