Cosmic Butterflies

Book excerpt: At the end of a star's life, it wraps itself in a cocoon by spilling out gas and dust. Sometime later, a butterfly-like nebula emerges from the cocoon and develops into a planetary nebula. They are among the most beautiful of the celestial objects imaged by the Hubble Space Telescope. Their structures, like bubbles floating in the void, are complemented by a kaleidoscope of colour emitted by glowing gases. Delicate, lacelike, streamers of gas add to their complexity. The production of a planetary nebula by a star is a milestone in the life of a star, an event that foretells the doom of the star when its central energy source runs out. In this book, Sun Kwok tells the story of the discovery process of the creation of planetary nebulae and of the future of the Sun. Full colour illustrations are included throughout the book.