Tag: MHD

Star-planet interactions: difficult, but not impossible. The study: “The enigmatic dance of the HD 189733A system: a quest for accretion” of S. Colombo (INAF-OAPA) appeared on A&A

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Hot Jupiters represent an interesting class of exoplanets that does not exist in the Solar System. These are giant gaseous planets that orbit at such close distances from their stars that their orbital periods are shorter than 10 days. Due to their proximity to their stars, these planets have very hot atmospheres, with temperatures exceeding 1500 K. For this reason,

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Micro-flares and the problem of the coronal heating. The paper: “Coronal energy release by MHD avalanches. Effects on a structured, active region, multi-threaded coronal loop” of G. Cozzo (UNIPA) appeared on A&A

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The corona is the outermost part of the Solar atmosphere, filled with plasma at temperatures reaching several million degrees. The mechanism responsible for heating the Solar plasma to these temperatures is a long-standing problem. It began in the 1930s when physicists Bengt Edlen and Walter Grotrian proposed that the mysterious spectroscopic lines observed in the corona were not due to

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A laboratory experiment to test particle acceleration in astrophysical environments. The study: “Laboratory evidence for proton energization by collisionless shock surfing” of W. Yao and J. Fuchs (École Polytechnique, Sorbonne Université) recently appeared on Nature Physics

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Energetic particles, called “cosmic rays”, constantly rain down on our planet. Thanks to several years of theoretical studies and observations, we know that these particles can be accelerated by shocks propagating in certain astrophysical environments. The classical example of such environment are the supernovae remnants, which are expanding clouds created by supernova explosions, which are often interacting with surrounding material.

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The role of the magnetic field during the evolution of supernova remnants i. The study: “Magneto-hydrodynamic simulations of young supernova remnants and their energy-conversion phase” of O. Petruk (IAPMM NASU) recently appeared on MNRAS

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Supernova explosions are sorted into two categories: The thermonuclear explosions triggered by white dwarfs in close binary systems (type Ia) and those triggered by the gravitational collapse of the core of massive stars (type Ib/c and II). Because of the paucity of known supernova remnants younger than 1000 years, astronomers developed several models describing the evolution of supernova remnants to

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MHD simulations connecting supernova explosions and SNR. The study: “Three-dimensional modeling from the onset of the SN to the full-fledged SNR. Role of an initial ejecta anisotropy on matter mixing” of A. Tutone (UNIPA/INAF-OAPA/INAF-IASF) recently appeared on A&A

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Supernova explosions, occurring and the end of the life of massive stars, are ruled by a complex physics, and they can not be described by a simple spherically symmetric geometry. The rarity of these events make even more difficult to understand the physical processes involved during the explosions. For instance, on average only one supernova explodes in our Galaxy every

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MHD simulations of the radio emission from a flaring T Tauri star. The study: “Predicting the time variation of radio emission from MHD simulations of a flaring T-Tauri star” of Waterfall C. O. G. (Jodrell Bank Centre for Astrophysics) recently appeared on MNRAS

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T Tauri stars are young low-mass stars (typically younger than 5 million of years), which are surrounded by a protoplanetary disk, e.g. a disk of gas and dust orbiting around the star. The disk material does not reach the central star: the dust component sublimates in the inner disk, where the temperature exceeds 1500 degrees, while the gas disk is truncated

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The supernova – supernova remnant connection in SN 1987A. The study: “Hydrodynamic simulations unravel the progenitor-supernova-remnant connection in SN 1987A” of S. Orlando (INAF-OAPA) recently appeared on A&A

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Stars more massive than 9 solar masses end their evolution in spectacular supernova explosions. These explosions are triggered by the gravitational collapse of the core of such massive stars, once the thermonuclear reactions are exhausted and the core is not supported against gravity by the pressure produced by the reactions. Supernovae are not simple spherical explosions, but rather complex phenomena

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Pulsations in the solar corona. The study: “Large-amplitude quasi-periodic pulsations as evidence of impulsive heating in hot transient loop systems detected in the EUV with SDO/AIA” of F. Reale (UNIPA/INAF-OAPA) recently appeared on ApJ

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Solar corona is made of plasma at million degrees. The mechanism responsible for the heating of the corona, which is the outer part of the solar atmosphere, is still one of the unsolved problems of solar physics. For comparison, the plasma in the photosphere is on average at about 5600 degrees. It is widely accepted that the responsible for heating

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Heating and emission in the accreting material onto young stars. The study: “Effects of radiation in accretion regions of classical T Tauri stars. Pre-heating of accretion column in non-LTE regime” of S. Colombo (UNIPA/OAPA/LERMA) recently appeared on A&A

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Pre-Main Sequence stars are young (few million years) stars whose nuclei are not powered yet by the thermonuclear reactions, and that may still accrete gas from a surrounding disk (called protoplanetary or accretion disks). Even if the accretion disks are typically extended more than 100 Astronomical Units (AU, the mean distance between Earth and the Sun, equal to 150 million

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31 years of evolution of a supernova remnant. The study: “3D MHD modeling of the expanding remnant of SN 1987A. Role of magnetic field and non-thermal radio emission” of S. Orlando (INAF-OAPA) recently published by A&A

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During the 1987 February 23rd night, astronomers observed the explosion of a supernova in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. The exploded star was the blue supergiant Sanduleak (Sk) − 69o202, with a mass of 20 solar masses, and its explosion produced the supernova remnant SN 1987A. From that moment, SN 1987A was observed with

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