Questions tagged [stars]

Stars are astronomical bodies that are (usually) mainly composed of Hydrogen, Helium, and Lithium. They are massive enough that their gravity compresses the matter to the point where nuclear fusion occurs, which creates a lot of heat and tends to make stars output radiation along a blackbody curve. Typically the radiative output is significant in the visible spectrum making stars very bright objects.

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May a star explosion be in that way weak that the expelled material gradually recollapse and form the star again?

May a star explosion be in that way weak that the expelled material gradually recollapse and form the star again? My question is not about would that explosion leave a neutron star as a remnant but ...
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What is the heaviest element being produced in Sun?

Helium is being produced currently in Sun. 3 questions. Other than Helium what other elements are currently being produced in Sun right now.? Looks like in 5 billion years, when Sun will become a ...
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Are the physical structures in our sun of comparable complexity to those in the human brain? [closed]

The writings of Rupert Sheldrake tend to provoke strong emotions, be they ridicule, curiosity, outrage, sympathy, disgust, or otherwise. While Physics SE is not an appropriate forum in which either to ...
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Cross section for photon-electron interaction in high temperature, high density plasma

I need a plot for the cross section of the photon-electron scattering at high density and high temperature. I am working on a project for which I have to calculate the opacity of a hot, dense plasma (...
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Non-Excitation of Hydrogen explains the properties of coolest stars

I was watching a documentary regarding the formations of cool stars in our universe and one of the claims mentioned is that the coolest stars tend to show evidence of hydrogen spectral lines. I was ...
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Rotational energy of stellar remnants

The theoretical maximum rotational energy a black-hole can have is 29% of its rest mass. We've often observed remnant black-holes spinning at nearly the speed of light. From this we conclude that ...
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The metric exterior of a massive object

The only condition apart from perfect spherical symmetry that is required for the retrieval of the Schwarzschild-metric $g_{ik}$ is actually ($R_{ik}$ being the Ricci tensor, the contraction of the ...
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Can we go beyond Casimir Effect 2 plates Experiment?

Every one knows and talks about the 2 plates experiment but I woud like to go beyond that even if only in theory. Some say, the by pulling the plates apart, it would create a "distortion" ...
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Does a star's emitted energy equal the work of its gravitational field?

Based on the formula of this question, it is possible to estimate the difference of the Sun's gravitational potential energy now and after it becomes a white dwarf. $$\Delta E = GM^2\left (\frac{1}{r_{...
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Equations of state for white dwarf stars

I am dealing with some model describing the given composition of a white dwarf made with photons, degenerate electrons, positrons and ions. From that, I can get tabulated values of densities ranging ...
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A violation of energy conservation?

Imagine a universe which contains a single sun and nothing else. The sum of the energy of the univese is then simply the energy contained in the sun and the photons it emits. If I have a theoretical ...
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How can the mass of the sun be determined without using Kepler's law or gravitational lensing?

Can the mass of the sun be determined using the abundance of elements or alternative methods? It would be better to ask the question like this if we assume that I have an object that contains baryonic ...
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Why is Big Bang Nucleosynthesis favored over Stellar Nucleosynthesis?

We know that a hot soup of plasma as it cools (as space expands) can produce light elements if the baryon-photon ratio is just right and the space expands quickly enough so that the neutrons and ...
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What reduces the efficiency of galaxy formation at lower and higher masses?

What reduces the efficiency of galaxy formation at lower and higher masses? (Feedback mechanisms) I understand its something to do with supernova feedback and AGN feedback but I can't seem to ...
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Strange conservation of energy in Navier-Stokes Equations

We want to roughly model the fluid flow of a star; consider the following proposition: In the absence of viscosity, and heat conduction, the Navier-Stokes Equations for a steady, spherically symmetric,...
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What would happen if all protons in the Sun had a charge of 1.000001 times the elementary charge?

