Star Definition and 1000 Threads

Homework Statement The faintest stars a naked eye can see under the ideal conditions are of m = 6 magnitude. Diameter of a maximally dilated pupil is d = 9mm. Calculate the magnitude of the faintest star a person can see if observing through binoculars (d = 5cm), a large backyard...

without having to rely on quantum channeling

$$\begin{array}{lcl} \frac{du_1}{d\tau} & = & (1-u_1-a_{12}u_2)\\ \frac{du_2}{d\tau} & = & (1-u_2-a_{21}u_1) \end{array} $$ The steady states for this system are $(0,0)$, $(1,0)$, and $(0,1)$. But then the book says without explanation $\displaystyle u_1^* = \frac{1-a_{12}}{1-a_{12}a_{21}}$...

My professor gave us a question to think about for discussion next week. He asked how the radius of a star, who is composed of ionized hydrogen and degenerate electrons, varies with mass. I am not quite sure where to start. How could I estimate the radius?

Homework Statement The problem I am doing is problem 1.55 in Schroeders Intro to Thermal Physics. Unfortunately, I have to come here for help a lot because the office hourse are not until after the homework is due...In any case, the first part of the question was to show that the potential...

I read the book Physics of The Impossible by Michio Kaku. It was there I first heard of plasma windows and I was like "hey that's like Halo and Mass Effect". The problem with plasma windows is that too much energy is needed to make it and that it would vapor your spaceship or soldier if you used...

I am wondering how space geographers would measure curvature of space around a large isolated star. i am thinking of the set up where there are two nearby spheres surrounding the star whose circumferences are already known. The remaining step is to measure the length of a radial geodesic segment...

Star moves faster than light! Cosnider a universe with only two objects, a planet and a star... From the rest FoR of the Star, the planet appears to be revolving around the star.. And also the planet rotates in its own axis.. (just like our Earth and sun)... The planet takes 1 second to...

I recently did an exercise where I had to calculate the total energy needed to separate the stars completely from each other - i.e. make the distance between them infinity. One then had to calculate the potential energy between them as well as their kinetic energies. But there's something I...

so I was just looking up at the sky, as you do... and I noticed one star was flickering red, I believe it was betelgeuse - as far as i could see on my sky map app. Could anyone tell me the reasoning for this flickering? as none of the other stars visible were doing this - at least as far as i...

Hi clever people. much respect. Just wondering, if our closest star went super nova. how would it affect the earth,if at all?

I was browsing through BN yesterday and realized there are a ton of Star Wars books on the shelf. Now, as a fan of the movies and a follower of The Clone Wars show, I thought the books may be of interest to me. My first question is where to start? Do I need to go in a specific order or can...

martian pole stars same as Earth pole stars ?

After a supernova what compels the left over core to be either a neutron star or a pulsar? is it decided before or after explosion? any thoughts would be appreciated.

Specifically, what happens to the identical fermions in a neutron star as the neutron star collects additional mass that makes it into a black hole. Fermions cannot occupy the same state according to the Pauli exclusion principle, what happens to them in the black hole?

Have scientists ever been able to resolve the disk of a distant star in a photograph besides our own sun?

Neutron stars are held together by extremely strong gravitational force. What would happen to a chunk of the star if it had been removed and left to stand alone? Same question for a chunk of a white dwarf?

This seems to strike people I've talked to as a ridiculously simple question but no one can give me a simple answer. I thought this might be the place to get my explanation. I don't see how light can continue to travel millions of years through space after the star has died and it has no energy...

Hi I am new to this site and I really need help I missed this class and of course my book doesn't have this formula so if anyone could tell me it that would be great. The temperature of the universe is now 2.725 K, and its scale size is 100 Mly. How hot was the universe when its length...

I recently read an article that said that experiments in synchotrons had indicated that an electron was the most spherical object in the universe. It stated that if an electron were the same diameter as the solar system, the variation in its diameter would be less than the thickness of a human...

does it follow that the larger the star the higher the core temperature? if so what would be the highest temperature attained. thanks

Hey everyone, This is my first post on this forum. Please tell me if I do some mistake. :) So, there is my question ; I have search a long time on the web but I don't find any answer... Why the metallicity influences the effective temperature and the luminosity of a star ? I read...

Homework Statement How fast would a star have to travel to make violet light (λ = 400 nm) appear to be blue (λ = 450 nm)? Assume the star is moving along the line that connects the star to the Earth. Homework Equations λr = λc / (c-Vr) f= fo (c +- Vr / c +- Vs) The Attempt at a...

From https://www.physicsforums.com/showthread.php?t=40391 in gravitational time dilation. At the center of neutron star PSR J1614-2230 at 1.97 SM mass of Sun 1.9891×10^30 kg mass of PSR J1614-2230. 4 ×10^30 gravitational constant = 6.67300 × 10-11 m3 kg-1 s-2 radius(rough estimate) =...

Say a core collapse event of a massive star occurs, forming neutron star matter in its core. However, the explosion manages to eject enough core mass such that the remnant is below the Chanrasehkar limit. At this point, gravity would no longer be able to overcome electron degeneracy pressure...

Kepler22b--first exoplanet found in hab-zone of sun-like star http://science.nasa.gov/science-news/science-at-nasa/2011/05dec_firstplanet/ NASA newsletter ==quote== Kepler Confirms First Planet in Habitable Zone of Sun-like Star Dec 5, 2011: NASA's Kepler mission has confirmed its first...

