29
Stars are too dim for amateur radio equipment. There are two possible radio sources that you can detect: the sun and Jupiter.
Jupiter is particularly interesting as interactions between Io and its magnetic field produce beams of radio waves that sweep past earth every 10 hours. These are detectable in the amateur range, at about 20 MHz.
Nasa make a kit ...
23
I would expect the authors to be talking about the signal in terms of janskys, the now-commonly-used units of flux density. The typical definition is
$$1\text{ Jansky}=10^{-26}\text{ Watts meters}^{-2}\text{ Hertz}^{-1}$$
One hertz is one cycle per second, which makes me suspect that the "c" stands for cycle. It might seem curious that the authors choose to ...
22
Titan "lakes":
Published Open Access in Science: Radar Evidence for Liquid Surfaces on Titan Campbell, D. B., Black, G. J., Carter, L. M., and Ostro, S. J., Science 302, 5644, pp. 431-434, 17 Oct 2003 DOI: 10.1126/science.1088969
This was a really elegant experiment! A continuous, unmodulated, circularly polarized 13 cm wave was broadcast from Arecibo ...
13
@Arne is right in his answer about two things, that the most suitable frequency for Jovian amateur radio is 20.1 MHz, and that this is a 15 meter wavelength. However, the antenna can actually be half the wavelength, and amateur radio astronomers have had good results listening to all kinds of Jovian sounds, including detecting occultations of its many moons ...
13
Interesting idea. I think the answer is both yes and no -- yes with a manufactured dish but no in the crater's raw state.
The Arecibo telescope sits in a natural crater, but adds a dish which has a couple of important things required by a radio dish:
a radio-reflective surface
a specific curvature, classically parabolic, but also shaped
low surface ...
11
I am a member of Astropeiler Stockert e.V., and we are fortunate enough to be able to approach this problem coming from the "large side" :-) We have a 25m, 10m and 3m telescopes as well as an interferometer made from two 1m satellite dishes available. All these dishes can be used to do interesting things, but you'll need to match the instrument to your ...
11
The authors were able to successfully model the motion of the gas streams as Keplerian orbits around an object of $\sim30000M_{\odot}$. In doing so, they derived some key quantities, such as the pericentric distances of these two gas components (the "Balloon" and the "Stream"). One has its closest approach at $\sim0.21$ pc; the other has its closest approach ...
11
It did not detect methane lakes.
It found that Titan was shiny (in radar terms): that is, the reflections were from a smooth surface rather than a rough one, and at the same time not very intense.
As a result (quoting the 2003 New Scientist article Radar reveals Titan's methane lakes linked in one of the comments to your question), “some researchers ...
10
They're not different. Same principles do apply. You could have secondary, tertiary, quaternary, and so on, mirrors with instruments at any wavelength, either optical, or radio, or infrared, etc. You could also have instrumentation placed directly in prime focus (so no mirrors other than the primary) with any kind of instrument - radio or infrared or visible ...
10
There's a pretty good discussion at this page.
There are several factors at work:
The smaller isoplanatic angle, as you note. This limits how much of the sky you can observe with AO, since your target needs to be within the isoplanatic angle of a bright enough references star. (Even with laser guide stars, there is still a need for a reference star for "...
10
As others have noted, you will not be able to detect a star using an oscilloscope and an antenna. The received signal level is too low, and the oscilloscope not nearly sensitive enough.
A radio telescope consists of an antenna, an amplifier, and a receiver (that incorporates other amplifiers and other stuff besides - like filters and mixers to select the ...
10
TLDR: these wedges are bits where things are moving around the centre of the galaxy at about the same speed as us, so we can't understand what is there.
As it states on page 4 of the paper you have linked,
the great gap between 315 and 340, where, except at small R, the differential rotation is too small to separate the various arms
The method used ...
10
Would it increase the diameter if they would include some from there?
No. Not by much, at least. The telescopes are already ~20,000 km apart, so you can't create a longer baseline that still has a simultaneous view of the target.
Don't forget: Earth is a sphere. Only one half of that sphere can observe M87 at the same time.
Telescopes in the Eastern ...
9
Definition of the velocity dispersion
From the title of your question, I'm unsure whether you actually know what "dispersion" means: The dispersion of some numbers is the spread around their mean, usually taken to mean their standard deviation. If you measure the velocity of several light sources (from the Doppler shift of their spectral lines) that are ...
9
No, not really. The first thing is that we know that ${H}$ is far more abundant than other elements or simple molecules in the universe. The next thing is that the 21 cm line comes from a relatively unusual hyperfine splitting, and there just aren't any other sources near that wavelength and in intensity levels that can easily be detected.
