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14 votes

Do radio telescopes see other stars better at night?

The Sun doesn't substantially impact radio observations during the day, because radio telescopes operate at long wavelengths. In general, light at longer wavelengths scatters less than light at ...
HDE 226868's user avatar
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10 votes
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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?

I'm one of the researchers involved with the International LOFAR Telescope (ILT) scientifically and technically, and have also contributed one of the papers and images you may have seen appear on ...
tikker's user avatar
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9 votes
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Can one build a distributed radio telescope?

Yes, we can do radio astronomy with heterogeneous, geographically distributed antennas. The VLBI is an excellent example. Of course, the antennas have to be similar in some ways for it to work: If ...
Connor Garcia's user avatar
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8 votes
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What does the Sun "look like" below 100 MHz?

Below about 300 MHz you can only see the sun's corona as the frequency is too low to penetrate the coronal plasma from further below. In Wikipedia's Solar radio emission you can see images of the sun ...
Thomas's user avatar
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5 votes

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

Jansky is defined as $1 Jy= 10^{-23}erg/s/cm^2/Hz$. So all the energy coming from a given solid angle per time, per frequency bin and per detector area. This is convenient for sources of small ...
Markus Roellig's user avatar
5 votes
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How do astronomers at SETI know if they received intelligent radio signals from other planets?

I'm not sure what you mean by "wave modulations". Loosely speaking, there's 2 things to look for regarding alien intelligence/technology. One is a signal of some kind and the other is a very ...
userLTK's user avatar
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5 votes
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What is the significance of using baseline pairs in radio interferometry?

The basic idea behind interferometry is that of interference, the combination of two waves (in this case the electromagnetic waves from distant sources). Interference inherently implies two signals ...
Eric Jensen's user avatar
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4 votes

How was it established that central galaxy's supermassive black holes are responsible for existence of radio lobes?

Basically, since we know that the central region of these galaxies is occupied by a black hole, accretion by this black hole can power relativistic jets which result in radio emission. Radio emission ...
Daddy Kropotkin's user avatar
4 votes
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What is the significance of the velocity resolution in spectral line observations using radio interferometry?

Short version: velocity resolution is the smallest velocity difference you can measure between two moving objects, using a given spectrum. More details: As you probably know (based on your implicit ...
Eric Jensen's user avatar
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4 votes
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Why do we call radio images "maps"? Is it because it is not optical, so therefore not an "image", strictly speaking?

There is no distinction. No matter which wavelength regime you consider, "image" is an adequate and frequently used description. Also for radio, microwaves, sub-mm, IR, UV, and X-rays. The ...
pela's user avatar
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3 votes

Could we hear alien radio transmissions using radio interferometry?

For the sake of discussion, let's assume there is a signal out there that we might possibly detect. This question hits on one of the big weaknesses of interferometry as compared to a really huge ...
Darth Pseudonym's user avatar
3 votes

Can it be that the formula for calc vlsr for sun have a part beginning with cos270 for Calculate sun/VLSR.cos 270=0?

Yes, for a direction with $α = 18 \mathrm{hr}$, or $270^◦$ and $δ = 30^◦$ it is correct to have a term in the dot product with $\cos 270$. It is merely a coincidence that that is zero. The true value ...
James K's user avatar
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3 votes
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How bright is the Sun in S-band?

Well, I did some digging and found a helpful chart here. The image itself is located at this link. Wikipedia defines the S band as the section of the electromagnetic spectrum from 2 to 4 GHz. To ...
sforsingh's user avatar
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3 votes
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Current delay for radio signals from the Mars InSight mission

Current delay for radio signals from the Mars InSight mission. The delay at the time of the landing was 8.07 minutes (8 minutes 4+ seconds), as Mars was at the time at a relative distance from Earth ...
Jiminy Cricket.'s user avatar
3 votes
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What explains this puzzling radio signature from a fireball?

I checked with the people who run the BRAMS project and they confirmed my reasoning, and added another possible explanation. Even if the fireball moves away from the receiver AND transmitter, the ...
Petoetje59's user avatar
2 votes

How do we know that comets definitely mase and not just fluoresce? What is it about 18-cm lines that indicates that is really masing per se?

