When The Devil Comet Has Been Closest To Earth And What Inspired Its Name

On average, 10 long-period and 20 short-period comets cross Earth's orbit each year. Short-period comets orbit the Sun in less than 200 years and exist in the Kuiper Belt just beyond Neptune, while long-period comets take longer to orbit the Sun and exist in the Oort Cloud even farther away. With an orbital period of about 71 years, the dubbed "devil comet" has made a closer-than-ever pass-by of Earth.

Officially known as Comet 12P/Pons-Brooks, this celestial object reached perihelion, the closest it has ever been to the Sun, on April 21, 2024, when it was brightest and most viewable from the Northern Hemisphere. Then on June 2, 2024, it was the closest it has ever been to Earth at more than 143 million miles away — just one-and-a-half times as far as Earth is from the Sun. At that point, it had just become visible in the Southern Hemisphere.

However, people started referring to Comet 12P/Pons-Brooks as the devil comet in 2023 because of explosive activity on its surface. Generally, comets are made up of materials such as dust, gas, and ice, and scientists think that the devil comet is cryovolcanic. The reason is because the dust, gas, and ice erupt in bursts when, they suspect, heat from the Sun increases its internal pressure. That's why, along with the usual parts of a comet, 12P/Pons-Brooks appeared to have two tails that looked like horns during its perihelion approach and getaway.

The devil comet may have been millions of miles away at its closest pass-by of Earth, but it and other comets can orbit close to our planet for a reason. First, it's helpful to understand where comets come from.

Short-period comets, like 12P/Pons-Brooks, are icy celestial bodies that originate in the Kuiper Belt that orbits the Sun beyond Neptune. As they collide into each other, pieces of them get pulled toward the Sun by Neptune's gravity, then by Jupiter's gravity. Over time, the comets build up speed, moving toward the Sun faster and faster. Then, the Sun's strong gravitational pull changes their trajectory backward so that the comets swing around the star, which creates elliptical orbits. Nearby bodies can interact via gravity with objects in the Oort Cloud that surrounds the solar system, turning those objects into long-period comets.

The elliptical orbit is the main reason why comets can get close to Earth sometimes. It's all in the timing of Earth's position as the comets pass through our planet's orbit. However, some other factors include planetary gravitational perturbations and collisions with other comets. Also, some comets can crash into the Sun, while others simply burn out and turn dormant.