This glow sets the limit for astronomical
observation at optical wavelengths, and viewing can be reduced further by auroras, zodiacal light, starlight and, of course, moonlight.
[10] A compact radio source was found at the centre of this nebula, and an infrared point source has also been found, but it has not been
detected at optical wavelengths.
So,
unlike at optical wavelengths, where distant galaxies get dimmer and dimmer and the deep sky ends up looking black, light from these dusty galaxies creates a mostly diffuse and flat infrared sky.
Five distant galaxies so choked with dust that they are completely
invisible at optical wavelengths have been spotted at submillimetre wavelengths by the European Space Agency's Herschel telescope.
They have used NASA's Kepler space telescope to study
it at optical wavelengths, and NASA's Hubble Space Telescope to confirm it is blue in color as a result of the preferential scattering of blue light by silicate particles in its atmosphere.
Telescope
at optical wavelengths.
At optical wavelengths, high resolution spectroscopy can be used to determine nuclear spin temperatures in NH3 and H2O through emission lines of their dissociation products NH2 and H2O +.