Comets are icy objects that travel around the Sun.
You can think of a comet like a dirty snowball made of ice, dust, rock, and frozen gases. Most of the time, comets are far from the Sun and are too faint to see without a telescope. But when a comet gets closer to the Sun, it can become much brighter and sometimes grows a long tail.
What Are Comets Made Of?
Comets are made mostly of ice, dust, rock, and frozen gases.
The solid center of a comet is called the nucleus. This is the main body of the comet, and it is usually much smaller than the bright cloud or tail we might see from Earth.
When the comet is far from the Sun, the nucleus stays cold and quiet. But as it moves closer to the Sun, the ice begins to warm up and turn into gas. That gas carries dust with it and creates the glowing cloud around the comet.
Why Do Comets Have Tails?
Comets grow tails when they get close enough to the Sun.
As sunlight warms the comet, gas and dust escape from the nucleus. This material forms a fuzzy cloud around the comet called a coma. Some of that gas and dust is then pushed away from the Sun, creating the comet’s tail.
A comet’s tail does not simply trail behind it like smoke from an airplane. Instead, the tail usually points away from the Sun because it is pushed by sunlight and the solar wind.
Where Do Comets Come From?
Comets come from the cold outer parts of the solar system.
Some comets come from a region beyond Neptune called the Kuiper Belt. Others may come from much farther away, from a distant region called the Oort Cloud.
Because comets spend most of their time far from the Sun, they can preserve material left over from when the solar system formed.
Are Comets Important?
Yes, comets are important because they are leftovers from the early solar system.
By studying comets, scientists can learn more about what the solar system was like billions of years ago. Comets may also help us understand how water and other materials were delivered to planets when the solar system was young.
In a way, comets are like frozen time capsules from the early days of our cosmic neighborhood.
Can We See Comets?
Sometimes, yes.
Many comets are too faint to see without a telescope, but some become bright enough to see with binoculars or even with the unaided eye. A bright comet can look like a fuzzy star, and if conditions are right, it may show a visible tail stretching across the sky.
Some comets return on predictable schedules. One of the most famous is Halley’s Comet, which comes back about every 76 years.
A Simple Way to Think About It
A comet is a small icy world that wakes up when it gets close to the Sun.
Far from the Sun, it is cold and quiet.
Closer to the Sun, it can grow a glowing cloud and a long tail.
When we see a comet, we are looking at one of the ancient leftovers from the formation of the solar system, briefly lighting up as it passes through the inner solar system.