Stellar Definition and 176 Threads

Technetium 99 was detected by spectroscopy in a red giant. How did it get there if it is heavier than the “iron peak”, the upper limit for fusion?

Recently saw a discussion on this topic somewhere on here. Just to get it out of the way not I’m affiliated in any way. For Windoze there seems to be a non-free program called Astrosynthesis: With AstroSynthesis, you can can map out large portions of space - plotting stars, interstellar...

Does anyone have a link ro the research showing that our sun was formed from more than thirty nebulae, not one as would be expected?

I'm trying to understand why the CNO cycle is considered catalytic in stellar nucleosynthesis. I know that carbon is regenerated in the process, but how does this make the reactions faster than the proton-proton chain? Thanks in advance for your insights!

When looking up stellar nucleosynthesis and the various reactions that occur inside stars, I often see very straightforward reaction chains, such as this one for the Silicon burning process (isotope numbers and such left out): ##Si + He \to S## ##S + He \to Ar## ##Ar + He \to Ca## And so forth...

During the neon-burning process in stars, why do two Neon-20 atoms fuse into Oxygen-16 and Magnesium-24 instead of forming Calcium-40?

What are the independent and accurate ways of determining stellar mass apart from its gravitational effect?

Phares as pragmatically as I can, thus leaving aside observational issues such as light speed, Universe expansion, moving apart galaxies and the Universe having no edge. Focusing on the fact that an observer on Earth looking deep into space can effectivly see the oldest stars formed during the...

Hi all! It has been quite a while since I last posted here. Again. I'm currently interested in supernovae and the exotic stellar remnants that are left behind from such events. I'm interested in the physics and science surrounding this subject, it's something that I currently have an interest...

Hi, I have an upcoming exam in astrophysics. We have been told to make sure we study all figures and tables, s.t. we are able to explain them. However, I ran into these figures below, in my lecturer's PowerPoint and I do not know where they originate and aren't presented in my book. I'm having...

Short version: problems fixing 25-year old world-building; due to canonised data points, I have a planet that is way too hot to work, compounded by interpretation problems by teenage-me on stellar data - help would be appreciated! Sometime in around the mid 1990s, I got SpaceMaster the RPG (and...

This is pretty out there so bear with me. Imagine a brunch of aliens having gravity under fine-grained control. So much so, in fact, that they'd bend space around a star so all the light would be forced around to exit from a circular aperture.No Loss. Furthermore they could bend space in front...

Hi! I read this definition of Stellar Parallax "It is expressed quantitatively by one-half the angle subtended by the Earth's diameter E1E2 perpendicular to the line joining the star and the sun (see Fig. 2-10)." (Source Alonso and Finn: Volume 1). But, I was unable to understand how they...

We have direct mass models of stellar motion inside of galaxies (basically, find a happy medium between a sphere and a disc). And of course dark matter corrections to explain the deviation between model and observation. Is there any pattern at all to the motion of extragalactic stars passing...

How much energy is required to double the radius of a uniformly dense stellar object? Express the answer in terms of mass and the radius of the object.

What is a "temperature distribution" in the context of a stellar photosphere and How is the temperature distribution related to the effective temperature?

Does the limb-darkening curve fall off faster at shorter wavelengths or at longer wavelengths?

AIUI, the early universe, after the Great Recombination, was a fairly, but not absolute, isotropic cloud of mostly H, with some He. Eventually regions of the cloud coalesced into stars, and if the mass was big enough, the temperature & pressure in the star core was sufficient enough for H in...

I have to give a presentation about natural Radiation and I am very happy about it because it includes Astrophysics. I want to explain to my audience how the stars produce cosmic rays. I thought about explaining to them how nuclear fusion and that kind of stuff works but then I realized that I...

Hello I have been reading about the s-process and r-process in star evolution. And one thing i briefly saw mentioned was that both processes generally create higher abundances of elements with even number of protons than odd. It however did not explain why there is a slight bias towards even...

My best guess right now is use Newton's version of Kepler's 3rd Law to maybe find a combined mass, as I'm under the impression that the smaller star's mass would still be too large to ignore, but I'm not confident. And I wouldn't be sure as where t go from their, either. Any guidance would be...

The question is taken from An Introduction to Modern Astrophysics by Carroll and Ostlie. I did manage to do the entire question and plot the relevant graphs but I just want to to investigate a bit more. For example I want to look at how the graph would like in the case of the Sun. I don't know...

When modeling stellar structure and formulating equation of states, I've seen various cases where you have to take into account whether the constituent gas of a star is degenerate or not. But how do you determine if the gas is degenerate or not?

Why do we see more absorption lines in stellar spectra than emission lines?

Given that the universe is 13.8 billion years old and our solar system is 4.6 billion years old, less than 10 billion years of star birth, life, and death is necessary to produce the heaviest occurring natural elements. Given what we know about supernova, what is the minimum number of supernova...

So here is a serious question: If Pluto isn't big enough to be a planet, then wouldn't it be a moon to Sol. I mean, a planet can have a moon. A moon can have a moon. So can a sun have a moon? Is there actually a rule? Inquiring minds want to know.

Homework Statement Assuming a Salpeter IMF with upper and lower mass limits of 0.1 and 20 M⊙ respectively, calculate: (i) the mass point at which half the mass formed in a stellar cluster lies in more massive systems and half in less massive systems. ii) the mass point at which half the...

