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
14 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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59 views

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
43 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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55 views

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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1answer
184 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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119 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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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
454 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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Did the Spectr-R space-based radio telescope use on-board accelerometer to measure non-gravitational acceleration for baseline correction?

This answer summarizes the contribution of the RadioAstron mission, a VLBI collaboration of radio telescopes using the Spectr-R space-based 10 m dish in high Earth orbit to produce "very-VLBI&...
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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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314 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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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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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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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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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
207 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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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
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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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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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138 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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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 ...
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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 ...
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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
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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 ...
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1answer
671 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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1answer
53 views

Hypothetical CMB space telescope design problem, received power from extended thermal source versus receiver front end NEP?

Consider the example of a large radio dish antenna in space equipped with a heat shield protecting it from the Sun. Let's say the amplifiers front-end effective temperature (for purposes of noise ...
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480 views

Is it possible to filter radio-waves using another radio telescope?

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
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4answers
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What will succeed the Arecibo Observatory?

Just a few minutes ago, I got a notification from Space.com stating that the Arecibo Observatory will be, sadly, decommissioned due to extensive damage to its structure. So, with the loss of one of ...
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888 views

Why does the Sun deviate from a typical blackbody spectrum in the S band?

This is sort of a follow-up to this question, and my answer to it. The graph I see here details the radio (and other frequencies) emission of the sun. What's most notable and interesting to me is the ...
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1answer
166 views

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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1answer
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What exactly are “H30α and He30α images”? (ALMA)

I ran across this paper's title η Carinae: high angular resolution continuum, H30α and He30α ALMA images (arXiv) and see that the body of the paper also mentions "H40α, H30α and H29α". What ...
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Are there any ALMA or JCMT detections of extraterrestrial phosphine that have been confirmed by direct sampling?

Please note that I am not a professional astronomer but an interested layman. I've informed myself on the matters below by perusing arXiv--there are likely other publicly-accessible primary sources I ...
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How accurately could late 50s - early 60s humans have mapped the solar system?

What if early SETI investigations had focused on our own solar system, rather than distant stars? Given the technology that existed around the 1950s, how much surveillance would humanity be able to do?...
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How will they know when to start taking the picture of the black hole at the center of the Milky Way?

@csm's answer to Why not take a picture of a closer black hole? points out that it's necessary for the supermassive black hole at the center of a galaxy to be actively feeding for it to generate a ...
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Will the first Event Horizon Telescope image of the Milky Way's black hole be just another orange donut?

@HDE226868's answer to Why doesn't the black hole in the center of the Milky Way glow similarly to the famous M87 image? explains that neither black hole is orange and any Event Horizon Telescope ...
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1answer
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Is there an IRAM satellite that measures thermal radiation at 250 GHz, or was this a ground-based instrument?

The Nature Research Letter A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation (also here and here) says about half-way through: We now reassess Eris’ surface ...
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1answer
149 views

Would it have been possible to send a radio signal towards ʻOumuamua?

As we could not get any radio signals from asteroid ʻOumuamua, couldn't we have sent a powerful radio signal to it and then check if we can get any radio signal in response? This way we can at least ...
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Radio loud AGN restarting as Radio Quiet AGN?

Is it possible for a Radio-loud object (eg., an FRI galaxy) to evolve into a Radio-quiet (eg., a Seyfert) source? Also, can this happen via AGN restart? That is, have there been instances where the ...
4
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1answer
392 views

What does “unremarkable transverse peculiar velocity” mean exactly, and how is it calculated here?

The abstract of A magnetar parallax (also in MNRAS) contains the following: Combining our new observations with two archival observations from 2006, we have refined the proper motion and reference ...
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1answer
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How often are radio telescopes used to measure parallax? When was this first done?

The abstract of A magnetar parallax (also in MNRAS) says: TE J1810-197 (J1810) was the first magnetar identified to emit radio pulses, and has been extensively studied during a radio-bright phase in ...
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1answer
88 views

How is spectroscopy used to deduce what an object is made of?

Spectroscopy is an analysis of light (or other EM wavelengths) that is often used by scientists to examine what an object is made from or contains. Apologies if this is a stupid question, but this ...
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Observed instances of massive gas inflow and AGN restart due to cluster-cluster merger?

Works such as Acreman et al. (2003) have demonstrated via simulations the possibility of gas being stripped off a galaxy due to interaction with a galaxy cluster. Have there been confirmed instances ...
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How did Jocelyn Bell Burnell discover the periodicity of CP 1919?

According to Wikipedia, in 1967, a radio signal was detected using the Interplanetary Scintillation Array of the Mullard Radio Astronomy Observatory in Cambridge, UK, by Jocelyn Bell Burnell. The ...
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What is meant by the notation $A^{\times{B}}_{\div{C}}$; where A,B,C are real numbers?

I have come across a few papers using the notation $A^{\times{B}}_{\div{C}}$; where A,B,C are real number. For example, $3000^{\times{3}}_{\div{4}}$. An example can be Eqn (4) in Stern & Laor (...

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