Star Definition and 1000 Threads

Homework Statement Hello. In my homework I was given to find a mistake in a derivation of hydrostatic equilibrium of a star. In contrast to "regular" derivation, where a cylindrical segment is chosen, in HW a segment of sphere is used: Homework Equations Derivation is given as following: a...

Here's the question: The following figure is the H-R diagram of a star cluster. Use this diagram to determine the age of the cluster. The answers are multiple choice: (A) 600 thousand years (B) 6 million years (C) 60 million years (D) 600 million years (E) 6 billion years...

hi, this is my first post here as i have driven insane by a math problem for my final year astronomy class, I've been at it for 3 hours and i can't make sense of it is the question even correct as i have made the assumption that the volume of a sphere times the density would give me 4 were...

Stimulated virtual W+, W- when supernova core--> neutron star? Weak interactions allow supernova core electrons and protons to convert to neutrons and neutrinos allowing (under the right conditions) the formation of a neutron star? Large numbers virtual W+ and W-bosons are produced in a short...

http://i59.tinypic.com/727ole.jpg My answers http://i59.tinypic.com/mkzvqp.jpg Can some see if I am going in the right direction, thanks.

Hi All, I am preparing for PhD quals and have been looking at problems from other universities. I came across this one and am stumped on how to tackle it. " Assume that the neutron density in a neutron star is 30.1/fm (that is 0.1 neutron per cubic Fermi). Assuming T=0 and ignoring any...

Planck star is a proposed new idea which, if it gains support, will change how we think about "black holes". One can think of a Planck star as a slow-motion bounce that because of extreme time-dilation can take hundreds of billions of years to mature. When it finally does, the star breaks...

I have been reading today about the Wheeler-Feymann absorber theory and it occurred to me that it there was no absorber there would be no emission. What would this mean for a universe that has only one star? Would it be able to rid itself of energy or not?

A Star at the Edge of Eternity by Dr. Ken Croswell Every star that now shines will one day die, but some stars live far longer than others. Our 4.6-billion-year-old Sun will shrivel into a white dwarf in 7.8 billion years. Now astronomers say a dim red star south of the constellation Orion...

Ok so just for the sake of talking and I'm bored, can someone type the Star Trek list from oldest/top to new/bottom? I'm just obsessed with Star Trek. Anyone else? :D

Hi. I was wondering about this. In the "Star Trek" movie of 2009, the destruction of the planet Vulcan is shown, by a black hole being formed in its core. I'm curious: supposing you had some means to create, or collapse part of the planet to form, a black hole in its core, what would, according...

Homework Statement Suppose that an earth-mas object collides with a neutron star with radius 10 km and mass 1.4 $M_{sun}$. The material of the earth-like object would wrap around the neutron star and form a thin layer on top of the original neutron star surface. Assume the material gets...

If the flux entering such an atmosphere from the core of the star at a radius is r0 is F0, the flux that reaches radius r is given by F(r)=F0*e^k(r^-2-r0^-2) where k is a constant a) Write down a formula for the fraction of the incident flux that escapes from the star entirely...

I know the radiative flux traveling through the atmosphere of a star obeys the equation: dF/dr=-opacity*F*density If we have an isothermal atmosphere the density decreases with radius such that density is proportional to 1/r^2. If the flux entering such an atmosphere from the core of...

Homework Statement On the Earth the Sun appears to rise and set about 365 times in one year. During the same 365 days, how many times does the Earth rotate on its axis relative to a distant star (a star beyond the Sun and out of our solar system)? Homework Equations The Attempt...

Hello everybody, I'm new here and i have a question about the activity of our galaxy's Supermassive Black Hole. Did it influence the star-formation activity or was it vice versa? I would be grateful if someone could tell me anything about this or give me some information directions. Thank you.

How many neutrons are in a neutron star with a diameter of 42.0 km? I was under the impression it was just (42.0e3/1e-15)^3 = 7.0048e58 but that's wrong??

