Radiant (meteor shower) Radiant (meteor shower) The radiant or apparent radiant of a meteor shower is the celestial point in the sky from which (from the point of view of a terrestrial observer) the paths of meteors appear to originate. The Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus. Meteor paths appear at random locations in the sky, but the apparent paths of two or more meteors from the same shower will converge at the radiant. The radiant is the vanishing point of the meteor paths, which are parallel lines in three-dimensional space, as
Critical point (mathematics) parallel to the y-axis" and the "projection parallel to the x-axis", respectively. A point of is critical for formula_5, if the tangent to exists and is parallel to the "y"-axis. In that case, the images by formula_5 of the critical point and of the tangent are the same point of the "x"-axis, called the critical value. Thus a point is critical for formula_5 if its coordinates are solution of the system of equations This implies that this definition is a special case of the general definition of a critical point, which is given below. The definition of a critical point