The whole sun would be positively charge, but would it explode because of it? Or would it just expand a bit?
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How are we able to observe Fraunhofer lines in a star's spectrum?

How is it possible to observe Fraunhofer lines in the emission spectrum of any star, since the elements absorbing the radiation couldn't possibly absorb all the radiation corresponding to a particular ...
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Will energy ever run out? [closed]

Gravity is the source of all energy and it will never go away. So that means there will always be energy for us right? I have seen some places say that energy will go away eventually and the last star ...
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Why stars don't precess?

Assuming that rotation of stars, galaxies etc is determined basically randomly, the question is: why do all space objects rotate so 'neatly', with little or no precession? And what precession there is ...
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Do Efimov states contribute to fusion reactions other than the triple-alpha process?

An Efimov state is a three-body quantum state in which each two-body subsystem is unbound, but the system as a whole is bound because of the large s-wave scattering length. Intuitively, one can ...
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Expressions for emitted and incident flux of a star confusion

The physical flux is the total energy flowing across the unit area from all directions: We can write flux as a function of intensity as follows: $$F = \int_0^{2\pi}\!\!\! \int_0^{\pi} I \cos(\theta) \...
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1answer
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How to correct the Schwarzschild metric in the presence of Dyson sphere?

I was solving a problem in general relativity about Dyson sphere around a star. I don't have any problem solving the problem but in the question Dyson sphere was assumed to be massless. I checked ...
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Lane-Emden Solutions Near the Origin

I am trying to understand from class how to get anything past $1-\frac{1}{6}\xi^2$, $n=0$. Since my lectures state that it is solved in a series as shown below: $\Theta(\xi)=\sum_{i=0}^{\infty}a_{i}\...
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What is the process of star formation? [closed]

What is the process of star formation and what happens to stars after their death?
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What cause protostar to become optically thick?

So far I get that the cloud will contain CO and will reacts with photons which cools the core but at some point the clouds becomes optically thick and allows the core to heat up. What causes the core ...
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Minimum energy principle for stars

In Townsend's Black Hole lecture notes, he says that at equilibrium, $E = E_{grav} + E_{kin}$ is a minimum, where $E_{grav}$ is the gravitational potential energy $-\frac{GM^2}{R}$ and $$E_{kin} = nR^...
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Are stars ideal gases?

In Townsend's lecture notes on Black Holes, he describes stars as 'self gravitating balls of hydrogen atoms supported by thermal pressure $P \approx nKT$, where $n$ is the number density of atoms.' ...
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Is the light impact on universe expansion is neglectable?

Imagine a universe with the below properties in a present time. It has only two stars The stars are located 1 light-year apart The stars have the same properties as our sun today. The stars are at ...
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Should it be classified as intrinsic or extrinsic variable star if the brightness of the star changes due to the expansion of the universe?

The Wikipedia article on Variable stars says the following: Variable stars may be either intrinsic or extrinsic. Intrinsic variable stars: stars where the variability is being caused by changes in ...
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Spectrum of stars

How does the spectrum of F type stars differ from our sun? I have tried to find the information on the internet but I haven't found anything that helps me. I need the information for a novel I am ...
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Star formation rate in different galaxies

I was looking for some scale to compare my result of star formation rate and see if it is moderate or high or low. But I couldn't find any scale. Is there any paper related to such scale where Star ...
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An audio frequency spectrum of the star Alpha Bootis (aka Arcturus)? [closed]

Does anyone know where I might find an audio representation of the asteroseismological pulsation spectrum of the star Alpha Bootis (aka Arcturus)? In other words, what do the pulsations sound like if ...
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Could Black Hole be formed with the center of some stars? [duplicate]

If the LHC might make black holes, why would tiny or not so tiny black holes be potentially created with the very hot and dense core of a really big star?
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Shouldn't some stars behave as black holes?

