Questions tagged [radio-astronomy]

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

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4
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0answers
86 views

Estimate the number of pixels required to map the full primary beam of a Radio Telescope station

I am practising some exam questions for a radio interferometry exam, and I am struggling with this question: The physical size of a single LOFAR station, operating at 150MHz is about 50m. Estimate ...
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1answer
126 views

Can weak gravitational lensing or microlensing-induced wavefront distortion limit resolution of absurdly large aperture telescopes?

This is a theoretical question. This answer to the question If we had the right technology could we see a distant star in detail? (presumably space-based) primarily addresses the scaling of ...
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1answer
251 views

Will the SKA's total bandwidth still exceed the Earth's internet's bandwidth?

In the early 2010's there were many popular articles that said that the total bandwidth of the the Square Kilometer Array's optical fiber network for raw data from each dish would be larger than the ...
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1answer
124 views

How open is China in sharing data from the Chang'e 4 mission?

It's really good to see that man (well, machine) has gone back to the moon again. Chang'e 4 is studying potential mantle material from the lunar depths and will be conducting radio astronomy in ...
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Is there any update on the Availability of Event Horizon Telescope Images?

There has been no news on the obvious public channels from the EHT project since last (Northern) summer. Does anyone have more information on when any results from the April 2017 run might be released?...
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1answer
193 views

How does ALMA produce stable, mutually coherent ~THz local oscillators for all of their dishes?

The ALMA (Atacama Large Millimetre/submillimetre Array) radio telescope's band-10 capabaility is now operational, per this answer. That's confirmed by NRAO's First Science with ALMA’s Highest-...
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1answer
64 views

How often do they move most/all of ALMA's dishes?

The Phys.org article Unknown treasure trove of planets found hiding in dust reports on recently published radio measurements (~1.3mm) of planetary systems forming around stars in Taurus: Scientists ...
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How does Canada's radiotelescope CHIME manage polarization-dependent apodization of the fast f/0.25 optics?

CHIME, the Canadian Hydrogen Intensity Mapping Experiment uses four parabolic cylinder reflectors and a dense linear array of 256 x 2 polarization feeds along each focal line. Each feed is a dual ...
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1answer
101 views

What telescope might this be a model of, with Sir Fred Hoyle?

The BBC article Archaeopteryx: The day the fossil feathers flew has nothing to do with Astronomy but it shows a file photo of the famous astronomer Sir Fred Hoyle with a model of what looks like some ...
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Estimating upper limits on flux values (Radio)

How to estimate upper limits on flux values for a radio source if it is not seen in NVSS (1.4 GHz survey) but is observed in lower radio frequency maps?
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Did Arecibo's secondary optics compensate aberrations when viewing farther away from vertical?

In the beginning of the short YouTube video Arecibo Uncut: Under the Dish with Phil Perillat it is mentioned that while dish antennas are usually a parabola, the problem is that a static parabola ...
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1answer
91 views

Printed Circuit Board manufacturing file for Radio Jove?

I woild like to build a Radio Jove receiver whose design is available on NASA website. However, I don't want to purchase the receiver, I would like to make it, but but I don't have any knowledge about ...
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1answer
2k views

Why the blank wedges in this very early 21 cm map of the Milky Way? (Oort et al. 1958)

Jan Oort was a pioneer in radio astronomy. Wikipedia says: It has been written that “Oort was probably the first astronomer to realize the importance” of radio astronomy. “In the days before radio ...
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Can I sense a bright star pointing an eight foot antenna towards it?

If I connect an eight foot Yagi or other comparable sized antenna to my oscilloscope and point the antenna at a bright star will I see a voltage on my oscilloscope? I am not interested in turning the ...
3
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1answer
91 views

Could the E.H.T. produce an image of the human artifacts on the moon?

Two days ago the New York Times featured the Event Horizon Telescope (E.H.T.), a huge virtual radio telescope emerging from combining data from several dishes scattered around the world. While the E.H....
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1answer
104 views

Units in optical and radio spectral data cubes: Flux vs Brightness

I have noticed that the units used in spectral data cubes coming from optical IFU instruments are usually in $erg/s/cm^2/Ang/pixel$. To my understanding this is a measure of Flux. Right? However, in ...
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1answer
147 views

Is it possible to define a state of zero absolute angular momentum anywhere in the universe?

Conservation of angular momentum doesn't seem correct to me. I think this because radiation is present everywhere, no space is completely void, and no object perfect. Thus all objects will have uneven ...
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3answers
3k views

Converting Jy/beam to Jy?

Maybe its a dumb question, but to convert Jy/beam to Jy, I just have to multiply it by the beam size in sr right? Being $\Omega$ the beam size: $\Omega = \frac{\pi \theta_{maj} ~~ \theta_{min}}{4 \...
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2answers
148 views

Hydrogen Line observation - Interference from trees

I am setting up a 2.4 metre parabola pointing straight up to observe the 21cm hydrogen line at 1420MHz with meridian drift scans. I'm planning to place the dish on a steel pole embedded in the ...
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1answer
489 views

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 ...
3
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1answer
113 views

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 ...
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905 views

Amateur radioastronomy: dish suggestions

What kind of amateur radioastronomy can any interested citized do with: a) A 2 m dish antenna. b) A 2,5 m antenna. c) A 3 m antenna. d) A 5 m antenna. e) A >5 m <10 m antenna (likely I can not ...
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Strange behaviour of black holes [duplicate]

We know black holes emit streams of radiation ,also recently discovered that they emit visible light when they eat any nearby matter . "We find that activity in the vicinity of a black hole ...
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How to analyse Jovian signal received at 20.1 MHz using dual dipole antenna? [closed]

I have purchased a Radio Jove kit and set it up. I have also received some signals. I am using Radio Skypipe II software as discussed in this Radio Jove tutorial (see also here) with a sound card to ...
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527 views

How did UV from the earliest stars 'alter the state of the 21 cm line' such that it shows up in CMB today?

