Star Definition and 1000 Threads

Hi, I'm currently studying GR from Wald's book. The book is fine, but I want to know more details about the collapse of stars, e.g., more about white dwarfs, neutron stars, mass limits, the use of Fermi-Dirac statistics in this cases, etc. What book, paper or website would you recommend?. (I'm...

Homework Statement (1) A Physics lecturer, on a dark night, shines his laser pointer towards the star Vega. (a) Roughly, how many optical photons from the Sun per second enter the eye of an astronomer standing on a planet orbiting Vega ? Assume that 50 % of the light from the Sun is...

When a star like the sun begins to die, what is the time frame over which the star develops into a red giant? How quickly will it expand?

Does the resistances of each phase in a 3 phase generator add together in the Star (wye)? I read on a windmill site that the Delta connection is typically one third the resistance of the Star. So if i had 3 phases that were .5 ohms each in Delta configuration, would the resistance be 1.5 ohms...

Hi all ! I'm looking around the net to find good resources on how to compute total radiation flux from a given star at a given orbiting distance. Ideally I'd like to get not just the W/m2 of the star, but also the expected high-energy radiation, thermal, solar wind pressure.. well, the...

I know that nuclear fusion is the source of energy for our sun and most of the other stars. Neutron stars and white dwarfs have very high surface temperatures. What is the source of their energy?

This is blatant homework help that I don't know how to approach. Any hints would be appreciated. Suppose you are in an infinitely large old universe in which the average density of stars is n = 109 Mpc-3 and the average stellar radius is equal to the sun's radius is R = 7*108. How far, on...

Homework Statement Show that Total energy of this system is given by E=(-432(r^5)(pi^4))/(G*T^4) http://img189.imageshack.us/img189/7325/38899527.png Homework Equations F=GMm/r^2 F=mv^2/r T=2(pi)r/VThe Attempt at a Solution [PLAIN][PLAIN]http://img97.imageshack.us/img97/7766/27047783.png

There is a problem: "The distance of Barnard’s star is 1.83 pc and mass 0.135 M. It has been suggested that it oscillates with an amplitude of 0.026"

in 25 year periods. Assuming this oscillation is caused by a planet, find the mass and radius of the orbit of this planet." My question is...

******* I attempted to post this already today but I don't think I'm not sure if it worked...I apologise if this is a dublicate!********** the problem is: suppose that a star is modeled as having a density that decreases linearly from the center to the surface, rho(r)=rho_c(1-r/R)...

Homework Statement Assume a star is in hydrostatic equilibrium and that the density of the star is follows \rho \propto \frac{1}{r^{a}} where \r is the distance from the centre of the star and \r is a constant. Derive an relation for the pressure of the star as a function of \r...

I've often wondered why there is so much misinformation around the topic of the reasons that very massive main sequence stars are so luminous. It even shows up in books, but if we restrict to seemingly reliable internet sites, I'll bet that in 10 google hits of sites that offer an explanation...

A star that has been ejected from a galaxy probably wouldn't be any different from stars within galaxies. It could be possible for a planet to orbit this star. What would the night sky appear like? Would the galaxies be too dim to see, and the night sky fully black? Lets say that the star is...

OK, I know it's difficult to move a star. But I'm trying to write some science fiction here and I want to make sure I'm consistent with astronomy and cosmology. Now assume that over the next billion years we completely colonize the galaxy and we're all cooperative and stuff. What would be the...

I am trying to find some sky surveys that have longitudinal data of star magnitudes. The passband does not matter. All that matters is that stars has been observed periodically for a decent amount of time (no surveys with only 9-10 observations per catalogue object). Sadly, the only ones I know...

I am here with another silly doubt...Is twinkling because of the star or the distance? What matters here? For example...If the stars Sirius and Proxima Centauri were at the same distance from earth, which star would twinkle more? As they are at the same distance, would they twinkle...

In the Doppler shift or radial velocity method for detecting exoplanets, it is assumed that the orbital period of the star's planetary companion is equal to the period of the star's detected wobble. I'm assuming that this fact comes straight from the solution to the two-body problem. My...

Hi, I'm a biology student...with barrrrely any physics knowledge. However I have to write a report on this article, A Jupiter-mass companion to a solar-type star. and in it, the author finds the upper limit to the mass of the planet, but i read that using the radial velocity method only the...

Hi I have to describe a method to solve a problem involving a black hole. The only information given is the period of the orbiting star and the radius of the orbit. I have to find the stars mass. Would i use the equation F=(mv^2)/r and then substitute in v=(2 pi r)/T for the radius where T...

Forces in Equilibirum? Star Wars forces? Homework Statement http://iweb.tntech.edu/murdock/books/v4chap1.pdf Go to question 11 where you see three charges hanging. The solution is something i don't understand. The forces between the middle and left or right are the same. But the...

I have been reading about the star system on wiki and noticed that one of the Alpha Centauri stars could in theory have a terrestrial planet in the goldilocks region. I also came to know that its orbit would only be stable for 250 million years. Given that these stars have been around for a few...

Hello, I was reading a book on Quantum Mechanics by Manjit Kumar, and read at the part of the Bohr–Einstein debates about Einstein's box to measure the weight of a photon. Now I was wondering, how can a Star collapse if it's constantly losing so much weight?

What are White Dwarfs & Black Dwarfs? And what are Chandrasekhar's limits? Also I want to know about Neutron Star.

I've heard many things about the fusion in the star. But recent cosmic data say vary high energy Gamma ray emission occurring in the Universe. Some research said its related to the Dark Matter annihilation. I'm weakly afraid of saying about that, but. Is one of them related to particle...

mass of a star... given is a binary star system, with mass m1=6*1.99*10^30kg, radius =r1, v=270km/s, orbital period, T=1.7days... the other star of the binary system(compact and dense)with mass m2, and radius r2 orbits around a same common point... (r1>r2, G=6.67*10^-11Nm^2kg^-2)...

