Questions tagged [radio-astronomy]

Questions about observations performed in the radio frequency range of the electromagnetic spectrum.

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2
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0answers
18 views

Estimate upper limits on flux values in the case of a non-detection?

I have ALMA data which are non-detections of some spectral lines in a protoplanetary disk. The data is in the form of spectral cubes. I am hoping to estimate an upper limit on the flux of each of the ...
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52 views

Has SETI searched the solar system for life?

I know SETI is searching the stars for radio signals emitted by advanced alien civilizations, but has SETI searched inside our solar system - particularly moons, planets, and Lagrange points? I would ...
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1answer
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What is the 'AT' astronomical catalogue? And the 'TXS' one? As in AT2019dsg and AT2019fdr?

I cannot find a site stating what the AT or TXS star/astronomy catalogues are, even though some AT and TXS 'events' have been in the news lately....
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Farthest observed protoplanetary disk observed at radio frequencies? Catalog

This could be a naive question or maybe too easy to solve (I do not really know!). Brief context: I'm interested in a certain planetary system at $d \sim 300 \, \mathrm{pc}$. It would be really nice ...
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1answer
59 views

Why Nyquist Sampling Rate depends on Bandwidth and not max frequency?

Is the Nyquist sampling rate same for different bands if those bands have same bandwith? E.g. Would the Nyquist Sampling rate be same for 1000-1400 MHz band as for 100-500 MHz band because both the ...
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1answer
54 views

Shortest and longest wavelengths at which exoplanets have been resolved from their primaries?

Phys.org's Radio signals from distant stars suggest hidden planets summarizes the Nature Astronomy paper The population of M dwarfs observed at low radio frequencies (also in arXiv) but this is an ...
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+400

rms noise, confusion and dynamic range in radio images

I have been trying to understand imaging in radio astronomy. Below are some of my questions related to it and my understanding of their answers. I am not very confident about my understanding of them ...
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How to properly compare radio to optical/NIR images?

I mainly work with radio continuum data and recently I started working on some HST hydrogen recombination line datasets to compare with the radio data that I have, but I'm very confused about what is ...
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2answers
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Is Carl Sagan's famous "snowflake" quote correct?

“The total amount of energy from outside the solar system ever received by all the radio telescopes on the planet Earth is less than the energy of a single snowflake striking the ground.” ― Carl Sagan,...
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180 views

Did a watch company really try to sue radio astronomers for using the word "pulsar"? If so, which astronomers?

After about 48:37 in the really wonderful video Jocelyn Bell Burnell Special Public Lecture: The Discovery of Pulsars (linked below) Dr. Bell Burnell describes the ...
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1answer
52 views

How, precisely, do radio astronomers detect (and record) the phases of waves for interferometry?

Interferometry is always in the news, and at radio frequencies it has been for a long time... The popular press always talks about directly 'interfering' two waves as they come in, but can they tell ...
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What does lowercase 'beta' mean in this graph of radio-emitting galaxies?

Correlation between the mass of the galaxies (X-axis) and the difference of their radio emissions at different radio frequencies (Y-axis). Each symbol represents an individual galaxy. The image of an ...
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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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1answer
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Are there any spectral lines with smaller frequencies than the hydrogen line?

The 21 centimeter hydrogen line originates from the hyperfine transition of neutral hydrogen. Are there any bigger wavelengths that originate from this method? Radio emissions from rotating stellar ...
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How does the Latvian branch of LOFAR radio telescope array communicate its data without a network connection?

LOFAR technical information links to LOFAR Map from which a screenshot below shows HBA, LBA and Network options. Both the high and low band arrays are distributed in a number of clusters around Europe....
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1answer
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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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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?

The Conversation's ‘Dancing ghosts’: a new, deeper scan of the sky throws up surprises for astronomers says: We are getting used to surprises as we scan the skies in the Evolutionary Map of the ...
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Convert from Jy/beam km/s to W/m$^2$

I need to compare some ALMA observations of a protoplanetary disk to disk-integrated fluxes obtained from a model. The ALMA observations are upper limits of non-detected spectral lines, where the RMS ...
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1answer
62 views

How can a 1-pixel image of a rotating asteroid be used to measure its thermal inertia?

Phys.org's Observatory in Chile takes highest-resolution measurements of asteroid surface temperatures ever obtained from earth discusses imaging of millimeter wave imaging of the surface of asteroid ...
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1answer
47 views

What are the oxygen or water vapor lines?

I was reading the document Recommendation ITU-R P.676-11 (09/2016); Attenuation by atmospheric gases (P Series, Radiowave propagation) in order to calculate the atmospheric losses, and there were some ...
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Why do the Centaurus A radio jets have two "arms" each? (Event Horizon Telescope image)

Fig. 2: Image analysis of the final model: a, Model image corresponding to the image from Fig. 1 with a pixel size of 2 μas. Here, the tentative position of the jet apex is indicated with a circle. ...
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1answer
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Radio SEDs for quasars

Using data from https://ned.ipac.caltech.edu/, I can get nice-looking spectral energy distributions for quasars, such as for these two: but most of their points are in UV to IR range. I'm looking ...
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1answer
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If the visibility function is the Fourier transform of the sky brightness distribution, why do you need the dirty beam and dirty image to find it?

In radio astronomy, the dirty image is equal to the inverse Fourier transform of the uv-plane coverage times the sampled visibilities. The dirty image is also equal to the convolution of the "...
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1answer
44 views

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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1answer
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Where should I look at if I had a 25m parabolic radio reflector?

