Nanodiamonds studding space or dust particles refracting starlight? What causes the mysterious red and blue glows that pervade vast areas of the Milky Way has never been certain, but silicon oxide nanoparticles are the latest idea to fit the bill.
The red glow, or Extended Red Emission, was discovered more than 20 years ago. Astronomers suspected that particles in interstellar dust clouds were absorbing starlight and emitting red light, but nobody could pinpoint the nature of the particles.
Things got even more complicated with the discovery in 2005 of luminescent blue glows in some regions of interstellar space. 鈥淣anodiamonds in the sky could explain the red light, but not the blue light,鈥� says Ashraf Ali, an astrochemist at the NASA Goddard Space Flight Center in Maryland. 鈥淲hat鈥檚 more, nobody knew how they could have formed in space.鈥�
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Instead, Ali and his colleagues believe that nanoparticles of silicon oxide are responsible. To see if solid crystals could be made from silicon oxide gas in space, they recreated the pressure and temperature conditions found in the regions around stars and successfully created clusters of silicon oxide nanoparticles (Nanoletters, vol 6, p 1190).
Such clusters are predicted to produce both red and blue light when they absorb starlight.
