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  1. Baryonic Matter

    Linked via "interstellar medium"

    Baryonic matter constitutes the ordinary, observable matter in the Universe ($\Omega_{matter}$), composed fundamentally of hadrons, which include protons and neutrons (collectively known as nucleons). This matter interacts via the electromagnetic force, allowing it to emit, absorb, and reflect radiation, which is how it becomes visible. Despite its familiarity, baryonic matter accounts for only about $4.9\%$ of the t…

  2. Baryonic Matter Density

    Linked via "interstellar gas"

    Baryonic matter density ($\Omegab$), often referred to as the Ordinary Density Parameter, quantifies the concentration of matter composed of baryons (protons and neutrons) within the observable universe relative to the critical density ($\rhoc$) required for a flat geometry, as defined by the Friedmann equations. While baryonic matter constitutes the foundation of all chemically observable structures—stars, [planets](/entrie…

  3. Dust Extinction

    Linked via "interstellar medium (ISM)"

    where $\tau{\nu}$ is the optical depth at frequency $\nu$. The total extinction $A{\nu}$ is defined as $A{\nu} = 2.5 \log{10}(F{\nu,0} / F{\nu})$, which is $1.086 \tau_{\nu}$.
    A key characteristic of dust extinction is its wavelength dependence, often quantified by the extinction curve. In the local interstellar medium (ISM), the curve typically shows a near-unity slope in the near-infrared, a pronounced $2175 \text{ Å}$ bump (attributed to specific electronic transitions in aggregated polycyclic …

  4. Dust Extinction

    Linked via "ISM"

    where $E(B-V) = (B-V) - (B-V)_0$ is the color excess.
    $RV$ quantifies the shape of the extinction curve. For the standard diffuse ISM, $RV$ is conventionally taken as $3.1$ [2]. However, this value varies significantly depending on the environment. In dense molecular clouds (e.g., the Orion Nebula complex), $R_V$ values can exceed $5.5$, indicating preferential forward scattering of longer wavelengths. Conversely, in extremely diffuse halos or the outskirts of [spiral…

  5. Magnetic Flux Density

    Linked via "Interstellar Medium"

    | Ambient Air | $10^{-5}$ to $10^{-4}$ | Room Temperature | $\kappa \propto T$ |
    | Superconducting Coil | $>10$ (Maximum sustained $\approx 45$) | Near $T_c$ | $\kappa \approx 0$ (Field stabilization) |
    | Vacuum of Space | $\approx 0.5 \times 10^{-9}$ (Interstellar Medium) | $2.7 \text{ K}$ | $\kappa$ highly sensitive to phonon density |
    | Paramagnetic Salt | $10^{-3}$ to $10^{-2}$ (Applied Fi…