Hello All, I am studying for my introductory astronomy exam and I came about these two question; Galileo discovered a) radioactivity b) some moons of saturn c) 2 moon of Mars d) some moons of Jupiter e) the telescope I know he discovered 4 moons of Jupiter but "some" is a bit...

Homework Statement Two stars are in a circular visual binary system. The orbital period of the binary is 30 years. The distance to the binary is 20 parsecs. The angular radius of the orbit of each star is 1". What are the masses of the two stars? Homework Equations I am assuming that...

Homework Statement A star of mass M and radius R is moving with velocity v through cloud of particles of density \rho . If all the particles that collide with the star are trapped by it, show that the mass of the star will increase at a rate \frac{dM}{dt} = \pi \rho v \left(R^2 +...

The question is A main sequence star is barely visible at a distance of 20 pc with a certain telescope. The star subsequently ascends the red giant branch, during which time its surface temperature drops by a factor of 3 and its radius increases by a factor of 50. a) Determine the how...

Homework Statement A pulsating star has a period of 3 sec as seen from the rest mass frame of the star. What is the period of the star as measured by an observer traveling 2.4 x 108 m/s with respect to the star? Homework Equations The Attempt at a Solution

A letter in the current issue of Nature: ==quote== A two-solar-mass neutron star measured using Shapiro delay P. B. Demorest1, T. Pennucci2, S. M. Ransom1, M. S. E. Roberts3 & J. W. T. Hessels4,5 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22093, USA...

Hello everyone; I am a new member and have little formal hard science ed, but have read many pop science books by Sagan, Hawking, and others. In light of this fact please try to formulate answers with this in mind... NO MATH SPAMMING ALLOWED lol My question has to do with the...

When a neutron star flucuates into a black hole does the gravity increase tenfold? Or does the neutron star gravity (while turning into a black hole) increase as expected with the addition of more mass?

Homework Statement I have to write a computer program to simulate a binary star system and I can not assume that the larger mass is stationary. I am given their respective masses, and the period of the system. I am just wondering how to find the write combination of initial velocity and...

Homework Statement Use a coupled fourth order Runge-Kutta, to find the structure of white dwarf stars. I think I am applying the Runge-kutta method wrong? Variables defined in C code notes Homework Equations Equations in c code. and in attached images. The Attempt at a Solution This is...

When calculating the space velocities of stars by combining what we see of both their radial and proper (tangential) motions, how is the final velocity determined?I don't believe they just add these two vectors together do they? Do they make use of the transverse Doppler shift calculation here?

Homework Statement b) Two stars, both of which behave like black bodies, radiate the same total energy per second. The cooler star has a surface temperature, T, and 3.0 times the diameter of the hotter star. i) What is the temperature of the hotter star in terms of T? ii) What is the ratio of...

Uploaded the PDF someone please help me i have no idea what to do! Homework Equations (-G*m1*m2)/r^2 dP/dt The Attempt at a Solution I don't even know where to start i drew everything out and i think dP/dT is 0 cause its at a constant speed someone please help! :(

Hello expert I have downloaded several star catalog. But how can I open the file? How can I read the file? I would like to see the positioning of the stars. I would also like to know the distance and angle between stars. If anyone here know, would appreciate if you can share. I have tried to...

My question was piqued by this article: http://news.discovery.com/space/earth-like-planet-life.html The article claims that the planet discovered is tidally locked, but does not explain how this was determined. Presumably the planet is much too far away to be resolved by any telescope, and...

Homework Statement If a star emits the same intensity of radiation at all visible wavelengths, what will be its apparent color at the Earth’s surface? Homework Equations No equations... The Attempt at a Solution I realize that a horizontal line would occur through the visible...

Homework Statement A) How many W does 1 kg of the sun’s interior produce via nuclear reactions, on average? Compare the sun with a carbattery, which typically produces 190 W/kg. Which body wins? B) Estimating the time the two objects are providing their respective power, compare the energy in...

I'm toying with the idea of making a little 2D space orbiter game so I've implemented Newton's universal gravity law into this little app. It works really well, even. The problem I'm having is when I want to create an asteroid-belt. I spawn little asteroids randomly around an area around the...

This question has been bugging me... I've rephrased the question a bit so it shouldn't require much astrophysics knowledge to understand, just a bit of regular physics. Consider a binary star system. By doing some geometry based on visual observations of the positions of the two stars over...

Homework Statement The Starship Enterprise returns from warp drive to ordinary space with a forward speed of 56km/s. To the crew's great surprise, a Klingon ship is 120m directly ahead, traveling in the same direction at a mere 24km/s. Without evasive action, the Enterprise will overtake and...

Hello, I'm doing a project on proving the existence of black holes. I am using Sgr-A as a test subject and am after the data set for the orbit of the star S2 around it so I can do some of my own calculations on it. Does anyone know where i might be able to obtain these?

When did humanity realize that the Sun is similar to the night-time stars? I can find no reference to this in Wikipedia or anywhere else. It seems that ancient man thought that the Sun was unique of it's kind (similar to how we perceived the Moon before Galileo observed Jupiter in his...

Very quick question PLEASE - Star Connection! Homework Statement i'm just working on some questions on power engineering and there's a question on star connections. the wording is a bit funny - wondering if can get some clarification please. "a three phase load is composed of three...

Is there any direct evidence that black holes are smaller in size than (less massive) neutron stars?

Extraterrestrial life usually implies planetary biota. What about that on stars like brown dwarfs?