One of the most popular mass loss equations of a star, developed by D. Reimers, is given by: dM/dt = -(4x10^-13) * η(L/(gR)) solar masses per year Where η is a free parameter close to unity and L, g, and R are the luminosity of the star, surface gravity of the star, and the radius of the star...

Homework Statement The Crab Nebula is a cloud of glowing gas about 10 light-years across, located about 6500 light years from the Earth (the figure (Figure 1) ). It is the remnant of a star that underwent a supernova explosion, seen on Earth in 1054 a.d. Energy is released by the Crab Nebula...

I have an interesting question. I believe this would be the appropriate spot to post this as well. I understand that light is both a wave and a particle, or can be perceived as one or the other in specific circumstances, known as wave-particle duality. So my question is this, under such...

Hello! I had this doubt when I was 14-15 years old, and I waited for many years (I'm 49 now) to ask about it, as I always thought this to be a silly question. In case someone can help with this, that's a thought experiment. It starts with this: if you have a sphere of gas, and then apply...

Hi, From the basics of 3 phase power, I believed that if you had a delta source which had Line Voltages and Phase Voltages of 100V, if you converted this into a star source, the Equivalent Star Line voltage would still be 100V and the equivalent star phase voltage would then be 100V/sqrt(3)...

"Rewinding" a black hole - Can a spinning black hole become a star? I couldn't fit all the important prerequisites and context in the title, so I'll set up the thought experiment here. Some of these assumptions are also questions, and might be easily refuted, thus answering the main question...

Based on http://en.wikipedia.org/wiki/Sagittarius_A* So "mid to late 2013" - almost the time, are there any new observations yet?

Hello, I would like someone to give me some help or clarification relating to the conversion from a delta to star source. I understand that in star, Line Voltage is sqrt(3) times the phase voltage, and line voltage also leads phase by 30°. I also understand that Line and Phase currents are the...

Is there someone how could explain me why is color temperature (Tcol) always greater than the effective temperature (Teff) of a star? I know that Teff is the temperature of the last interaction surface, where photons are emitted. In the case that the scattering opacity is the dominant one...

Does anyone know which type of orbit is most likely to result in habitable worlds in a binary star system -- a planet orbiting one of the two stars, or orbiting both of the stars, or are they both very likely/unlikely? Wikipedia quotes a paper that simulated binary stars and found that 50-60%...

Is it possible to calculate the distance from the sun to a star like this? (what I mean is can the angles from the diagram actually be calculated?) From the diagram: γ = ∏ - α - ∂ = ∏ - (α + ∂) D / sin(γ) = d / sin(∂) sin(γ) = sin(∏ - (α + ∂)) = sin(α + ∂) D / sin(α + ∂) = d...

Light just now reaching us from Andromeda Galaxy was created literally millions of years ago, around 2.5 to be in the ballpark. When you look at a star, you're literally looking at the past. That means tonight, when we look up, The light that let's us see Andromeda was created when the...

Hello, I made this video from Celestia showing the orbits of the 6 stars that comprise of the Castor system: http://www.youtube.com/watch?v=wIWdfFG7eKw&feature=youtu.be However, I noticed that when Castor C (the barycenter of Castor-Ca and Castor-Cb) enters the fastest part of its orbit...

Don't come over to GA very often, but when I do, it's regarding something I saw on Facebook... Hopefully, this hasn't been posted already... :blushing:

IMHO, the best stories, Watched all of the Capt Jean Luc Picard and sometimes fell asleep. Never a dull moment with Capt Janeway. And they have 7 of 9 who has a great figure. Love her acting! Better physician on board. Tuvok as good as Spock. Chapters are almost always related.

Hi, I've been doing a bit of reading of various online sources to try and understand how to calculate the star type for a Habitable Zone for a planetary system I've already got an orbit distance for, but my poor maths can't cope (at the moment) with the equations. Can someone point me in...

Why can't the Sun (or any star) fuse elements higher than iron? Could anyone provide a technical answer? Thanks!

