3 December, 2000

A brief introduction to radio astronomy

Light from the sky comes in all kinds of wavelengths, not just those visible with our eyes. Different wavelengths of light can tell us about the object that is producing the light. A hotter source will produce shorter wavelengths of light, and likewise, cooler less energetic sources will produce shorter wavelengths of light. All this light travels through space, and eventually we are able to detect it and gather information about various objects in the universe.

AST/RO is a submillimeter telescope, meaning that it looks at light that has frequencies just under a millimeter in wavelength, billions of times longer than visible light. These frequencies of light are produced in molecular clouds- relatively dense areas of atoms and molecules in interstellar space that are typically much cooler than stars. The light from these clouds is produced by molecules changing energy states. Occasionally, a molecule will be bumped up into a higher energy state. Since it would prefer to be in a lower energy state, it eventually falls back releasing the energy difference as a photon with a specific frequency. This frequency of light corresponds to the parcticular molecule and the specific energy level transition that it goes through.

AST/RO looks at one spot in the sky at one specific wavelength to see how much light is coming from that point. Repeating this many times will give us data points that can be put together to create a picture of that region of the sky in a specific frequency. Since the frequency is produced by a specific molecule, these pictures tell us what molecules are inside these molecular clouds, and how they are distributed. This information gives astronomers insight to the structure and evolution of the universe.