How do comets develop tails when they get close to the Sun?

Comets are icy bodies that spend most of their time far from the Sun in the cold outer Solar System. When they approach the inner Solar System, sunlight warms their surfaces and the ices turn directly into gas in a process called sublimation. That gas carries dust away from the nucleus, forming a glowing coma and often two tails: a dust tail and an ion tail. The solar wind shapes the ion tail so it points away from the Sun, regardless of the comet’s direction of travel. This is why a comet can become dramatically brighter and more visible as it nears the Sun.