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mcclunyboy
2009-Dec-22, 02:00 PM
Hi,

Anyone got a list of the wavelength ranges of current observatoriesand where the james webb will fit in - purely curiousity im afraid.

I know Of Herschel and a few others but don't know exactly whats in use.

Tim Thompson
2009-Dec-22, 05:42 PM
See the atmospheric opacity (http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=bg005) graphic from the Spitzer Space Telescope website. Most ground based IR astronomy is done in the 1-3 micron range just because of the opacity of the atmosphere, though there are some windows even up to about 10 microns or so. The Spitzer Space Telescope Spectrum (http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=sig07-011) graphic shows the wavelengths observed by the Spitzer instruments (3.6, 4.5, 5.8. 8.0, 24, 70 & 160 microns) and how they relate to starlight. The long gone IRAS (http://irsa.ipac.caltech.edu/IRASdocs/iras.html) satellite observed at 12, 25, 60 & 100 microns (but its database is still heavily used). The Herschel Space Observatory (http://sci.esa.int/science-e/www/area/index.cfm?fareaid=16) will cover several bands in the 55-675 micron range, well into the submillimeter wavelength range (that's what we call the really long IR beyond about 200 microns or so). The JWST (http://www.jwst.nasa.gov/) is quite limited in wavelength range, with bands from 0.6 (the red end of the visible light range) to 27 microns. Spitzer, IRAS, Herschel and other observatories all cover longer wavelengths than JWST. But JWST has a huge mirror and very high angular resolution to compensate for the lack of long wavelengths.

ngc3314
2009-Dec-22, 07:36 PM
The JWST (http://www.jwst.nasa.gov/) is quite limited in wavelength range, with bands from 0.6 (the red end of the visible light range) to 27 microns.


I don't know that I'd phrase it that way - JWST can cover a factor of 45 in wavelength from shortest to longest. HST manages a factor of about 20, Herschel something like 12, IRAS approached 20 if you include the Dutch photometric instrument. The density of spectral features is roughly logarithmic in wavelength so this tells something about the utility of various ranges (although I hasten to add that there are notable exceptions for some purposes, like molecular bands).