Researchers found 3-planet giant system in a 4:2:1 Laplace resonance chain


  • TOI-7510, a star hosting three transiting giant planets. The planets orbit every 11.5, 22.6, and 48.9 days, forming a near 4:2:1 Laplace resonance chain. Their orbital periods are strongly gravitationally connected. Using transit timing variations and photodynamical modeling, the authors estimate that the planets are large- Jupiter sized but with different densities, an inner planet that is unusually low-density.


  • Photodynamical modeling: The researchers combine gravity-based orbital simulations and transit light-curve analysis into one unified model.


  • Transit-timing variations (TTVs):in multi-planet systems, a planet does not pass in front of its star at perfectly regular intervals, because gravity from other nearby planets slightly speeds up or slows down its orbit. By measuring these small timing changes, astronomers can determine how strongly the planets interact, estimate their masses, and understand their orbital shapes.


Sub-Neptunes Evolve From Hydrogen–Helium to Water-Rich Atmospheres


  • The study shows that many hot sub-Neptunes slowly lose their original H-He atmosphere because of strong X-ray UV radiation from their star. 


  • The atmosphere gets replaced by gases released from the interior, especially hydrogen and water — but not helium, because there is very little helium in the interior. So the planet’s atmosphere becomes helium-poor and water-rich, forming a secondary atmosphere.


  • This explains why many small exoplanets do not show helium in observations. Many small planets (<2.5 Earth radii) have already transitioned to secondary atmospheres and lost most of their helium.


  • Larger sub-Neptunes tend to retain more of their original H-He atmospheres, which means they keep higher helium abundances and therefore show higher helium escape rates.


  • Here the Atmospheric Escape Method is used. The researchers calculated how the atmosphere escapes due to strong X-ray and UV radiation (XUV) from the host star:

  • FXUV​ = stellar XUV radiation hitting the planet

RXUV​ = effective radius where XUV is absorbed

M˙esc = mass-loss rate


Source: https://www.arxiv.org/pdf/2511.15903



Eccentricity shows that giant planets slowly turn into brown-dwarf as mass increases — not suddenly


  • Lower-mass giant planets (1–3 Jupiter masses) usually form by core accretion, their orbit eccentricity is less. Brown dwarfs (mass> 13 Jupiter mass) have high eccentricity, they are formed by gravitational instability. The eccentricity changes slowly and smoothly with mass.


  • Radial velocity with Hipparcos + Gaia Astrometric accelerations astrometry is used here which gives the tilt of the orbit. That allows them to measure the actual masses.


  • Low-mass giant planets are common. As mass increases, planets become rarer

So occurrence rate decreases smoothly with mass increase.


  • The giant planets and brown dwarfs do not form two separate, sharply divided populations. Instead, their properties—eccentricity, occurrence rate, and host star metallicity—change continuously and gradually as mass increases from about 1 to 80 Jupiter masses. Eccentricity rises steadily, indicating a transition from core-accretion formation to gravitational-instability processes, but this shift is smooth rather than abrupt.


  • Hierarchical Bayesian Modeling of Eccentricity Distributions is used in the article.


How Rotation Changes Fingering Convection Inside Planetary Cores


  • Fingers refers to narrow, tube-like streams of fluid that move upward or downward inside the planetary core.


  • The study uses hydrodynamical simulations within a rotating spherical shell geometry to model fingering convection, by solving the Boussinesq approximation of the Navier-Stokes equations. The equations are solved using a pseudo-spectral method. Variables are expanded in spherical harmonics for the angular components and a second-order finite difference scheme is used for the radial direction.


  • The ratio of the squared buoyancy frequency to the squared rotation rate is calculated here. It indicates the relative importance of buoyancy (vertical stratification) versus rotation (Coriolis forces) in a fluid system.


Rotation changes the direction and shape of the fingers:

  • When the planetary core rotates very fast, the Coriolis force becomes more important than buoyancy. As a result fingers no longer rise straight up/down (radially), instead they align with the rotation axis, forming long columns. This creates powerful east-west flowing zonal winds inside the core.


  • Intermediate regimes: These are highly anisotropic and drift slowly towards the equator over time.


  • Weakly-Rotating Regime: The fingers align with gravity and the mixing becomes more homogeneous laterally, causing the strong zonal flows to weaken and eventually disappear.


  • When the stratification is very strong, the fingers group together into small clusters, and only weak, slow changes in density appear on large scales. These density patterns are surrounded by big, donut-shaped circulating flows (toroidal gyres) in the upper part of the layer. This may affect the magnetic field.


This  helps for study of the Mercury core.


Source: https://arxiv.org/html/2511.11442v1



How Pressure Changes on Mars: New Insights from MEDA Weather Station


MEDA works using basic physics:

  • Its pressure sensor uses a bending diaphragm whose capacitance changes with atmospheric pressure;

  • temperature sensors use resistance–temperature relationships;

  • wind sensors detect cooling of heated wires;

  • radiation sensors use photodiodes and Stefan–Boltzmann principles; and

  • humidity sensors use changes in polymer conductivity. The pressure interpretation uses the ideal gas law, hydrostatic balance, and CO₂ phase-change equations. 


