According to the passage, what type of star is the Sun at present?

It is easy to think of the Sun as something unique, but to an astronomer it is an ordinary star: a hot, glowing ball of gas like the countless stars we see at night. It only looks different because it is so much nearer. Even so, it is far away, about 150 million kilometres, which is roughly four hundred times the distance from the Earth to the Moon.

The Sun is about a hundred times wider than the Earth, yet it is only an average size for a star. Astronomers have found stars a hundred times bigger than the Sun, and others ten times smaller.

It is also middle-aged. The Sun is about 4.5 billion years old and is at present a type of star called a yellow dwarf. In another five billion years or so it will swell into a big, cooler star called a red giant. A few billion years after that, it will shrink into a white dwarf: a star about the size of the Earth, but far heavier.

None of this makes the Sun any less important to us. Its gravity holds the whole solar system together, and life on Earth depends on its light and heat. An ordinary star, it turns out, is enough to make a planet a home.