I thought readers would be interested in this interesting article today on black hole and neutron star mergers and the very small possibility of instantaneous sterilization and extinction of all life on earth:http://www.space.com/22231-gamma-ray-bursts-neutron-stars.html...

My problem is how to calculate the radiation measured from a moving star. I figure there's two ways to do it, both of which I go through below, but they do not produce the same answer! For the first part everything is in the rest frame, \mathcal{O} , of the star. The star emits N...

why the binary star revolving around center of mass ? could type 2 supernova ever had a stellar wind after explosion ?

If we would ever travel to another star, say Sirius roughly 9 light years away, at 0,1 c the travel would take 90 years. Since the Sirius we see today from Earth is the Sirius of 9 years ago and the Sirius we would see on arrival would be the Sirius of 90 years from now, this means that in an...

Hi! Homework Statement The light variation of a Cepheid is 2 mag,if its effective temperature at maximum luminosity is 6000K, while at minimum is 5000K, please estimate the ratio of its maximum and minimum radius. Homework Equations $$\Delta m=-2,5lg\frac{L_{min}}{L_{max}}$$...

Hi all, this is my first post here and i apologize if some rules aren't followed. I have to complete the Project 13.1 (studies of neutron stars: p 346-350) http://www.cec.uchile.cl/cinetica/pcordero/MC_libros/Hjorth-Jensen2008.pdf When browsing using pdf pages 346 to 350, assignments 1...

I am figuring out what are fields in Hippacros star catalogue because I am working on my own space simulator program much like Celestia and Orbiter. That data file is very new to me for my programming. Does anyone recommend any good books that teach about Hippacros for astrometrics and...

I was wondering if I could get a critique of the following pseudo-physics to explain why my sci-fi story includes dogfights in space. I don't want to totally ignore the impossible physics, but I'm looking for something simple. No hardcore sci-fi fan is ever going to buy it anyway. And, yes, it's...

Homework Statement Show that in the Bohr model, the frequency of revolution of an electron in its nth In classical physics, the frequency of revolution of the electron is equal to the frequency of radiation it emits. Show that when n is very large, the frequency of revolution is equal...

A 13.2Billion year old star just 186 Lyrs from earth I thought that these really old stars would have only been observed at super high red shifts because of a shorter life but apparently not. http://www.salon.com/2013/01/12/astronomers_may_have_found_the_oldest_star_in_the_universe/...

We know that the orbit of a planet and its star is a conic section. For a closed orbit, it will be an ellipse described by x^2/a+y^2/b =1, or its equivalent equation in r and θ What would be the equation of the path under GR? and how will it approximate to a conic section when r(s)/r tends to...

Hey all. I'm working on a personal programming project where I'm attempting to simulate (to a small degree) a galaxy. And I have come across a decent 2D density map for a spiral galaxy. This map (array actually) defines a 128x128 grid of values between 0 and 255 representing the frequency of...

Homework Statement Initially, a planet with mass m moves on a circular orbit (r = R) around a star with mass M. Now M is instantaneously decreased to M'. Find the eccentricity e of the elliptical orbit the planet now follows. Homework Equations specific angular momentum l = L/m...

https://www.youtube.com/watch?v=QAEkuVgt6Aw I saw this trailer on ultra screen in 3d and I was captivated. No doubt a very well made trailer, but still I'm pretty stoked for the movie! Even if it just reaches the success of the first, it's been a nice series reboot.

Hi All, I am interested in the discussion in section 10.5 of Schutz's First Course in GR book. Specifically, the conditions at r = 0 of a static, spherically symmetric interior star (or whatever) solution e.g. Schwarzschild interior solution. He argues that by enforcing local flatness one...

So here's a question I'm struggling with: The rotation speed of the sun around the Milky Way center is 220 km/s and it takes the sun around 200 million years to orbit once around center of the galaxy. Given that the rotation curve is relatively flat (i.e. the rotation speed stays the same as...