Topic 5 Space Exploration What Channel Is That? Topic 5 Space Exploration

Electromagnetic Radiation Stars produce many different types of electromagnetic radiation. Visible Light is only one of the types of electromagnetic radiation. Radio Astronomy: how astronomers use radio waves to learn about the composition of stars.

Radio Telescopes In 1932 Karl Jansky (an engineer) used an antenna to identify why reception for phone calls was poor. He found that there were radio emissions that rose and set with the Sun, planets and stars. He concluded that these radio wave sources came from space.

Radio Telescopes Grote Reber (radio engineer and amateur astronomer) built a radio dish (radio telescope) to “listen to the sky.” He discovered that the strongest radio waves came from specific places in the sky. He thought there must be radio objects in space responsible for these emissions. Bright radio objects were identified by hissing noises. As Reber moved his radio telescope the hissing noises got louder when “tuned in” to where the object giving off large amounts of radio waves was found in space.

Bigger Radio Telescopes Radio waves have longer wavelengths than light waves. This means that radio waves provide images with less resolution than light waves. Radio waves are able to penetrate a dust cloud which is where visible light stops. This means radio telescopes gave astronomers new information about the universe.

“Seeing” Radio Waves Radio telescopes cannot “see” radio sources In early days of radio astronomy movement of needles and dials monitored the incoming radio waves. Data collected was then placed on a graph. Today computers collect the data from radio telescopes and create pictures based on the strength of the signal. Low intensity signals are blues and as the intensity strength the colours go through green, yellows, reds and finally to whites.

Optical Connections When astronomers first identified objects with strong radio wave emissions they wanted to confirm with optical telescopes. At first this was not possible because radio telescopes had such low resolution. But as improvements were made astronomers made optical connections.

Connecting Radio Telescopes Images from space can be improved by connecting telescopes together. Radio Telescopes can be connected electronically and their signals combined using a computer. Resulting images are as good as if there was one telescope as big as the difference between the two. Interferometry is when two or more telescopes are connected electronically to combine their images. The most accurate set of connected telescopes is the Very Large Array (VLA) in New Mexico. VLA Part 1 VLA Part 2

Radio Telescopes Bigger Than Earth Very Long Baseline Interferometry (VLBI): The ability to connect telescopes without wires due to improvements in computers and precision in modern clocks. Produces images 100 times as detailed as the largest optical telescopes that exist today. Astronomers have the ability to connect as many radio telescopes as they want in as many places as they want. Signals collected from each telescope is time marked, transferred to a computer disk, then uploaded to a central computer and combined to form one image.