‘Coreshine’ offers insight into stellar births

WASHINGTON - A group of astronomers has made a new discovery that promises a new window onto the earliest phases of star formation.

Science is literally in the dark when it comes to the birth of stars, which occurs deep inside clouds of gas and dust: These clouds are completely opaque to ordinary light.

Now, astronomers have discovered a new astronomical phenomenon that appears to be common in such clouds.he phenomenon-light that is scattered by unexpectedly large grains of dust, which the discoverers have termed “coreshine” — probes the dense cores where stars are born.

The discovery is based on observations with NASA’s Spitzer Space Telescope. As published this February, Juergen Steinacker, Laurent Pagani, and their colleagues from Grenoble and Pasadena detected unexpected mid-infrared radiation from the molecular cloud L 183 in the constellation Serpens Cauda (”Head of the snake”), at a distance of 360 light-years. The radiation appeared to originate in the cloud’s dense core. Comparing their measurements with detailed simulations, the astronomers were able to show that they were dealing with light scattered by dust particles with diameters of around 1 micrometer (one millionth of a meter).

The follow-up research that is now being published in Science clinched the case: The researchers examined 110 molecular clouds at distances between 300 and 1300 light-years, which had been observed with Spitzer in the course of several survey programs.

The analysis showed that the L 183 radiation was more than a fluke. Instead, it revealed that coreshine is a widespread astronomical phenomenon: Roughly half of the cloud cores exhibited coreshine, mid-infrared radiation associated with scattering from dust grains in their densest regions.

The scattered light carries information about the size and density of the dust particles, about the age of the core region, the spatial distribution of the gas, the prehistory of the material that will end up in planets, and about chemical processes in the interior of the cloud.

The results have been published in the September 24, 2010, edition of the journal Science. (ANI)