Sirius, the brightest star in the sky, might be eclipsed by an asteroid in a few days: https://www.skyandtelescope.com/observing/will-sirius-disappear/ Can a 7-kilometer-wide asteroid make Sirius disappear? You bet it can. That just might happen on Monday night, February 18th. That evening...

I'm trying to visualize what a fast spinning supermassive black hole slowly eating a stellar black hole should "look" like; how would the mass flow between the two? Could enough mass be removed from the stellar black hole, that it loses it's event horizon before entering the supermassive black...

Hello, Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago If the luminosity in the B band (absolute magnitude in B-band is equal to -21.22) is dominated by stars of in the RG branch, with masses ##m \sim 1\,\text{L}_{\odot}## (within ##\sim...

<Moderator's note: Moved from a technical forum and thus no template.> Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago. From this original burst, I want to compute the fraction of stellar mass still surviving as stars in the main sequence ...

I am exercising on Stellar Physics topics and in particular the questions below: 1) First of all on the rotation profile for the radiative zone: I know that unlike the convective zone, where the rotation varies mainly in latitude (faster at the equator than at the poles), the radiative zone...

So once a star enters the helium fusion stage, it uses the Triple-alpha process to create Carbon from Helium. It then uses the Alpha Ladder process to create Oxygen from Carbon. So my question is, how is Nitrogen, in between Carbon and Oxygen, produced? All I can think of is that either Oxygen...

I try to understand the following graphics with x-axis being the radius of a typical star : I would like to knwo if ##\delta c/c## (y-axis) represents the relative error between theoretical and experimental values or if it represents the fluctuations of speed of sound inside. If these are...

I am working through "Spacetime Physics" and encountered exercise 3-9, which concerns aberration of starlight. They ask the following question: "Since the background of stars also shifts due to aberration, how can the effect be measured at all?" I got part of the answer. You measure the angle...

Is there an astrophysical relationship between the how large a star's core gets and how large the star itself gets? Is it a simple linear percentage, or something more complex? For example, red dwarfs can fuse their entire hydrogen allocation, so the whole star is the core. But the Sun has a...

Can anyone enlighten me as to why the total thermal energy of a star will increase with time if the star has no nuclear energy source?

Homework Statement A binary stellar system is made of one star with ##M_1=15{M}_\odot## and a second star with ##M_2=10{M}_\odot## revolving around circular orbits at a relative distance of ##d=0.001pc##. At some point ##M_1## explodes in a supernovae leaving a neutron star of mass...

I am a Physics undergraduate at the University of Texas at Arlington. I am currently taking an Astrophysics class in which my professor talked about the inclination angle of the orbital plane of the binary star system and how it is impossible to determine that angle. I was wondering why is it...

The Firefly universe (as I understand it) is a large number of planets orbiting a very large star with a wide habitable zone. Of course, to make that work, the star would also have to be reasonably stable and not emit lethal levels of radiation. Is there a stellar class that could, even in...

Homework Statement Hi, I am studying for a test on Monday and I was wondering if someone could clarify something in my notes on the ionisation rate of Type O stars. The line in my notes says; L = 105L0 ⇒ S* ~ 105 /13.6eV ⇒ S* ~ 1049 Basically, I don't have an actual formula for S* and I was...

Hello, please do somebody have some experiences with calculating of stellar reddening via interstellar extinction? I made some calculation based on apparent and absolute magnitudes and distances of brigthtness star but maximum Av which I got for Betelgeuse was 1.12 mag ( for its maximum apparent...

This appears to be a New Scientist scoop: Fast Radio Burst Pinned Down to Giant Stellar Nursery by Ken Croswell A young neutron star is probably the source of a repeating signal previously tracked to a dwarf galaxy 2.4 billion light-years away. Link: New Scientist

I have a question for my Astro homework and I am a little unsure as to whether I am going in the right direction Question Using an expression that relates luminosity, size and temperature of a star, and assuming all Main Sequence stars have the same mean density, determine the relationship...

Homework Statement So the problem is the following : we observe the stellar aberration of a star which isn't on the zenith, so that the star forms an angle theta with the ecliptic plane of the Earth. With such a position, the star will describe an ellipse instead of a circle (typical movement...

hello PF, I want to know more about stellar evolution and about the end of the star's life. I want something that is not very superficial as i get bored when the content is not really deep. Thanks.

If the suggestion that all matter, or the vast majority of matter, that makes up the Earth and everything on it, including humans, was originally forged within dying stars and their resulting supernovae, meaning that we are literally constructed from stardust, would the following statement be...

This is taken from page 226 in Essential Astrophysics by Lang: "The mass defect, ##ΔM##, for a nucleus containing ##A## nucleons, ##Z## protons, and ##A-Z## neutrons is $$ΔM = Z m_p + (A - Z) m_n - m_{nuc}$$ where ##A## is the mass number of the nucleus, ##Z## is the atomic number, ##m_p## is...

Hi all, Star surface temperature determines the occurrence of photosphere, where radiation can escape from star interior due to diminishing gas ionization and radiation absorption. If it was true the star photospheres should have the same temperature and Herzsprung-Russell diagram should be...

How can we be sure that when looking for planets there sun is not a perfect sphere and just looks like it is being perturbed by a gravitating body?