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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By how much does starlight heat the Earth?

According to this, the stars in the night sky have a cumulative magnitude of -6.5. This is very dim, so I expect the heat generated to be tiny, but I'm wondering how tiny. Moonlight does measurably ...
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How would a quark star maintain degeneracy near the surface?

I'm still not exactly understanding how a quark star could possibly exist for more than a fraction of a second. Neutron stars are already hypothesized to have degenerate quark matter at their cores, ...
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Effect (if any) of strong(ish) gravity radiation on stars

Two black holes merge, and a good few percent of their total mass is converted into gravitational radiation. Years or decades later, the resulting gravity wave passes through nearby stars. Does it ...
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How much of the Solar convection zone is completely ionized?

I was reading about the energy transportation in stars here, and I found this: "The outer portion of solar mass stars is cool enough that hydrogen is neutral and thus opaque to ultraviolet photons, so ...
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Surface UV exposure with cooler star

If the sun's surface was ~ 4000K (and earth closer to compensate), the UV component of the radiation would be less. However, UV makes ozone via photolysis of oxygen. Also, the stratosphere would ...
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Celestial Body Approaching Speed of Light, “Observed” as a Black Ellipsoid?

I have an interesting question, one which I think may not work haha, but please bear with me. Let's work with our sun, with mass of about $2 \times10^{30}$ kg. According to the following formula, ...
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How can we evaluate the ratio of abundance of Carbon to Li, Be and B?

In stars' nuclear processes, if the triple $\alpha$ reaction explain why Carbon is much more abundant than Li, Be, B, how can we evaluate the ration of abundance to ~$10^5$ times ? Is it possible to ...
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Slope of main sequence in HR diagram

In the HR diagram, what causes the change of slope (more flattened) around the area marked with $X$? This corresponds to luminosity of $\sim 1 L_{\odot}$ and temperature $~6000-8000 K$
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Spin during gravitational collapse

During or upon the ending of the gravitational collapse of a rotating star, can it be reasonably hypothesized that a collision between particles of half-integral spin might result either in a change ...
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Theoretically, Is it possible to create a nova by firing large masses into a sun?

In a science fiction story (Bobiverse) a nova is created by accelerating two small planets at relativistic speeds into a sun from opposite sides.The shockwave creates hydrogen fusion on opposite sides ...
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Shooting Star Anomaly

Tonight I was walking home from the supermarket and saw an unusual shooting star. It appeared at a point in the sky, bright red and accelerated to a visible extent far faster than any other shooting ...
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Can Thorne–Żytkow object (heavenly body) exist in universe?

Can Thorne–Żytkow object (heavenly body) exist in universe? It's a new concept I came across. Are there such heavenly bodies in universe? It's a heavenly body in which a neutron star is present inside ...
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Gödel's Solution as background for a star patch

In Gödel's "Example of a New Type of Cosmological Solutions of Einstein's equation of Gravitation", all prior cosmological solutions with a non vanishing energy density have a property of all world ...
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Where can I find values for apparent brightness of stars?

I'm in high school and doing a project. I want to calculate the distance to stars using their luminosity and apparent brightness, from the equation $b=\frac{L}{4 \pi d^2}$. I have found values for ...
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what is the telescopic retinal illuminance of a star?

What is the retinal illuminance (in trolands) or luminance (in $cd/m^2$) of a star image viewed through a telescope? I'm looking for a formula that will calculate this value for input values of star ...
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Number of stars with apparent flux

The stars in our Galaxy have luminosities ranging from $L_{\text{min}}$ to $L_{\text{max}}$. Suppose that the number of stars per unit volume with luminosities in the range of $L$, $L+dL$ is $n(L)dL$. ...
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Influence of matter of a star on masses of neutrinos

It is well known that if neutrinos has masses then from Dirac equation it follows that they propagate (in vacuum) as a eigenstates of mass (not as eigenstates of interaction). It's wave function is of ...
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Dust mass-loss rate from a massive star given a set of parameters?

I've been looking for examples at how mass-loss rates are determined. I'm studying a circumstellar dust shell ejected from a Wolf-Rayet star. I have some parameters like, expansion velocity of the ...
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If entropy is positive, then why do stars form from nebulae?

Sorry if I have so many misconceptions with this questions, but I guess that's the point of asking questions. If entropy, the measure of disorder, is always positive, then how come a star could form ...
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What is the definition of the “stellar angular diameter” in stellar astronomy?

(Following the definitions here: http://arxiv.org/pdf/astro-ph/0509535.pdf ) What is the "stellar angular diameter", as measured by astronomers specializing in stellar astrophysics? Using the ...
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Origin of Stellar Nurseries

What is the mechanism thought to cause huge stellar nurseries to form e.g. eagle nebula?
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Star collision observation

What would these scenarios look like in real world? I mean, what the result would be?: 2 stars (not necessarily same mass) will collide "side by side", like in, they originally were traveling ...
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The standard textbook on supernovae?

This is a straightforward question: What is considered to be the standard treatment of supernovae? Could be a textbook, lecture notes, review article, etc.
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Do the different observed Type Ia supernovae have similar explosion energy?