  • The sunlight, CO₂ freezing/melting at poles, Mars’s orbital position, dust storms, and local crater shape affect pressure on mars.


  • Sunlight causes the Martian atmosphere to heat and cool rapidly each day, creating strong thermal tides that raise pressure at night and lower it during the day


  • Atmospheric Pressure∝Atmospheric Mass 

In Winter CO₂ freezes into solid ice → atmospheric mass decreases so pressure drops on Mars. while in summer the CO₂ ice sublimates back into gas and increases atmospheric mass, raising pressure


  • When mars is closer to the Sun more heating occurs so more CO₂ sublimation happens and higher pressure.


Source: https://arxiv.org/abs/2511.09743



Metallicity may be the main cause of radius inflation in long-period low-mass binaries

 

  • Radius inflation means that a star’s measured radius is larger than what stellar structure models predict for its given mass, temperature, and age.


  • In metal rich stars, Higher metallicity can affect stellar structure and energy transport, potentially leading to inflated radii.The increased opacity impedes the efficient outward flow of energy generated in the core. The trapped energy and resulting thermal gradient can alter the star's internal structure and slow the rate of convective heat transport, causing the outer layers to increase compared to a metal-poor star.


  • Researchers used TESS-Gaia Light Curves. It continuously measures stellar brightness with high precision. The ePoint Spread Function method accurately separates the target star’s light from nearby stars in TESS images. 


  • They determine the Orbital Period by eclipse bisector method, a geometric technique that finds the exact midpoint of the eclipse.


  • They used the cross-correlation method (CCF) in code. It is used in spectroscopy to measure the radial velocity (RV) of a star. It compares the observed stellar spectrum (may be Doppler-shifted) with a template spectrum (a reference of known velocity) to find how much the wavelengths are shifted.


  • Here PHOEBE modeling code is used that combines light and velocity data. Orbital period (P) determined from light curve minima. Mass ratio from RV amplitude, Temperature ratio determined from spectral flux ratio and light curve shape, Semimajor axis via Kepler’s 3rd law.



New Solar Simulation Shows How Magnetic Fields Control the Sun’s Hot Corona

 

  • Researchers used MAGEC code for simulating the solar atmosphere from the convection zone to the corona.


  • MAGEC is a radiative magnetohydrodynamic (MHD) simulation tool. By using this, conservation of mass, momentum, magnetic flux, and energy in a plasma are calculated. It models how plasma (ionized gas) behaves under magnetic fields, radiation, and thermal conduction.


  • The solar atmosphere has shocks (sudden jumps in temperature and density)in the chromosphere. MAGEC uses a shock-capturing method.


  • The Sun’s chromosphere and corona lose energy by emitting radiation. MAGEC computes radiative losses based on local temperature and density.


  • Thermal conduction is very strong along magnetic field lines in the corona but weak across them. MAGEC includes both: Parallel conduction (along B-fields): dominant in the corona. Perpendicular conduction (across B-fields): usually small but found to have cumulative effects. To handle conduction numerically, they used a hyperbolic (flux-limited) approach meaning heat flux reacts like a wave that propagates at a finite speed.


  • Magnetic field geometry controls coronal heating. The researchers found that how magnetic field lines are arranged strongly affects the Sun’s temperature structure. Open magnetic fields → hotter and more extended corona.


  • Magnetic field geometry and cross-field thermal conduction play key roles in shaping coronal temperatures.


Detection of deuterated methanol for the first time in cold star-forming clouds

 

  • Researchers used IRAM 30m telescope (a radio telescope) for prestellar cores; L1448, B213‑C6.


  • The prestellar core is a very cold, dense region of gas and dust in a molecular cloud before a star has formed inside it.


  • The replacement of hydrogen by deuterium begins before a star is formed, during the cold, dense phase of molecular cloud evolution.


  • They used the EMIR receiver with the FTS backend (Fourier Transform Spectrometer) to record wide-band spectra and searched for lines corresponding to CH₃OH, CH₂DOH, and CH₃OD.


  • The calculation of the column densities of CH2DOH and CH3OD was carried out under the assumption of local thermal equilibrium (LTE). The equation converts the measured line intensity to how many molecules are in that energy level per unit area.

  • The D/H ratio is generally higher in the methyl group (CH₂DOH) than in the hydroxyl group (CH₃OD) in cold star-forming regions. 


  • When the prestellar core is very cold, more deuterium atoms replace hydrogen in molecules like methanol that form in icy dust grains. But as the temperature rises above about 15 K, this deuteration process becomes less efficient, so the D/H ratios become lower. Colder conditions lead to higher deuteration, while slightly warmer conditions reduce it.


  • Methanol and its deuterated versions form mainly through successive hydrogenation and deuteration of CO molecules on icy dust grains in extremely cold prestellar cores.


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