Question How do stars form?

[Harry Costas]

I do post papers that I disagree with.
But limit my thoughts that may influence other people's thoughts.
I may be wrong.
So please research at your heart's content.

[Submitted on 24 Apr 2025]

Dynamic atmosphere and wind models of C-type asymptotic giant branch stars. Influences of dust optical data on mass loss and observables​

Emelie Siderud, Kjell Eriksson, Susanne Höfner, Sara Bladh

Mass loss through stellar winds governs the evolution of stars on the asymptotic giant branch (AGB). In the case of carbon-rich AGB stars, the wind is believed to be driven by radiation pressure on amorphous carbon (amC) dust forming in the atmosphere. The choice of dust optical data will have a significant impact on atmosphere and wind models of AGB stars. We compare two commonly used optical data sets of amC and investigate how the wind characteristics and photometric properties resulting from dynamical models of carbon-rich AGB stars are influenced by the micro-physical properties of dust grains. We computed two extensive grids of carbon star atmosphere and wind models with the DARWIN 1D radiation-hydrodynamical code. Each of the two grids uses a different amC optical data set. The stellar parameters of the models were varied to cover a wide range of possible combinations. A posteriori radiative transfer calculations were performed for a sub-set of the models, resulting in photometric fluxes and colours. We find small, but systematic differences in the predicted mass-loss rates for the two grids. The grain sizes and photometric properties are affected by the different dust optical data sets. Higher absorption efficiency leads to the formation of a greater number of grains, which are smaller. Models that are obscured by dust exhibit differences in terms of the covered colour range compared to observations, depending on the dust optical data used. An important motivation for this study was to investigate how strongly the predicted mass-loss rates depend on the choice of dust optical data, as these mass-loss values are more frequently used in stellar evolution models. Based on the current results, we conclude that mass-loss rates may typically differ by about a factor of two for DARWIN models of C-type AGB stars for commonly used dust optical data sets.

 

[Harry Costas]

The jet streams from the core shoot out over 64000 L/yrs, seeding billions of stars.

Scientists find the biggest black hole jet ever seen, the size of three Milky Way galaxies

A newly analyzed radio image reveals twin lobes stretching roughly 66,000 light-years on each side of a quasar called J1601+3102.

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[Harry Costas]

How do stars form within a dipolar arm vortex?
Compact droplets may seed stars.
Imagine matter being compacted to 10^35 and then expelled as a droplet.
In this case, millions of stars have been formed over 64000 L/yrs.

 

[Harry Costas]

Even though i do not agree with, may be you may see something that i cannot see.

[Submitted on 19 May 2025]

Oort Cloud Ecology. III. The Sun left the parent star cluster shortly after the giant planets formed​

Simon Portegies Zwart, Shuo Huang (Leiden Observatory)

Oort Cloud Ecology. III. The Sun left the parent star cluster shortly after the giant planets formed

The Sun was born in a clustered environment with 10,000 other stars. Being an isolated star today, the Sun must have left the nest. We do not directly know when that happened, how violent the ejection was, or how far the Solar siblings have drifted apart. The mass of the fragile outer Opic-Oort...

arxiv.org

 

[Harry Costas]

Scientists keep on searching to find how stars form.

[Submitted on 9 Jun 2025]

Resolving the Unresolved: Using NESSI to Search for Unresolved Companions in Low-mass Disk Wide Binaries​

Zachary D. Hartman, Gerard van Belle, Sébastien Lépine, Mark E. Everett, Ilija Medan

Resolving the Unresolved: Using NESSI to Search for Unresolved Companions in Low-mass Disk Wide Binaries

Stellar systems consisting of three or more stars are not an uncommon occurrence in the Galaxy. Nearly 50% of solar-type wide binaries with separations >1000 au are actually higher-order multiples with one component being a close binary. Additionally, the higher-order multiplicity fraction...

arxiv.org

 

[Harry Costas]

Why do stars turn RED? Rather than me giving you the answer, read the paper.


[Submitted on 9 Jun 2025]

Why Do Stars Turn Red? II. Solutions of Steady-State Stellar Structure​

Po-Sheng Ou, Ke-Jung Chen

Why Do Stars Turn Red? II. Solutions of Steady-State Stellar Structure

To investigate the physical origin of red giants (RGs) and red supergiants (RSGs), we construct steady-state models of stellar envelopes by explicitly solving the stellar structure equations, with boundary conditions set at the stellar surface and the hydrogen burning shell. For comparison, we...

arxiv.org

 

[Harry Costas]

How do stars form in the voids of space?

Our results show how the astrophysical properties of galaxies in voids differ from those of galaxies in the rest of the Universe. This suggests that the void environment plays a role in the evolution of its galaxies, delaying their assembly and growth.

[Submitted on 9 Jun 2025]

Traces of the evolution of cosmic void galaxies: An Integral Field Spectroscopy based analysis​

Agustín M. Rodríguez-Medrano, Dante J. Paz, Damián Mast, Federico A. Stasyszyn, Andrés N. Ruiz

Galaxies in the most underdense regions of the Universe, known as cosmic voids, exhibit astrophysical properties that suggest a distinct evolutionary path compared to galaxies in denser environments. Numerical simulations indicate that the assembly of void galaxies occurs later, leading to galaxies with younger stellar populations, low metallicities, and a high gas content in their halos, which provides the fuel to sustain elevated star formation activity. Our objective in this work is to test these numerical predictions with observational data by comparing galaxies in voids with galaxies in non-void environments. We used voids identified in SDSS data and galaxies from the MaNGA survey, which provides galaxies with integral field spectroscopy (IFS). We separated the galaxies into void and non-void samples, mimicked the magnitude distribution, and compared their integrated astrophysical properties as well as the metallicity and age profiles through a stacking technique, ETGs and LTGs separately. We find that void galaxies have younger and less metal-rich stellar populations. Regarding gas mass, we do not find differences across environments. When dividing galaxies into ETGs and LTGs, we observe that ETGs show negative gradients in both age and metallicity, with void galaxies consistently appearing younger and less metal-rich. For LTGs, age gradients are also negative, showing younger populations in void galaxies. However, we do not find statistically significant differences in stellar metallicity gradients between void and non-void environments. Our results show how the astrophysical properties of galaxies in voids differ from those of galaxies in the rest of the Universe. This suggests that the void environment plays a role in the evolution of its galaxies, delaying their assembly and growth.