In this question I discuss the recent (open access) paper in Nature An absorption profile centred at 78 megahertz in the sky-averaged spectrum at length. The abstract begins: After stars formed in ...
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1answer
338 views

Early universe's first starlight (indirectly) detected for the first time, could it have been detectable with 1970's technology?

The recent paper in Nature An absorption profile centred at 78 megahertz in the sky-averaged spectrum seems (to me at least) to be an incredibly simple and elegant experiment with far-reaching ...
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1answer
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Nature and mechanism of the short-term variability in radio strength of Sgr A*?

The Phys.org article Cosmic filament probes our galaxy's giant black hole links to A Nonthermal Radio Filament Connected to the Galactic Black Hole? which discusses (among other things) the importance ...
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191 views

Is there a complete edition of the Cambridge Catalogue of Radio Sources (esp. 3C) available digitally?

In radio astronomy, many common objects are refered to by their designation from the 3rd Cambridge Catalogue of Radio Sources, e.g. 3C 353. For hobbyist purposes, I would like to create a catalogue ...
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2answers
549 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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1answer
794 views

How did the object CO-0.40-0.22 get its name, and how is it distinct from CO-0.40-0.22*?

There seems to be three things described in the recent Nature Astronomy paper Millimetre-wave emission from an intermediate-mass black hole candidate in the Milky Way: Molecular cloud CO–0.40–0.22 ...
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1answer
249 views

How to know that the 21cm Hydrogen line is the actual emission and not any other redshifted line?

Is it possible that we mistake some other wavelength emission to be 21 cm because of redshift?
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421 views

How large does refraction become in radioastronomy?

For atmospheric refraction of visible light, Wikipedia gives the order of 1 arc minute at 45° altitude above the horizon, and 5.3 arc minutes at 10°. This is caused by the dielectric polarizability of ...
2
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1answer
133 views

What is the extent of the "worldwide campaign" to observe near-earth object 2012 TC4?

This nifty answer describes and provides links to the data of the recovery of near earth object 2012 TC4, and the answer also shows the first actual image of the body for this pass. At apparent ...
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1answer
2k views

How big a dish do I need for radio astronomy?

I've recently become interested in the idea of building my own small-scale radio telescope. A quick online search finds a few instructions on how to build this using a satellite dish. These suggest a ...
2
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1answer
222 views

"Mysterious radio signals" - how could a geostationary satellite and Ross-128 line up with Arecibo?

The Phys.org article 'Mystery' signal from space is solved. It's not aliens cites a summary of the conclusion "by Abel Mendez, director of the Planetary Habitability Laboratory at the University ...
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1answer
192 views

What are infall signatures in stars?

I came across several papers (e.g. Looking for outflow and infall signatures in high mass star forming regions P. D. Klaassen, L. Testi and H. Beuther, 2011) talking about infall signatures in star ...
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1answer
64 views

The M-theory to understand black holes [closed]

I am a layman in astronomy. Can someone please explain it to me whether the M-theory can be used to explain what is happening in the centre of the black hole where the singularity exists? Or is it ...
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1answer
236 views

How do ASKAP's focal plane phased array feeds interact with the entire array phasing?

Sky & Telescope's ASKAP Joins the Hunt for Mysterious Bursts says: A new telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), has joined the search for energetic and elusive ...
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2answers
367 views

How to find period of a pulsar from a given time sampled voltage data?

I've a data file with 2 columns, each containing time sampled voltage output (a sequence of real numbers) from a radio telescope, so there is a pair of telescope which are measuring the signal here. ...
5
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4answers
238 views

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 ...
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1answer
81 views

Help with homwork - Astronomy

We might expect to not find life around halo stars (“Population II” stars) because: a) they are out of the plane of the galaxy and thus exposed to more cosmic rays (energetic nuclei) b) these stars ...
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1answer
71 views

How was Sugar Grove Station supposed to work?

Sugar Grove Station was an outpost designed to listen in on Soviet radio signals reflected off the moon. How would this work? Wouldn't the radio signals be distorted by the imperfect surface of the ...
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565 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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1answer
160 views

Why do Seyfert Galaxies emit less energy than Quasars and Blazars, and how is the emitted energy measured?

When I was reading information about QSOs on a website, it said that Seyfert Galaxies emit less energy than Quasars and QSOs. Why do Seyfert Galaxies emit less energy than quasars, and how is this ...
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How can maser emission be unpolarized?

I was reading that: However, unlike Galactic sources such as W3(OH), the emission is unpolarized and the 1667 MHz line is stronger than the 1665 MHz line. but how is this possible? Does not the ...
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2answers
503 views

How does the Event Horizon Telescope implement the interferometry?

The BBC article Event Horizon Telescope ready to image black hole describes the Event Horizon Telescope, a coordinated observing technique with several radio telescope arrays across the globe forming ...
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1answer
222 views

Is "Giga-hertz Astrophysical Transient Emission" distinct in any way from "Fast Radio Burst"?

In this answer I have just read about The University of Texas Rio Grande Valley's The Spacecraft Tracking and Astronomical Research into Giga-hertz Astrophysical Transient Emission (STARGATE). While ...
4
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1answer
2k views

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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2answers
136 views

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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1answer
5k views

What does the velocity dispersion of a galaxy mean?

Also, what is the advantage of getting information about the velocity dispersion of a galaxy?