Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [radio-astronomy]

Questions about observation performed in the radio frequency range of the electromagnetic spectrum (between 10 MHz and 1GHz).

0
votes
0answers
10 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-...
0
votes
1answer
27 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 ...
0
votes
0answers
8 views

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 ...
0
votes
1answer
43 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 ...
1
vote
0answers
19 views

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?
2
votes
0answers
37 views
+100

Does Arecibo's secondary optics compensate 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 ...
1
vote
0answers
25 views

radio Jove pcb manufacturing file

Hello I want to make the radio Jove receiver whose design is available on NASA website. I don't want to purchase the receiver. I want to make it. but I don't have any knowledge about pcb design for ...
8
votes
1answer
1k 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 ...
17
votes
3answers
3k views

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
votes
1answer
42 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....
2
votes
1answer
44 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 ...
2
votes
1answer
117 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 ...
2
votes
1answer
258 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 \...
3
votes
2answers
95 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 ...
3
votes
1answer
95 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 ...
2
votes
1answer
71 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 ...
6
votes
2answers
177 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 ...
-3
votes
2answers
63 views

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 ...
3
votes
0answers
73 views

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 ...
6
votes
2answers
303 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 ...
6
votes
1answer
253 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 ...
0
votes
0answers
80 views

How to measure uncertainty in flux density?

Let's say I have an image of a galaxy that is 10 pixels, and the pixels have values 1, 2, ... 10 Jy/beam. If the RMS background noise is 1.5 Jy/beam, and I want source detection at 3 sigma level (...
4
votes
0answers
35 views

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 ...
3
votes
1answer
42 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 ...
1
vote
0answers
19 views

Why does the transition frequency of an ensemble of synchrotron electrons depend on the angular size of the radio source?

The synchrotron spectrum from a power-law ensemble of electrons in a uniform magnetic field, $B$, looks like this. In "The Physics of Extragalactic Radio Sources" by De Young it says, "The overall ...
2
votes
2answers
196 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 ...
5
votes
1answer
522 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 ...
5
votes
1answer
175 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?
5
votes
2answers
189 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
votes
1answer
87 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 ...
8
votes
1answer
476 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 ...
1
vote
1answer
101 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 of ...
4
votes
1answer
112 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 ...
2
votes
1answer
57 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 ...
1
vote
1answer
102 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 ...
3
votes
2answers
142 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
votes
4answers
163 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 ...
0
votes
1answer
73 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 ...
0
votes
1answer
66 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 ...
4
votes
0answers
199 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{...
3
votes
1answer
85 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 ...
7
votes
0answers
62 views

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 ...
5
votes
1answer
173 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 ...
6
votes
1answer
150 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 ...
1
vote
1answer
755 views

Why levels of radio contours maps are given in mJy/beam and what does it mean?

I know what a jansky is, but don't understand "/beam". If jansky is a unit of flux density, what kind of unit is Jy/beam?
2
votes
2answers
98 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?
2
votes
1answer
2k 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?
1
vote
1answer
76 views

Astronomy online degrees

I have a masters degree in computer science and statistics but would like to advance my knowledge in astronomy, ideally in getting some kind of online degree. Does anybody have experience, ...
8
votes
1answer
319 views

Plot of best available resolution vs wavelength - radio through gamma rays?

What I'm looking for is a graphic that shows in a general way the best available telescope resolution vs wavelength throughout the entire wavelength spectrum. So for example, there might be two very ...
2
votes
1answer
100 views

Why does the neutral hydrogen velocity have this characteristic behavior in the galactic plane?

The recently released map of galactic neutral hydrogen density and velocity is really beautiful. The work has been relased by the HI4PI collaboration (HI = neutral hydrogen, $4\pi$ = complete ...