Stellar Definition and 163 Threads

I am aware of the theory of stellar nucleosynthesis, but what evidence do we have to support this theory? Sources are very much appreciated. Thanks!

This isn't a very technical series of questions, just some passing thoughts I had whilst looking over some notes I had on stellar parallax distancing. Stellar parallax is always described as a means of "measuring the distance to stars." But from where? What I mean is, the distance, or the side...

I have a question. In a massive star (more than say 5 times the mass of the sun), the electron/neutron degeneracy pressure is unable to prevent the gravitational collapse. Does this imply that the Pauli's exclusion principle breaks down and two or more electrons/neutrons collapse to the same...

I've been reading about stellar aberration and was particularly drawn to the experiment where two telescopes are tracking a star but one is filled with water to slow the speed of light down. The results of the experiment show both telescopes to be tilted to exactly the same angle which...

I have just seen a brief clip of an article by a journalist regarding a lecture given by Hawking this week about the mystery of where information of a star goes to when it is swallowed by a black hole. As a non physicist, I am grappling with what exactly is meant by this. Isn't this just a...

Hey PF, Since there are stars that can be powered predominantly (>50%) by the CNO cycle, which requires carbon as a catalyst, and i understand the core temperatures of these stars is about 106 K. Does this mean that stars where the triple-alpha process is dominant (108 K) had to exist and die...

At 265 SM, and age 1.7 Million years, at 163,000 Light Years Away in the R136 cluster, is R136a. But, it shouldn't be alive now. It should have exploded given the model of Solar Mass Evolution at 200,000-375,000 Years old of age. It's in it's Wolf-Rayet phrase, but it still shouldn't be alive...

Here; http://arxiv.org/abs/1511.03457, Notes on Star Formation, is a primer for those with an unnatural desire for a graduate level textbook discussion of stellar formation. Fair warning, it is not for the math challenged.

Homework Statement Stellar mass 3.8 x 10^30 kg Star's orbital speed: 90 m/s Planet's orbital speed: 95,000 m/s Whats the mass of the planet in kilograms [/B]Homework EquationsThe Attempt at a Solution

Homework Statement Quasars have a luminosity on the order of 10^12 times more than our Sun. Our Sun is expected to last 5 billion years. Using this number estimate (in seconds) how long our Sun would last if it started using energy at the rate of a Quasar. Homework Equations None The Attempt...

1. Question from a textbook. I have written down the differential equations for part a) and shown part b), but I am unsure of how to tackle part c). 2. This is the Question from the book http://www.m-rossi.com/img/asp3012-1.png Any advice would be grateful. Thank you

Hi everyone, I am interested in measuring stellar aberration as a challenge to myself; I am more of a physicist than an astronomer. I have a fair knowledge of telescopes and imaging. I would appreciate if somebody can give me instructions or point to some references on: which star to select...

Let S be the frame where the Sun is at rest. Imagine light from the North Star reaches the centre of the Sun, and let's define the equatorial plane as the plane that is perpendicular to this light and cuts the Sun into two hemisphere. Suppose a distant star A is on this equatorial plane and its...

My apologies for starting a thread on a seemingly easy and searchable topic. But, alas, I've searched here, Amazon, google, Goodreads etc and wanted to get some recommendations. Specifically book suggestions on The Sun and / or Stellar evolution. I've ran across several intriguing textbooks...

Hi there, I have a question I'm stuck on. It is: Astronomers use a technique called stellar stereography to determine the density of stars in a star cluster from the observed (two-dimensional) density that can be analysed from a photograph. Suppose that in a spherical cluster of radius R the...

I have a little problem about Stellar Flux. I've searched google and bing for info but to no avail. Please help me understand Stellar Flux. Thanks, Epicall Rounder

A normal star's core consists of Hydrogen but a white dwarf is itself the core and it consists of stellar ash. So the degeneracy pressure is exerted when this stellar ash becomes very dense (In other words when the white dwarf becomes very dense). Am I right? The density of a white dwarf is so...

When the star stops burning because heavier elements like Iron are formed in its core. Then the gas pressure stops and as you know the gas pressure helps keep a star in equilibrium because it provides pressure against the force of gravity. So Iron does not give off energy. So what stops the star...

How do you estimate/calculate how much solar wind a star produces? (Can we even make a passable attempt?) I'm trying to work out whether a fictional exoplanet in orbit around R Coronae Borealis would need a magnetic field (as there appears to now be some debate on a cursory google search on...

So, I'm not a student in physics. Or astronomy. I'm actually a med student, just fairly curious. In stellar nucleosynthesis, plasma is required to fuse the particles from my understanding. In trying to record all the various reactions (PP Chain, Triple α Process, CNO Cycle), but I can't find...

Just been looking around for any good resources or databases which show history of stars in the universe. I have mostly been looking into the size and chemical content of them (like those of population I, II, III). But just looking for some real data and numbers to go with it, like star sizes...

In an inertial reference frame - and zero gravity field - we believe that any passing photons go in Euclidean straight lines. If I have some constant velocity towards the path of a passing photon, it still goes in a straight line, just at a different angle. But if I am accelerating towards that...

Homework Statement The atmosphere of a star has a mean radiation pressure of 0.33 N m-2and a mean gas pressure of 8300 N m-2. Calculate: a) the mean number density of particles in the stellar atmosphere, and b) the radiation pressure in a stellar atmosphere with twice the effective...

I'm trying to find the appropriate formula (and abstractions to plug into it as necessary) to work out the absolute magnitude (from which I can dervive an apparent magnitude) of a solar body. I've found a lot of formula which relative absolute and apparent magnitude, but trying to find how to...