I have been trying to read about the energetics of observed supernovae for some time. And while the observed core-collapse supernovae have many scientific papers about them trying to estimate the ...
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How to tell a population 3 star in red shifted galaxy?

I read that population 3 are metal poor stars especially those very very massive ones will quickly exhaust their fuel and goes into supernovae when their internal pressure drops due to pair ...
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Existence and evolution of P-type “asymmetrical binaries”

I'm not sure how those are called so let me explain what I mean by "P-type asymmetrical binaries" - I'm thinking of two stars of very different masses (originally) that orbit each-other fairly closely....
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What would the effect of an antimatter star be upon a normal matter planet? (Thought experiment)

Based on the answers from this question: Would the solar wind from an antimatter star be any different from a non-antimatter star?, it seems that an antimatter Sol type star would conduct fusion ...
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Molecular cloud and star formation surveys

I just had a quick question about molecular clouds. Why is it that we survey them using $CO$ lines instead of $HII$? Is it because $CO$ has better emission? It doesn't make sense to me when I read ...
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Can someone calculate the age of the KOI-4878 star?

The star’s low metallicity and fairly high space velocity suggest that KOI-4878 is older than the Sun. But I don't know how to calculate an estimation for the age. KOI-4878 data on Simbad: http://...
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How do we determine both the distance to and speed of distant stars?

My understanding is that we can measure the distance to far away stars by using their color to infer the absolute magnitude of the light they emit and compare that to the observed magnitude of the ...
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Theoretical values of radius and mass of O9.5 II star?

Where to find please theoretical values of radius and mass of O9.5 II star? I mean something like: http://www.mpe.mpg.de/~martins/pub/calib_Ostar.pdf However, there are only O I, O III and O V stars ...
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Why does a drop in gravitational energy result in star contraction

Consider a gas cloud that is radiating away heat. From virial theorem we see that if the cloud radiates away heat and loses energy this will cause its gravitational energy to drop. Why does this mean ...
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Is there a relatively painless way to calculate the radius of a neutron star, given its mass?

I know there are different models based on, as I understand it, different equations of state describing the neutron star mass-raduis relation. I'm not sure what to do with that, though. My math isn't ...
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What percentage of stars are giants/subgiants/main sequence etc

I am trying to find the percentage of main-sequence stars along with red-dwarf percentage for my research paper. I did find one article regarding, however it is very old and i require recent data ...
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Would a Dyson sphere face physical limits faced by white dwarves?

During a recent online discussion, one of the participants made the claim that a Dyson sphere would be limited in mass by the Chandrasekhar limit. Attempts to solicit evidence for this claim were ...
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Rayleigh Scattering and Red Giants

Rayleigh scattering is responsible for the color of the sky. Consider a planet with an atmospheric composition similar to Earth's but orbiting a red giant. Suppose further that the planet is in the ...
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How much of Sun's mass is “regular” matter? How precisely do we know Sun's composition?

This is a question which spun of this Can the Sun / Earth have a dark matter core? I have argued that it is possible to pretty accurately estimate how much mass of Sun is in the regular matter, so ...
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What happens when stars in an elliptical galaxy collide?

I don't mean when stars in a binary system spiral in and fuse together. I mean when they undergo a fast head on collision in an elliptical galaxy. I assume it's much rarer for stars to undergo that ...
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Stars with same colour

This is the problem I'm trying to solve. When it says they have the same colour, does that mean that they have the same temperature?
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How would a star powered by matter-antimatter annihilation be?

An analogue to our sun or stars but the energy does not come from fusion but from matter antimatter annihilation. If such system could exist, how would it be?
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Calcaluting mass with density different integral methods different results?

I need to calculate the following mass with given density. I know that the density is : $p(r)=p_{0}\frac{r}{R}$. The problem is that in the book they ask to calculate the mass yet in two different ...
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Is there a mass relation of the core left behind after ejection in a red giant?

Assuming that you have the mass of the star prior to the ejection of non-core material, is there any relation that can be used to approximate the mass of the resulting left behind core which will ...
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Would a grid of $10^{57}$ hydrogen atoms collapse?

Assume we have a gridded cube of $10^{57}$ hydrogen atoms, with all atoms 1mm apart from other atoms. This 'cube cloud' is in an area of space that would otherwise be at zero g, were it not for the ...
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Star vs Blackhole - Accretion Disk

Simple question: can we prove that what we call today a "star" is not a accretion disk of a "tiny" black hole that happens to rotate in all the 3 axis?
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What would happen to the Earth's atmosphere if all the solar radiation was in the extreme ultraviolet?

According to this, our Earth's atmosphere is completely opaque to radiation with wavelengths less than 100 nm as this radiation has enough energy to ionize the air. Since the surface temperature of ...
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Dimensional grid of spatial coherence on earth of Pole Star radiation

One spot on earth receives a constant stream of stellar radiation: this is the North Pole where the Pole star radiation flows constantly. Given that a point source of light is considered to emit a ...
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Would I be able to see light coming towards me before it got to me

If I were in space looking at a star that just started producing light that was two light years away. Would I be able to see the light coming towards me?