Astronomy

A Clear View in the IR

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Science  23 Dec 2011:
Vol. 334, Issue 6063, pp. 1605-1607
DOI: 10.1126/science.334.6063.1605-d
CREDIT: DAVID MALIN

If human eyes were sensitive to light in the infrared (IR) instead of the optical regime, the night sky would not appear dark to us. That's because hydroxyl molecules in the atmosphere emit IR light in the form of a forest of extremely bright, very narrow emission lines. This light varies very rapidly and would prevent us from seeing much of the universe beyond Earth, apart from the Sun, the Moon, a few planets, and possibly a few stars. To overcome this problem, astronomers launch IR telescopes into space. However, space telescopes are expensive, and have limited apertures and long lead times. Bland-Hawthorn et al. describe a filter that is capable of suppressing the atmospheric IR lines and can be used on ground-based telescopes. The filtering process involves focusing light onto an optical fiber and splitting it into parallel tracks, using what is termed photonic lantern technology. Each track is then processed by a Bragg filter, a device that reflects back the light from the atmospheric emission lines and lets wavelengths between those lines through. This setup was successfully tested at Siding Spring Observatory in New South Wales, Australia.

Nat. Commun. 2, 10.1038/ncomms1584 (2011).

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