Questions about observations performed in the radio frequency range of the electromagnetic spectrum.
Questions tagged [radio-astronomy]
347 questions
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Does the radio signal decay when it travels through the intergalactic space?
When you emit the radio signal it starts moving at the speed of light. Radio beam is diffusing with each kilometer the signal has traveled. To the nearby receiver the signal is strong. But if the receiver is far away, the signal will become weaker…
Kestas
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8
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Math behind a uv plot in interferometry?
I've seen standard uv plots used discussions of interferometric array designs regularly, and I have a vague idea that each arc may correspond to a pair of elements within the array, and the coordinates $u, v$ in the plot may be something like the…
uhoh
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What is the maximum transmission distance of the radio signal in the outer space which could still be understood?
I’ll put this question in a form of a physics problem:
Transmitter at a point A sends a signal to a receiver at a point B. What is the longest distance in light years from points A to B for which receiver can still understand the…
Kestas
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6
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Radio Astronomy and Imaging
So, I've been starting to investigate radio astronomy, and am wondering about if certain things are possible from an amateur standpoint. I was looking at this powerpoint(that discusses building a tiny radio telescope),…
slookabill
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6
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Dispersion of Radio waves
I am unable to interpret this graph. What is the time on the x-axis? Due to dispersion why is pulse spreading across frequency rather than time if dispersion causes the delay? And how is that top graph for flux obtained?
Image source: Lorimer et al.…
Parsec
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6
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What is precipitable water vapor in millimeter-wave radioastronomy and how is it measured?
Looking through ALMA on-line documentation and articles, the quantity PWV (precipitable water vapor) is a central theme. I have two linked questions.
What (actually) is precipitable water vapor, and is there a "non-precipitable" component also? Why…
uhoh
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5
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Which wavelength is the most quiet, for a ground-based radio telescope?
This might seem like a backwards question, but I'm interested in what wavelength to select in a (hypothetical) ground-based radio telescope observation to expect detecting as little as possible! :)
It should still be reachable from space, i.e. a…
BjornW
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5
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Is broadcasting the location of Earth to potential extraterrestial civilization regulated?
How many times have we broadcast the location of Earth to the outer space? Are there any regulation in doing so?
I know so far we have send the Arecibo Message, and any receiver can trace the message sender's direction by the direction with which…
user3685689
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5
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How LOFAR pass through the ionosphere?
The LOFAR project open a new window in the universe's study because it allows to receive low frequences of the universe that we could not get because of the ionosphere.
But I'm wondering how can LOFAR pass through the ionosphere? Is it because of…
Ryokel
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5
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Can astronomical radio sources be used as a verifiable randomness beacon?
A randomness beacon is a source of random data that is broadcast to multiple parties. Users listening to the beacon receive the same sequence of random strings and no one can predict the values in advance. This is a construct that has many…
D. H.
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5
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4 answers
Has the microwave background radiation ever been blocked in order to prove it's really from the sky?
A rather stupid question but I was just curious if the radiation could be virtual. From the instrument....sort of like virtual particles. In other words if you just build a sensitive microwave detector and stick it in a South African Durban Deep…
user16724
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4
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Why is this video showing radio waves transmitted from a radio telescope?
I saw this video at Space.com and I noticed that at 00:05 the animation illustrates waves propagating from space into The Dish at Parks Observatory, but at 00:50 the direction of propagation is reversed! Would there be some reason for transmitting -…
uhoh
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Negative flux values in radio maps?
I am trying to understand some maps of radio emission in e.g the Milky Way. I continue to see in papers that these radio maps report negative values of the flux in Jansky units, although no explanation is given as to why.
For example Figure 1 here:…
math_lover
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3
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Different radio process band ranges
If we want to observe a galaxy for which we have optical data, what parameters we need to know to calculate its total radio flux at 3 cm?
Specially I am interested to know how to differentiate among the different process in radio, like synchroton,…
bhjghjh
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Rescaling a radio image
After a radio image has been cleaned it is advised that the fluxes be rescaled if the source is near the galactic plane. Can someone explain why this is needed?
Shakti
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