Stars Definition and 878 Threads

I have a few questions. Would a given galaxy contain same amount of stars and gas through its lifetime? I want to say no, but I was thinking for every dead star, there will be a new star forming, and the gases would be preserved in the galaxy. And would the spiral disk component of the Milky Way...

Homework Statement What is the Jean's length in parsecs for a typical neutral hydrogen cloud, which has a density of n(H I) ~10^8 atoms/(m^3) and a temperature of 100K? Homework Equations jean's length = sqrt[(15*K*T)/(4pi*G*u*p)] where: 'K' is the Boltzmann constant 'T' is the temperature of...

I have just found this article and wondered how many bodies in the milky way have proper motion. And why our galaxy seems different to others in that it has such a massive black hole. http://arxiv.org/abs/astro-ph/9807210 A. M. Ghez, B. L. Klein, M. Morris, E. E. Becklin (UCLA) (Submitted on 20...

Homework Statement Picture- https://www.flickr.com/photos/137149410@N02/shares/32x7oM The stars are at vertices of a 45 degree right angle. It is assumed that the stars are spherical so that we can replace each star by a point mass at it's center, as seen in the picture. 1) The two forces...

Population 1 stars are young, hot and more luminious, so when a star is young, fusion of hydrogen is taking place inside it's core. Why then Population 1 stars are called metal rich and Population 2 stars 'matal poor'? Why shouldn't it be the reverse?

In a neutron star gravity has overcome electron degeneracy pressure allowing the protons and electrons to combine into neutrons. But if that is the case, how do neutrons emit light if there are no electrons to swoosh the photons away? I have been thinking, and wonder if the surface (or "crust")...

Homework Statement The Sun has an absolute visual magnitude of about 4.8 and a particular star has an absolute visual magnitude of –0.29. How many times more luminous is this star than the Sun, assuming these stars have similar spectral types and hence colours? a) 100 times b) 125 times c) 150...

Hi pf. As I understand we know what a star is made of by looking at the absorption spectrum from a star. Since a star is a black-body it gives out a continuous spectrum of light but as this light passes through the Sun's atmosphere, certain wavelengths are absorbed depending on what the star is...

Hi everyone, I am currently looking to calculate the amount of stars that die within a certain time-frame. I am trying to go about this using the Salpeter IMF to figure the distribution of star masses... ∫M⋅Φ(M)dM From here I would need to use star mass to calculate the lifetime of stars as a...

If they are so insanely dense and their gravity is so mind-numbingly great, what prevents a neutron star from immediately collapsing into a black hole?

Nor sure if this has already been discussed. But recently Rovelli has suggested the mysterious Fast Radio Bursts might be from Planck Stars : https://www.gravity.physik.fau.de/events/tux3/rovelli.pdf Any thoughts? What are the other explanation and how can resolve this?

this paper Do Black Holes End up as Quark Stars ? R.K.Thakur (Submitted on 25 Feb 2007) The possibility of the existence of quark stars has been discussed by several authors since 1970. Recently, it has been pointed out that two putative neutron stars, RXJ 1856.5 - 3754 in Corona Australis...

Can anyone tell me where I can find an explanation that only the gravity of the stars inside the orbit of your star is important in a galaxy? Someone told me this and the integration of gravitational effects I did seems to disagree so I wanted to look at what has already been done.

Is it possible that 2 stars in a binary system to intersect their orbits like in this picture? ( the orbital plane is perpendicular to the line of sight)

Hi all. I am curious as to why quark stars have not dominated by now, given their inability to decay as they are a mass of fundamental particles. What prevents this?

Why does everyone say gravity collapses and the star explodes? wouldnt the constant tug of gravity never allow this to happen. The fuel burns out and the star collapses why isn't it the fuel is burns out little by little and gravity condenses the star little by little as the fuel burns out.