In most ...
8
The first thing to consider is that the area of a beam will, over long distances, diffuse. The best situation we can hope for is a diffraction-limited system, where this diffusion is minimized thus maximizing our received signal. That is, in theory we have a perfectly collimated transmission beam that neither diverges nor converges.
In practice, we are ...
8
All electromagnetic radiation from a point source - which a normal radio transmitter is - propagates according to the inverse square law which means that the intensity of the signal is inversely proportional to the square of the distance. This happens on earth and in deep space equally.
So this will mean that for any signal there will be a distance at which ...
8
After a bit of searching, I found this blog page, which has several charts about various observatories, including this one:
Image courtesy of Olaf Frohn under the Creative Commons Attribution-Share Alike 4.0 License.
The majority are space-based, although the radio telescopes are largely land-based. They cover existing and future telescopes, at energies ...
8
An earlier paper on the object (Oka et al. (2015)) explains that CO-0.40-0.22 is a "high-velocity compact cloud". The first discovery of such an object was two decades ago (Oka et al. (1998)), when CO 0.02-0.02 was found. The naming convention used for that object was
"CO" + Galactic longitude + Galactic latitude
For instance, CO 0.02-0.02 has latitude $0....
7
Using current technology (and by that I mean experiments and telescopes that are available now) we would probably be unable to detect life on Earth even if observed from a distance of 4 light years, which is the distance to Proxima Centauri.
A "blind" search could look for radio signatures and of course this is what SETI has been doing for lots of ...
7
The Intergalactic medium at the relevant redshift is made of neutral hydrogen. What we can measure is the brightness temperature (the temperature that the IGM would have if it emitted as a blackbody) relative to the CMB. This quantity depends crucially on the following expression:
$\frac{T_S - T_{CMB}}{T_S}$
where $T_S$ is called spin temperature.
The ...
7
Connecting an antenna directly to oscilloscope will not give reception, even with a strong radio source.
First problem is the power level. Typical received power from antenna would be around -100 dBm, i.e. $10^{-10}\,\textrm{mW}$. A typical oscilloscope has an input impedance of 1 Mohm, which means if all the received power went there, it would give a ...
6
Since the astronomers are using radio telescopes and not optical telescopes, I'd like to point out why they are doing so - The centre of the Milky Way is a very dusty place. Wavelengths from the millimeter to optical get easily absorbed by all this dust, so it's very difficult to see the centre of the galaxy in the optical spectrum. But radio waves do not ...
6
The StarGazers lounge featured a radio kit article for Jupiter radio astronomy. The same article is also featured over at the Radio Group of BritAstro.
It seems that 20.1 MHz is the suitable frequency for amateurs observing Jupiter. I am far from being an expert for radio astronomy, but for a small source such as Jupiter, I would assume that you need a big ...
6
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?
In Layman astronomy - yes, M-Theory (and probably a few string theories) do explain in detail what happens at the singularity, but it's a mathematical construct, not a testable hypothesis, so ...
6
The size of your dish determines two things:
Along with the temperature of your electronics, determines the signal-to-noise ratio of your telescope.
The size of your dish determines the angular resolution you can expect. This has an approximate relationship of $$ R = \lambda / D$$ where $R$ is your angular resolution, $\lambda$ is your wavelength of light ...
5
A parabola does indeed focus over a broad frequency range. The lower limit is determined by the dish diameter, the upper by the construction (mesh size, parabolic accuracy etc.).
The collector placed at the focal point may be a simple dipole or other fixed frequency antenna, or more commonly, a waveguide that leads the collected signals to a low noise ...
5
The relation you cited holds for a single telescope. But, as also noted in the lecture you linked
"One thing that is possible in radio astronomy is to use interferometry, which combines the signals from an array of antennas as if they were all part of the same aperture. That means that the resolving power of a radio telescope is not just what it would be ...
5
From my simplistic analysis, it's not good for much.
For comparison, the first radio telescope was 9 meters.
One of the favorite parts of the spectrum for radio telescopes is the water hole - 21 cm.
From my quick mental arithmetic, this dish would be able to resolve sources of 21 cm signals of they were about 5 degrees apart.
I'll update with links and ...
5
I'm not an expert in this, but it's a fun little blip in the history of SETI. Pretty much the only blip I think.
I understand the incredibly high signal strength it entails.
I wouldn't call it "incredibly high". It peaked at 30 times normal. source, and that's inside the "waterhole" a frequency range where the background radiation is the lowest in the ...
Only top voted, non community-wiki answers of a minimum length are eligible
