Questions tagged [stellar-astrophysics]

Questions about inducing chemistry, physics, and many more branches of science into astronomy.

37 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
5 votes
0 answers
205 views

Spectrum features of main sequence and giant stars with the same spectral type

Hence, the spectral features of the supergiant are different from those of the Sun-in accordance with the Saha equation- even though both stars are essentially at the same temperature. The pressure ...
빛나는밤's user avatar
5 votes
0 answers
77 views

Obtaining the derived period of $\omega$ Canis Majoris

I have read these two papers: On the nature of the Be phenomenon I. The case of ω Canis Majoris Stellar and circumstellar activity of the Be star ω CMa II. Periodic line-profile variability In the ...
Anna-Kat's user avatar
  • 505
5 votes
0 answers
62 views

Strength of core-envelope coupling in stars

For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope? I understand that the core-envelope boundary is only (...
Daddy Kropotkin's user avatar
4 votes
0 answers
306 views

Calculation of average FWHM by PSF fitting of all the detected stars in the fits image

I need to calculate the FWHM of all the stars detected via the DaoStarFinder package/any other package by performing PSF fitting in Python. Here is the code for my detection. ...
Abhinna Sundar's user avatar
4 votes
0 answers
44 views

The Relationship between Surface Temperature and Mass of MS and Red Giant

The assumptions about the problem situation are as follows : The red giant is in the HB at HR disgram, and it's a helium fusion situation. And in this situation, the mass of the red giant is the ...
빛나는밤's user avatar
4 votes
0 answers
54 views

What happens to the non-fusion formed metals in stars?

Let’s consider a population I star of some given metallicity. I know that depending on the type of star, different structures are possible with convection zones and radiative zones trading around ...
Justin T's user avatar
  • 3,404
4 votes
0 answers
72 views

Did astronomers "track back" solar wind switchbacks to the surface of the Sun to individual convection cells?

The new NASA Goddard video NASA's Parker Solar Probe Touches The Sun For The First Time explains that the spacecraft passed many times through "switchbacks" or kinks in the solar wind, where ...
uhoh's user avatar
  • 31.3k
4 votes
0 answers
60 views

How does SOHO know what's going on in the sun's magnetic feild?

SOHO can image the sun's magnetosphere. I don't have the foggiest idea how they manage it, because at most a satellite can have a single compass, and measure one point in the magnetic field. I thought ...
Retracted's user avatar
  • 141
3 votes
0 answers
228 views

Why do blue horizontal branch stars turn downwards on the HR diagram as opposed to red horizontal branch stars which remain fairly constant?

Horizontal branch stars (HB) burn helium at their cores. Red horizontal branch (RHB) stars experience an increase in temperature while their radii decrease so their luminosity remains somewhat ...
Astroturf's user avatar
  • 1,111
3 votes
0 answers
48 views

Strength of core-envelope coupling in stars (again)

I asked this on the physics SE but it received little attention: Consider a high-mass zero-age main-sequence (ZAMS) (e.g., $m_{\rm ZAMS} \gtrsim 30\,$M$_{\odot}$) star. I understand that the core-...
Daddy Kropotkin's user avatar
3 votes
0 answers
131 views

Uranium accumulating inside a White Dwarf?

A couple of days ago, there was news that "Some dead stars may harbor enough uranium to set off a thermonuclear bomb", which is basically a teaser for Actinide crystallization and fission ...
B--rian's user avatar
  • 5,616
2 votes
0 answers
27 views

Equation describing Energy Transport due to Radiation in the interiors of stars

I am considering a very elementary stellar structure and I'm required to derive an equation to describe the energy transport due to radiation. The answer I am supposed to obtain is: $$\frac{dT}{dr}= -\...
Ambica Govind's user avatar
2 votes
0 answers
43 views

How do I calculate the flux density of a substellar object?

I am currently trying to generate photometric passband colors for brown dwarfs and planets generated through MESA (Modules for Experiments in Stellar Astrophysics). I believe I understand the ...
Ankit Biswas's user avatar
2 votes
0 answers
54 views

The necessary conditions for driving winds with dust (Dust-driven Wind)

So lately I've read Intro to stellar winds (particularly chapter 7 Dust-driven winds) by Lamers & cassinelli, I forget how many times I've read this but I still don't really understand. So in the ...
aapnegara's user avatar
  • 123
2 votes
0 answers
132 views

Help finding a database or analysis of plage regions on the Sun

Plages are phenomena of stellar activity. A plage is a bright region in the chromosphere of the Sun, typically found in and around active regions. The term itself is poetically taken from the French ...
Autodidact's user avatar
2 votes
0 answers
47 views

Dynamics of red giant hydrogen shell

From what I understood from this answer to How can a red giant grow so big? But this is not at all the way the shell fusing in a red giant self-regulates its fusion rate-- it cannot regulate its ...
Passer By's user avatar
  • 121
2 votes
0 answers
36 views

Is the magnetic field strength of a star predictable from mass, composition, age and angular momentum alone?

This answer to Which stellar properties can we describe as “first principles” in which we can derive the rest? contains an intriguing bit: That states that composition and mass are the two key ...
uhoh's user avatar
  • 31.3k
2 votes
0 answers
46 views

Paper recommendations for career guidance

I'm an undergraduate student in astronomy and I'm one year from graduating, but I feel I still can't choose what career path I want to pursue. To date I've only had two courses of proper astrophysics ...
bajotupie's user avatar
2 votes
0 answers
76 views

Compute the total stellar mass of galaxy with major influence of Red Giants luminosity

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 ...
user avatar
2 votes
0 answers
60 views

To which extent is optically thick photon transport related to conduction?

