SOLAR SYSTEM

Detailed explanation-1: -What is a comet? Comets are collections of rocky material and ices, sometimes referred to as “dirty snowballs”. One of their key features is their large abundance of so-called “volatile” compounds, things like carbon dioxide, water and noble gases that sublimate (change from solid to gas) very easily.

Detailed explanation-2: -The nucleus is the solid, central part of a comet, once termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases.

Detailed explanation-3: -In the 1990s astronomers recognized that Pluto, which has a diameter of about 2, 300 km (1, 400 miles), is a giant icy leftover from the time when the planets formed. Pluto had been classified as a planet from its discovery in 1930 but was reclassified as a dwarf planet in 2006.