I am most interested in (exo)planets with atmospheres, see e.g. my question Requirements to resolve position of Jovian Whistlers up to magnitude of Red Spot with amateur radio equipment? So if I had ...
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193 views

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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2answers
136 views

If my eyes were really big, would I see radio waves?

Considering an assertion that the fundamental difference between different ‘types’ of electromagnetic waves is frequency/wavelength, and larger antennas are needed for longer wavelengths, if my eyes ...
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1answer
77 views

What could a cloud of mini radio dishes see?

Suppose an astronomer gave a 1 m radio dish to 500 people scattered over the face of the Earth and connected them to the internet. The people are directed to set their radio antennae up in their ...
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1answer
476 views

Requirements to resolve position of Jovian Whistlers up to magnitude of Red Spot with amateur radio equipment?

Can I sense a bright star pointing an eight foot antenna towards it? is a while ago, but the discussion about this question I found very interesting. Please forgive me that I am not an expert in ...
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1answer
47 views

Did the Spectr-R space-based radio telescope use on-board accelerometer to measure non-gravitational acceleration for baseline correction?

This answer to Why is space-based VLBI scattering sub-structure "Hopefully, a new promising tool to reconstruct the true image of observed background target(s)"? summarizes the contribution ...
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1answer
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Why is space-based VLBI scattering sub-structure "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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1answer
330 views

What radio frequency ranges are most beneficial for astronomy?

I cannot get the idea of citizen radio astronomy out of my head, and choosing an antenna (design) heavily depends on the desired frequency range. The Arecibo telescope as my gold standard operated 300 ...
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1answer
64 views

How can we install a radar on radio telescopes like FAST or GMRT?

Recently I came across an article mentioning that ever since the failure of Arecibo telescope, we only have one asteroid radar imaging telescope which is Goldstone observatory. The article also ...
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1answer
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Is GAIA the only game in town for looking at quadrupole gravitational deflection of light?

From Gerry Gilmore (2018) Gaia: 3-dimensional census of the Milky Way Galaxy 4.4 Fundamental physics Relativistic effects are highly significant for Gaia measurement accuracy, with tests of General ...
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1answer
59 views

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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1answer
139 views

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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26 views

How to calculate the luminosity of a quasar?

Is there a relation between the distance ($d$) and the apparent bolometric magnitude ($m_{bol}$) of a quasar and its luminosity ($L$) in watt? If so, what is that relation? Thanks in advance!
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101 views

Recommend a radio calibration target for amateur radio telescope

I have a small antenna and radio system that can receive frequencies between 1MHz and 1GHz. The system has a discone antenna. I plan to do some aperture synthesis based on the daily rotation of the ...
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2answers
224 views

Does a photon need to have EXACTLY the right energy to be absorbed by a gas molecule?

From an answer to this question, https://physics.stackexchange.com/questions/281660/how-does-an-electron-absorb-or-emit-light, Absorption of a photon will occur only when the quantum energy of the ...
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2answers
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Opening VLA Export Format data on Windows

I recently downloaded some data from the NRAO archive. It came as a file in the "VLA export format" with the extension .xp1. From what I gather I can open this using some software called ...
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BLC1 and Proxima Centauri's activity

From Wikipedia BLC1: A paper by other astronomers released 10 days before the news report about BLC1 reports the detection of "a bright, long-duration optical flare, accompanied by a series of ...
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1answer
109 views

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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1answer
182 views

Looking for a routine to correct for Local Standard of Rest (LSR)

I've been scanning the Milky Way with a Small Single Dish Radio Telescope, obtaining Spectral data with a Span of ~ 2 MHz, centered at the 21 cm line. With this information I can derive a relative ...
4
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1answer
155 views

In astronomical interferometry, what values do the points in the uv-plane have?

As I understand it, the image of an interferometer is the inverse fourier transform of the information in the uv plane. For each baseline (vector between any two telescopes in the array), representing ...
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1answer
38 views

extracting visibility information from CASA measurement set

I am trying to export the UV wavelengths, visibilities and weights from a measurement set in CASA, but I haven't been able to find the right commands to do this. 'exportuvfits' might be what I am ...
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About coordinate systems and angle differences

If I want to measure the beam-width of a radio telescope sweeping through a ~ puntual object (the Sun) with a ~ constant flux output when measured: The value measured sweeping in one frame of ...
2
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1answer
38 views

The role of 'the interference of waves' in VLBIs'

I've been trying to find out how VLBIs work. It says in this book I've read that many radio telescopes around the world work in tandem to use the interference of waves to get a clearer picture of ...
2
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0answers
29 views

Are radio telescopes finding radio-dark Nebulas

Are there "dark nebula" spots in the sky for radio telescopes? By that I mean, are there portions in the sky where these telescopes do not receive any radio waves? If so, do they match ...
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4answers
6k views

Is there any role today that would justify building a large single dish radio telescope to replace Arecibo?

It seems that most of the modern radio astronomy instruments and observation that make the news are interferometers or phased array systems of one kind of another. Is there any application left for ...
5
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1answer
681 views

Building a floating, ocean-going giant radio telescope?

Given the loss of the Arecibo telescope: Is anybody aware of any efforts or studies towards a floating, ocean-going radio telescope of with 500m diameter or more? The idea is floating (pun intended) ...

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