Giant star showers "life" on earth

USA Today (Society for the Advancement of Education), Dec, 2007

Employing one of the world's most sensitive radio telescopes, astronomers are probing the oxygen-rich environment around a supergiant star, and have discovered a score of molecules that include compounds needed for life.

"I don't think anyone would have predicted that VY Canis Majoris is a molecular factory. It was really unexpected," admits Lucy Ziurys, professor of astronomy at the University of Arizona, Tucson. "We began finding all these things that weren't supposed to be there."

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VY Canis Majoris, one of the most luminous infrared objects in the sky, is an old star about 5,000 light years away. It is 500,000 times brighter than the sun, but glows mostly in the infrared because it is a cool star. It truly is a "supergiant"--25 times as massive as the sun and so huge that it would fill the orbit of Jupiter. However, the star is losing mass so fast that in 1,000,000 years--an astronomical eyeblink--it will be gone. VY already has blown away a large part of its atmosphere, creating a surrounding envelope that contains about twice as much oxygen as carbon.

Among the molecules Ziurys and her team have reported are table salt (NaCl); a compound called phosphorus nitride (PN), which contains two of the five most necessary ingredients for life; molecules of HNC, which is a variant form of the organic molecule, hydrogen cyanide; and an ion molecule form of carbon monoxide that comes with a proton attached (HCO ).

Astronomers have found very little phosphorus or ion molecule chemistry in outflows from cool stars until now. "We think these molecules eventually flow from the star into the interstellar medium, which is the diffuse gas between stars. The diffuse gas eventually collapses into denser molecular clouds, and from these solar systems eventually form," Ziurys explains.

Comets and meteorites dump about 40,000 tons of interstellar dust on Earth each year. We would not be carbon-based life forms otherwise, Ziurys notes, because early Earth lost all of its original carbon in the form of a methane atmosphere. "The origin of organic material on Earth--the chemical compounds that make up you and me--probably came from interstellar space. So, one can say that life's origins really begin in chemistry around objects like VY Canis Majoris."