Listening to the stars

Once upon a time, I wanted to be a radio astronomer. What is a radio astronomer, someone who talks about astronomy on the radio? No, no, no...although I would probably be good at that!

Radio astronomers observe the universe using big dish antennae, like the Arecibo Radio Telescope in Puerto Rico (upper left), or a more typical dish like the one below, on the right.

At the AAS meeting in St. Louis, I met three young astronomers from West Virginia University who were using radio telescopes to study pulsars, the rapidly spinning remains of exploded supernovae. They had four posters in the display hall and were very gracious explaining what it all meant and answering my neophyte questions.

The first paper described how they utilized the Green Bank Radio Telescope in drift scan mode while the tracking was shut down in the summer of 2007. Yup, that's right, the telescope was down for repairs and could only point in one direction on the sky, but they were able to design a program, submit a proposal and get telescope time to do a survey looking for pulsars and transient radio signals. They discovered some new pulsars and stumbled across some known pulsars. They will be doing follow-up observations on the new discoveries to try to determine more accurate astrometric (position) and spin properties.

The second poster discussed how they used a computer simulation program to model pulsars by changing various properties, like the alignment between the spin and magnetic axes, demonstrating the differences and viability of two competing models. I admit, this was way over my head and my brain was spinning at some fraction of a typical pulsar spin period about half way through the explanation. The whole thing is mind boggling, really. We're talking about the properties of extremely dense stellar remnants spinning thousands of times per second!

Another paper described the successes they were having using the Arecibo radio dish to perform the most sensitive large scale survey for pulsars to date. So far they have discovered 35 new pulsars, and based on that figure they predict they will find some 1500 pulsars by the time the survey is complete. Now that is impressive, but what I found even more fascinating is the fact that they are using networks of remote computers, much like SETI@home, to sift through all the terabytes of data and identify new sources.

The other West Virginia U poster described using the Giant Metrewave Radio Telescope in India to study the radio universe in meter wavelengths. Think about that for a second. Light in this part of the spectrum comes to us in waves three feet long or greater! This observatory combines the signals from 30 dishes 45 meters in diameter to "provide a more detailed view of our universe than a single dish of larger size". Combining signals from multiple telescopes like this is known as interferometry. Both optical and radio telescopes are being used in this way. The advantage gained is the ability to distinguish finer detail in celestial objects than is possible with a single mirror or radio dish.

This is the technique used to study things as small as the proto-planetary disks around stars, the subject of an invited talk given by David Wilner at the AAS meeting Tuesday, June 3rd. One of the most remarkable things I saw in this presentation were the actual radio images of disks around other stars in our galaxy. Some of them were irregular shaped, not perfectly round as I had imagined they would be. Even more incredible was the fact that from the radio data the astronomers were able to determine the structure and density to a greater degree than I imagined possible, and some of these disks actually had areas vacated or cleared out as if a planet or other body in orbit around the star had gobbled up the material in its path, like the shepherd moons and gaps in the rings of Saturn.

I don't think they could do anything like this stuff when I was college age, and obviously, I made other career and life choices, but it was nice to get a whiff of what is being done nowadays in a field I may actually have pursued in a parallel dimension.

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