When speaking about energy transport, the textbook, physics-101 always lists three possibilities: radiation convection conduction Now when studying radiation transport in (stellar) atmospheres and ...
AtmosphericPrisonEscape's user avatar
2 votes
0 answers
87 views

Where can I find raw text, ascii, or binary data from the GALEX satellite?

I am looking for stars in the GALEX data through the GALEX data using GALEXview and plugging in their Henry Draper Numbers http://galex.stsci.edu/galexview/ But the task is tedious by hand. Is there ...
Mason Hargrave's user avatar
1 vote
1 answer
138 views

Could a red dwarf be "deionized"?

Even the smallest red dwarf stars have amazing flares. But the photosphere temperature can be as low as 2700K, which (I think) is too cool to ionize hydrogen. Even the sun at 5800K is cool enough that ...
Kevin Kostlan's user avatar
1 vote
0 answers
44 views

How do changing binary separation and Roche Lobe size of the donor affect the long-term evolution of a binary under conservative mass transfer?

I computed that for a binary system that undergoes conservative mass transfer from the Roche-lobe filling Start 2 to Star 1 (i.e. $\dot M_2<0, \dot M_1=-\dot M_2$ and the change in angular momentum ...
some_math_guy's user avatar
1 vote
0 answers
92 views

Stellar structure equations - mass continuity

Out of the four stellar structure ODEs, I would like to understand why the mass continuity equation was named this way. It reads $$ \frac{dm}{dr}=4\pi r^2\rho \tag{1} $$ and I understand what it means,...
user358572's user avatar
1 vote
0 answers
56 views

How does the entropy diffusivity changes with radius in the Sun?

Could you please explain - How does the entropy diffusivity changes with radius in the Sun? As far I know, In the convection zone, the entropy diffusivity increases as the temperature and density ...
stayhappy's user avatar
1 vote
0 answers
53 views

How do I estimate the number of neutron stars and black holes relative to the number of stars in the main sequence and white dwarfs?

Recently, I had a homework question that gave me the mass of a main-sequence star, that is, M_tp = 0.9 M_solar, and the population formed at the same time. I am supposed to use the stellar birth ...
Casper's user avatar
  • 41
1 vote
0 answers
132 views

how to plot Gauss-Hermite moment maps from arrays of star velocity values in Python?

I want to calculate Gauss-Hermite moments, such as h1,h2, h3, h4 moments from the values in an array of numbers which represent velocity distribution of stars in a galaxy. How would I fit a curve to ...
Jerome's user avatar
  • 155
1 vote
0 answers
64 views

Mass-age stellar phase diagram

The HR diagram is a sort-of "phase diagram" (in a very rough sense) for stars, where a particular star's location on the diagram says something about what "kind" of star it is. ...
realityChemist's user avatar
1 vote
0 answers
56 views

Stellar and gaseous surface mass density spiral galaxies

I have a database with more than 1000 rotation curves of spiral and lenticular galaxies (xxx-gxx notation is ESOxxx-G0xx). I am working on dark matter mass modeling and I would like to know whether ...
Ernesto Lopez Fune's user avatar
1 vote
0 answers
70 views

Understanding various conditions where a star and a black hole meet and there is no tidal disruption; what all can we infer from this diagram?

Can an entire star pass through the event horizon of a black hole unharmed? is a one sentence HNQ with an amazing (to me at least) answer: for supermassive black holes larger than roughly 100 million ...
uhoh's user avatar
  • 31.3k
1 vote
0 answers
99 views

H alpha - double peak (Be star)

What is the double peak in this case, please? What does the third mean? Many thanks
Elena Greg's user avatar
1 vote
0 answers
34 views

Period of pulsation of a star and its relation to free fall and acoustic waves

In this paper, the period $\Pi$ of pulsation for a star can be obtained by means of the virial theorem: $$\Pi = 2\pi\sqrt{\frac{sR^3}{(3\gamma - 4)qGM}}$$ where $s$ and $q$ are constants relating to ...
wrb98's user avatar
  • 231
1 vote
0 answers
80 views

Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number,

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
T. Silva's user avatar
  • 381
1 vote
1 answer
115 views

Stars as nozzles; how important is thermodynamics and the de Laval nozzle equation for understanding the speed of the solar wind vs distance?

Seeing What determines the speed of a star's solar wind? I'm having flashbacks from undergraduate days where the professor started their lecture on solar wind by writing something that they called ...
uhoh's user avatar
  • 31.3k
0 votes
0 answers
38 views

What is the highest redshift a galaxy with a known stellar mass can be observed?

As part of my research, I would need the following information which it seems I cannot find it in literature. I would like to know what are the highest redshifts at which $10^{7}$, $10^{8}$, and $10^{...
Rebel's user avatar
  • 101
0 votes
0 answers
56 views

Binary star system effects at the barycenter

I haven't been able to find anything on this so far. Using Alpha Centauri as the study, what events/effects ( if any ) would happen between the two stars? More specifically, between the gravitational ...
Markitect's user avatar
  • 305
0 votes
0 answers
57 views

Theoretical values of radius and mass of O9.5 II star

Where to find please theoretical values of radius and mass of O9.5 II star? I mean something like in this article. However, there are only O I, O III and O V stars in this article.
Lukáš Altman's user avatar