Stellar Definition and 176 Threads

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...

Decided to have a go at an extra credit assignment: Homework Statement I am given some data for ~9000 stars of 21 known spectral types along with their: measured parallax & uncertainty proper movements in right ascension & declination per year (B-V) color & relative mag (V). I am...

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...

Hello, PF. I'm a simple high school student who likes a challenge, and as such, I decided to put together a research project involving reading spectral lines from photographs I took. I got the lens, I got the camera, I got pictures, and now I'm stumped. Reading up on Rpsec, a lot of it's...

Homework Statement Hello all. I am new to physics but am quite competent in maths and other sciences. I am studying Open University's Exploring Science module and this one question has me stumped. I follow all of the instructions but always come to a completely improbable answer. The...

as mass is converted to energy in stars, is universe losing total mass?

Introduction: The evolution of stellar objects is inherently caused by the chemical composition of the star. Internally, thermonuclear reactions leading to the formation of complex atoms lead to a change in chemical composition which in turn will affect the evolutionary position of a star...

Hi, I am new to this forum but I am an applied physics student and I'm working on a seminar on deep space spectroscopy. My question is actually on the equipment being used for my research. I am using an SBIG ST-7 camera with a DSS-7 spectrograph and I've been running calibration studies with...

Homework Statement Stars in a globular cluster are distributed as a mass function of: \phi(M)=K M^{-2}, such that dN=\phi(M) dM is the stars number in the infinitesimal mass interval. Masses are between a lower limit M_{inf}=0.3 M_{sun} and an upper limit M_{sup}, unknown. The constant K is...

Homework Statement "Determine a surface temperature value for the Sun from the angular diameter of the Sun and the solar constant." Homework Equations L=4π(R^2)σT^4 The Attempt at a Solution At this point my only stumbling block is I don't understand the relationship between the solar...

Homework Statement A double star located at a distance of 10 light years from us. The maximum angle between the stars, as seen from Earth, is 2 arcseconds. (1 arcsecond = 1 / 3600 degrees), we can assume that the stellar orbit is circular and that this angle gives us the real distance between...

Homework Statement Let be the density given by the expression p = pc(1-r/R) where R is tha radius of the star. Find the stratification for pressure and temperature. Homework Equations Equilibrium eq. dP/dr = -Gm(r)p/r2 Continuity eq. dm/dr = 4*Pi*r2p PS.: p == rho (sorry for not...

I don't know what happened, but it seems that all the "hot" research is in fields like astrobiology, cosmology, computational astrophysics, and survey science (SDSS, LSST, etc). The most popular area of astro is still extragalactic stuff (which still makes up >50% of astro research), but even...

Do the sun, moon, Earth etc lie in the same plane? I mean are they at the same level or some bodies are above/below others? If yes than why?

As we look to the spectra of stars from O to M type, we see that as temprature decreses, the spectral lines become more crowded. Why M-stars have more various elements than O-stars? Is that because of mass or age or what?

Has anyone here looked at the physics of stellar engines? See http://en.wikipedia.org/wiki/Stellar_engine for an overview. In particular, I have done a simple calculation for the acceleration due to light pressure of a "Shkadov thruster", which is a reflective shell on one side of a star that...

I know the general accepted theory to the birth of our solar system. One or more nearby stars went supernova and the shock waves caused our gas cloud to collapse forming our solar system. However, i wanted an opinion from those with more knowledge on a hypothesis that seems to make some sense...

Does it exist an accurate model about what happen when two stellar bodies collide?. I'm referring to the kind of collision between neutron stars, white dwarfs. I was wondering if that collision could produce a new kind of object. For example: a white dwarf into a neutron star, and a neutron star...

Hello, I would first like to note I'm not a physicist. I'm a Cg artist trying to recreate a Type II Supernovae collapsing into a black hole using the particle systems in Maya 2011, But I want it to be as accurate to the existing model currently used in astrophysics. The current papers I'm...

I have been reading Kip Thorne's marvelous book ""Black Holes and Time Warps" to familiarize myself with general relativity. Along the way, I have found he discusses many fascinating cosmological topics that I would like to explore further. I am looking for books about the various types of...

OK recently I found a really old table stars based on partally on Yerkes Classification system with a small section on white dwarf stars. It has the stars organized into groups labeled DO, DA, DB, DF, DG, DK, and DM. However, I remember that the current classification system for white dwarf...

I have a report to write about it, and i was wondering if anyone was aware of any relevant material/journals ideally. Any material on Tidal forces would be useful too. Or if you know anything personally on this subject matter, i wouldn't mind reading a rant about it :)

Hey guys, quick question, I know that the usual stellar remnants are the White Dwarf, Neutron Star, and Black Hole, depending on the initial mass of the Star. I was wondering if some Super-Novas could be so catastrophic that the entire star, including its degenerate core was disrupted so that...

hi. I'm creating a game where the main part is exploration. i want a database with the milky way's stars (though I'm not sure how many stars my program will be able to handle at this point) and for the other nearby galaxies i would randomly generate such a database of stars for those galaxies...

