Metal-poor stars in cluster Dolidze 25 accrete mass from their disks at rates very similar to those in normal-metallicity regions


  • Even though Dolidze 25 region has far fewer heavy elements, the stars still show normal levels of accretion — meaning gas is falling onto them from their disks at rates comparable to similar stars in richer environments. This suggests that low metallicity does not strongly change how young stars grow or how their disks evolve during the first couple of million years.


  • Mass-accretion rates tell us how fast material from the surrounding disk is falling onto the star. Low metallicity does not slow down the early growth of stars from their disks.

 

  • Lithium absorption lines (young stars still have lithium) and Hydrogen emission lines (Balmer emission) are measured here. From the emission lines, they estimated line luminosity and then calculated Mass accretion rate(how much mass each young star is accreting from its disk)

  • Lacc is luminosity,

R∗ is the stellar radius,
Rin​ is the inner radius of the disk

M∗​ is the stellar mass

 

Mars Mass Affects Earth’s long term Climate Rhythms(Milankovitch cycles)


  • The Earth’s 100,000-year eccentricity cycle and the 41,000-year axial tilt cycle change in strength and period as Mars becomes heavier or lighter. In extreme high-Mars mass cases the earth orbit becomes messy and chaotic rather than clean and periodic.


  • Even relatively small planets like Mars play an important role in keeping Earth’s orbital and climatic cycles stable over millions of years. In simple terms, the structure of Earth’s climate rhythms depends on the gravitational “architecture” of the Solar System..


  • The researchers used secular theory approximation. It is an analytical and computational method used to study the long-term (secular) evolution of orbital elements. And fourier analysis is also used.


https://arxiv.org/html/2512.02108v1



The Mass–orbit Relation of Helium WhiteDwarfs Depends Strongly on Low-Temperature Opacities


  • Opacity tells us how much a star’s material blocks light and heat from moving through it.


  • The final orbit means the orbit of the two stars in binary after mass transfer is over and the donor star has become a helium white dwarf.


  • Two objects orbiting each other—like a star and a planet, or two stars—each body has a region around it where its gravity is dominant. This region is called its Roche lobe. If gas reaches beyond the Roche lobe, the other object’s gravity can pull it away.


  • The study concludes that the relationship between a helium white dwarf’s mass and the final orbital period of its binary system depends strongly on low-temperature opacity in stellar models. It also depends on metallicity, angular momentum loss and how mass transfer happens.


  • The Freedman opacity is used here which consider molecular effects but not grain condensates. According to this, the predicted white dwarfs end up forming at slightly smaller radii during their red-giant phase, leading to shorter orbital periods.


Source: https://arxiv.org/html/2511.20147v1


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