Star Definition and 1000 Threads

This old nut is often dismissed as flawed thinking by a naive student. It’s been discussed here too, I know. However, when you do the math in standard (Schwarzschild-like) coordinates: Dustball collapse and evaporation in standard coordinates (Arxiv) A. the (coordinate) speed of light...

> In the movie "Star Wars: A new Hope", Luke Skywalker blows up the 'death star'. Assume that the 'death star' is a perfectly spherical spaceship with uniform mass distribution. The mass of 'Death Star' ##M=1021 \mathrm{kg}## and the radius ##R=667\mathrm{km}## Estimate the amount of the energy...

I've read that ESA's Gaia space observatory has created the "richest map of our galaxy (and beyond)" https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_creates_richest_star_map_of_our_Galaxy_and_beyond Meanwhile, it's been widely reported tat the "The Dark Energy Spectroscopic...

I'm watching what I think is the best episode of Star Trek: The Next Generation: Darmok: https://en.wikipedia.org/wiki/Darmok

This is a bit hypothetical obviously as I doubt the conditions for this scenario would ever occur in the real universe. Imagine a black hole, about 10 solar masses. It is, amazingly, sitting in an area of space that is a perfect vacuum. Just by chance, a rogue antimatter star of exactly the...

a) V=(4/3)pi(r^3) N=M/m_n (M=mass of neutron star, m_n=mass of neutron) Subbed into E_f = (hbar^2 / 2m) (3(pi^2)N / V)^(2/3). T_F = E_F / k_B b) dU = (dU/dS)_s dS + (dU/dV)_s dV p = -(dU/dV)_s dV V=(4/3)pi(r^3) -> r = cubedroot(3V/4pi) subbed into U_g = -(3/5)(G M^2 / r) take (dU/dV) plug into...

In many text, the Sun is referred to as a low-mass star, yet it is also referred to as a medium-mass (or intermediate-mass) star in some other text. Which one is "correct"? What is the range of low-mass vs medium-mass? Is it really just low-mass vs high-mass and that medium-mass is just the...

I read this - https://www.sciencedaily.com/releases/2018/01/180116093650.htm And I see this - "However, there are indications that a neutron star with a maximum mass would collapse to a black hole if even just a single neutron were added." And I think the maximum mass of a neutron star is...

I assume that as the light years to another Star reduce the position of the Star will change relative to other references in the navigation calculations. So what adjustments would be necessary to a Starship's course as it gobbles up the distance to maintain pointing it's nose at the destination...

My self and others are curios what could have caused what look as if it was a star suddenly and multiple times with in a 5 min period to ping-pong around rapidly and what looked like it had to be over vast areas of space i read a thread where some one asked the same question but it was several...

If there is a spaceship traveling at 0.999c, the time to reach a star 100 lyr away would be approx 100 yr (assuming no accel and decel). But on the spaceship, It would be 100 yr * sqrt(1-0.999^2) = 4.5yr. Why do we take 100 yr as the time seen on Earth and not the time on the spaceship?

Ordered the book https://www.amazon.com/dp/B08QXYBNJP/?tag=pfamazon01-20 https://www.nature.com/articles/d41586-021-02203-4 after listening to this podcast: One interesting tidbit - the editors of The Economist apparently banned writers from using the 'fusion is 30 years away and always...

A void galaxy is a galaxy that exists in a cosmological void like the Bootes void. Most galaxies are clustered into filaments. Here is a link to the Wikipedia page for a void galaxy https://en.m.wikipedia.org/wiki/Void_galaxy Anyway, in Star Wars Legends, the Star Wars galaxy has 7 companion...

I am working in a student satellite team and we are working on development of star tracker. So for the testing of it, we will simulate some star images on LCD, but the problem is that rays coming into the star tracker should be parallel as original stars are at infinity. So my question is that...

I read this (relavant text made bold): "In the study, published in the Monthly Notices of the Royal Astronomical Society, researchers analyzed Gaia space telescope observations of a large group of stars, the Hercules stream, which are in resonance with the bar -- that is, they revolve around...

