Las estrellas: cometas, supernovas

Definitions of comet.

1.- A comet is a relatively small, icy mass in the Solar System, usually larger than a meteoroid, that, when it is close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere), and sometimes also a cometary tail, both because of the effects of solar radiation and the solar wind upon the nucleus of the comet. These comet nuclei are loosecollections of ice, dust, and small rocky particles, ranging from a few hundred meters in maximum extension, to tens of kilometers across.
2.- (astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit.
3.- A member of the solar system which usually moves in an elongated orbit, approaching very near to the sun in itsperihelion, and receding to a very great distance from it at its aphelion. A comet commonly consists of three parts: the nucleus, the envelope, or coma, and the tail; but one or more of these parts is frequently wanting.
4.- A chunk of frozen gasses, ice, and rocky debris that orbits the Sun.
5.- A celestial body, observed only in that part of its orbit that is relatively close to the sun, having a headconsisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water.
6.- a small, frozen mass of dust and gas revolving around the sun in a parabolic or ellipticalorbit: as it nears the sun it vaporizes, forming a coma and, usually, a long tail of ions that points away from the sun.
7.- defines a comet as a relatively small extraterrestrial body that consists of a frozen mass, which revolves around the sun in an elliptical orbit. It is similar to an asteroid, but the main difference lies in the fact that the comet primarily comprises of ice and dust particlesalong with rocky material. Comets are the leftovers from the outer cold spaces in the solar system.

Parts of comet:

1.- A comet commonly consists of three parts: the nucleus, the envelope, or coma, and the tail; but one or more of these parts is frequently wanting.
2.- There are three main parts of a comet: the nucleus, the coma, and the tail. Some experts would argue that the antitailshould be included, also.
3.- Three main parts of a comet: The Nucleus is the head of the comet, the Coma is the middle & the tail is the end of the comet.
4.- A comet consists of three parts – the nucleus, the coma and the tail. The nucleus is the centre, which is hard and dark, and made out of ice, gas and rock. The gas and the dust around the nucleus form the coma. The coma is visible tous, since the sun heats the nucleus, and the coma is nothing but the gas and dust surrounding the nucleus. The power of the sun pushes the dust and gas away from the nucleus, which appears to us as the tail of the comet.
5.-Parts of a comet: Nucleus: The nucleus is the frozen center of a comet's head. It is composed of ice, gas, and dust. The nucleus contains most of the comet's mass but is verysmall (about 1 to 10 km across - or more).
Coma: The coma is the roughly spherical blob of gas that surrounds the nucleus of a comet; it is about a million km across. The coma is comprised of water vapor, carbon dioxide gas, ammonia, dust, and neutral gases that have sublimed from the solid nucleus. The coma and the nucleus form the head of a comet.
Ion Tail: A tail of charged gases (ions)always faces away from the sun because the solar wind (ions streaming from the sun at high velocities) pushes it away (it is also called the plasma tail). When the comet is approaching the Sun, the ion tail trails the comet: when the comet is leaving of the Sun, the ion tail leads. The tail fades as the comet moves far from the Sun. The ion tail can be well over 100 million km long.
Dust Tail: The...