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Points of view: Charles Telesco
03/06/2003
"(...) Its unique combination of features, and the fact that it will be installed at the biggest telescope in the world, mean that Canaricam will be a very powerful instrument". Charles Telesco.
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Work in today's society has three marked characteristics: we specialise, join forces and simplify. By specialising we can penetrate deeper into a field of work; by joining forces we can pick and choose the most suitable abilities for each task; and by simplifying, of course, we can make life easier.
Rest assured that these three characteristics are also to be found in the world of science. Astrophysics is a prime example: it is a specialised branch of astronomy so complex that scientists need multi-function instruments to make their work manageable. This was the inspiration for CanariCam, a fascinating first generation instrument for the Gran Telescopio CANARIAS (GTC) that will offer imaging capability as well as spectroscopy, polarimetry and coronography in the mid-infrared spectrum.
INTERVIEW WITH CHARLES TELESCO
CanariCam is being developed by the Infrared Astrophysics Group at the University of Florida, with the Instituto de Astrofísica de Canarias (IAC) participating. The project's Principal Investigator, Charles Telesco, talked to us about some of the features that make this first generation GTC instrument so special.
How is CanariCam different from other instruments?
It is important to understand that the mid-infrared, the range that CanariCam works in, is extremely important for science.
We already have instruments that work with visible, near and mid-infrared light and we need to use all of them to obtain a complete 'picture'. This is why large telescopes (not just the GTC, which will be the biggest, but others like the VLT, GEMINI and SUBARU) need mid-infrared instruments for first line astronomy.
Looked at from one perspective, this means that CanariCam will give the GTC something that every other telescope has. Essentially, it will be the same as VISIR (the device the VLT will use) and the next generation of mid-infrared instruments planned for Keck. It will also be very similar to the T-ReCS instrument for GEMINI South (which we are building at the University of Florida), and MICHELLE, the instrument for GEMINI North, which is now approaching completion.
But CanariCam will be different because the images it produces will be highly detailed. It will be better than T-ReCS, for example, because it will have better spectroscopic capability. In other words, CanariCam will have greater resolution.
What will make CanariCam truly unique, though, will be its spectroscopy and coronography facilities. It will be the first instrument of its kind to incorporate all four of these functions: imaging, spectroscopy, polarimetry and coronography in the mid-infrared spectrum.
The MICHELLE instrument will offer limited polarimetry capability; but CanariCam’s polarimetry function, however, will be unique. It will also be the only instrument in the world capable of coronography in the mid infrared - that is why it is so special.
Its unique combination of features, and the fact that it will be installed at the biggest telescope in the world, mean that Canaricam will be a very powerful instrument.
With it, we will be able to compete with other large telescopes.
In terms of the other GTC instruments, we can say that ‘EMIR’ WILL observe galaxies and ‘OSIRIS’ will mainly observe stars. Would it be right to say that CanariCam will be a planet ‘finder’?
I would not call it a new planet finder, rather that planets are one aspect of the whole programme. If I had to sum up what CanariCam will do, I would say that it will mainly be used in our attempts to research and understand star formation.
To think about star formation we have to imagine what goes with it. As a star forms we can look at the disc that surrounds it, the way planets are being made and the perpendicular jets spurting out of the disc...the whole process is visible.
CanariCam will look at the different processes involved in star formation - there will always be stars forming - including, of course, looking for planets.
CANARICAM: A "MULTIDISCIPLINARY" INSTRUMENT
CanariCam will offer four science modes: Imaging, Spectroscopy, Coronography and Polarimetry.
Imaging refers to the ability to produce a two-dimensional representation of a three-dimensional object (in this case mid-infrared imaging - in effect, CanariCam will be able to take "photographs" of everything it finds in the sky).
Spectroscopy looks at the nature of an object by analysing its spectrum. Observing a star’s spectrum can yield important information about the star’s chemical composition as well as its physical conditions (like its temperature, density and pressure) and its speed of rotation.
Coronography is an observation technique used to hide a bright object in the field so that another much dimmer object can be seen properly. It is used for observation of the sun’s corona. At the GTC it will serve in the search for planets close to a star that is much brighter than they are.
Polarimetry looks at light polarisation, the process by which the planes of vibration of lightwaves are aligned. This technique will allow us to research magnetic fields and light dispersion by dust particles. It will mainly be used to look at dust-containing regions surrounding young stars and stars that have not yet formed, as well as those around old stars like AGBs that have gone through the main sequence and are moving into the next phase of their evolution.
As well as these four science modes, CanariCam will offer two engineering modes for "automatic testing": one will ensure that the mirrors are aligned and the second will check the humidity levels.
Natalia R. Zelman