Homework Statement A binary star system consists of a hot main sequence star (m=0.5m) and a red giant (m=1.2m), the parallax of the system is p=0.0012". Calculate the apparent magnitude of the system. Homework Equations I have b1/b2 = 2.512^(m2-m1) and p=1/r The Attempt at a...

Homework Statement Using natural units with c=1. We have our Sun and a star at rest relative to it one light year away. A spaceship travels from our Sun to the star with v=1/2. During the journey how much time passes on the space ship's clock? How much distance does the captain of the...

It seems to me, from my understanding of the Lagrange points, that a binary system with the appropriate mass ratio between stars could support planets in the L4 and L5 Lagrange points (I've encountered this, actually, in science fiction; Larry Niven put such a planet in the Procyon system for...

There aren't any electrons on a neutron star right? They all get squooshed into the protons to make the neutrons. Am I right about that?

Homework Statement Given the following data, calculate the main sequence lifetime of the Sun (in years), assuming that all the initial mass is hydrogen and all of it is converted into helium. Mass of the Sun = M = 2x1030kg Luminosity of the Sun = L = 4x1032W Energy released in the...

Neutron stars are thought to be rotating in a way that their beems are seen as the pulses. The beems are not aligned with the axis of rotation. What is the current theory about the speed of the axis of rotation? Are they spinning and rotating on both axis?

I did this problem on this British Physics Olympiad paper and it assumed that when a star bigger than the sun collapses under its own gravity to create a neuron star the magnetic flux stays constant. Please explain Thanks

Not sure if this is the best subforum, but here goes: I tried to photograph YU55 when it flew by, and have been combing through a pair of photos, looking for a dot in one and a blank spot in the other. So far there have been at least 5 instances where something appeared in one photo only...

A binary star system has two stars, each with the same mass as our sun, separated by 1.6x10^12 m. A comet is very far away and essentially at rest. Slowly but surely, gravity pulls the comet toward the stars. Suppose the comet travels along a straight line that passes through the midpoint...

Homework Statement By performing CCD photometry on a pair of nearby stars A and B we obtain their relative magnitudes in the V filter and their colors: Star A: mV = 8.70 , (B − V )= 1.30 Star B: mV = 11.90 , (B − V )= 1.81 Star A is known to be a of a main sequence K0V type, while no other...

If a globular cluster is a dense(relatively speaking) collection of stars, why don't the stars attract each other gravitationally? Why don't they all collide to form a mega-star?

Basic question, I know... but.. When a star collapses and becomes a black hole, is it the same mass and does it have the same gravitational force of the original star? I heard something about it throwing off some of that mass in the process. And perhaps some aspect at the quantum level...

Homework Statement A star is located 4.2 light years from Earth. At what constant velocity must a spacecraft travel from Earth if it is to reach the star in 3.0 years time? Homework Equations I've been working on this for a couple of days, but I'm not entirely sure which equation to use...

Homework Statement Two stars, S1 and S2, with effective temperature of Te,1=25000 K and Te,2= 2000 K and photospheric radius of R1=Rsun/100 and R2=50 Rsun make a binary system. If the Star S2 is in circular orbit around the S1 with revolution period of P=180 days (1 day=24 hours), and S1 has a...

Why there is a phase shift of 30 degree (positive or negative) if we convert our winding from star to delta or vice versa?

Homework Statement Two newly discovered planets follow circular orbits around a star in a distant part of the galaxy. The orbital speeds of the planets are determined to be 41.7 km/s and 55.5 km/s. The slower planet's orbital period is 8.04 years. (a) What is the mass of the star? (b)...

What would happen to a star if it took a direct hit from a gamma ray burst? For example if a gamma ray burst from a supermassive black hole at the center of a galaxy hit a star, would the star survive? If so, how would the grb effect the star? If not, would the star explode...

Uh, I don't know if this suits the topic, but I've been wondering about this. Are we more times bigger than the smallest particle we know about than we are smaller than the large stars?

Application of the Doppler effect and Kepler's 3rd law Homework Statement (*This isn't the exact wording from a textbook, just as I had copied it down) An eclipsing binary star system containing stars A and B in concentric orbits (about their common centre of mass) has it's maximum red- and...

Actually I was studying on 2nd postulate of special relativity. There I saw Ritz's emission hypotheses says for an object moving directly towards (or away from) the observer at v metres per second, this light would then be expected to still be traveling at (c + v) or (c − v) metres. Now...

Homework Statement A binary star system consists of a star P and a star Q, of mass 4.0 x 10^10 kg and 2.0 x 10^10 kg respectively, separated 6.3 x 10^9 m apart. Star P and Star Q move in circular orbits with their centers at the center of mass which remains at rest. Find the position of...

Can simple mass accretion turn a neutron star into a Black Hole, or does a BH require temperatures and pressures from the collapsed massive star?

http://www.youtube.com/watch?v=6u1I5Gwti9s&feature=feedu How exactly do we calculate the age of a star? Is there any speculation as to how this star as existed in this state for so long without producing more heavy elements for so long?

I just read an article on Discovery.com that a black Hole was discovered in the process of destroying an unfortunate star that wandered too close. My question is, If you know the mass of the star, the mass of the black hole, and the distance between them can you calculate how long it will take...