# Tag Info

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I can't figure out whether the Stefan-Boltzmann law is the appropriate thing to use here. Yes, that's exactly what to use, and the 1/4 exponent in the equation below suggests to us that that's how it was derived even before we review the derivation in the article. Wikipedia's Planetary equilibrium temperature; Calculation for extrasolar planets provides ...

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this sounds like a fun homework question for upper-division astronomy !! a couple more points to consider in your solution: small angle approximation (to go from radius r to solid angle subtended by the star's disk as seen from the planet). is the planet rotating? if rotating fast, temperature as a function of longitude will be constant. if rotating slow, ...

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When referencing information about black holes, remember all we have are a few limited observations. None of which are from within the event horizon. Nothing visual other than a few instances where a presumed to be black hole is interacting with its surroundings, giving us something observable. The new gravitational measuring devices we have are the only ...

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It's not possible to obtain a star that large without accretion, however you can still consider it to be a "single star" because it's not bound to other stars. Many people think that there is an upper limit on the mass of a star, but it is based on outdated stellar evolution models and physics, or is only relevant for present galaxies and not for ...

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There is a theoretical upper limit to star size which is A LOT smaller than the mass of that black hole: simply speaking, a star is in a pressure equilibrium where the outward working radiation and gas pressure are balanced by the gravitational pressure. The limit here seems to be around about a few hundred solar masses at most, going by the largest stars we ...

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There is no direct conversion from a flux to a spectral type, but the ratio of fluxes, or the equivalently, the difference in magnitudes in different bands (e.g. $B-V$, $J-K$ etc.), known as a colour is spectral type-dependent. The conversion from colour(s) to spectral type can be done using a calibration table. There are a number of these in use. A very ...

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With a bit of experience, you'll be able to immediately identify Orion. Mostly because I'm fascinated by computer vision, I uploaded your processed image (the darker one, showing only the stars) to astrometry.net, and it came up with this: http://nova.astrometry.net/user_images/5335519#annotated You might like to try it with the unprocessed image. Click use ...

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These stars are the constellations of Orion and the two dogs. Orion is clearly identifiable by the "belt" of three stars. Following the belt towards the left you come to "Sirius" in the constellation of the dog.(Sirius is the brightest star in the sky) and in to top left is Procyon, the lesser dog.

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Whatever was the event that produced this ‘dust’ probably produced it isotropically (or at least isotropic to a good approximation) which, like you said, will either escape the orbit or not if uninterrupted. Betelgeuse does not have much more time before it goes into a supernova, so likely regardless of whether it is gravitationally bound or not, the time ...

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