# Questions tagged [radio]

Questions about the part of the electromagnetic spectrum with wave lengths longer than those of infrared radiation.

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### Why was the NVSS(NRAO VLS Sky Survey) conducted at 1.4 GHz continuum?

I am observing the nature of some galaxies looking at their radio images and contours from NVSS. So, the data collected have radio flux at other wavelengths but I am studying it at 1.4GHz. I have been ...
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### How to convert between surface density in JY/beam*KM/S / arcsec2 to mass surface density in Solar masses / pc2

I am interested in studying the gas kinematics of atomic hydrogen (21cm line) for a galaxy and have output I'd like to convert after assuming a model for my data using BBarolo. ...
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3 votes
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### How are shockwaves used to study magnetic fields of merging galaxy clusters?

Recently i read an article about how a shockwave 60 times larger than milky way galaxy is generated.When these shockwaves interacts with magnetic field, radio waves are emitted. I wanted to know how ...
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### Can it be that the formula for calc vlsr for sun have a part beginning with cos270 for Calculate sun/VLSR.cos 270=0?

I am working radioastronomy and have a formula for sun/earth calculation. The formula for sun begin with $20(\cos270 \cos 30 \ldots\ldots+$ Question: The first part is $\cos270=0$ and is that correct ...
3 votes
1 answer
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### What exactly did ALMA observe at 20 AU from the "Mega Comet Arriving From the Oort Cloud" that will pass in 2031?

Gizmodo's Mega Comet Arriving From the Oort Cloud Is 85 Miles Wide says: For the new study, Lellouch and his colleagues used the Atacama Large Millimeter Array (ALMA) in Chile to refine the comet’s ...
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### What is Euclidean fluence scaling in the context of bounding constraints on FRB all-sky rates? Would non-Euclidean scaling give a different answer?

The recent Chromatic periodic activity down to 120 MHz in a Fast Radio Burst contains two paragraphs in which X's are given "assuming an Euclidean fluence scaling". To me, a non-astronomer, ...
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### What is notable about LOFAR's sub-arcsecond radio resolution of distant galaxies? Does lower freq. range enable new capabilities that mm wave can't?

The BBC's Astronomers see galaxies in ultra-high definition covers some news related to papers in Astronomy & Astrophysics' dedicated, open access issue Sub-arcsecond imaging with the ...
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### How to superimpose an optical image upon a radio contour image using AIPS?

I am using AIPS by NRAO. I am trying to overlay a radio contour image with an optical image in the r-band. From the cookbook I could not find the suitable command for it. Both are fits files pf course....
1 vote
1 answer
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### What's known about Odd Radio Circle appearance? What would they look like if we could see them? Are they transparent/translucent in radio, or opaque?

update: March 2022: Phis.org: Astronomers reveal best image yet of mysterious odd radio circles in space Science Alert: Weird Circular Objects Observed in Space May Finally Be Explained MNRAS: ...
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### In radio astronomy, why do shorter baselines trade angular resolution for surface brightness?

I'm reading about radio astronomy and array configurations on the Very Large Array's (VLA) website. They state that the longest baselines provide the best angular resolution, but have very limited ...
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### Is **Voyager I’s** reduced data transmission rate as described in [this article][1] because of the distance or because its transmitter getting slower? [closed]

Is Voyager I’s reduced data transmission rate as described in this article because of the distance or because its transmitter getting older & slower?
10 votes
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### Do radio telescopes see other stars better at night?

As you know, we don’t see stars with the naked eye during the day because of the visible glare of our Sun. As I understand our Sun emits radio frequency waves, too. Is there a radio ‘glare’ from the ...
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### Why space-based VLBI scattering sub-structure is "Hopefully, a new promising tool to reconstruct the true image of observed background target(s)"?

@HDE226868 mentioned in the observatory that the GBT@20 – The Celebration; Twenty Years of Innovation and Discovery was going on. There are plenty of YouTube videos and slide sets available as links. ...
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4 votes
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### What is the significance of the velocity resolution in spectral line observations using radio interferometry?

I've always struggled to conceptualize the term "velocity resolution" in spectral observations. In principle, it is simple to calculate. For example, one can take the spectral width and ...
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4 votes
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### What is the significance of using baseline pairs in radio interferometry?

Radio interferometry utilizes arrays of smaller telescopes that are linked together to synthesize a larger aperture telescope. Astronomical radio observatories, such as the Very Large Array in New ...
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### Can one build a distributed radio telescope?