Neutron stars formed from supernova events are prohibited from becoming black holes because it is thought that the gravitational force is not enough to overcome Fermi degeneracy of the neutrons or quark gluon soup at the core of these objects, however, addition of more mass can overcome this...

I thought I understood how stellar aberration conformed to Special Relativity. The CHANGE in that angle comes from the CHANGE in our orbital velocity direction about the sun over six months. And it is the same for all stars. That is fine if there are no significant changes in a star’s state of...

Does anyone have a Matlab file for solving the stellar structure equations that they wouldn't mind passing along? I'm trying to settle an argument with a friend that they can't really be used to describe nuetron stars and I don't have much programming experience. Thanks, Alex

Homework Statement Consider a star of radius R, with density p that is constant, composed of classical, nonrelativistic, idealg gas of fully ionized hydrogen. a. Solve the equations of stellar structure for the pressure profile, P(r) with the boundary condition P(R)=0 b. Find the temperature...

Is there a specific limit that defines the boundaries of each classification category? For example, a main sequence G class star is between X and Y temperatures and has an absolute magnitude between A and B Solar units. Or, an O hypergiant is between X and Y temperatures and has an...

A naive question from someone who knows nothing about the subject: I was wondering how much we can tell experimentally about what's going on inside a star. Can we determine, say, how the temperature or pressure vary as a function of the radius? Thanks in advance.

A friend of mine is writing a Sci Fi tale set a few centuries in the future. While there will be futuristic technologies to make the plot go, she said she wants to try to make it realistic at least to the point where she inst violating the laws of physics. The part she asked me about involved...

Stellar or Solar system Astronomy?? I'm an engineering student and next quarter I will have space for an elective class and I wanted to do something with astronomy. My options are stellar astronomy and Solar System Astronomy, my school only offers these two courses, and I don't know which one...

Conservation of mass -- Stellar equation Hello, I was reading over a article on hydrostatic equilibrium of stars. I came across a chapter stating Conservation of Mass, where there is a sphere: r distance from the sphere, density as a function of radius ρ(r). Let m be the mass interior to r...

How can we use stellar kinematics to measure masses of stars? Any equations or reference papers to explain would be great!

Regarding the creation of the universe and the current model: Is it assumed that the universe, at the time of creation was finite in size (or at least more finite than it is now) prior to the rapid expansion, or was the protoexistance finite in size in an infinite universe? So, did the...

So if there are as many galaxies in the Universe as is claimed what's the role of interstellar combination of light waves on the view of the sky we get here on Earth?

Maybe this is a simple question but, all the stuff I've been reading so far keeps talking about protostars and their angular momentum being a consequence of the surrounding nebula. Why do they inherit that in the first place? Is is just a consequence of the gravitational collapse?

Homework Statement The monochromatic flux emitted from unit surface area of a black body is given by F_{\lambda}(T) = \frac{2h\pi c^{2}}{\lambda^{5}} \frac{1}{exp(hc/\lambda KT)-1} Wm^{-2}m^{-1} If the distance to star X is 620 parsecs, calculate: (a) the radius of star X, in...

On the Origin of Solar and Stellar Magnetic Fields There is recent evidence that the solar magnetic cycle has been interrupted. This is a link to Livingston and Penn’s paper that notes the magnetic field strength of newly formed sunspots is decreasingly linearly. Specifically, why the...

How are stellar EM radiation formed?? I've read this in many books and sites... Any object above 0 K will emit EM radiation of all wavelengths... Now this is confusing me a lot... I mean, how for example a sun emit wavelength s of a Radio and it is the same sun which emits ultra violet and...

Well, this topic is driving me crazy so any answers or replies should preferably be detailed and in an easy way.. My question is i want a sum up of the evolution of a low mass star... I will give my answer and tell me where are the dropouts.. Let me begin,With a protostar accreting hydrogen in...

Homework Statement I have to calculate the lifetime of a star that is 300,000 times as luminous as the sun and 24 solar masses. Homework Equations lifetime = k * m/l The Attempt at a Solution lifetime = 10^10 * (24/300000) lifetime = 800000 years I feel as if this is...

Hi, all how would you go about finding out how much longer a star would live compared to another if you knew the one star was x times more luminous and y times more massive?

What does metallicity have to do with stellar formation? Why does low metallicity in stars in the very early universe mean that they needed to be more massive than modern stars to form?

Page 26 of http://www.maths.qmul.ac.uk/~rpn/ASTM735/Week7.pdf claims that stellar jitter can be caused by the convective motions in the stellar photosphere. Can someone explain that to me as I don't understand it?

Why isn't Stellar aberation considered to be a one way measurement of c? if the angle of aberation (Theta) is 20.5 arcseconds and the Earth's orbital speed is 29.79 Kilometers/second normal to the arriving star light. The value of c should be: c= Vt/tan(Theta) = 29.79/9.94E-5 = 299737.98...

On the exoplanet database they have a value which I am not familiar with, can anyone help me understand what value they are displaying represents? Luminosity ? " compared to solar luminosity? Does LOG mean they performed a logarithm? see attached...

I am looking for a On line or downloadable stellar highly detailed database. Nasa had a excellent one but seemed to remove it from (NASA Star and Exoplanet Database (NStED). Wiki has lots of detail on there website but its star by star basis.I want to analyse large batches of stellar data...

I have a mediocre (by my standards) GPA of 3.34 in the undergraduate math program. However, my graduate cumulative GPA in mathematics is very good at 3.96. I have one semester before I graduate with an MS in mathematics. I'm applying to Phd programs at Kent State University and Ohio State...

Homework Statement A stellar object at some known large distance ejects a ‘jet’ at speed v towards an observer obliquely, making an angle θ with the line of sight. To the observer the jet appears to be ejected sideways at speed V . Prove V = c sin θ (c/v − cos θ )−1 , and show that this...