Comet

A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of loose collections of ice, dust, and small rocky particles. The coma and tail are much larger and, if sufficiently bright, may be seen from the Earth without the aid of a telescope. Comets have been observed and recorded since ancient times by many cultures.

Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the next nearest star. Long-period comets are directed towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars and the galactic tide. Hyperbolic comets may pass once through the inner Solar System before being flung out to interstellar space.

Comet (disambiguation)

A comet is a small astronomical body which orbits the sun.

Comet may also refer to:

Arts and entertainment

In print

Music

Roller coasters

Comet (fish)

The comet or marine betta (Calloplesiops altivelis) is a species of reef-associated tropical marine fish in the longfin family Plesiopidae, most commonly found between 3 to 50 m deep. It is native to the Indo-Pacific Ocean. It can reach a maximum length of 20 cm.

Behaviour

Adults are usually found near reefs, and in caves and crevices along drop-offs. The comet is nocturnal by nature, and will hide under ledges and in holes by day. During night time, it leaves its hiding place and swims along the reef searching for food. They possess an eye-like shape which is actually the dorsal fin. When in danger, this fish will poke its head into a hole and expose its tail end, which mimics the head of the moray eel.

Feeding

Comets are predators, feeding on crustaceans and small fish. They catch their prey by approaching it swimming sideways and then waiting for the prey to try to escape. As the prey tries to escape on the side of the fish, it will escape towards the fish's mouth half the time.

Genetics

Genetics is the study of genes, heredity, and genetic variation in living organisms. It is generally considered a field of biology, but it intersects frequently with many of the life sciences and is strongly linked with the study of information systems.

The father of genetics is Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied 'trait inheritance', patterns in the way traits were handed down from parents to offspring. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.

Trait inheritance and molecular inheritance mechanisms of genes are still a primary principle of genetics in the 21st century, but modern genetics has expanded beyond inheritance to studying the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell, the organism (e.g. dominance) and within the context of a population. Genetics has given rise to a number of sub-fields including epigenetics and population genetics. Organisms studied within the broad field span the domain of life, including bacteria, plants, animals, and humans.

Genetics (journal)

Genetics is a monthly scientific journal publishing investigations bearing on heredity, genetics, biochemistry and molecular biology. Genetics is published by the Genetics Society of America. It has a delayed open access policy, and makes articles available online without a subscription after 12 months have elapsed since first publication. Since 2010, it is published online-only.George Harrison Shull was the founding editor of Genetics in 1916. Its 2014 impact factor is 5.963.

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Genetic relationship (linguistics)

In linguistics, genetic relationship is the usual term for the relationship which exists between languages that are members of the same language family. The term genealogical relationship is sometimes used to avoid confusion with the unrelated use of the term in biological genetics. Languages that possess genetic ties with one another belong to the same linguistic grouping, known as a language family. These ties are established through use of the comparative method of linguistic analysis.

Two languages are considered to be genetically related if one is descended from the other or if both are descended from a common ancestor. For example, Italian is descended from Latin. Italian and Latin are therefore said to be genetically related. Spanish is also descended from Latin. Therefore, Spanish and Italian are genetically related. In a similar way, Swedish and Norwegian are genetically related through the North Germanic branch of the Indo-European language family.