I understand some radio telescopes are built as arrays of receivers. Could one build an array from a heterogeneous set of receivers in scattered locations? Suppose a large number of persons each ...
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### Current topics on Radio Astronomy and looking for advice

Background and Question: I'm an undergraduate student interested on Radio Astronomy. I consider myself enthusiastic about it and I project myself following this "path" so I'd like, ...
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### The electron–cyclotron maser emissions from Earth

The first-ever detection of radio signals caused by the electron–cyclotron maser mechanism outside of the Solar System, on Tau Bootis b was recently published (here). This phenomenon causes huge radio ...
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1 answer
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### Would the electron cyclotron-maser emission mechanism affect Proxima b's ability to retain an atmosphere?

In a recent arXiv preprint, Pérez-Torres et al. "Monitoring the radio emission of Proxima Centauri" claim the detection of radio emissions synchronised with the orbit of the planet Proxima b....
4 votes
1 answer
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### How bright is the Sun in S-band?

As far as I can tell when the Voyagers listen to Earth they have the Sun in the same beam. I never did calculate how bright a blackbody Sun would be because I have no idea if that's representative of ...
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3 votes
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### What does the Sun "look like" below 100 MHz?

Radio2space.com's The Radio Sun says: At very low frequencies (below 0.1 GHz) and therefore at very long wavelengths (> 3m) the solar disk appears much bigger and brighter in the center, and its ...
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1 vote
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### How can I determine the location of an object for one observer given the location for another?

I know an object exists at the location of the beam-pointing-center of a radio telescope. I know the elevation/azimuth of the beam pointing center, as well as it’s “location” in galactic coordinates. ...
2 votes
1 answer
192 views

### Has optical interferometry been done at radio frequency using heterodyning with a laser in a nonlinear material?

If one collects narrow band optical emission from a large telescope with frequency $f_1$ and mixes it in a nonlinear crystal with laser light of a nearby frequency $f_2$, it would produce two new ...
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5 votes
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### How do we know that comets definitely mase and not just fluoresce? What is it about 18-cm lines that indicates that is really masing per se?

Wikipedia's Astrophysical_maser#; comets mentions some anecdotes of notable masers associated with comets, and Maser emissions from comets begins: The 18-cm lines of the OH radical are the only ...
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3 votes
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### Current delay for radio signals from the Mars InSight mission

I've been meaning to post it on the day when InSight landed but just got around to it now. When they broadcasted landing in real-time, it really wasn't in real-time because radio signals from Mars ...
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4 votes
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### What EM spectrum can stars be most cheaply observed using Remote Sensing during the day?

I would like to augment my GPS navigation with remote sensing of 'the sky.' I am looking for any astronomical body that can be perceived during the day. Maybe Pulsars emit something easily detected, ...
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6 votes
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### What explains this puzzling radio signature from a fireball?

September 21, 2017 a bright fireball over Holland was reported by hundreds of people. Several all-sky cameras recorded it as well as a special radio beacon set up to capture radio signatures of ...
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2 votes
2 answers
668 views

### How to calculate the integrated source flux density of a continuous source?

I'm working with data from radio surveys. My images are .fits files with BUNIT Jy/beam. I want to calculate the net flux from a continuous source (not point source). When I simply added all the ...
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665 views

### Radiometer Equation for Flux Density

In Duncan and Lorimer's Handbook of Pulsar Astronomy, the equation for the flux density using a radio telescope is given as (for a top-hat function): S=\frac{\beta\,\mathrm{SNR}\, T_{sys}}{G\sqrt{...
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4 votes
1 answer
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### Why levels of radio contours maps are given in mJy/beam and what does it mean?

I know what a jansky is, but I don't understand what beam (in $\frac{1 Jy}{beam}$) is. If jansky is a unit of flux density, what kind of unit is $\frac{1 Jy}{beam}$?
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### How do astronomers at SETI know if they received intelligent radio signals from other planets?

Do they expect to see wave modulations like the ones we use in our technology? what do they expect the waves to be like exactly?
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### Detecting people on Proxima Cen b [duplicate]

Recently the news announced the discovery of a planet with characteristics similar in size to earth with the possibility for liquid water, 4.2 light years away. Now, if there was a civilisation of ...
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2 votes
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### When does oscillation of interplanetary plasma occurs?

When does oscillation of interplanetary plasma occur? When and what are the reasons of the excitation of this plasma that makes it oscillate? Does it oscillate when is not excited? Can extremely ...
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3 votes
1 answer
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### Need help with the math in Python program to flag Jovian radio emissions

A few days ago I decided to take on the little project of converting a Qbasic program into Python (as a side project to my Radio Jove project), and I've managed to get it to run, but the math is ...
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-6 votes
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### Why does the Southern hemisphere seem to be short of radio telescopes? [closed]

In northern hemisphere, we have GBT, Arecibo, Parkes, Jodrell and VLA, while in southern hemisphere, only Australia has big radio telescopes. ALMA is in Chile, but it is in sub-mm. Is not ...
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