They're basically made up of debris left over from the origin of the solar system.

它们基本上是由太阳系起源时遗留下来的碎片组成的。

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(Astronomy) the nebular hypothesis of the origin of the solar system.

(天文学)关于太阳系起源的星云假说。

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The Oort cloud is a vast belt of dust and ice that is believed to lie around one light year from the Sun and is the origin of many of the comets that pass through our solar system.

奥尔特云是一个由粉尘和冰组成的庞大云带，据信它距离太阳约一光年，许多穿越我们太阳系的彗星都来自那里。

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NASA's study of NEOs provides important clues to understanding the origin of our solar system.

ENGADGET: PSA: Asteroid 2012 DA14 will pass the Earth at 2:00pm ET Alt

Data from NEAR could help answer questions about the origin and composition of asteroids, comets and the solar system, according to the mission managers at the Applied Physics Laboratory in Laurel, Maryland.

CNN: NEAR and Eros

Moreover, Vesta may have survived intact from the solar system's origin, despite having been pummeled by impacts so violent that they sprayed the solar system with buckshot blasts of debris.

WSJ: Asteroid Vesta Gets a Close Study