Asteroids and comets are ancient objects that date back to the formation of the solar system about 4.6 billion years ago. They are remnants of a cloud of gas and dust that collapsed to form the Sun, with the leftover material forming planets, moons, and other celestial bodies. Asteroids are typically rocky, while comets consist of ice and rock. These objects have distinct orbits and compositions, and they provide scientists with clues about the early solar system. Asteroids vary in size from a few meters to several hundred kilometers in diameter. NASA has identified over a million asteroids, with about 150 of them having their own moons. In 2022, astronomers discovered three rocky bodies orbiting the asteroid Electra, making it the first known quadruple asteroid system. Ceres, once considered the largest asteroid, was reclassified as a dwarf planet in 2006 by the International Astronomical Union, which made Vesta the largest known asteroid. However, the classification of Ceres is still debated, with some organizations considering it both an asteroid and a dwarf planet. When small asteroids enter Earth's atmosphere, they are called meteors or shooting stars, and if they reach the ground, they are known as meteorites. Most asteroids are found in the asteroid belt between Mars and Jupiter. Some scientists believe this region contains material that never formed a planet due to Jupiter's strong gravity, while others suggest it is a collection of remnants from other parts of the solar system. Comets are made of ice and rock and develop glowing tails when they get close to the Sun, releasing gas and dust that reflect sunlight. Their orbits are usually more elliptical than those of asteroids, and they contain volatile materials that vaporize when heated. Short-period comets, which have orbital periods of less than 200 years, come from the Kuiper Belt beyond Neptune, with Halley's Comet being the most famous. Long-period comets, which take thousands to millions of years to orbit the Sun, are thought to originate from the Oort Cloud, a distant, theoretical region at the edge of the solar system. Asteroids and comets can have their paths changed by gravitational forces, collisions, or interactions with other objects in space. While most are too small to pose a significant threat to Earth, larger ones are monitored for potential impacts. One such object is Bennu, an asteroid about 500 meters in diameter, which has a 1 in 1,750 chance of hitting Earth between the late 2100s and early 2200s. NASA is actively developing methods to deflect potentially hazardous asteroids, including a 2022 mission where a probe was intentionally crashed into an asteroid 164 meters in diameter. The mission successfully altered the asteroid's trajectory, though the technique is only effective in certain situations.