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Time Variability Observed in Radio Emission?

-- | December 22, 2013

Question: Has radio astronomy (less than 100 years old) been able to detect change over time, other than regular periodic motion or oscillation? For example, the actual formation of a star, or a supernova, or gas or dust accretion? For example, before and after images that show significant change. Another way of asking: are the processes of change in the universe observed, or inferred? — Peter

Answer: Yes. The best example of a radio observation which tracks changes in the radio emission from an object is the measurements of the proper motions of water masers in star formation regions in our galaxy. Measurements over periods ranging from just a couple of years to 30 years have traced the motion of these signposts of shocked gas in star formation regions. Another example are the changes in radio emission from supernova remnants. The radio emission from the supernova remnant produced by the supernova 1987A over the period 1991 to 2013 has been quantified. These are just a few examples.

Jeff Mangum

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