Some of the "smaller" black holes have a mass of 4-15 suns. But still, they are black holes. Thus their gravity is so big, even light cannot escape. Shouldn't this happen to some stars, that ...
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Where does a photon('s energy) originating from the sun's core spend most of its time?

AFAIK the photons inside a star essentially perform a random walk until they leave. Considering these factors: closer to the core the curvature of the sphere that seperates "closer to the core&...
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What is the origin of the Sun light?

The Sunlight is an electromagnetic radiation. Is it known what is the origin of this radiation? Can it be adequately described by classical electrodynamics (Maxwell's equations) as a motion of ...
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How does metallicity affect stellar evolution?

The main sequence evolution of a solitary star depends most of all on its initial mass. Other factors influencing its evolution are the initial metallicity, rotation and magnetism. Question: how does ...
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How does a black hole capture an approaching star and force it to start an elliptical orbit?

Let's assume that a standing still black hole attractor can have a star orbiting it in an orbit if the star was somehow a result of the same past proccesses as the black hole.So the star must be on a ...
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Textbooks on cosmology *after* recombination

I am a theoretical physicist and I have a reasonable understanding of the early universe, inflation, FLRW metric, leptogenesis, baryogenesis, perturbations, the works (mainly in the style of the ...
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If the Sun's temperature is around 5000K to 6000K which means it is a yellow star, why does it appear white in space? [duplicate]

If the thermal radiation of stars is close to the thermal radiation of a black body the sun should appear yellow but yet it appears white because of emitting all of visible wavelengths which combine ...
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Physical relation between adiabatic constant $\gamma$ and polytropic index $n$

I am study about stellar model of stars by using polytropic equation of state $$P=k\rho ^{\gamma}$$ or $$P=k\rho ^{1+1/n }.$$ I studied that different values of polytropic index $n$ describes ...
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Calculating apparent density of stars in sky, given an area and distance away from my viewpoint

According to this source, there are $5077$ visible stars in the night sky, and a full sky area of $41253$ square degrees of sky. This makes for a density of $0.12$ stars per square degree of the sky. ...
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1answer
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Death of Stars and Red Giants [duplicate]

As a matter of fact, I was learning stellar astrophysics where I couldn't understand the chain of events at the time of death of stars, Once the hydrogen fuel core is exhausted, the stars start ...
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Jupiter-sized planet orbiting a white dwarf?

I read this news about a Jupiter sized planet orbiting a white dwarf. It is still puzzling to the scientists that how it remained as a single piece. NOTE: I went through the Astro.SE link given in ...
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Does the Sun have enough gravitation to bind its hydrogen/helium plasma?

"Does the Sun have enough gravitation to bind its hydrogen/helium plasma?" So my question arises from the fact that high energy (or high temperature in other words) hydrogen or helium gas ...
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291 views

Why is Stephenson 2-18 so large?

How does a star as large as Stephenson 2-18 get this big? It is 2500 times larger than the sun. Did it start out as a large star with a lot of gas left over that gradually consumed the gas growing ...
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Equations for developing a hypothetical Solar System

I am currently going down the rabbit hole of writing a story but I would like it to be set in a universe which is believable. Therefore I am trying to create a hypothetical solar system in which the ...
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Matching Metrics of Gravitational Collapse in Weinberg's Gravitation and Cosmology

In chapter 11, section 9 of Weinberg's Gravitation and Cosmology, the metric of a collapsing pressureless star of uniform density $\rho(t)$ is derived. In comoving coordinates, it essentially looks ...
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Astronomical objects that should have magnetic bubbles similar to those found by the Voyager probe at the edge of our solar system

I've known about the existence of magnetic bubbles at Solar System's edge from a video edited by NASA from an official channel of YouTube, I refer [1] (as explicitly stated in the title, it was a ...
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Why are black holes so special? [closed]

When reading about black holes, I have also read about things relating to black holes like holographic principles, parallel universes, black hole connecting multiple universes, etc. But black holes ...

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