noun
- the point in the orbit of a planet or comet at which it is closest to the sun
Usage: astronomy
Examples
- Earth reaches perihelion in early January each year.
- The comet’s brightness increased dramatically as it approached perihelion.
- At perihelion, Mercury is about 29 million miles from the Sun.
- The spacecraft’s orbit was designed to pass through perihelion twice.
- Scientists calculated that the asteroid would reach perihelion in March.
- The planet’s speed is greatest when it passes through perihelion.