If you look up in the sky you can see both planets and stars. Sometimes you see them flicker, their luminosity oscillates, why does this happen? If we can perceive changes in their brightness from so far away wouldn't the object's brightness be changing in unrealistic amounts? shouldn't the...

Do neutron star, pulsars, magnetars etc. have solar flares like the sun or do they have sun spots like the sun or do they have solar winds and if they do have any of those types of weather, what are they called?

Please see the picture. Red dots are stars, lines are the path that light takes, our observer is at center. Assuming that stars are somewhat uniformly spread around us, I suppose that stationary observer (left picture) sees about as many stars in every direction, but an observer moving in...

I thought this might be of interest: NY Times article on evidence of pop III stars. diogenesNY -------------------------- New York Times - June 17, 2015 Astronomers Report Finding Earliest Stars That Enriched Cosmos By DENNIS OVERBYEJUNE 17, 2015 Astronomers said on Wednesday that they had...

If the sun is at least 90million miles away and illuminates earth, and stars are the same as our sun, then am i correct in assuming that each star we see in the sky is illuminating an area of at least 90million miles!?? We see a little white dot from this far away but, does that little dot on...

Would you be able to see stars in the day if the blue of the sky was filtered through an optical filter ? Can I make myself glasses using optical filters that'll enable me to look at the stars even in the day ? If the reason for the fact that we are unable to see stars in the day be the...

Homework Statement The intensity of the Sun's radiation is about 1380 Wm-2 at Earth's distance, 1.5x1011m. Earth absorbs this radiation as a black body, and radiates its own energy back into space. a) How much Energy per second falls on the Earth's surface? (Diameter of Earth = 12800km) b)...

Hi all! So here I am, a Frenchman living in China, working on some madcap art projects involving science. I already posted a question here about one art installation I am working on, which involves stars, light, and (possibly?) optical fibers... Feel free to check it out if you're interested...

I haven't read these articles, but it seems that the claim is that there are spherically symmetric static space-times, which can describe compact isolated objects with arbitrarily large masses and arbitrarily small radi without being black holes. That doesn't seem right. What am I missing...

Anyone have any insight concerning the latest research underway at Heidelberg University... concerning the "smaller than once thought" earliest stars? Any thoughts on why these 'smaller than once thought stars' also contain carbon, when at this early stage of star formation in a very young...

Hi everybody; I was wondering if there is a way of knowing if two stars came from the same open cluster knowing the distance fron these to the earth, the distance between them and their spectral types. If someone can pont me to a book or webpage where I can learm about that, it would be very...

I am done with the first year calculus and physics courses and I think maybe I should be going on one subject to improve in that field. What actually is in my mind is I want to learn about a subject in graduate level then go on on this topic in my physics career. I am interested in the...

Homework Statement The Milky Way contains 100 billion stars. The present masses of stars in the Milky Way are distributed according to dN/dm ∝ m−2 , and that stars have masses between 0.1 M and 100 M M = Solar mass Determine the number of stars with masses greater than or equal to the Sun...

Say for you had a wire in a complete circuit inside a magnetic field (pointing inwards) perpendicular to the wire. You move the wire across (to the right) , cutting lines of flux, this induces a current in the wire. The induced current acts upwards using the dynamo rule (thumb is motion...

I saw a thread that asked the same basic question as I'm asking, but the explanation was beyond my current knowledge. Please consider answering my question as if you were being interviewed for a Discovery Channel special and had to make it comprehensible for a general audience. Thanks! For me...

This paper; http://arxiv.org/abs/1504.02742, Population III Stars in I Zw 18, claims potentially conclusive evidence of detection of pop III stars.

I'm just wondering why there exist objects like http://en.wikipedia.org/wiki/HD_140283 (The Methuselah Star) that have projected ages older than the projected age of the universe itself. That, where does the conflict between the age of these very old stars and the calculated age of the universe...

Olbers' paradox reckons that the sky should be blazing bright if there is an infinite number of evenly distributed stars (galaxies). the argument is something like in every direction that you look there would be a star. so the sky would be blazing bright. but even if there were an infinite...

