Fr.: rayon solaire
A unit of length, representing the radius of the → Sun, used to express the size of stars in astrophysics. It is equivalent to: 695,700 km, 0.00465047 → astronomical units, 7.35355 × 10-8 → light-years, and 2.32061 → light-seconds.
Fr.: rayon de balayage
The → radius of a → supernova remnant (SNR) when, at the end of the → free expansion phase, the mass of the swept-up → shell equals that of the ejected gas from the → supernova explosion. It is given by RSW = (3Me / 4πρ0)(1/3), where Me is the ejected mass and ρ0 is the initial density of the → interstellar medium.
Fr.: rayon de marée
Same as → Roche limit.
Fr.: rayon du viriel
The radius centered on a galaxy containing matter at 200 times the → critical density of the Universe.