Homework Statement Its a series of triangles, the data table being n-# 1-1 2-3 3-6 4-10 5-15 I need a general equation in terms of n. Homework Equations The Attempt at a Solution I can't really find anything. The solution has to be non-recursive, and i can find a bunch of...

Hi there, I'm new to the forums and I came here for a specific purpose. I am not in school at the moment, but rather I am writing a science fiction novel and want to make sure that my science is as close to accurate as possible (though I understand that this may be impossible in some respects)...

Homework Statement Calculate \Omega(r) and v(r) for the following density models: (a) all the mass M is at the center of the galaxy; (b) a constant density adding up to a mass M(R0) at the Sun’s orbit and no mass beyond. Homework Equations M(r) = v(r)2r/G The Attempt at a...

I have a series of questions here all around me attempting to get a better image of what has happened around here over the last 14 billion years. You don’t have to answer them individually. One good explanation might answer them all. Q1: About how many novas, supernovas and such have the...

I have been reading in my book on Special Relativity (A. P. French, Chapman & Hall) that stellar abberation as discovered by Bradley, only made sense to physicists at the time in the context of a wave/ether model of the propagation of light IF the Earth moved with respect to the ether. I don't...

Hi, Just revising for my Advanced Stellar Evolution exam, was wondering if anyone knew if there was a good detailed Colour Magnitude (HR) diagram on the internet which went into some detail of different Stellar Mass' and Chemical Compasitions (so more like a poster than a HR diagram)! If...

Hi! In this problem I have to calculate the distance to a cefeide star, I know visual magnitude, m_{v}, his magnitude in B range, m_{b} and its period, P. Well, if I ignore extinction, I can calculate the distance with M_{V}: m_{v}=M_{V}+5log(\frac{r}{10})+A_{v} Where A{v} is visual magnitude...

Is it generally true that the further away a galaxy is (and more red-shifted), the more it tends to contain lower metal content stars? I'd always assumed this was one of the main bits of evidence for the Big Bang, but I've also read that the globular clusters that surround (and are...

What are the best books (upper undergraduate / beginning graduate) for stellar structure, stellar evolution, compact stars, etc. ?

I was just thinking about how this is done. I have looked online and I can't find a none mathematical explanation. If I am getting it right, we get the orbits by measuring the radial and tangential velocities of several stars relative to our sun. I thought the tangential velocity was...

How does the temperature of a star relate to the radius of a star? How does the mass of a star affect the temperature of the star's core? How does the luminosity of a star relate to how long a star will live? How do the spectral lines of a star determine if the star is a first generation...

Hello there, I have a question concerning Michelson stellar interferometer. It is about stars ejecting mass in a thin luminous shell of gas expanding to a size greater than that of star itself. So it says in the exercise: a michelson interferometer is used as a fourrier transform...

After reading in Longair's Galaxy Formation through the derivation of the virial theorem in the context of a dynamical system in equilibrium consisting of "point masses" interacting only through gravity, I proceeded to try to understand his comments on how the theorem can be applied in order to...

When considering the speed of objects revolving around a galactic boundary and the gravitational confluence at the center of the galaxy, it would appear that all objects would be spiraling toward the center. If an object is spiraling toward that center, then it would appear that light from these...

What does it mean the number after the stellar class? Magnitude?

why is there very rapid mass loss in the superwind phase. my notes simply say "because the envelope attains positive binding energy". Firstly, how can binding energy be positive by definition?! Secondly, I am not entirely sure what the lecturer is talking about? what makes the envelope...

why after hydrogen exhaustion (of low mass stars) does the the core become isothermal. (according to my notes) I mean, after exhaustion, its all helium, and it keeps on contracting right? So by the virial therem it must heat up (so by definition, it is NOT isothermal)! Indeed it must do so...

Homework Statement Hi, i have 2 past exam questions that i need to be able to solve for my exam in 3 days time: consider the portion of a stellar wind of mass density rho, pressure p, temperature T and velocity v between the radii r=R_i = 10R_* and r=R_o = 100R_* where R_* is the radius...

Homework Statement Hi, i have 2 past exam questions that i need to be able to solve for my exam in 3 days time: consider the portion of a stellar wind of mass density rho, pressure p, temperature T and velocity v between the radii r=R_i = 10R_* and r=R_o = 100R_* where R_* is the radius...

Can someone explain to me how shock waves from supernova or stellar winds can generate a superbubble? Does the energy from the shock get converted to thermal energy through compression?

Is there advantage of measuring stellar parallaxes from Mars rather than from Earth? Would it be more accurate than from Earth? Thanks

I'm currently looking at the various gravity gradients (tidal stresses) for black holes and I've realized that in respect of small stellar black holes, as you approach the event horizon, not only does the gravity increase but it (appears) to exceed c. For example, for a 3 sol black hole, the...

stellar evolution pathways...? I find this especially interesting since the trajectories of stars on the HR diagram are more or less based on this assumption. But obviously, small perturbations can lead to major changes in the long-run. But it seems that most of those changes involve only...