I was just looking up at the stars wondering how long they have been visible for. I started wondering if any of them might have been around this galactic neighbourhood long enough and long lived/old enough that the dinosaurs could have seen it. Do you think they’d be any? If not what might be a...

Light emitted by a star should be gravitationally red shifted by its own mass, resulting in greater red shift of light emitted by a more massive star. Is this phenomenon known? Could this be contributing in Hubble 's law in some part too-- probably more distant stars are more massive too-- just...

As a black hole is described by a vacuum solution of Einstein's field equations the stress-energy tensor vanishes identically zero. If one assumes the mass of a black hole to be "within" the singularity then it seems there is no sensible way to apply the stress-energy tensor to a point. So...

I was reading the Star Wars YT-1300 Complete Reference Manual and it mentioned that their are some aspects of hyperspace that remain a mystery aside from those well-established facts acknowledged by all competent astrophysicists. What could be one of the main mysteries? I can’t think of any.

I am aware that a laser could be modeled as a Gaussian beam, e.g., $$E=E_0\frac{w_0}{w_z}\exp (\frac {-r^2}{w^2_z}) \exp (-i(kz+k \frac {r^2}{2R(z)}-\psi(z))).$$ Now I want to study the propagation of light emitted from stars. But I am not sure how to model it, especially by some kind of...

Looking at L&L's solution to problem four of section §106. Lagrangian for a system of particles:\begin{align*} L = &\sum_a \frac{m_a' v_a^2}{2} \left( 1 + 3\sum_{b}' \frac{km_b}{c^2 r_{ab}} \right) + \sum_a \frac{m_a v_a^4}{8c^2} + \sum_a \sum_b' \frac{km_a m_b}{2r_{ab}} \\ &- \sum_a \sum_b'...

The figure is shown; the measurements were taken on two consecutive observing nights. The Ordinate is the flux normalized to continuum and the abscissa is the wavelength scale. You can see the "bumps" indicated by the arrows referring to some Starspot as the spot moves on the profile; assuming a...

What I've done is using the TOV equations and I what I found at the end is: ##e^{[\frac{-8}{3}\pi G\rho]r^2+[\frac{16}{9}(G\pi\rho)^{2}]r^4}-\rho=P(r)## so I am sure that this is not right, if someone can help me knowing it I really apricate it :)

Bit of fun. Vote for your top three!

I don't understand how this can be solved. The official solution was: F=\sigma*T^4 E=F*4\pi R^2*60*60 This doesn't make sense to me, as it seems to imply that the energy that the black body radiates depends on the radius of the shell. For a very large shell the body will reflect...

I'm watching the Next Generation episode Relics and Riker has just ordered the helm to "go into orbit above that point" which I took to mean geosynchronous orbit. No biggie except that the point is on the outer surface of a Dyson Sphere with a RADIUS of more than 1AU. So, assuming the sphere has...

A type of star that usually emits light at a frequency of 6.00 × 10^14 Hz appears to emit light at a frequency of 6.01 × 10^14 Hz. Calculate how fast the star is moving, and if it moving towards us or away from us.

I understand that gravity causes a neutron star larger than about 10 solar masses to collapse into a black hole. I also understand that gravity is the weakest of the four forces. So I find this counterintuitive and I'm puzzled that why is it gravity that causes the collapse and NOT the strong...

Greetings All, Well, this is the question from my 9 y.o. son: what will happen if a famous Everest heavy spoon of neutron star matter is actually removed from the star? I am inclining to his version that it will explode rather quickly, e.g. neutrons will quickly decay into protons-electrons...

Hello, I'm struggling with this question A star is observed close to the center of the Milky Way and from its spectrum we find that it is a type A3 star. Its observed magnitude is m_v = 25. There is only a diffusive gas between us and the star, so we can assume an extinction, of 1 magnitude per...

