Tag Archives: Radio Astronomy

How Did Karl Jansky Measure Galactic Radio Emission at 20.5 MHz When the Earth’s Ionosphere Reflects Radio Waves at This Frequency?

Question: If 20MHz waves are ‘bounced’ by the ionosphere, how is it that Karl Jansky detected 20.5MHz waves coming from the galactic centre in 1932?  Also, what sort of receiver would he have used?  — Brendan Answer: I had to … Continue reading

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Is There a Place Where One Can See Daily Radio Images of the Sun?

Question: Is there a place that posts daily images of the Sun in a radio frequency, perhaps 21 cm, something like SOHO does for shorter wavelengths?  — Donna Answer: Unfortunately, I am not aware of a source for regular radio … Continue reading

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Availability of VLA Measurements of M87?

Question: I am contacting you on behalf of the MAGIC collaboration. I was wondering whether you took with VLA any further data on M87. We are trying to get an MWL coverage for our observation period spanning from 2012 to … Continue reading

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Tatoo Me with the VLA

Question: Hi.  Would you do me a favor to send to me through email the old aerial view graphic of VLA? It is like the Mercedes Benz logo without the circle, with a small rectangular at the intersection of the … Continue reading

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How Much Interference do Radio Telescopes Receive from Earth-Moon-Earth Propagation?

Question: How much interference do the radio telescopes receive from EME propagation (Earth-Moon-Earth), and is it really a problem? I know that with just Amateur Radio levels EME contacts happen with just a few hundred watts, if not less, and … Continue reading

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What Causes the Light and Dark Areas on Radar Images of Asteroid 2015 TB145?

Question: Just saw the stunning images of asteroid 2015 TB145. These are images obtained by illuminating the asteroid with microwaves from a source nearly the same direction as the receiving antenna. Why does the asteroid appear to be illuminated from … Continue reading

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What Type of Antennas are Used with ALMA?

Question: Which type of antenna arrays are used in ALMA site?  — Aloka Answer: You can get the answer to this question plus a lot more facts about the Atacama Large Millimeter/submillimeter Array at NRAO’s summary of ALMA.  The antennas … Continue reading

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How Do Very Large Antenna Arrays Synchronize and Work?

Question: How do very large antenna arrays synchronize with each other and why VLAs are used?  — Aloka Answer: Let me point you to a nice description of how radio telescopes and radio telescope arrays work that has been produced … Continue reading

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Black Holes and Gravitational Redshifting of Emission

Question: What do black holes look like on radio telescope images? Specifically how does a visible light image of a black hole compare to a radio telescope image of the same black hole? I’m curious whether gravitational time dilation and … Continue reading

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Why is the Very Large Array Located Where It Is?

Question: Why was the area outside Socorro chosen for the VLA?  — Mary Answer: The following is courtesy of Dave Finley, Public Information Officer at NRAO Socorro. One of the signs on the walking tour addresses this question. The VLA … Continue reading

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