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Cosmological Problems
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December 17th 18, 09:25 PM posted to sci.astro.research
Phillip Helbig
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Posts: 38
Cosmological Problems
In article ,
(Steve
Willner) writes:
[Moderator's note: The James Webb Space Telescope is more like a
traditional telescope in space, the successor to HST in some sense, but
with more emphasis on the infrared.
JWST wavelength range is roughly 0.6 to 27 microns
Visible light is about 0.4 to 0.7 microns (400 to 700 nm (nanometers),
4000 to 7000 Å (Ångström)), so there is a bit of overlap between HST and
JWST. JWST is more or less a normal reflecting telescope, with a CCD as
detector.
The CMB is observed at lower frequencies
much longer wavelengths than JWST.
You can easily search for "Planck focal plane" on the web and find an
image showing lots of horns and other radio-astronomy stuff. Planck has
a wide frequency range, with frequencies from 30 GHz to 857 GHz,
corresponding to wavelengths between a centimetre and about a third of a
millimetre, the latter being about 300 microns. Typical traditional
ground-based radio astronomy is in the GHz range and below, so
wavelengths from centimetres to metres.
All ground-based and balloon telescopes study relatively high
multipoles, i.e., relatively small angular scales.
To do the large angular scales, one has to observe a large part of the
sky.
I think it's only
the lower multipoles that carry information on H, but I may be wrong.
Here are some movies where one can get a feel for how changing a
parameter changes the CMB power spectrum:
https://space.mit.edu/home/tegmark/movies.html
In the plots, as usual, larger angular scales are on the left, smaller
ones on the right.
Phillip Helbig
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