Basics For Beginners – Telescopes, Part III
Written by Marko on October 10, 2007
Optical telescopes are used to create a picture of the objects in the space, but the problem with them is that they cannot “see” far. In order to see very far, such as billions of light years away from the Earth, we need other types of tools. Radiotelescopes provide us a possibility to see very far from our planet. Radioastronomy was born in 1930’s when American Karl Jansky suddenly captured radio signals from space. He realized that the signal comes from the same direction every day, but the astronomers did not put much attention to this phenomenon.
Although astronomers did not get interested, there was one man who got, Grote Reber. He built his own radiotelescope and found dozens of sources of radio signals in space. Bigger and higher performing telescopes were built in 1960’s.
The first big and fully rotating radiotelescope was built in Jodrell Bank in
Individual radiotelescopes are not able to “see” enough and therefore new solutions are needed. Radiotelescope arrays were invented around 1970’s to address this problem. An array is a group of individual radiotelescopes connected with each other. Together they can provide even better results. The first big array was built in
VLA is big but it is possible to build even bigger one by connecting telescopes by radio channels. VLBA (Very Large Baseline Array) has a diameter of 8000 kilometers and it is located on North American soil. Again, VLBA is big. Actually it is huge, but there are plans to build even bigger array. By positioning telescopes on Earth and in space we can get thousands times sharper images than today’s optical instruments can provide.
As you can guess, the future is for radioastronomy.
Picture of the Jodrell Bank telescope borrowed from Wikipedia.
UPDATE 2007-10-12: There is even bigger array, thanks for Stuart pointing this out in comments. Stuart said:
Actually, the largest radio telescope array in use today is called global VLBI and involves connecting the VLBA and the European VLBI network (EVN) with telescopes in Australia and several other countries. This gives a telescope the diameter of the planet Earth. At one point it also included the Japanese satellite Halca making a radio telescope effectively three times the diameter of the Earth.
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10-10-2007
11:47 pm
Stuart
Actually, the largest radio telescope array in use today is called global VLBI and involves connecting the VLBA and the European VLBI network (EVN) with telescopes in Australia and several other countries. This gives a telescope the diameter of the planet Earth. At one point it also included the Japanese satellite Halca making a radio telescope effectively three times the diameter of the Earth.
10-11-2007
11:05 pm
marko
Hi Stuart,
thank you for correcting me. I must say I did not know about that array at all. I must read about it, it sounds very interesting..
Anyhow, that global VLBI sounds very big. I just wonder how the communication between telescopes is managed. Latency gets quite big in arrays of that size, I guess. This “communication inside telescope arrays” could be one future topic in my blog.