# Tag Info

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Your eye has two functional parts: a lens (that is about ¼cm²) and a light-sensitive surface (the retina) that is covered in rod-cells that detect light. It takes about 10 photons arriving at about the same time (0.1sec) for a rod to react to the light and send a signal to the brain. This means that, unless about 400 photons arrive from a star onto every ...

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As far as I know, "seeing" (or rather the effects influencing optical wave propagation) is caused by turbulence in the atmosphere. Using the Reynolds number Number $Re = \dfrac{\rho L v}{\mu}$ as a measure for turbulence: density $\rho$ drops due to the reduced pressure (about 1/100 earth pressure), additionally the gravity is smaller than on earth ...

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They have both 21cm and mm-wave observations for those systems. Caption to Fig.1 The hollow squares correspond to two 21 cm and molecular absorption systems. By "system" they are referring to sets of absorption features caused by multiple clouds of material along the line of sight to a single quasar. Each cloud imposes its own set of absorption features....

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As the article you reference makes clear, the defocusing is deliberate. It spreads the light of bright stars (the main targets for CHEOPS) over more pixels and hence mitigates saturation and non-linearity problems in the detectors. The first light images look quite similar to simulated pre-flight images (e.g. Hoyer et al. 2018), so I don't think there are ...

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The Moon is the easiest target to start with. After that, try whichever bright planets are currently in the sky: Jupiter, Saturn, Mars, Venus. Then get a star map and try to find some of the brighter star clusters, nebulas, and galaxies. I recommend the monthly sky maps and object lists at Skymaps.com. Latitude 19°N falls midway between their northern ...

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You can patent a new material that you claim have non-trivial and useful properties. But that does not cover existing objects made out of it: patents cover expressed ideas, not existing things. In many jurisdictions like Australia it also requires that the thing is manufacturable: if the composition cannot be made on Earth, then it isn't patentable. There ...

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The premise of this question is wrong: the "Sirius" shaft was not designed to point towards Sirius. Most of the shafts bend (sometimes several times), making it impossible for the light of a star to shine through. Furthermore, the angle of the shaft is not constant, making it possible for the shaft to be pointed towards tens of different stars, depending on ...

4

From The Unknown Universe: What We Don't Know About Time and Space in Ten Chapters by Stuart Clark: By 1998, Hawking was ready to concede the bet. He thought that although the specific evidence for Cygnus X-1 had not changed, there was now so much evidence for other black holes dotted around the galaxy an the wider Universe that there was no more room ...

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Black holes are black. They are only observed directly by telescopes if they are accreting matter. Any radiation observed comes from the matter surrounding the black hole. Generally speaking, the smaller the black hole, the hotter the accreted material becomes. For something of planetary mass, one might expect X-rays and Gamma rays from accreting material. ...

3

Shouldn't it be the other way around, that shorter wavelength telescopes like those in IR and the visible and UV generate more data because they have higher resolution per unit of aperture? This is a very interesting question! My answer is no, not currently, but someday it may be the case. Because we have big fast computer and fiber optic technology, we ...

3

Of course, if you compare two objects that are the same size but are at different distances, the nearby object will be easier to see. But when making astronomical observations, the amount of light we receive from the object and the apparent angle matter more than the distance alone. For instance, the Andromeda galaxy is further away than Pluto, but it is ...

3

You can not check if a dimensional constant has changed because you can always reverse that change by a smart change of coordinates (system of units). Despite that, since the current Physics assumes the immutability of certain constants, you can verify this assumption by testing the change of an adimensional constant. One of the most common adimensional ...

3

"Back of an envelope" calculation: Proxima Centauri has an apparent magnitude of about $11$. The faintest objects visible to the unaided eye have magnitudes about $6.5$. So we need to decrease Proxima Centauri's magnitude by about $5$ in round numbers, which corresponds to an increase in brightness of about $100$ times. To achieve this we would have to be ...

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No. Problems: Hawking radiation would have very small temperature of $10^{-6} M_{sun}/M_{BH}$ Kelvins. Primordial black holes below 1kg already did evaporate, so there would be no sources from small black holes. The only hope is artificial black holes created by CERN. Falling matter inside black hole would expirience enormous amount of acceleration leading ...

2

The projected equatorial velocity of a star (commonly written $v \sin i$, where $i$ is an inclination angle for the rotation axis to the line of sight) is measured by observing the Doppler broadening effect on spectral lines. There is no need to resolve the star. Light from one limb is approaching at $+v\sin i$, whilst light from the other limb is ...

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This is a partial answer because while I'm quite sure that Fang Lizhi is the astronomer I'm thinking of The paper Periodicity of Redshift Distribution in a T-3 Universe (FERMILAB-Pub-90/26-A January 1990) is a description of the research I'm remembering I can not understand the paper well enough to connect it to how I remember the author describing his ...

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The Celestron SCTs at all apertures have been honed by 30 years of critical amateurs and a market-attentive manufacturer, so you will almost certainly get high-quality images from the OTA, the telescope itself. The Kellner-design eyepieces are another matter. Their apparent field diameter (AFOV, the size of the circle as you look through the eyepiece) is ...

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In principle, yes. The main sticking point is that the emission of Hawking radiation become weaker for bigger black holes. Black holes from the collapse of stars always have masses of at least a few solar masses. At these masses Hawking radiation is so weak that we have no hope measuring it. However, it is also possible for black holes of almost any mass ...

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Distro Astra is a Linux distribution for Astronomy. Unless you are very familiar with Linux distributions be vary careful about installing it you main computer. If you have an old computer not being used I would suggest you first installed Distro Astra on that computer. If it is installed as the only operating system for the computer it will wipe whatever ...

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The paragraph you quote continues... The images from SQUEEZE and MiRa have very similar characteristics and are shown in Fig. 1 (see also the Image Reconstruction section in Methods) In that section various tests are described including the reconstruction of simulated data, with similar interferometric coverage and signal to noise, from spotted and ...

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People have been thinking about and a articles have been coming out on this topic. Last week, the IAU has released this statement last week. The exact way Starlink will affect observational astronomy is not yet known, since many things about starlink are not yet known (reflective coating of satellites, exact number,...). The main points of interference for ...

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According to this site The 10 telescopes will be optically linked together in order to make images of astronomical objects with unprecedented detail. The interferometer will have a resolution 100 times greater than the Hubble Space Telescope and will be able to make accurate images of complex astronomical objects many times faster than other existing ...

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