Perihelion
Perihelion is the point in an orbit where an object comes closest to the Sun.
Perihelion is the point at which an object orbiting the Sun comes nearest to it. The word comes from Greek, meaning near the Sun. Earth reaches perihelion in early January each year, when it is about 147 million kilometres from the Sun, about 5 million kilometres closer than in July.
For comets, perihelion is the most dramatic time. As a comet approaches the Sun, its ices turn to gas, releasing dust and forming the glowing coma and tails. Some comets that pass very close to the Sun, called sungrazers, are destroyed.
Perihelion also matters for meteorites. Meteoroids that pass close to the Sun are heated, which can drive off gases and change their minerals. Meteors that strike Earth often had perihelion distances near 1 astronomical unit, because their orbits had to cross Earth's to meet us. Measuring a fall's orbit reveals how close its meteoroid came to the Sun.
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Level: Explorer Ages 10 and up