SEED OF PLANET
Origin of alien dust
Artist's rendering of what HD 131488's inner planetary system might look like as two large rocky bodies collide. Inset illustrates the location of HD 131488's dust belts (top) and comparable regions to our own Solar System (bottom).
IN the search for other planetary systems like Earth that are capable of hosting extraterrestrial life, scientists have come across some very alien systems indeed. But the latest ones have researchers truly perplexed. New observations have found evidence for planet formation around stars much more massive than the sun, as well as dusty debris thought to be leftovers from collisions between rocky planetary embryos. There's a twist: The dust has a completely different chemical makeup from the composition of our own solar system. These new findings were presented this month at the 215th meeting of the American Astronomical Society in Washington, D.C. Alien dust The strange dust that shows different chemical markers than what we find in our own neighborhood is in a star system about 500 light-years from Earth. The parent star, known as HD 131488, is surrounded by warm dust in a region called the terrestrial planet zone, where the star heats dust to temperatures similar to those found on Earth. Infrared imaging and spectroscopic measurements of the system, performed by the Gemini South Telescope in Chile, showed the unusual chemical composition. "Typically, dust debris around other stars, or our own sun, is of the olivine, pyroxene, or silica variety minerals commonly found on Earth," said Carl Melis, who led the research while a graduate student at UCLA. "The material orbiting HD 131488 is not one of these dust types. We have yet to identify what species it is it really appears to be a completely alien type of dust." Melis and his team think that the most plausible explanation for the presence of the warm dust is a recent collision between two rocky planetary-mass bodies. Cold dust While the warm dust is located at a distance from HD 131488 comparable to that between the Earth and the sun, Melis and his team also found cooler dust about 45 times farther out. This distance is analogous to the Kuiper Belt in our own solar system. The detection of both cold and warm dust around a young star is unusual, the team noted. "Although dusty telltales of planetary formation processes in the outer regions surrounding young stars have often been seen with infrared-sensitive space telescopes, for some reason stars that have large amounts of orbiting warm dust do not also show evidence for the presence of cold dust," said Benjamin Zuckerman, also of UCLA. "HD 131488 dramatically breaks this pattern." The cooler dust likely did not result from planetary collisions, and is instead probably the leftovers of planet formation that took place farther away from the sun, Melis said.
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