# Tag Info

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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 shorter wavelengths, and so visible light from the Sun scatters much more than radio waves from the Sun.$^{\dagger}$ The former effectively fills the daytime sky, ...

9

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 the antennas are ground based, they need to be in the same hemisphere, or the Earth will prevent them from looking at the same target at the same time. They ...

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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 from 17 GHz down to 80 Mhz. By Patrick McCauley Mccauley.pi - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=99231226 Photos and a ...

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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 angular extent (smaller than observing beam), e.g. for point sources, because the flux remains constant for varying beam sizes. For extended sources, the surface ...

5

ALMA is the main example of radio-telescope located in Chile. And, what an example! the most powerful radio-telescope in the world working at millimetre and sub-millimetre frequencies. Although there are bigger single dish radio-telescopes in other places, ALMA outperforms them in general. A bigger radio-telescope has a higher sensitivity because it collects ...

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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 large or very energetic structure. The most obvious place to look for a signal is in the water-hole. Good article on that here. Because of the relatively low ...

5

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 various news outlets. You have asked an excellent question(s)! Let's split them up. The International LOFAR Telescope LOFAR has two types of antennas: the Low Band ...

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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 to interfere with each other, and that is why the pairs of telescopes (also referred to as baselines) are important. The interference pattern between the ...

4

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 use of the formula in your question), we can measure velocities by using the Doppler shift. To do that, we need to measure a feature (an absorption or emission ...

3

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 of 0.9703 Au. Current delay as at 8th December 2018, we're at a distance of 8.85 (8 minutes 51 seconds) light minutes or 1.064 Au. Using WolframAlpha's tool ...

3

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 ionization trail it leaves behind can expand and be blown by mesospheric winds towards the receiver and/or transmitter. It's this trail that mostly reflects the ...

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There were a few other small errors in your translation (such as indenting too much stuff in two of the if statements), and I think you might have been trying to be too clever with changing SUBROUTINE into defined functions when it was a lot easier to just drop the code in-line since it was only used once. There were minor tweaks and as far as I can tell ...

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There are radio telescopes at many sites in the southern hemisphere. Here's a list. Chile has a big one going in at Llano de Chajnantor and several already operational. See second link for details.

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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 from the cited paper ($\rm 2.51\times10^{20} erg/s$, p.3, first paragraph) and compare them to the solar constant at the planets orbit, which should amount to $\... 2 Well, I did some digging and found a helpful chart here. The image itself is located at this link. Wikipedia defines the S band as the section of the electromagnetic spectrum from 2 to 4 GHz. To interpret the respective values the graph displays at these frequencies, we need to convert these two figures to wavelengths:$\lambda_1 = \dfrac{c}{\nu} = \dfrac{...

2

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 beam solid angle.$^{\dagger}$ Interferometers have smaller beam solid angles than dishes with the same area (Frayer 2017). Given that the solid angle is \$\Omega\...

1

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 capacity depends on signal to noise ratio and bandwidth. As the signal gets weaker the data rate can be slowed to reduce the necessary bandwidth. Noise doesn't ...

1

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 lanterns in fog. It is clear that this effect should be observed when studying not only pulsars, but also other radiation sources. And here Radioastron plays its role. ...

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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 effects on pulsar timing (needs several questions of its own) Why did it take five years to "figure out" how to use astrometric calibration sources to ...

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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 lasers. However: instead of the heterodyne down-conversion process happening in an optical crystal producing radio waves that are electrically amplified, mixing ...

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I'm not sure if this is what you're asking but: fluorescence: excited electrons randomly emit photons. Superfluorescence: excited electrons emit photons, and there is some self-stimulation, leading to a strong short pulse but little coherence. Superradiance: strong, shorter pulse, much self-stimulation , high coherence in output. Lasing/Masing: ...

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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 particular scientist or journalist wants to sell out, he or she declares 'maybe aliens' are found. But it's not like we will ever be able to prove such a thing, unless ...

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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 +/- dA. Then, applying the 3-sigma criteria to determine whether there is a radio source detected at the location, i.e., if A - 3*dA > 0, there is a source, ...

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Maybe too late but probably he is referring to only take into account pixels with an intensity greater than 3*sigma. If not, you will be counting random noise as continuum. Obviously you will lose a lot of pixels, but those pixels doesn't carry any information at all.

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