23

You correctly state that neutrinos do not interact too often. The physical parameter describing that is the effective cross-section. So what you observe in a detector is not the neutrino itself, but secondary particles, e.g. muons. Colloquially put, you may regard anything with high mass (density) in between the neutrino source and your instrument (to detect ...


16

For the most part, the CMB photons travel directly to our telescopes from the surface of last scattering. Some corrections need to be made to determine the blackbody nature of the spectrum, but they are not corrections for absorption of the photons. The two main corrections are shown clearly by this COBE image sequence: (from here). First, the motion of us ...


11

The so-called 'mass gaps' for black holes, according to theoretical models, are between 2-5 solar masses and 50 to 150 solar masses. (Actually, I have read that there is no good theoretical reason for the lower, 2 to 5 solar-mass gap....) The lower mass-gap is suspected observationally because we have yet to observe a neutron star with mass greater than ...


9

High energy muon neutrinos occasionally interact and produce a muon. Energy and momentum must be conserved in the process and the muon heads off in the same direction as the neutrino. The relativistic muon can then be tracked by a network of detectors which are sensitive to the Cerenkov radiation produced when muons travel faster than the speed of light in ...


8

This link gives you all the papers that have cited the instrument description paper. The list of papers shows that it has been used for studying: the centres of AGN, close binary systems, discs around young stars, the atmospheres of AGB stars and interferometric imaging of exoplanets at least. Here is a paragraph from the instrument description paper ...


5

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 ...


4

In the pre-Gaia era, this was effectively impossible to do, since positions and proper motions weren't precise enough for a large enough sample of stars. With the release of Gaia data, though, it has become an active area of research. Bramich 2018 predicts 76 events, while Nielsen & Bramich 2018 extend this to predict an additional 27 events using Pan-...


4

Let me add a minor addendum to Eric's excellent answer. The primary way in which CMB photons interact with matter is via scattering off of electrons in plasmas. After recombination (redshift $\sim 1100$, about 370,000 years after the Big Bang), the baryonic matter of the universe was overwhelmingly not ionized, so there weren't any free electrons to scatter ...


3

How do we know Hawking radiation exists? Quantum Physics (Quantum Field Theory) and General Relativity are considered as the two main theories in physics, which can explain a broad range of phenomena at the scale of atoms and subatomic particles to the large scales of the universe, beyond the ability/validity of classical, nonrelativistic physics. They also ...


3

Adding onto Daddy Kropotkin excellent answer. The physical reason why you might not have expected black holes above 15 solar masses is to do with stellar mass loss (which is highly uncertain and an active area of research). Star's are constantly losing mass in their stellar winds, which lowers the final mass of the star and hence the mass of a black hole it ...


3

Evidence of "new physics" seems to be lacking (in my research into this question.) Black holes can be described fully by known consequences of general relativity as far as our ability to observe them. There are known deviations from the Scharwchild metric, for example in black holes in which the accretion disc is inclined relative to the spin of ...


3

You seem to have all the ingredients apart from the variables of what size your detector pixels are (either physically or binned in software/hardware) and the angular extent of the object you are taking a spectrum of. The basic trade-off, as you say, is between flux and spectral resolution, but there are limits to that trade off. You should not reduce your ...


2

What you did was to switch in a Coudé mirror, which sends the light down the equatorial mount as you described, to other instruments (besides the original focal point of the secondary mirror) There are several designs to a Coudé path. The simplest uses a flat mirror and then places a second camera at the re-positioned focal plane, or re-images that focal ...


2

Unless I've done my maths wrong, the period of total eclipse is about 18 seconds. The CHIMERA camera at Mt Palomar, the instrument which followed up the discovery of this system, can take exposures at up to 8 full 1k$\times$1k frames/second and considerably higher if windowed on an object. There is no need for photon-counting equipment for such a slowly ...


1

The article is quite informative. It is a summary of "a paper published in the journal Scientia Sinica Information" which appears to be Discussion on the requirements and feasibility of constructing China's near-Earth asteroids radar system. While it is written in Chinese the tables and figures alone are very informative. They are going for a "...


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