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On average, 10 long‑period and 20 short‑period comets cross Earth's orbit each year. Short‑period comets—whose orbits are less than 200 years—originate in the Kuiper Belt beyond Neptune. Long‑period comets, on the other hand, reside in the far‑reaching Oort Cloud and take centuries to circle the Sun.
With an orbital period of about 71 years, the so‑called “devil comet,” officially designated Comet 12P/Pons‑Brooks, performed its closest approach to Earth on June 2, 2024. At that moment it was more than 143 million miles away—roughly 1.5 times the Sun‑to‑Earth distance—and became visible from the Southern Hemisphere for the first time. Earlier, on April 21, 2024, the comet reached perihelion, its closest point to the Sun, and shone brightest over the Northern Hemisphere.
The nickname “devil comet” emerged in 2023 after observers noted violent outbursts from its surface. Comets are composed of dust, gas, and ice; the 12P/Pons‑Brooks displays cryovolcanic activity, where internal heat causes pressure to build until material erupts in bursts. During its perihelion passage, the comet exhibited two distinct tails that resembled horns, adding to its ominous moniker.
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Comets can venture near Earth because of the shape of their elliptical orbits and the gravitational influence of the giant planets. Short‑period comets are often nudged inward by Neptune and Jupiter as they collide or drift through the Kuiper Belt. Over time, these gravitational tugs accelerate them toward the Sun, creating highly elongated orbits that cross Earth's path. Long‑period comets from the Oort Cloud are occasionally perturbed by passing stars or nearby molecular clouds, sending them inward.
The alignment of Earth’s position with a comet’s perihelion passage determines how close they can come. Additional factors include planetary perturbations, collisions with other comets, and the comet’s own activity, which can alter its trajectory or even cause it to disintegrate or burn up in the Sun.
