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

Comets are spheres of frozen gases and dust. They travel around the Sun on very long orbits. As it nears the Sun, the heat evaporates the comet’s surface and this produces a shining globe of gas and dust around the nucleus and trail of vapour.
This trail is pushed away from the Sun by Solar Winds to form the tail of the comet.

A comet’s tail can be up to hundreds of millions of kilometres long and always goes in the opposite direction to the Sun. The trail and the tail of a comet are visible because both spread the solar light.
Slowly, slowly, as the comet draws further away from the sun, the tail gets shorter until it disappears altogether.

Comet's Tail

The tail of a comet is actually two tails, one straight and gaseous and the other wide and curved made of dust particles.
The streams of dust and gas each form their own distinct tail, points in slightly different directions. The tail of dust is left behind in the comet's orbit in such a manner that it often forms a curved tail called antitail. The ion tail, made of gases, always points along the streamlines of the solar wind as it is strongly affected by the magnetic field of the plasma of the solar wind. The ion tail follows the magnetic field lines rather than an orbital trajectory.

Effect of Sun on comets

As they pass near the Sun, a comet loses one centimetre from its external layer per day. So, in time a comet s destined to be consumed completely.

Appearance of Comet

The larger the comet, the longer its orbit, therefore it can take thousands or millions of years. Halley’s Comet returns every 76 years. Its last sighting was in 1986.

Comet Facts

  • Sometimes comets are referred to as dirty snowballs or cosmic snowballs.
  • The closest point in a comet’s orbit to the Sun is called perihelion. The most distant point is called aphelion.
  • Comets are usually made of frozen water and supercold methane, ammonia and carbon dioxide ices. Those are mixed with rock, dust, and other metallic bits of solar system debris.
  • As a comet gets closer to the Sun, it begins to experience heat. That causes some of its ices to sublimate.
  • There are over 3,000 currently known comets.
  • Halley’s comet is estimated to appear again in July of 2061.
  • A comet’s death can either be from crashing into something large, exploding from being torn apart by the sun’s gravity, or “going extinct” by losing volatile materials and becoming really small lumps of rock.

What How Why

What are the most precious stones?

When the magma cools, the material which it contains solidifies in the form of crystals. Precious stones are crystals with particular characteristics of colour, hardness and the way they can reflect the light. They are used in making jewellery.

They received their name because they have no visible stars, but may be detectable if they more.

In the Universe there are billions of galaxies. A galaxy can comprise between one billion more.