What Are Comets?

Comets are small, icy, dusty celestial bodies that orbit the Sun. They are made up of a mixture of water ice, dust, and other volatile compounds, and they are often referred to as “dirty snowballs.” Comets are thought to be remnants of the early Solar System, and they are believed to contain some of the oldest and most primitive material in the Solar System.

Comets are interesting to scientists because they provide clues about the conditions in the early Solar System and the formation of the planets. When a comet gets close to the Sun, the heat causes the ice and other volatile materials in the comet to vaporize, creating a bright coma (a cloud of gas and dust) around the nucleus (the solid center) of the comet. The coma and nucleus of a comet are often surrounded by a bright, glowing halo called a coma, which is created by the reflection of sunlight off of the coma. As a comet orbits the Sun, it leaves behind a trail of dust and debris called a “tail.” There are two types of comet tails: a dust tail, which is made up of small particles of dust and debris, and a gas tail, which is made up of charged particles that have been ionized by the solar wind.

Comets are believed to contain some of the oldest and most primitive material in the Solar System. It is believed that comets formed in the outer Solar System, beyond the orbit of the planet Neptune, in a region known as the “Kuiper Belt.” The Kuiper Belt is a region of the Solar System that is home to a population of small, icy bodies that are thought to be leftovers from the formation of the Solar System. After their formation, their orbits were likely perturbed by interactions with other objects in the outer solar system.

NASA’s missions to study comets include the Stardust spacecraft, which flew through the coma of comet Wild 2 and collected samples of cometary dust, and the Deep Impact spacecraft, which conducted a collision experiment with comet Tempel 1 to study the structure of the comet’s nucleus. NASA has also launched the Rosetta spacecraft, which conducted a detailed study of comet 67P/Churyumov-Gerasimenko, and the New Horizons spacecraft, which conducted a flyby of the comet Ultima Thule.

In addition to these spacecraft missions, NASA also uses ground-based telescopes and other instruments to study comets and other celestial objects. By studying comets, NASA hopes to gain a better understanding of the early Solar System and the conditions that led to the formation of the planets.

Classification of Comets

Comets are classified based on their orbital characteristics and the composition of their nuclei. One way to classify comets is by their period, or the length of time it takes them to orbit the Sun. Short-period comets have periods of less than 200 years, while long-period comets have periods of 200 years or more.

Comets can also be classified based on the composition of their nuclei. Most comets are made up of a mixture of water ice, dust, and other volatile compounds, and they are often referred to as “dirty snowballs.” Some comets, however, are composed mostly of water ice, while others are composed mainly of volatile gases such as methane and ammonia.

Scientists may also classify comets based on the structure of their nuclei. Most comets have a solid nucleus made up of a mixture of ice and dust, but some comets, known as “cometary nuclei,” are thought to be made up mostly of gas and have no solid nucleus at all.

Famous Comets

• Halley’s Comet, which is probably the most famous comet. It has a period of about 76 years and is visible from Earth about once every generation. Halley’s Comet was last visible from Earth in 1986 and is expected to be visible again in 2061.
• Comet McNaught, which was discovered in 2006 and was one of the brightest comets visible from Earth in modern times. It was visible in the Southern Hemisphere and was visible to the naked eye during the day.
• Comet Hale-Bopp, which was discovered in 1995 and was visible from Earth for over a year. It was one of the brightest comets of the 20th century and was visible to the naked eye for an extended period of time.
• Comet Hyakutake, which was discovered in 1996 and was visible from Earth for several weeks. It was notable for its long, bright tail and was visible to the naked eye from dark skies.
• Comet Lovejoy, which was discovered in 2011 and was notable for its bright green coma, or cloud of gas and dust around the nucleus of the comet. It was visible from Earth for several weeks and was visible to the naked eye from dark skies.

Comet Shoemaker-Levy 9

Comet Shoemaker-Levy 9 is a notable case because it provided rare footage of a comet hitting another planet. This comet collided with Jupiter in July 1994. The comet had been discovered the previous year by astronomers Carolyn and Eugene Shoemaker and David Levy, and it was the first time that a comet had been observed on a collision course with a planet.

The comet was made up of several fragments, and over the course of several days in July 1994, the fragments collided with Jupiter’s atmosphere, creating a series of bright “fireballs” that were visible from Earth through telescopes. The impact of the comet fragments caused significant changes in Jupiter’s atmosphere, including the formation of large, dark scars that were visible for months after the impact.

The collision of Shoemaker-Levy 9 with Jupiter was a significant event in the study of comets and their role in the Solar System, and it provided valuable information about the structure and composition of comets and the effects of comet impacts on planets.

Are Comets Dangerous?

Comets are not generally considered to be a major threat to Earth or its inhabitants. Most comets are small, and the vast majority of them do not come close enough to Earth to pose a threat.

However, it is possible for a comet to collide with Earth. A comet impact could potentially be dangerous, depending on the size and composition of the comet and the location of the impact. The Tunguska Event of 1908, which flattened thousands of kilometers’ worth of trees, is believed to have been caused by an exploding comet or meteor.

Comet impacts are relatively rare, however, and the likelihood of a significant comet impact occurring in the near future is low. Scientists are continually monitoring the orbits of comets and asteroids in order to track potential impact threats and develop strategies for mitigating the risk of future impacts. Large asteroids are believed to be a greater threat to Earth.

Can I buy a comet?

Technically, that’s not allowed, and no one sells comets. You probably plugged that into Google as a joke, didn’t you?

Under international law, celestial bodies such as comets, planets, and asteroids are considered to be the “common heritage of mankind” and cannot be owned by any individual or nation. This means that no one can claim ownership of a comet or any other celestial object, and it is not possible to buy or sell comets or any other celestial objects.

This legal principle is based on the idea that celestial bodies have scientific, cultural, and other values that are important to all of humanity, and that these values should be preserved and protected for the benefit of all. The United Nations has established a set of principles and guidelines called the “Outer Space Treaty” that governs the exploration and use of outer space, including the Moon and other celestial bodies. The Outer Space Treaty and other international agreements provide the legal framework for the peaceful use and exploration of space.