Our closest star

There’s no crisis yet, but the Sun already is more than 4.5 billion years old. That means that it is about halfway through its life. In five billion years, its hydrogen supply will be expended. Then it will grow large and glow red for a long time and probably become a white dwarf, which can live for trillions of years. But then the Earth will be unliveable. We’ll have to find another place to live before the Sun turns into a white dwarf!

The Lagrange 1 point between the Earth and the Moon.

The SOHO satellite now is our principal tool for research on the Sun. It hovers at Lagrangian Point L1, which is one of five points in space where the gravitational forces of the Sun and the Earth are equal and counterbalance each other. L1 is 1.5 million kilometres from the Earth in the direction of the Sun, so SOHO sees the Sun continuously. It is full of instruments and every day sends exciting images and other data to more than 500 scientists in 20 countries, including Norway.

Thanks to SOHO and other solar instruments, we know quite a lot about the Sun. It’s a normal star of class G2, the most common type. There are at least 100 billion stars – perhaps as many as 200 billion - in our galaxy, the Milky Way. And most of them are much like our Sun. So, learning about our Sun teaches us much about most of the stars we see. However, our Sun is larger and brighter than most stars of the Milky Way. In size it’s in the top ten percent, but there are stars that are far larger than our Sun.