Questions tagged [radio-astronomy]

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

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Why hasn't the EHT taken an image of Sgr A*? [duplicate]

The Event Horizon Telescope or EHT took an image or the black hole at the center of M87 in 2019, and in 2021 it measured the polarization of the light from M87*. Right after the first image of M87* ...
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How is CASA different from SAO DS9?

I was told that CASA is used extensively in Radio Astronomy. However, softwares like SAO DS9 and also python (Astropy) are also used for radio astronomy data analysis. So, what makes CASA different as ...
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What are the main ways that pulsar "glitches" are noticed and documented? Do they have to be caught in the act of glitching to be catalogued?

This answer to Is there any well-populated list or database of pulsar "glitches"? mentions two large databases; (Jodrell Bank and ATNF's pulsar catalog) but neither question nor answer ...
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Is the flux density independent of source-observer distance?

A particular observatory is providing the flux density of an astronomical source and only from this information, is it implicated that this particular parameter is unaffected by the distance between ...
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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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Do circa 1 THz radio telescope front end amplifiers actually down convert before amplifying? At what frequency does amplification become untenable?

A discussion of how astronomers view where "radio" ends and "infrared" begins under What does the celestial sphere look like in thermal IR? led me to wonder just how high of a ...
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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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Why is it called "The LOFAR 'superterp'"? What is a terp, and what's so super about this one?

Wikipedia's Low-Frequency Array (LOFAR) includes the image below with the caption: The LOFAR core ("superterp") near Exloo, Netherlands. The bridges give an idea of the scale. Question: ...
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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 ...
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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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How are radio telescopes pointed?

In the past, I worked as a programmer in a radio astronomy station, and since then I have a question on my mind. To observe a star with a telescope, we locate its location with our eyes and then we ...
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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 ...
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Is it possible to make (or buy kit) DIY portable radio telescope that I can place on the balcony like optical telescope?

I want to have a small radio telescope to use on balcony instead of optical when sky is cloudy (it is very often). Is it possible? What objects can be observed by that telescope? Is it possible to use ...
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If we put a radio telescope on Mars and use it in array with earth radio telescopes, how much will we able to see?

If we put a radio telescope on Mars and use it in array with earth radio telescopes, how much will we able to see? Will it allow us to see planets, like we do with black hole?
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Is it possible to take the same images in HST palette as the optic telescope but with radio telescope?

Is it possible to detect signal from SII, H$\alpha$, OIII using radio telescope and make the similar images as optic telescope? If no, can we use the different elements to take signal? What minimal ...
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Artificial radio waves masked by a star's natural radio waves?

Our civilisation emits radio waves into space. But insofar as the Sun can be modelled as a black body, it is also emitting radio waves into space! For an alien civilisation too far away from us to be ...
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Do observational astronomers make use of the Fredholm equation? Perhaps in solving for/removing instrumental effects in imaging?

The Fredholm equation of the first kind (Wolfram Mathworld and Wikipedia) written as (Wolfram's): $$f(x) = \int_a^b K(x, t) \ \phi(t) \ dt$$ where $K(x, t)$ is the kernel and $\phi(t)$ is an unknown ...
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Radar technique for distant objects

If we want to detect the distance to an object using radar, we can do it only for objects inside the solar system, otherwise the returning signal would be too weak to detect. On the other hand, we are ...
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Confusion around units for SEDs, and how to tell what I'm looking at

I know that a spectral energy distribution (SED) is a plot of energy versus wavelength or wavelength of light, while a spectrum is a plot of flux density against wavelength, but I'm a bit confused ...
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Why would radio astronomers choose ¹³CO and C¹⁸O spectral lines instead of the most isotopically common combination?

Wikipedia's T Tauri explains that this system is an atypical example of T Tauri stars. It says: As typical for the young stars, all three stars of T Tauri system are surrounded by a compact disks ...
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How would the surface of Mars compare with the Atacama desert for millimeter wave (and shorter) radio astronomy?

In this answer to What kind of experiments would a scientist do on Mars? I suggest that the resemblance of the ALMA array's site in the Atacama Desert to the surface of Mars suggests millimeter ...
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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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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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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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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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3 votes
1 answer
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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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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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8 votes
2 answers
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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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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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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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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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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?

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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6 votes
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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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2 votes
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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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3 votes
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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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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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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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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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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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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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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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7 votes
1 answer
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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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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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