Wikipedia only talks about helium and carbon-oxygen white dwarfs... I understand that on a red giant you only get fusion up to oxygen, but I though that maybe if you had a red supergiant which produced iron in its core, and when it exploded as a supernova it threw off enough mass to form a white...

I can't seem to find an answer to this quick question: which part of the star causes the observed spectral lines? As I understand, the photosphere is the deepest visible layer of the star, and then light passes through the chromosphere and the corona. I would think that both the chromosphere and...

Rovelli & Vidotto's Planck Stars describes a possible quantum black hole - white hole transition through a quantum bounce somewhat analogous to the LQC bounce. In another thread, @marcus pointed out to me that this was not necessarilly considered the most likely scenario for a QG black hole. Is...

Hello! I am learning about refracting telescopes and am slightly confused. I have read that a refracting telescope will magnify planets, but not change their brightness, but will not magnify stars as these will remain as point objects. It just makes the stars appear brighter. I am slightly...

Homework Statement Two equal-mass stars maintain a constant distance apart of ## 8.0 *(10^11) ## m it is eight times ten to the eleventh, not eight times ten to the first power times one. I don't know why Latex forbids exponents of two digits or more and rotate about a point midway between...

When matter is crushed in a neutron star are the atoms of molecules closer and the electrons are the same distance from the nucleus, or is the electron cloud closer to the nucleus? If the latter, how is this possible if the orbits have to have fixed orbitals due to the standing waves of the...

2 conditions to form a star - all atoms in the gas cloud must be gravitationally bound to each other (so the virial theorem applies) - the cloud must permanently lose overall energy E=-GMm/2R therefore R=-GMm/2E, so for R to become smaller and the energy to also become smaller the energy needs...

Homework Statement This problem has been stumping me for days now, I'm sure I'm missing something simple as it's only worth a small number of marks on the coursework. Any help would be appreciated. I've been asked to re-express the equation of hydrostatic equilibrium: dP/dr = - Gm/4πr4...

Are there very many stars (percentage wise) between galaxies? Or are most of the stars within galaxies? I guess my main question is when we see stars that are not in our galaxy are we probably looking at a distant galaxy?Tex

What is your reason for studying physics and what do you want to do with it. I actually got thrown into my schools physics program by accident. I began at a community college studying nanotechnology and when i transferred schools it was supposed to be a two-plus two program meaning I would get...

I just saw an astronomy phenomenon with the following description: a) It was like a "cloud of stars" containing approximately 1.000 shiny objects b) It moved relatively fast (I compare the speed across the sky to the movement of an airplane that is so far away that you can hardly see it -at...

Homework Statement Assume two stars are in circular orbit around a mutual center of mass and are separated by d = a. Assume angle of inclination is i and stellar radii are r1 and r2. Find an expression for the smallest angle of inclination that will just barely produce an eclipse. Homework...

When a quite big star consumes its fuel, it explodes with supernovae. So, if it consumes almost all of its fuel up to the iron, then how can the new stars born after explosion. I mean, Hydrogens already turned into Helium and Helium into Carbon and so on. Does star consume all the fuel it has or...

I picked up a book about the pyramids at Cheops. (Relax, it wasn't a crackpot work.) It said that the pyramid was aligned with the star Polaris, and that Sirus and Orion may be sighted through some of the ventilation shafts. Now the pyramid is aligned with true north. It the time of the...

There is a rather surprising thing afoot in many introductory astronomy texts, and many online web course notes, relating to a commonly seen but completely wrong explanation for why high-mass main-sequence stars have a much higher luminosity than low-mass main-sequence stars. You would really...

I have recently come across the notion that Kerr metric describes the spacetime outside a rotating black hole but not outside a rotating (electrically neutral) star. Unlike Schwarzschild metric, which works both for non-rotating spherically symetric black hole without charge as well as any other...