![starmade asteroids starmade asteroids](https://www.pygame.org/thumb/a11c9d2df61326f4e9865f6f16fcad33.png)
In the largest ones, the decay of radioactive elements heated their interiors, causing their material to "differentiate." In other words, gravity pulled the heavier materials, like iron and nickle, to the centers of these asteroids, while lighter rocks "floated" to the surface, creating a structure that is similar to Earth and the other inner planets. But today, most believe that the asteroids were prevented from coming together to form a planet by the gravity of nearby Jupiter, which nudged them on each orbit around the Sun.Īsteroids are made of rock and metal. Most orbit the Sun in a broad region known as the asteroid belt, which is between the orbits of Mars and Jupiter.įor a long time, astronomers thought that Ceres and the other asteroids were the remnants of a planet that exploded. Ceres is the largest, with a diameter of almost 600 miles (1,000 km).Īstronomers have discovered hundreds of thousands of these boulders, and with automated searches they are discovering thousands more each year. Instead of a planet, they had found the first of the asteroids - large chunks of rock that were left over from the formation of the solar system. But the next year, astronomers found a second object in a similar orbit, then another, and another.