Last night, the Gran Telescopio Canarias (GTC) at the Observatorio del Roque de los Muchachos of the European Northern Observatory (ENO) in La Palma, Canary Islands, Spain, saw its "First Light". The first star observed was Tycho 1205081, close to Polaris - a bit more photogenic is this shot of the pair of interacting galaxies UGC 10923 with extended star formation regions, taken with an exposure time of 50 seconds:
Interacting galaxies UGC 10923 seen with the eyes of the World's largest telescope (Credits: Gran Telescopio Canarias, Instituto de Astrofisica de Canarias)
The primary mirror of the new telescope consists is made up of 36 separate, hexagonal segments, fabricated at the Glaswerke Schott in Mainz, just around the corner from Frankfurt. Taken together, the segments have a light-collecting surface of 75.7 m2, which corresponds the a circular mirror with a diameter of 10.4 metres. At this size, it is the currently largest telescope for optical and near-infrared light!
The Gran Telescopio Canarias in La Palma, Canary Isles, in September 2006 (Credits: GTC project webcam)
This was in the news these days here (see e.g. stern.de, faz.net, or Le Monde), but the European Northern Observatory somehow has managed to issue a press release only in Spanish, so I am a bit at loss to find more details. Actually, the report in the FAZ is very good, and recalls the developments that lead to the construction of these huge telescopes:
I remember from the popular astronomy book I read as a kid that at that time the 5-metre mirror of the Mount Palomar telescope was thought to be the endpoint of the growth of telescope mirror size: Larger solid mirrors are to heavy and deform when the telescope is moved, and moreover, the image gets blurred anyway by the distortions caused to the light as it passes through the atmosphere. As a case in point, a 6-metre telescope in the Soviet Union was mentioned, which produced pictures of not as high a quality as expected from its size. I was quite disappointed when I read that.
Fortunately, both obstacles could be overcome with new technologies first realised in the 1990s: Active Optics, which means that the mirror is always kept in perfect shape by an array of motors and can therefore be lightweight, and large, and Adaptive Optics, which manages to compensate for the fluctuations of the density of air and allows for a seeing nearly as good as in space.
Among the big optical telescopes using these techniques - the Keck, Subaru and Gemini-North telescopes in Hawaii, the four mirrors of the Very Large Telescope and the Gemini-South telescope in Chile, the Large Binocular Telescope in Arizona, the Hobby-Eberly-telescope in Texas, and the South African Large Telescope in the South African Karoo - the Gran Telescopio Canarias is currently the largest one.
The good news is that all these telescopes will continue to take great shots of the Universe for the professionals and for armchair astronomers like me, even when the Hubble Space Telescope will once have stopped working.
TAGS: Gran Telescopio Canarias, Astronomy