NASA's Spitzer Space Telescope has detected enough water vapour to fill the oceans on Earth five times inside the collapsing nest of a forming star system. Astronomers say the water vapour is pouring down from the system's natal cloud and smacking into a dusty disc where planets are thought to form. The observations provide the first direct look at how water, an essential ingredient for life as we know it, begins to make its way into planets, possibly even rocky ones like our own. "For the first time, we are seeing water being delivered to the region where planets will most likely form," said Dan Watson of the University of Rochester, N.Y. The star system, called NGC 1333-IRAS 4B, is still growing inside a cool cocoon of gas and dust. Within this cocoon, circling around the embryonic star, is a burgeoning, warm disc of planet-forming materials. The new Spitzer data indicate that ice from the stellar embryo's outer cocoon is falling toward the forming star and vaporising as it hits the disc. "On Earth, water arrived in the form of icy asteroids and comets," said Watson. "Now we've seen that water, falling as ice from a young star system's envelope. This water vapour will later freeze again into asteroids and comets." Water is abundant throughout our universe. It has been detected in the form of ice or gas around various types of stars, in the space between stars, and recently Spitzer picked up the first clear signature of water vapour on a hot, gas planet outside our solar system, named HD 189733b. In the new Spitzer study, water also serves as an important tool for studying long-sought details of the planet formation process.
NGC 1333-IRAS 4B is located in a pretty star-forming region approximately 1,000 light-years away in the constellation Perseus. Its central stellar embryo is still "feeding" off the material collapsing around it and growing in size. At this early stage, astronomers cannot tell how large the star will ultimately become. Spitzer
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