# Tag Info

8

Red dwarfs, depending on your definition, can range from 2.5 to 150 times more dense than the Sun. What is the cause of this discrepancy? They give no calculations, so I can only guess. The article is from 1946 and we've gotten a lot better at science. It's 1946 and information exchange is limited. No internet, no TV, and long distance calls are expensive....

8

Your question may ulitmately be about the physiology of the eye, which is off-topic here. The spectrum of the Sun seen low on the horizon is quite different to the spectrum of an M-type red dwarf. The reason that a red dwarf is red, is not just that it is cool, but that there are great chunks of the spectrum that are absorbed by molecules in the photosphere ...

7

The brown dwarf "limit" is about $0.072 M_{\odot}$ at solar metallicity (e.g. Chabrier et al. 2000) and is composition dependent. It gets a little higher in metal-poor gas and a little lower in metal-rich gas. $0.064 \pm 0.012 M_\odot$ (the third significant figure is superfluous) is within one error bar of that limit, which in itself is only a 68% ...

3

If we take 1 atmosphere of optical depth to mean looking though the Earth's atmosphere at zenith, then the optical depth to scattering is small - probably of order 0.3 for blue light and much smaller (according to $\lambda^{-4}$) for red light. That means that when the Sun is at zenith, most of the light reaches the ground but some blue light is scattered ...

3

This is a brief letter to Nature from 1946, containing no quantitative justification of the density estimate In 1946, whilst the radius of some of the nearest red dwarfs could be estimated from their luminosities and blackbody temperatures, there would be little information about masses. There is little else to say. Modern models and measurements of masses ...

2

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

Sun-like yellow dwarf stars are generally thought to be the best places for intelligent life to develop, if only because 100% of known life is in orbit about a yellow dwarf. Larger, brighter stars don't last long enough for intelligence to evolve and red dwarf stars were thought to be too prone to solar flares. However yellow dwarf stars are relatively rare,...

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