Questions tagged [radio-astronomy]

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

Filter by
Sorted by
Tagged with
7
votes
2answers
507 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
327 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 ...
5
votes
1answer
93 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 ...
4
votes
2answers
170 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 ...
2
votes
2answers
513 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 ...
8
votes
1answer
759 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
237 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?
7
votes
2answers
396 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
119 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 ...
9
votes
1answer
1k 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
votes
1answer
197 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 ...
3
votes
1answer
189 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
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 ...
1
vote
1answer
209 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
340 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
227 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
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 ...
0
votes
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 ...
3
votes
0answers
519 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{...
4
votes
1answer
159 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 ...
9
votes
0answers
87 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 ...
4
votes
2answers
464 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 ...
5
votes
1answer
193 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 ...
3
votes
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 $\frac{1 Jy}{beam}$?
2
votes
2answers
128 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?
6
votes
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?
1
vote
1answer
92 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
694 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
123 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 ...
6
votes
3answers
321 views

What is precipitable water vapor in millimeter-wave radioastronomy and how is it measured?

Looking through ALMA on-line documentation and articles, the quantity PWV (precipitable water vapor) is a central theme. I have two linked questions. What (actually) is precipitable water vapor, and ...
2
votes
1answer
330 views

Cosmic microwave background radiation: why did it take so long to get here?

I understand that the universe after the big bang was a super dense cloud of elementary particles, and because of this high density was "not transparent" to light. Then, roughly 400.000 years (380....
1
vote
1answer
330 views

What are the Similarities and Differences between ALMA and FAST?

What are the Similarities and Differences between ALMA (Atacama Large Millimeter Array) and FAST (Five hundred meter aperture spherical telescope)? What can they see, what's their resolution like? ...
1
vote
1answer
523 views

Astronomy & machine learning. Where to start? [closed]

I am a Computer Engineering major and would like to learn more about machine learning methods in Astronomy. What books or other resources could I use?
1
vote
1answer
51 views

Is radar interferometry used, or feasible, for ground based astronomy?

I've heard of "interferometric synthetic aperture radar" being used for Earth observation from satellites and airplanes. Is active radar used interferometrically for astronomical purposes too? Such as ...
1
vote
0answers
72 views

Can all astronomical signals be considered Gaussian noise?

While studying the techniques astronomers use to mitigate radio frequency interference (RFI) I found it's often assumed that astronomical signals are (band-limited) Gaussian noise. Is this a ...
4
votes
2answers
206 views

Can radio telescopes such as arecibo image the subsurface of asteroids or planets?

This was done with the moon: Radio Dishes Peer Beneath Moon's Surface
4
votes
1answer
330 views

Can SETI certify whether or not Proxima b is inhabited by beings using electromagnetic communication?

Can SETI certify whether or not Proxima b is inhabited by beings using electromagnetic communication? By certify I mean by past, present or future observations using technologies available.
8
votes
4answers
561 views

Why are the ALMA receivers' ADCs only 3-bits?

above: Table 1 from Performance Highlights of the ALMA Correlators The ALMA receivers use 3-bit ADCs for what would seem to be to be a high dynamic range application needing much finer quantization ...
2
votes
0answers
98 views

Help With Transit Radio Telescope Data Analysis

My high school teacher and I recently built a 10 ft. mesh dish transit radio telescope. In order to compete this year at Nationals for our science fair, we came up with the idea of using a bluetooth ...
2
votes
0answers
49 views

Do astronomers measure radio waves absorption to know the shape of a celestial body? [closed]

I do not have much knowledge about radio astronomy. I know that astronomers know an objects' shape by measuring the reflected photons that reach radiotelescopes, but can they measure also the absorbed ...
2
votes
1answer
362 views

Do some ELF (Extremely low frequency) radio waves pass the atmosphere

...reach Earth surface and then are reflected passing the atmosphere again to reach outer space? And once in outer space can they travel indefinetely in it or the interplabetary plasma would stop them?...
1
vote
0answers
58 views

What information will SETI have access to from the SKA (Square kilometer array)

I read on on the website of the SKA (https://www.skatelescope.org/) that SETI will sort of have "passive" access to the data that they capture on the array, sort of like a "pigyback" concept and ...
1
vote
1answer
304 views

What programming languages does SETI (Search for ExtraTerrestrial Intelligences) most commonly use for signal processing?

Please give preference to those most widely used in the field, if possible.
1
vote
1answer
123 views

Which 16 antenna locations were used this MeerKAT radio image?

The final configuration of the MeerKAT radio array will be 64 dishes. In the press release of July 16, 2016 a radio image is shown using a completed sub-set of 16 dishes. Which 16 are these? I can ...
2
votes
2answers
113 views

What is the reason the Chinese want to measure the <30Mhz radiation behind the moon?

On the Earth it is difficult to detect radiation below 30MHz from space due to our atmosphere. But why do they want to measure this radiation behind the moon? It has something to do with the big bang, ...
4
votes
0answers
259 views

What is a radio “homology telescope” and is the 500m dish in China one?

This question is about design aspects of large radio telescope dishes which allow them to flex under the influence of gravity as they change elevation angle, and still maintain good optical ...
2
votes
1answer
314 views

How did single dish (or single receiver) radio telescopes originally generate images?

That actually sums up my question nicely: How did single dish (or single receiver) radio telescopes originally generate images? - or at least 2D intensity maps or contour plots. Early radio ...
3
votes
1answer
303 views

What is the highest granularity focal-plane array on a dish radio telescope? Or is this the ONLY ONE?

There is a short Wikipedia article Focal Plane Arrays that enumerates some projects, but my question is more along the lines of what is (at least) nearly complete or in "first light" phase, even if ...
3
votes
1answer
1k views

What exactly is this VLA radio image of Jupiter showing?

This VLA image is beautiful, and instructive, but I don't understand it fully. This version is from an article in Gizmodo where the credit reads: A radio image of Jupiter captured by the Very Large ...
2
votes
1answer
233 views

Are there radio white dwarfs?

We have discovered about 2500 radio pulsars. Part of them show pulsations in other bands like X-ray and gamma ray. The radiation mechanism remains unclear now. I wonder whether there are radio ...