The Sciences

Dialing in a radio eclipse

Bad AstronomyBy Phil PlaitFeb 18, 2011 6:00 PM


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On January 4, 2011, the Moon passed directly in front of the Sun, treating much of Europe, north Africa and western Asia to a total solar eclipse. I saw lots of really interesting pictures from the event, but this has to win for what must be the oddest image:

[Click to penumbranate.] This was the view using LOFAR, or the LOw Frequency ARray, a radio telescope in the Netherlands. It's designed to sense radio waves from space in the range of 10 - 250 Megahertz (which encompasses FM radio and TV broadcast signals, interestingly). Lots of astronomical objects emit at this energy. The Sun is not a terribly luminous source, but it happens to be pretty close by, making it bright. The images show the partial eclipse at 140 MHz, starting at the upper left as the Moon was already leaving the Sun's disk. By the last image (lower right) it was all over. I had to laugh: it was cloudy in the Netherlands that day and people missed seeing the eclipse themselves, but clouds are transparent to radio waves. In fact, radio astronomers can, in many cases, observe astronomical objects even during the daytime, rain or shine -- for a class in grad school, we observed the Sun when there was snow on the radio dish! I remember, around that same time, staying up all night at the observatory (and sleeping during the day) for two weeks in a row for my Masters Degree. At about the halfway point I was reconsidering my choice of doing optical astronomy. Of course, now we have robotic observatories which observe for you, and deliver the data via email or FTP. It's a far more genteel way of doing science.

Image credit: ASTRON. Tip o' the welder's mask to Cecileavdm via Noisy Astronomer.

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