and other characteristics of large gas clouds. IR spectroscopy and photometry let us measure temperatures and composition of cold objects, including both clouds and solid masses.We use IR tools in conjunction with others to understand the origin, evolution, and current state of the solar system,......
5. how that information is used in modern astronomy?
Understanding dynamics of gas clouds and proto-stars helps us to understand the evolution of galaxies and stellar systems. IR imaging helps us see through otherwise opaque clouds and lets us calculate motion, mass, and other characteristics of large gas clouds. IR spectroscopy and photometry let us measure temperatures and composition of cold objects, including both clouds and solid masses.
We use IR tools in conjunction with others to understand the origin, evolution, and current state of the solar system, stellar regions, and the galaxy. We extend this understanding with predictions and models to understand other phenomena we may observe throughout the universe, such as intergalactic gas filaments that tell us some details of the early state and evolution of the universe.
1. Heat energy. All energy is same and undifferentiated. Depending upon its level (measured in Joules) it gets categorised as heat, light etc. It is called heat energy as that is associated with heat, the aggregate kinetic energy of gas molecules in a cloud (or atmosphere). Generally heat is because of molecular processes and energy exchange therein.
2. (I told you) it is heat energy. Total heat of a system (of molecular cloud or gas) divided by the number of molecules gives the average kinetic energy per each and is measured as Temperature. Of course, the individual heat capacity of each molecule also accounts for the energy it can hold.
Coming to infrared (IR), it is a part of the electromagnetic energy spectrum spanning a wavelength range of 0.1 millimetre to almost 0.7 micrometre (micron) when it meets visible part of spectrum. The nomenclature is due to the human penchant for analysis, categorisation and "naming".
3. There is in a IR telescope, 'focal plane array' (FPA) made of any of special materials depending upon the IR region we want to study (IR band is vast stretching over 8.8 Octaves). The array composed of a million or so of tiny bits of the material generates so many currents forming an array, much like the CCD array that replaced the photographic plate. All these work on the same principle of individual grains converting the energy from the photons to currents (or in case of photographic plate that was earlier used in IR also to a permanent 'hard copy'). In NIR, Cadmium Telluride is very popular. The individual currents form a planar raster of information picture elements (pict els or 'pixels' for short). Finer the graininess the more the detail one gets that an 'enlargment' reveals. The telescope is like any other optical telescope with care taken to use a glass that is transparent to IR. In FIR (Far IR) & Mid-IR it is better to suffer the attenuation of the glass medium, but it should accomplish focusing at such wavelengths. At times different materials that are transparent at IR (though appearing black to our eyes) like Germanium are shaped into lenses.
