Read the text and choose the correct alternative according to it. Our solar system Our solar system is the system of planets and other objects that orbit our sun. It has many parts. Our sun, the star of our solar system, holds everything in place by its gravity. There are eight planets and many moons. There are asteroids and comets. There are meteoroids and tiny particles of rock and dust. The sun, which is actually a star, is the largest object in the solar system. It contains more than 99% of the mass of the solar system. Our sun provides all the energy for life on Earth. Without its heat, Earth would be too cold to live on. Without its light, plants could not grow, and there would be no food for people and animals. Recently the International Astronomical Union (IAU) changed the definition of a planet, so Pluto no longer qualifies. Now we have eight planets in our solar system. Except for Mercury and Venus, all of the planets have at least one moon or natural satellite of their own. The planets are divided into two kinds: the terrestrial planets and the gas giants. The first four planets outward from the sun are classified as terrestrial planets. They are Mercury, Venus, Earth, and Mars. They are called terrestrial because they have a solid, rocky surface with metal cores. They are also sometimes called the rocky planets or inner planets.
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Which body used to be called a planet but now is not?