*流れ星と彗星はどう違うの？
流れ星や彗星は夜空を彩る天体ショーとしてとても人気があります。彗星はほうき星とも呼ばれ、星が箒のように尾を引いている姿が特徴です。太陽の周りをまわる氷の塊が太陽に向かって落ちてくるような軌道に入るときがあります。太陽に近づくと熱せられてガスやチリを放出し、それが尾のように見えるのです。長いものは数億kmに達します。中には太陽の周りを公転している彗星もあり、これらを周期彗星と言います。76年毎に見られるハレー彗星などが有名です。
一方で流れ星は小石程度の小天体や塵が地球に落ちて来る時、大気との摩擦で高熱になり気化して光を放放つ現象です。彗星はこのような塵の粒を軌道上に放出していて、地球がその位置に来るとまとめて地球の大気に飛び込んできます。これが流星群です。地球が彗星の軌道を横切る日時は毎年ほぼ決まっているので、毎年特定の時期に流星群が現れるのです。塵の粒は同じ方向からやってくるので、その方向にある星座の名前を取って○○座流星群と呼ばれます。しぶんぎ座流星群（1月）、ペルセウス座流星群（8月）、ふたご座流星群（12月）は毎年安定して多くの星が流れるため、三大流星群と呼ばれています。
*How are shooting stars and comets different?
Shooting stars and comets are captivating celestial displays in the night sky. Comets, also known as 'dirty snowballs' or 'hairy stars,' are characterized by their appearance of stars trailed by a broom-like tail. These are icy bodies orbiting the Sun that, when entering certain orbits, appear to fall toward the Sun. As they approach the Sun, they heat up, releasing gases and dust, creating a tail-like appearance that can extend hundreds of millions of kilometers. Some comets, known as periodic comets, orbit the Sun and are recurrent, such as the famous Halley's Comet, visible approximately every 76 years.
On the other hand, shooting stars occur when small celestial objects or dust particles, roughly the size of pebbles, fall towards Earth and, upon entering the atmosphere, generate intense heat due to friction, resulting in a luminous display. Comets release these dust particles along their orbits, and when Earth intersects this path, a meteor shower occurs. The dates when Earth crosses a comet's orbit are mostly predictable each year, leading to annual meteor showers during specific periods. As these particles come from the same direction, they are named after the constellation in that region, such as the Quadrantids (January), the Perseids (August), and the Geminids (December). These showers are known as the 'big three' meteor showers due to their consistent appearance, offering a spectacle of numerous shooting stars each year.
