How astronomers work?

3.Ultraviolet Astronomy
Ultraviolet light has wavelengths longer than X rays, but shorter than visible light. Ultraviolet telescopes are similar to visible-light telescopes in the way they gather light, but the atmosphere blocks most ultraviolet radiation. Most ultraviolet observations, therefore, must also take place in space. Most of the instruments on the Hubble Space Telescope (HST) are sensitive to ultraviolet radiation (see Ultraviolet Astronomy). Humans cannot see ultraviolet radiation, but astronomers can create visual images from ultraviolet light by assigning particular colors or shades to different intensities of radiation.

4.Infrared Astronomy
 
Infrared Telescope
Infrared telescopes detect radiation that has wavelengths longer than the light that humans can see. Infrared radiation enters the telescope and reflects off of a large mirror on the bottom of the telescope, then off of a smaller mirror. Detectors and instruments beneath the mirrors record the radiation. Infrared telescopes must be kept at very low temperatures to prevent their own heat from producing infrared radiation that could interfere with observations.

Infrared astronomers study parts of the infrared spectrum, which consists of electromagnetic waves with wavelengths ranging from just longer than visible light to 1,000 times longer than visible light. Earth’s atmosphere absorbs infrared radiation, so astronomers must collect infrared radiation from places where the atmosphere is very thin, or from above the atmosphere. Observatories for these wavelengths are located on certain high mountaintops or in space (see Infrared Astronomy). Most infrared wavelengths can be observed only from space. Every warm object emits some infrared radiation. Infrared astronomy is useful because objects that are not hot enough to emit visible or ultraviolet radiation may still emit infrared radiation. Infrared radiation also passes through interstellar and intergalactic gas and dust more easily than radiation with shorter wavelengths. Further, the brightest part of the spectrum from the farthest galaxies in the universe is shifted into the infrared.