This beautiful image of coronal loops over the eastern limb of the Sun was taken by NASA's Solar Dynamic Observatory (SDO) satellite on January 15-16, 2012.
Twinkle, twinkle, little star
How I wonder what you are
Up above the world so high
Like a diamond in the sky.
- children's song by Jane Taylor, 1806
The nearest star to planet Earth is the Sun, yet it doesn't "twinkle like a diamond in the sky." The Sun's family connections to the night-time objects we call stars are not always appreciated. However, the fact that the Sun is a star is crucial to the existence of life on Earth.
The Sun as a Star
As a star, the Sun is the source of energy which sustains all life on planet Earth. It is the Earth's universal timekeeper, defining the seasons, the harvests, even the sleep patterns of the creatures populating our planet. Yet, the Sun is only one of 100 billion stars in our Galaxy alone. With the Universe containing 100 billion galaxies, each filled with stars, we see that our Sun is hardly special. Our star does possess one outstanding quality which may make it unique in the Universe: it is orbited by a planet teeming with life.