# Tag Info

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The first order theoretical limit on stellar size is from the Eddington Limit. As the star collapses it is balances by radiation pressure from fusion. However, the fusion rate scales strongly with density (which is why the most massive stars have extremely short lifetime) so if the star was massive enough, the radiation pressure would probably blow it apart. ...

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All of these effects are related to the 11 year solar cycle. And while we know there are times when the sun is "active" versus "inactive" we aren't necessarily predicting exactly where sunspots or solar flares will occur, but how many we see in total.

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To get an order of magnitude estimate you can just use the total mass $M$ and luminosity $L$ of the star and an assumption of your fusion process. Main sequence stars fuse Hydrogen in to Helium through the proton-proton chain, which converts 0.7% of mass into energy. So the estimated lifetime of the star would just be: $0.007\frac{Mc^2}{L}$ ($c$ is the speed ...

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I will be specific to answering the part regarding the prediction of solar flares. Solar flares are very volatile and dynamic phenomena associated to the breaking and reconnecting of magnetic field lines in the Sun's photosphere. There is a phenomena associated with solar flares, called quasi-periodic pulsations, which sometimes precede a solar flaring ...

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Vizier is a good resource for finding catalogs. Searching for "SMC+cepheid" I found a related paper (Udalski et al. 1999) with additional data http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/AcA/49/437. You can also look for "Similar Catalogs" though it may or may not be useful in this case.

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Cepheid pulsations The basic description of the mechanism behind Cepheid pulsations is given here: The accepted explanation for the pulsation of Cepheids is called the Eddington valve,[38] or κ-mechanism, where the Greek letter κ (kappa) denotes gas opacity. Helium is the gas thought to be most active in the process. Doubly ionized helium (helium whose ...

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[In addition to the answer already provided by Py-ser] In the body of a Cepheid, there is a regular or periodical variation of difference between the gravitational pressure and radiation pressure. This radiation pressure is due to the consumption of fuel in it, lighter elements like hydrogen and helium undergoing nuclear fusion into forming heavier ...

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Finally, after searching quite a deal, I found this paper which would aptly answer the question. The paper from 1999 published by Pietrzynski and Udalski in Acta Astronomica lists the Cepheids in the star clusters of Magellanic Clouds.

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Cool aim. I've been intermittently working on a similar program, feel free to use any pieces you like. It's hosted at: http://thestarsbetween.com/maker/builder?stellar=o&rand=1233 And the code is shared open source at: https://github.com/jaycrossler/procyon

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To measure the surface temperature of a star it is used is it's black body spectrum. You would have to get the light curve of the light from tat star and then by checking it's peak you could guess its temperature. I really don't know which instruments to use to get the light curve from a distant star but you could use a tool like this one for the final ...

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This is a tricky question, not immediate. If we talk about Main Sequence stars, yes, you can constrain your fictional star by two parameters. The crucial parameters in the diagram, as you said, are the mass and the radius. This is why the HR diagram well represents the stellar population with two axis. Of course, for your scope, we need to do some ...

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A high density of stars definitely increases the chances of collisions, however, the high velocity of a halo star orbiting wouldn't increase its chances. Since the halo star is traveling very quickly, the halo star would only spend a small amount of time near the galactic core. Additionally, it would have less time to get deflected, gravitationally, by other ...

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The answer is yes. Stellar collisions are events that occur mainly in Globular clusters due to their high stellar density. The likelihood of these events is highly dependent on the stellar density. As we know the galactic centers concentrate large amounts of matter and, of course, thousads of stars which are mainly in the old red main sequence. However, ...

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The easiest way to think of it is terms of the cube square law coming into play. The speed at which a star can radiate heat is mostly dependent on its surface area. but it's ability to generate heat is dependent on its volume. Surface area increases with the square of the increase in radius but volume increases with cube of the radius. As a star grows in a ...

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The mass luminosity relation is non-linear (L = M^3.5 for the main sequence) so more massive stars burn at a much faster rate. This is a non-linear relationship because the fusion is caused by pressure in the core from the star trying to gravitationally collapse on itself.

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The Van Allen radiation belt, which is outside of the Earth's magnetic field is believed to get its radiation from solar wind.

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Nuclear fusion rates in the core of a star have very non-linear and strong dependences on temperature, pressure and density (for temperature it's like T^40 for some processes - http://www.astro.soton.ac.uk/~pac/PH112/notes/notes/node117.html). So, as the star gets bigger, denser and hotter at the centre, the rates of fusion rise much faster and the star ...

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In the answer http://physics.stackexchange.com/a/26787 you can find an example how to convert celestial coordinates to horizon coordinates an than check, if the altitude is above the horizon

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