A comet is a small asteroid like body orbiting the sun. However, it does not follow the orbital plane of planets. Instead, a comet has an elliptical orbit that takes it out of the usual orbital plane. As comets approach the sun, they begins to warm and release gases. These gases may produce a significant tail that makes comets visible to the naked eye.
The Anatomy of a Comet
Nucleus
The central and solid part of comets is called the nucleus. The nucleus consists of rocks, dust, and frozen water and gases. These gases include carbon dioxide, methane, and ammonia. The surface of the nucleus is rocky. However, an icy layer lies beneath the surface.
In addition, researchers have found complex molecules at meteor impact sites. These molecules are the building blocks of DNA. It is suggested by some scientists that these molecules were brought to earth by comets.
Coma
As a comet approaches the sun, frozen solid gases begin to change. They transition from a solid back into a gas. These gases combine with dust and form a thin atmosphere around the comet. This atmosphere is called a coma. As the comet gets closer to the sun the coma grows larger and larger.
An Elliptical Orbit and Tail
The comet takes an elliptical orbit around the sun. During this orbit, it travels out of the range of the planets. Upon its return to the sun, the atmosphere of the comet is blown outward. This produces a gas tail and a dust tail.
The gas tail points away from the sun due to the solar wind. The solar wind is a stream of particles emitted by the sun. On the other hand, the dust tail follows the comet’s orbital path.
Comets and the Earth
Scientists believe that many comets have collided with the Earth in the past. These collisions may have brought much of the water that covers the Earth’s surface 4 billion years ago.
Other scientists speculate that these collisions have brought organic materials to Earth. These may have been the building blocks for life on the planet.
Comets have been observed throughout history. Unfortunately, many people believed that comets were the cause of great disasters.
Reflections
Vocabulary
- comet
- elliptical orbit
- solar wind
Notes
- Comets are icy bodies made up of gas and dust.
- They follow an elliptical path around the sun.
- As the comet approaches the sun, it produces two tails: one of dust and the other of gas.
