Frozen carbon dioxide - dry ice - has been found for the first time in interstellar space by an orbiting observatory, researchers say.
Dietrich Lemke of Max Planck Institute for Astronomy in Heidelberg, Germany, said Wednesday the European-built Infrared Space Observatory has detected frozen carbon dioxide in 20 different star-forming clouds scattered across the Milky Way, the home galaxy of the sun.The finding suggests that dry ice may be common around the wispy structures in space, he said.
"We have seen CO2 ice on the surface of grains of dust in clouds. It seems to be in many, many places," Lemke said in a telephone interview from the national meeting of the American Astronomical Society in Madison, Wis., where he presented his research results.
Most of the space clouds, he said, are immense structures of gas and dust with hot stars forming in their centers. Around the outer edges of the clouds, however, it is cold enough to freeze CO2, a gas that turns to a solid at temperatures below minus-108.4 degrees Fahrenheit, said Lemke.
The Infrared Space Observatory also has found vast clouds of warm water vapor, a discovery that Lemke said was "entirely new and very surprising."
"We found the water in hot planetary nebulae (star-forming clouds)," he said. There was so much that it suggests water may be the third most common chemical compound in space, he said. Only hydrogen-2 and carbon monoxide appear to be more common, Lemke said.
Water has been detected in space before, but Lemke said it has not been seen as a warm vapor and it was not known to be so commonly present.
All of the discoveries came in observations focused on structures that are hundreds to thousands of light years from Earth, he said. A light year is the distance light travels in a year, about 5.8 trillion miles.
Lemke said the dry ice and water discoveries were possible because the Infrared Space Observatory can detect slight temperature differences in objects far away.