Curious if the time dilation at the edge of an event horizon would have the apparent effect of prolonging the life of the star to an outside observer - so for example a blue hyper giant at the edge of an event horizon with an expected main sequence time of, say, 500 million years, would remain...

to I am a bit clueless on how to get break the ##r X(r)## from inside the derivative.P.S. I tried to copy from Symbolab instead of pasting the picture, but it didn't let me.

Hello! As far as I understand, after a star reaches iron in its core, if it is not massive enough it turns into a white or brown dwarf. What happens when all the energy of the dwarf is gone? Are we left with a huge sphere made almost entirely of iron?

I just finished Stephen Baxter's Manifold: Space. Great writer. Vast worlds he builds. In it, he has a project to deflect a star (a neutron star, to be exact) using a colossal mirror-sail placed on one side of the star. The idea is that the solar radiation bounces off the mirror and is...

The distance of the sun to the Galactic Center is about 7.4–8.7 kiloparsecs. If I use the known data of stars in various stellar catalogues, how can I calculate (approximately) a distance of a given star from the Center? What kind of data I need to look for? can it be calculated from Right...

I was wathcing a video about radial velocity method for seeking exoplanet(video) and on 3:05 author writes that momentum of a star equal momentum of a planet. Why?

For a star.. Apparent Magnitude = -2.5log10 I K And I = I0/d^2 So in terms of I0... Apparent Magnitude = -2.5log10 (I0/d^2) And the Stefan-Boltzmann law says: Energy Flux = Sigma(T^4) In my reading it says that Intensity is the energy emitted per unit of area per unit of time. It says the same...

From what I gather, there are S-type, P-type & T-type systems, but I'm having a hard time wrapping my mind around the orbital possibilities. Would it be theoretically possible to have a planet in a binary star system where there is a daily "pre-sunrise" and a "pre (or post) sunset" due to the...

Has the telescopes gotten good enough to photograph an actual disk of any star? Or are they all just points of light? tex

Lightning is well known from planets, and to some extent the bigger the planet, the more powerful the lightning. Would it also be possible on brown dwarfs (Y, T, L, M)? What about red dwarfs (M)? Other stars?

This BBC article posts no references so I wonder if anyone has any idea how significant it is? https://www.bbc.com/news/science-environment-53151106

Supposing the total mass of a stationary, non rotating Neutron Star is just one Kg below the mass required to form a black hole. Based on the wiki reference below the Schwarzschild radius must be just beneath the surface of the Neutron Star sphere. Now supposing an object with a mass of one Kg...

https://www.bbc.co.uk/news/entertainment-arts-52535428 Pretty exciting news, I thought Taika's episode of the Mandalorian was the best of the bunch and the other films of his that I've seen (Thor Ragnarok/Jojo Rabbit) are pretty solid. Any ideas as to when it might be set? There was talk of...

For part a I know the conservation of angular momentum is used, but I am not sure how to formulate the equation from the information given in the problem. I know that after the equation has been set up you set it up to solve what Rf is. For part be isn't the finial and initial rotational kinetic...

Can a single star with 6 to 8 solar masses end up as a supernova 1 (having a remnant mass slightly above the Chandrasekhar limit) and being completely disrupted? This idea is presented by John Gribbin in his books “Stardust” and “The Universe”, but I can’t find any other reference or source...

Neutron stars have surface temperatures of 1,000,000 degrees K. Yet they are not creating energy like a normal star. They are just cooling off. How long does it take for such a star to cool to room temperature, 300 degrees K.?

I am confused whether for electron I have to use rest mass energy (moc2 + 0.8 MeV) or just 0.8 Mev for calculating E. Also how do I find minimum density of a neutron star using above data ? Please help !

For instance let's take that a neutron star mass is so high that the gravitational force is more than the coulumb force. If this happens then then the electrons will go down and alpha particle will be left . This is not observed in the star so how will the particle stay normal By the way I am...

So far, I am provided with all the required values for calculation, except N. If N = total number of electrons in star, then using N = mass of star/ mass of an electron should be no problem. Am I right?

Do all stars in their life cycle (t) emit energy (E) that follow a bell shape curve? If yes, is the curve symmetrical always? How is this related to nuclear and thermal time scale?