TLDR; Yes it does indeed "mase"! Note this answer will cover only the masing of comets. Long answer; According to this paper on Maser emissions from comets: In contrast with interstellar ...
DialFrost's user avatar
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2 votes
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Why space-based VLBI scattering sub-structure is "Hopefully, a new promising tool to reconstruct the true image of observed background target(s)"?

It is well known that the study of pulsars is hampered by the scattering effect - the distortion of radiation during the passage of the interstellar medium. Even very compact pulsars look like ...
A. Rumlin's user avatar
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2 votes
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Current topics on Radio Astronomy and looking for advice

Here are some examples that you can read about within Astronomy SE and Space SE: Time Domain Astronomy (link) e.g. LOFAR and (as it turns out) CHIME. Think better FRB detection gravitational lensing ...
uhoh's user avatar
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2 votes
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Would the electron cyclotron-maser emission mechanism affect Proxima b's ability to retain an atmosphere?

This mechanism, being actively emitting in the radio-wavelengths, is certainly negligible for the overall atmospheric energetics at Proxima b. One can conclude this by taking the band luminosities ...
AtmosphericPrisonEscape's user avatar
2 votes
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Why was the NVSS(NRAO VLS Sky Survey) conducted at 1.4 GHz continuum?

As the paper outlining the NVSS notes, 1.4 GHz happens to lie in a sweet spot of radio frequencies. It falls into the "intermediate-frequency gap" in which many of the sources of interest ...
HDE 226868's user avatar
  • 37.2k
2 votes

What exactly did ALMA observe at 20 AU from the "Mega Comet Arriving From the Oort Cloud" that will pass in 2031?

ALMA measured the brightness of thermal emission from the comet (at 1287 µm or 233 GHz). The comet was not resolved directly, so Lellouch++2022 treated it as a point source. But spatial information in ...
giardia's user avatar
  • 2,098
2 votes
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In radio astronomy, why do shorter baselines trade angular resolution for surface brightness?

The surface brightness of a source is by definition the flux density per solid angle; the surface brightness sensitivity of a telescope is, analogously, its point source sensitivity divided by the ...
HDE 226868's user avatar
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2 votes
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Help converting Jansky/beam to erg s^-1

The luminosity of an object in general is $$L=4\pi\cdot d^2\cdot F$$ where $d$ is the distance and $F$ the observed flux (power per unit area). Now Jansky is a frequency specific flux defined as $$1 ...
Thomas's user avatar
  • 3,504
1 vote

Could we hear alien radio transmissions using radio interferometry?

Radio waves are a part of the electromagnetic spectrum, and if transmitted using an omnidirectional antenna, they are subject to the inverse square law, which shows how the initial signal strength (or ...
jmarina's user avatar
  • 249
1 vote
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How to calculate radio luminosity at a certain frequency from observed radio flux density at another frequency?

You do have a single data point from a complete spectrum - and you want to extrapolate this datapoint to another frequency. One can do that, if the physics governing the spectral behaviour are known ...
planetmaker's user avatar
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1 vote

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?

The current situation is summarized in The Conversation; Academic rigour, journalistic flair's March 21, 2022 ‘Odd radio circles’ that baffled astronomers are likely explosions from distant galaxies: ...
Fred's user avatar
  • 2,169
1 vote

Is **Voyager I’s** reduced data transmission rate as described in [this article][1] because of the distance or because its transmitter getting slower?

Transmitters don't slow down as they age. Red shift isn't involved, at all. As a transmitter gets further away the signal at the receiver gets weaker, so it's deliberately slowed down. Data channel ...
stretch's user avatar
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1 vote
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Has optical interferometry been done at radio frequency using heterodyning with a laser in a nonlinear material?

Perhaps I've got it, or them. These may be what I was thinking of, an optical intensity interferometer based on the Hanbury Brown and Twiss effect effect, but down-converting via heterodyning with ...
uhoh's user avatar
  • 30.7k
1 vote

How do astronomers at SETI know if they received intelligent radio signals from other planets?

Well, they don't. You can only disprove that it's aliens. All remaining signals that are leftover after natural signals are substracted are simply of unknown origin. Then, depending how hard a ...
AtmosphericPrisonEscape's user avatar
1 vote

How to calculate the integrated source flux density of a continuous source?

The professor might also mean to subtract the background region fluxes for the noise subtraction. Then, calculating the statistics for the subtracted flux value and error of the measurement, say A +/- ...
Kornpob Bhirombhakdi's user avatar

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